Author Topic: EEZ Bench Box 3 (BB3)  (Read 52704 times)

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Offline prasimix

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EEZ Bench Box 3 (BB3)
« on: June 21, 2018, 03:27:24 pm »
EEZ BB3 crowdfunding campaign on Crowd Supply
Forum discussion about crowdfunding: https://www.eevblog.com/forum/crowd-funded-projects/eez-bench-box-3-sequel-to-eez-h24005/

User manuals on English and German are available online: https://www.envox.hr/eez/eez-bench-box-3/bb3-user-manual/1-introduction.html



I'm opening this new thread since it does not strictly belongs to existing two threads: one about what is called EEZ H24005 programmable power supply and another discussing DIB ("DIY instrumentation bus").

This one is about making EEZ H24005 a) even more modular and b) more “completed” design/project that does not include ready-made modules. That also does not imply that EEZ H24005 project is dead, and that people who built it or get it via crowdfunding campaign cannot count on further support.

Currently EEZ H24005 is modular in the sense that so-called Power modules are independent from digital control (Arduino Shield). Theoretically one can make another Power module with different capability and functionality as long as its dimension are within 165 x 74 mm and can use 26-pin connector for both power and control lines.
One possibility is to redesign that module in line with proposed DIB where PCB could be 145 mm tall and 170 mm wide (or even wider). That gives enough additional space to host a complete AC/DC power converter, what will be presented in future posts.

More “completed” design mean replacing of used ready-made modules with "home made" design. In case of the EEZ H24005 that means giving up from Arduino Due, AC/DC module (from Mean Well) used to deliver 48 V for Power Board and AC/DC module (from Vigortronix) for delivering 5/12 V for powering Arduino Shield and 12 V cooling fan.

Mentioned changes are not trivial at all (i.e. cannot be done in few days): replacing Arduino Due means migrating firmware to the new platform and replacing AC/DC parts include playing with mains voltage that require different discipline during development and testing to stay alive and also provide something that is robust enough to be safe and secure during operation under all (or at least imaginable but practically possible) conditions.
Just that two reasons are enough to keep topic separated from existing EEZ H24005 project since even if I succeed with it that don't necessarily means that many people will be interested to cope with different MCU and especially with circuit that works with mains voltage.
« Last Edit: April 18, 2020, 01:48:36 pm by prasimix »
 
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Offline prasimix

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I was entertained with the idea to replace AC/DC power module or mains transformer with some “in-house” solution almost from the beginning of my programmable power supply adventure. But shortly after EEZ H24005 crowdfunding campaign fulfillment was completed I starts to think more seriously about it. The similar situation was with thinking about alternative for used Arduino Due. I'd like here first to address AC/DC power module since I spent much more time on it then to MCU alternative.

AC/DC power module that should replace existing Mean Well LRS-150-48 (48 V/155 W) is designed taking into account the following features:
  • Wide input AC voltage (e.g. 85-265 Vac) without using a 115/230 Vac switch (also called universal AC input, full-range input, etc.)
  • Widely adjustable output DC voltage 2-42 Vdc or more. Therefore it can replace not just Mean well's power AC/DC module but also pre-regulator stage of the Power board build around LTC3864.
  • Over-current/short-circuit protection
  • under-voltage and over-voltage protection
  • Min. 200 W of continuous power
  • Bias power supply with all needed fixed voltages for the existing Power board (replacing LTC3260 on the Power board for generating required negative voltages)
  • Active/Synchronous rectification for better power efficiency (e.g. lower thermal losses)
  • Compact design that both power and bias stage are within Mean Well’s module dimensions (i.e. 159 x 97 mm)
I've decided to give a try to the AC/DC converter topology that is possible unusual for such purposes but was recommended by the person who is a sort of “living legend” when comes to power analog electronics who is actively, massively and selflessly helping many DIYers (including me) on couple of regional (Serbian) forums. His name is Dragoljub Aleksijevic, known as Macola. Therefore presented AC/DC converter (that acts as power pre-regulator and bias power supply) is more or less my attempt to make alive what Macola in one moment suggested.
A couple of disclaimers/clarifications is needed here: first, he also suggested more advanced topologies that can serve as efficient power pre-regulator and has better EMI since there are not hard-switching, but since this was my first attempt to make power AC/DC converter I selected one that will be presented shortly.  As you will see there include a lots of interesting details and challenges. Secondly, I was already spent many months on it and I'll try to squeeze a whole adventure in a few posts. Therefore it's quite possible that I'll forget to mention many important details so feel free to ask any kind of questions and I'll try to answer it by myself or by asking Macola for assistance.

The topology is called current-fed dual inductor converter (CF-DIC), that evolved from single inductor converter (or SIC) presented for the first time in the article Filho, Barbi (1996), A comparison between two current-fed push-pull DC-DC converters-analysis, design and experimentation.

The following picture shows basic components for converter's topologies presented in above mentioned article:

SIC:



… and DIC:



A list of DIC benefits over SIC topology is also presented and I'll mention it here for getting a better picture:
  • Voltage across the switch is 50% lower, hence switching components stress is lower
  • Transformer require only one primary coil and peak volt-ampere is 50% lower
  • Input inductor current is 50% lower (a cheaper/smaller inductor can be used)
  • Smaller current ripple and rms current in the output capacitor
  • Slightly smaller switches rms current
  • Inductor switching frequency is 50% lower (hence smaller losses)
What Macola proposed is a little bit different and with having in mind from the start what controller IC could be used to serve that purpose:



It has buck stage at the input that can be used to change duty cycle when PP (push-pull) stage is working with fixed duty cycle. In a way PP stage serve as a “DC transformer” (mind quotation marks here) that isolate primary from secondary side of high-voltage buck. Both buck (synchronous) and PP driver stages can be found in TI's LM5041B PWM cascaded controller. It include push-pull outputs that can be used to drive PP stage directly but with fixed duty cycle that is set to 50%. Depends of chosen topology, i.e. voltage-fed or current-fed PUSH and PULL outputs can be generated with programmed dead-time or overlap-time.
Driver signals overlapping is of paramount importance since neither of DIC inductors should be disconnected at anytime. That will induce a huge voltage that will shortly destroy one of the switching elements (MOSFETs in our case).
PP switching frequency is derived from buck stage frequency that is twice as much higher and set with external resistor.

How it works

Using Macola's words the following steps is an overview of important facts during operation:

1. Vin is switched on (first half cycle). HI-BUCK MOSFET and one of the PP MOSFETs (e.g. PUSH) are turned on. DIC1 inductor between them is connected to the full voltage (almost Vin) and current in it is rising following the dI = U / L * dt

2. When PWM time is expired, HI-BUCK is turned off and DIC1 inductor is trying to keep its current (Iend) to flow in the same direction. That current flow is preserved thanks to LO-BUCK MOSFET that is turned on (when expire dead-time after HI-BUCK is turned off). The PUSH MOSFET is still conducting. At the DIC1 inductor ends we have almost short-circuit condition (i.e. the major voltage drop is caused only by Rds, on of LO-BUCK and PUSH MOSFETs). Following the same law of dI = U / L * dt current change will be minor since voltage is small (about 1 V) hence we can consider that current is constant (e.g. Iend is still unchanged).

3. Just prior then PUSH MOSFET is switched off, PULL MOSFET is switched on (as defined with overlap time) and connect its end of primary coil to the ground. Otherwise when PUSH MOSFET is turned off both primary coil's ends will be left unconnected and the voltage on both drains will go into infinity (with disastrous outcome for one or more components). PULL MOSFET also connect its inductor (DIC2) to the ground and new Buck cycle is starting that is now charging DIC2 inductor.

4. Short overlap time is expired and PUSH MOSFET is turned off and voltage on its drain reach primary coil's Vclamp value (since its other end is grounded). Other end of the primary coil, that is connected to the switched off PUSH MOSFET is now behave as an accumulator that is charging and has Vclamp potential. Current thru DIC1 has Iend value and is now flowing thru the primary coil.

5. DIC1 inductor potential is now Vin – Vclamp, because Buck hi-side period is active. Since it was previously shorted and preserve Iend current, that current is now decrease slowly since a small voltage difference exists between its ends.

6. HI-BUCK is turned off again, and its voltage drops to LO-BUCK voltage drop (e.g. -Vd). DIC1 inductor has now Vclamp - (-Vd). The voltage difference is now much higher and current thru DIC1 inductor is falling much faster supplying the primary coil. DIC2 inductor has a constant current and its captured by short-circuit caused by PULL MOSFET conduction state and waiting that PULL MOSFET be turned off that it can start to flow into primary coil that will be reversely polarized in that moment.

7. Prior then PULL MOSFET is switched off (during the overlap period) now the PUSH MOSFET is turned on and “catch” its side of the primary coil, PULL MOSFET is turned off and current is continue to flow in other end of the primary coil that is reversely polarized.

… and the whole cycle is repeated over and again.



CF-DIC with short overlap time can be interpret as two boost converters that works in counter-phase with duty cycle a slightly over 50% and which load behind rectifiers is Vclamp. That means that the almost same rule is applicable for DIC inductor's calculation, where their supply is the buck stage, and average voltage of it pulses can be used as a DC source.

Output Vclamp on the Cout is reflected/mirrored on the primary coil proportionally to the transformer transfer ratio (Np/Ns). For example if Vclamp (i.e. converter's output voltage) is set to 10 V with transformer ratio N = 2 we'll have 20 V on the primary coil ends despite the fact that DC bus voltage is 325 Vdc (rectified 230 Vac).

Vclamp that is reflected/mirrored on the primary side can be seen as a voltage source with certain internal resistance. Therefore primary coil behaves as voltage source what is result of such heavy capacitance load. That load is necessary since it directly define its Vclamp. That is quite opposite from voltage-fed converters.

Offline prasimix

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CF-DIC schematics, part 1
« Reply #2 on: June 21, 2018, 07:36:53 pm »
Now, I'll present what is assembled and tested so far, but first a short list of features:
  • Wide AC input 85-265 Vac
  • Wide DC output: 3-52 V controlled by tracker circuit
  • Max. current 5 A continuously (i.e. max. power is 260 W)
  • Synchronous rectifier
  • Over-current protection (OCP) set to ~7.3 A
  • Output over-voltage protection (OVP) set to ~54 V
  • fsw, buck= ~68 kHz, fsw, pp= ~34 kHz
  • QR flyback as bias power supply

A complete circuit (without QR flyback) can be split into two main section. Lets start with Buck/PP stage with DIC power inductors and transformer:



As already stated LM5041B is used as main controller for this CF-DIC. It's PUSH-PULL outputs can deliver respectable 1.5 A peak and it's used to drive directly PP stage MOSFETs. Situation with buck portion is different. Its outputs HD, LD are TTL and require driver IC. Buck is working with high voltage (e.g. 325 Vdc) therefore a HV driver is also required. But, additionally to just HV driver, an isolated driver Si8233 from Silabs is used that improve separation of low-voltage/small signal and hi-voltage/high power grounds. As two power inductors Murata 60B684C are selected and finally one very interesting part (also suggested by Macola): a transformer that is winded using VAC core (T60006-L2025-W380) with Vitroperm 500 F core material. It allows us to work with lower switching frequency (~34 kHz) while flux density could go easily up to 0.5 T instead of 0.3 T suggested as upper max. (Bmax for most of the other core materials.
Thanks for it's high permeability give us primary coil with high inductance using fewer turns. Making such transformer wasn't a big deal. I made first one in less then a ten minutes in the following way: first I make a braid with multiple wires for primary coil and insert it into heat shrinking tube with very small diameter. That tube alone is certified for 600 V that in combination with existing wire insulation is more then enough in our case, since voltage on primary coils in worst case (the highest Vclamp of 52 V) shouldn't go over ~104 V. Such prepared primary "braid" is combined with braid for secondaries of the same length (that is valid for 2 : 1 : 1 ratio), secondaries braid is bend on half and I simply start with windings. The end result is looks like this:



Doesn't look professional, but so far didn't make any trouble nor audible noise under any circumstances (if control loop compensation is properly set :)).

FB pin is grounded as usual in situation when secondary side is isolated and COMP pin is used instead for setting output voltage by changing duty cycle of HV buck stage.
LM5041B is powered from +12 V provided by QR flyback that will be presented later. But A-side of Si8233 needs +5 V and instead of providing additional bias voltage or stepped-down +12 V, a REF output from LM5041B is used for that purpose!
An diode clamping circuit is added in the PP stage to return back to the DCbus elcos (C34, C35) a part of reactive energy that exists due to L(sub)lk, pri(/sub) (primary coil leakage inductance)  reducing the stress of the RC snubber over primary coil. Anyway, that energy cannot be transferred to the secondary side.
As one can see all MOSFETs are SiC (Silicon-Carbide) that is especially beneficial for HV buck side. Also diodes D13, D15, D18 and D19 are SiC, too. SiC diodes are suggested since they don't have undesirable recovery time nor recovery current. Therefore they put less stress on related circuits: D13 to AUX bias power supply, D18 and D19 to PUSH-PULL MOSFETs (Q5, Q6). D15 is added as a “support” for low-side buck MOSFET (Q3) or its body-diode. D16 which is ordinary Schottky is added for more balanced supply between hi-side and lo-side buck supply (VOA and VOB).

Online jbb

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Hi Prasimix

I too have been wondering about a very similar topology (using a single buck inductor and H bridge for primary winding) for a similar application: wide range output.

There are three things I really like about this style: it only uses a single primary windin, is easy to protect against output short circuits, and should be able to provide a wide output voltage variation to efficiently supply the linear post regulator.  There are a couple of things which make me nervous: where the CT goes, and the transformer isolation.

Maybe I'm just chicken, but I'm worried about people making their own transformers.  This is because it's a safety part which has to stand off big surge and spike voltages of 2500 V or more.  I'm concerned that someone might nick the insulating sleeve, or not allow enough creepage distance from the ends, or have some trapped metal particle that gradually rubs through, or...   I suggest you plan to source a commercially built and Hi Pot tested transformer for this project.  It will provide a margin of safety for the less experienced builders, and probably reduce the risk of you getting in legal trouble ("Your Honour, I made sure that the safety critical part was tested.")  Also, the leakage inductance will be more consistent in a commercial product.

As it comes to the switching devices, I think your primary switches could be superjunction Si MOSFETs because they don't switch in pairs.  Also, maybe the buck stage could use one Si MOSFET and an SiC freewheel diode (with a little efficiency loss...)
 

Offline prasimix

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Hi Prasimix

I too have been wondering about a very similar topology (using a single buck inductor and H bridge for primary winding) for a similar application: wide range output.

There are three things I really like about this style: it only uses a single primary windin, is easy to protect against output short circuits, and should be able to provide a wide output voltage variation to efficiently supply the linear post regulator. 

Yes, in fact this topology is inherently resilient against output short circuit.

There are a couple of things which make me nervous: where the CT goes,

That is not visible on the first sheet of schematics. I'll explain that in the next coming post.


... and the transformer isolation.

Maybe I'm just chicken, but I'm worried about people making their own transformers.  This is because it's a safety part which has to stand off big surge and spike voltages of 2500 V or more.  I'm concerned that someone might nick the insulating sleeve, or not allow enough creepage distance from the ends, or have some trapped metal particle that gradually rubs through, or...   I suggest you plan to source a commercially built and Hi Pot tested transformer for this project.  It will provide a margin of safety for the less experienced builders, and probably reduce the risk of you getting in legal trouble ("Your Honour, I made sure that the safety critical part was tested.")  Also, the leakage inductance will be more consistent in a commercial product.

I was instructed when both primary and secondary wires are insulated with heat-shrink tube that gives margin of 3 kV, or 1.5 kV when only secondary wire is insulated. My hand-made transformer shown above has insulation of primary side only. I presumed that can provide an equal strength to the former example.
As already described we have here a much favorable situation then in case of e.g. flyback where on primary coil we have Vin, dc + Vclamp * N that could easily goes over 450 Vdc.
But, please note that if anything is happen with this project in the future I'm not going to wind dozens (or hundreds) of transformer by myself :). Therefore I already contracted Polish company Feryster that send me yesterday picture of a prototype built in accordance with specification:



As it comes to the switching devices, I think your primary switches could be superjunction Si MOSFETs because they don't switch in pairs.  Also, maybe the buck stage could use one Si MOSFET and an SiC freewheel diode (with a little efficiency loss...)

I've used MOSFETs in my first prototype, IPA60R380P6XKSA1 for hi-side buck and push-pull MOSFETs and IPA60R120P7 for lo-side buck. Results was disappointing, but I suspect mainly due to badly routed PCB. That is one reason why isolated driver is used in current prototype. Maybe on the next PCB prototype I can try Si MOSFETs again but I think that one for hi-side buck  should remain SiC. Lo-side could be removed and leave just SiC diode.

As you can already see I'm not so concern about BOM cost for this converter. I'm more interested to get robust and flexible design that can be easily scaled in the future if required. Selected topology promise easy upsize to couple of kW of output powers, but also a even wider output voltage. In that sense I'm particularly interested to build in the next step a converter which output voltage can go up to 400 Vdc and e.g. 500 W that can be used while building another SMPS :). Additionally (if that happen at all), with different transformer I believe that is possible to make a converter with output of few kV that can be used as source for some ESD testing and HV experimentation.

Offline prasimix

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Regarding MOSFET selection I think that is worth mentioning how buck output looks when output voltage is approaching minimum value. For example, if set voltage is 4 V (current is above 1 A) it looks like this:



Pulse (inverted) is just 320 ns long and this is for 120 Vac (170 Vdc) and for 230 Vac it has to be even shorter! With SiC MOSFET is works like a charm.

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CF-DIC schematics, part 2
« Reply #6 on: June 22, 2018, 12:25:34 pm »
The second sheet of the schematics include secondary side with current sense transformer, synchronous rectification, control loop and tracker circuit:



Current sense transformer is dual primaries Murata 54100C (1:1:100 ratio) that is connected on the less noisy point on the secondary side. It's isolation strength is 1.2 kVrms. Current sensing transformer could be also deployed on the primary side, e.g. between PUSH-PULL MOSFETs drains but in that case we could experience higher drain's “capacitive noise” since they are not connected directly to the power GND. Another possibility is to put it before buck stage, when single transformer with single primary coil is sufficient. I didn't test that possibility.
With dual primaries and full rectification we can count with nice output that can be used for current limitation that is on LM5041B set to 500 mV. Value of termination resistor (RT) is set about 6.8 Ω (R52, R53 in parallel) that limit output current to about ~7.3 Apeak that give us enough margin for working max. of 5 A. R51, C55 makes RC low-pass filter on the CS input pin.

Synchronous rectification (SR) is accomplished with IR1168 and MOSFETs with very low Rds, on. Today there is a quite a lot MOSFETs that are advertised as suitable for SR. But in our case with such wide output voltage we have to take into account (and I forgot that a couple of times, with predictable results :() that its Vds, max has to be twice as high then output voltage (if transformer ratio N = 2). Such MOSFETs are still easier to find in TO-220 package then e.g. in DPAK. Also regardless of how small is Rds, on, for 5 A output you can still expect dissipation that goes over 1 W. That shouldn't be a problem since if enough free or forced air circulation can be insured. Usually SR MOSFETs has extended temperature range of 175 oC. Otherwise TO-220 could be more practical, but it has to be mounted with terminals as short as possible.
Above mentioned IPP147N12N3 has Vds, max of 120 V and Rds, on of 14.7 mΩ. Another great candidate that is more expensive but still reasonably priced is IRFB4115PBF that goes up to 150 V with Rds, on of 9.3 mΩ.
You can find in attachment spreadsheet for calculating IR1168 working params that I made following its application note.
Of course, if dissipation and overall efficiency is not an issue SR can be replaced with suitable diodes (e.g. I've tested STTH802 for 200 V/8 A).

Finally, we have to close a loop to have regulated output voltage. Control loop resides on the secondary side and its output has to be isolated from COMP input pin of the LM5041B. Toshiba TLP291-GB.SE-T that is more compact then usually used optocouplers and also has swapped C and E output pins! First and obvious part for closing a loop is TL431 and it was used at the beginning and is enough if fixed output is needed (in that case neither separate aux power supply is needed, just additional secondary coil for AUX +12 V power). But, primary purpose of this CF-DIC is power pre-regulator that should provide variable output. That calls for tracking circuit that will monitor post-regulator Vout and modulate control voltage for the LM5041B. Usually, a PNP tracker is suggested (such solution is used between EEZ H24005 pre-regulator and post-regulator), but I found two disadvantages of TL431 + PNP tracker solution. First, it's more challenging to set loop compensation that works when post-regulator is in CV and especially CC mode. Another one that can be disastrous without adding additional protection (i.e. output OVP) is that any interruption/disconnection between tracker input and post-regulator output could easily increase CF-DIC output voltage to destroy secondary stage (what was happened to me twice when IR1168 and one or both SR MOSFETs were destroyed).
Therefore I was looking for other solution. First I came to pretty nice, and until recently a completely unknown for me TL103W that is also used for control loops of SMPS, especially when constant current is needed (as in LED drivers). It is consists of two op-amps where first one has internal voltage reference of 2.5 V connected to non-inverted input. That first op-amp is replacing TL431 (that is not an ordinary op-amp) and output voltage applied to its inverting input via voltage divider (R63R69 + R73) set max. voltage on the CF-DIC output, and represent output OVP. The tracking functionality is accomplished by voltage divider's GND potential (i.e. lower end of R73). If R73 is connected to 0 V we'll have max. output voltage and it can be decreased by increasing R73 potential and for +2.5 V (that corresponds to voltage reference value), its output will fall to zero. Such tracking control I was found in an Electronic Design article. Possible disadvantage of such tracker is that it require dual rail supply but that is not an issue in my case since bias power supply already offer +5/-5 V for powering post-regulator control circuits. The reference voltage has to be inverted (IC8A) and control voltage has to be within voltage reference range (0 – 2.5 V) and for that buffered signal (IC8B) from post-regulator CV control loop is used. IC8 is TL072 since it's already used on post-regulator side for lower BOM count.
This tracker works really nice and track CV to CC mode changes including short-circuit condition with voltage difference set to about 3 V. Currently it have only one obstacle: it cannot push output down to zero (it's about 0.11 V). Therefore when post-regulator output is approaching 50 V it cannot provide more then 1.5 V difference. Perhaps I failed to arrange TL103W and TL072 op-amps: if TL072 is used in place of second TL103W op-amp it could be possible to go down to zero since it is powered with dual rail. Here is what I have with current setup (I intentionally spread last few volts to highlight non-linearity caused by TL103W inability to pull output down to 0 V):



That is all for now about "theory" of CF-DIC. I'll start to publish some measurements before I continue with bias power supply that is also part of this design.
« Last Edit: June 22, 2018, 12:44:15 pm by prasimix »
 

Online jbb

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Current sense transformer is dual primaries Murata 54100C (1:1:100 ratio) that is connected on the less noisy point on the secondary side. It's isolation strength is 1.2 kVrms.

Hmm. The isolation rating on that CT seems a bit low.  I would happily put that somewhere int he primary side (e.g. in series with main MOSFET) but I suspect it only counts as functional isolation, and isn't sufficient for user safety.  It's more work, but I do wonder

Regarding MOSFET selection ... Pulse (inverted) is just 320 ns long and this is for 120 Vac (170 Vdc) and for 230 Vac it has to be even shorter! With SiC MOSFET is works like a charm.

That is quite short.  Maybe someone could look at a superjunction Si MOSFET as an optional cost-down.

I've used MOSFETs in my first prototype ... Results was disappointing, but I suspect mainly due to badly routed PCB. That is one reason why isolated driver is used in current prototype. Maybe on the next PCB prototype I can try Si MOSFETs again but I think that one for hi-side buck  should remain SiC. Lo-side could be removed and leave just SiC diode.

I do like isolated drivers for that - even if you allegedly don't need isolation they can really simplify design by breaking ground loops.
 
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Offline prasimix

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Current sense transformer is dual primaries Murata 54100C (1:1:100 ratio) that is connected on the less noisy point on the secondary side. It's isolation strength is 1.2 kVrms.

Hmm. The isolation rating on that CT seems a bit low.  I would happily put that somewhere int he primary side (e.g. in series with main MOSFET) but I suspect it only counts as functional isolation, and isn't sufficient for user safety.  It's more work, but I do wonder

Ok, the user's safety is of paramount importance that we can agree easily (hence your concern). Please let me know what is the worst case scenario here that CT could become dangerous? It's from one side connected to Out+, and on the other to the CS input of LM5041B that is isolated from HV buck using Si8233 and use AUX voltage from bias power supply (still not presented) that is isolated flyback. LM5041B is directly connected only to PUSH-PULL MOSFETs gates. Therefore we should have a multiple breakdown from buck isolator to LM5041B to CT or from AUX power to LM5041B to CT or from PUSH-PULL MOSFETs to LM5041B to CT.

If we want CT on the primary side, then I'd like to put it before buck stage rather then to PUSH-PULL drains to GND. In that case we don't need dual primary CT.

Offline prasimix

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Superjunction vs. SiC MOSFET prices
« Reply #9 on: June 25, 2018, 08:08:58 am »
I did a quick search for superjunction MOSFETs and price comparison based on Mouser offerings. The currently used SiC is the cheapest one but it is still 2.85 EUR. But most of the superjunction's from e.g. Vishay offerings easily goes over 3 EUR and their performance is still inferior to SiC. Let me know if you eventually find something that is worth testing (still I can bet on inferior performance with wide output voltage). The real issue with selected SiC (and most of the others from the same family/manufacturer) is possible supply shortage. I can easily imagine a huge demand for such kind of device.

It's obvious that this project is not BOM optimized, but that is not my intention. I'm not here in competition with other (more BOM friendly) topologies that is in the first place mostly built for the fixed output voltage.

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CF-DIC primary side measurements
« Reply #10 on: June 25, 2018, 12:42:01 pm »
In this post I'd like to present some measurements that were performed on the primary side of the CF-DIC and could be of interest for further discussion and to potential builders.

Input voltage was 120 Vac (using isolation transformer), and CF-DIC output is set to 20 V by tracking post-regulator output of 17 V since as you can seen in the following picture on this (second) prototype PCB (“DIB format”) I put together complete CF-DIC, bias power supply and post-regulator that is copied from EEZ H24005 project. Additionally a provisional AC filtering is added and DIB interface section (that has to be tested).



In this revision TL431 with PNP tracker was used and QR flyback is based on controller that I'm going to change in final release (but more about that later). Also I still have to decide between two options: to leave together pre-regulator and post-regulator on the same PCB or to separate them on two PCBs: one with pre-regulator for 2 channels and another with post-regulators for 2 channels!

A few words about how I started to test a whole thing that is well known to experienced builders but could be helpful for beginners like me.

First, a different discipline is highly required from the start. That means that you cannot simply start to play with such type of circuits when you are tired, or your attention is shared between e.g. nowadays uninterrupted “noise” flow from from PC or "smartphone" screen or with someone that just came into the room and want to chat about weather, sport results, home affair, etc. Single mistake and ... puff, you can count on various damages that could cost at least you time and money with presumption that you was lucky and wasn't injured! Some people are using Plexiglas shield that are usually advertised for conducting chemical experiments (perhaps something like
).

Secondly, I'd highly recommend that never, ever start with connecting the circuit to the mains voltage before you are completely sure that all parts works as predicted under load. I did it in few steps: at the beginning, with the first (non-SiC) prototype I was using EEZ H24005 set to its max. 80 V (that required to adjust ULVO voltage divider otherwise LM5041B will not start. You have to readjust it again when switch to the mains especially 230 Vac) and with foot pedal control for output control! Huh, that was a "life saver" few times :). Then I used next what I have on the bench as that is an old prototype of EEZ H24005 that goes a little bit higher up to 100 V. Of course in both cases a current limitation is used very conservatively/cautiously that resulted even in “soft-starting” of the HV bulk elco charging :). After that a 230/120Vac isolation transformer is used when working with 120 Vac is actually even more interesting since it put more stress on the input stage since required current is higher then with 230 Vac. Basically if everything seems to work fine with 80/100 Vdc power supply you can expect good results when connected to the AC input, first indirectly using isolation transformer and then directly.

Another important thing is scope, and I don't want to recommend such adventure without one. I'm using scope with ground connection isolated from the grid (since I don't have an differential probe). Don't ever try to think about using grounded one and touching anything on the primary side. Needless to say you cannot use same isolation transformer secondary to power both scope and CF-DIC. Use two separate transformers or one with dual and separated outputs.
Additional warning is needed for working with SiC MOSFETs: never, ever touch hi-side buck gate pin with your scope probe when circuit is powered on!
If you'd like to monitor signals on both primary and secondary side, take care about you GND connection. You'll broke in that manner ground separation (isolation) and when do that it's better to make it locally i.e. on the PCB then making a huge loop that goes over probe cable and ends up on the scope side.

On the picture below is shown how the latest working prototype PCB looks like from the bottom side. As one can expect there is a lots of modifications, one is already mentioned that is different control loop and tracker for what I made a small PCB instead of redoing a whole PCB once again. Instead of initially planned DPAK sync MOSFETs I'm using now more capable one (i.e. higher Vds, max) that are listed in schematics (IPP147N12N3GXKSA1). I've also added LC filter on the pre-regulator output and additional Cbulk (totaling 300 uF) for lower ripple when working with 120 Vac. 230 Vac works quite good with even single 150 uF, but in final version I'm going to use 2 x 120 uF.



Let's start with measurements of all LM5041B control signals: HD, LD, PUSH and PULL.
Iout=1 A and due to single GND connected to one end of Cbulk that are fare away from LM5041B signals looks a little bit “messy” but in reality they are way better with proper probe grounding.



With different timebase we can see e.g. that PUSH and PULL signals are overlapped.



Next measurement include buck output (DIC inductors input) and PP stage:



Without load primary coil ends (connected to PUSH and PULL MOSFETs) to ground:



… or better presentation when single probe is connected to the primary coil ends:



When Iout=1 A it looks like this (“top” voltage is 40 V for Vout=20 V):



DCbus ripple for 3.5 A looks like this:



… and current transformer output on its termination resistor (non-filtered) for the 3.5 A (it's a little bit below half of scale since Imax is set to ~7.3 A):



I don't have a current probe and cannot present any current measurement, neither thru DIC inductors, transformer or other parts of interest. Something that I'd like to have much more is thermal imaging. Phew, that could be something.

Please let me know if I forgot to mention some important measurement on the primary side, and I'll try to do it.

« Last Edit: June 25, 2018, 12:50:08 pm by prasimix »
 

Online jbb

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I suggest you check the voltages around the buck FET during the switching transition. You need to look out for big spikes or ringing.

The catch is that SiC devices are fast. As you said, the gates are very sensitive. Small stray capacitances and inductance can cause big problems. So crank up your scope to maximum bandwidth and see what you can see. Then work out whether the rise time in the screen is the rise time of the circuit or the rise time of your scope + probe. I have blown up circuits before because there was an short & nasty spike that I didn’t have the bandwidth to see.

While I do most of my power e work with the 20 MHz bandwidth limiter on, there are times when you need a 500 MHz scope to see the truth.
 

Offline prasimix

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I suggest you check the voltages around the buck FET during the switching transition. You need to look out for big spikes or ringing.

I'm not sure how to achieve this, just to put probe tip in the near proximity of gate pin? I can for sure pick up some switching noise. Or a whole exercise is to see if some glitches exists and are interpolated to hi-side control signal?

Offline prasimix

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A few screenshots of buck output, measured between hi-side MOSFET drain and source, with 70 MHz BW and 1K on probe tip. Vin=120 Vac, Vout=51 V,  Iout=3 A:



... Rising edge:



and falling edge:



EDIT: And same output without load:

« Last Edit: June 26, 2018, 08:29:13 pm by prasimix »
 

Online jbb

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Sorry, wrote some stuff just as you were posting.  Will address at lunchtime (gotta run to work).

Ok, the user's safety is of paramount importance that we can agree easily (hence your concern). Please let me know what is the worst case scenario here that CT could become dangerous? It's from one side connected to Out+, and on the other to the CS input of LM5041B that is isolated from HV buck using Si8233 and use AUX voltage from bias power supply (still not presented) that is isolated flyback. LM5041B is directly connected only to PUSH-PULL MOSFETs gates. Therefore we should have a multiple breakdown from buck isolator to LM5041B to CT or from AUX power to LM5041B to CT or from PUSH-PULL MOSFETs to LM5041B to CT.

If we want CT on the primary side, then I'd like to put it before buck stage rather then to PUSH-PULL drains to GND. In that case we don't need dual primary CT.

OK, the CT secondary is connected to main DC bus 0V by the LM5041.  This is connected to the incoming AC line via, I guess, a diode rectifier.  From a safety perspective, that counts as connected.  We therefore see that the weakest isolation between the DC output (which humans can touch) and the AC line is the CT.  If the AC line is subject to a big spike (e.g. a circuit breaker opens / closes under heavy fault 'nearby' in the power system), large transients can be generated (>1kV).  The CT probably isn't rated to reliably stop that, and if the insulation fails it will short mains potential into user-accessible terminals.

I see three approaches to resolving this:
  • Place CT on primary side somewhere.  This particular failure mode goes away.
  • Use CT with 'reinforced' isolation
  • Put LM5041 control chip on the isolated output side.  This will involve some messing about (e.g. how to power it, adding isolated gate drive to primary MOSFETs).  If you're using the DIB interface, there should be some DC power available to run the LM5041 for you, and maybe replace the QR flyback aux supply.  (Note: buck converter chips are available to generate a little bit of non isolated 12V from 100 - 400V DC to drive primary MOSFETs.)
 

Online jbb

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OK, morning tea time, so let’s have a look at those waveforms.

Straight away, they look suspiciously clean. Maybe your layout’s excellent, or maybe something is hiding.

Rise and fall times are approx 38 ns from ‘scope measurements. Given rule of thumb of BW (GHz) = 0.35 / tr (ns), get 0.35/38 = 0.0092 GHz BW, I.e. approx 10 MHz, which is within ‘scope capabilities. I suggest cranking the timebase up so we get more details on the transient. It should ideally take approx half the screen.

I’m a little concerned about the 1k series resistance. The Rigol 10x probe could have up to 15 pF capacitance, which gives a time constant of 10 - 15 ns. This is approx 10 - 16 MHz BW.

These bandwidths match up, so I suspect that what you’ve actually measured is the 1k resistor and ‘scope probe capacitance.

Also, were you using the probe clip and alligator clip ground? These aren’t good for higher frequencies.

Could you send a picture of your probe setup? We may be able to do much better.
 

Offline prasimix

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Ha, ha, now that looks funny for me. Yes, it's almost suspiciously clean that one can think that source is something else or that pictures are doctored/Photoshoped :). But it wasn't so funny with my first prototype, quite contrary. I believe that current result is combination of multiple factors: GND isolations (thanks to Si8233), better PCB layout and use of SiC MOSFETs.

1K in combination with probe makes a RC filter. I've repeated measurements from the last post this time just with x10 probe applied between drain and source as shown on the next picture:



"Zoomed out" buck output, no suspicious glitches are visible:



... rising edge:



... falling edge:



... and without load:



Offline prasimix

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I see three approaches to resolving this:
  • Place CT on primary side somewhere.  This particular failure mode goes away.
  • Use CT with 'reinforced' isolation
  • Put LM5041 control chip on the isolated output side.  This will involve some messing about (e.g. how to power it, adding isolated gate drive to primary MOSFETs).  If you're using the DIB interface, there should be some DC power available to run the LM5041 for you, and maybe replace the QR flyback aux supply.  (Note: buck converter chips are available to generate a little bit of non isolated 12V from 100 - 400V DC to drive primary MOSFETs.)

I think that first suggestion is the most practical one. I didn't find better CT so far with better margin or reinforced isolation. Most of them have just functional isolation of 500 Vrms for mounting on the primary side. Making a custom one just make things even more complicated.
Moving LM5041B on the secondary side asks for two additional gate isolation transformer for driving PP stage. Powering Si8233 is not a big issue since bias flyback AUX output can be step-down to required 5 V.

I'll try to incorporate Murata 53100C on the existing PCB and see what will happen.

Online jbb

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Ha, ha, now that looks funny for me. Yes, it's almost suspiciously clean that one can think that source is something else or that pictures are doctored/Photoshoped :). But it wasn't so funny with my first prototype, quite contrary. I believe that current result is combination of multiple factors: GND isolations (thanks to Si8233), better PCB layout and use of SiC MOSFETs.

1K in combination with probe makes a RC filter. I've repeated measurements from the last post this time just with x10 probe applied between drain and source as shown on the next picture:

That's more like it.  A 10ns fall time is approx. 35 MHz BW (and I think you said you had a 70 MHz 'scope?) so you're probably good.  We see a little bit of a spike, which is normal and expected.  I suggest you also measure the drain-source voltage on the other MOSFETs, with the following questions in mind: is the signal I'm measuring within the bandwidth of my equipment and am I seeing nasty spikes / oscillation?

We'll have to think up a method for measuring current flow - perhaps you could cut a track and solder in a low value shunt between the synchronous rectifier FET and the 0V point (without messing up the gate drive loop!)?

With rise and fall times around 10ns, you could go down to 100ns minimum pulse width (maybe even 50%), which may allow you to increase the frequency and reduce the size of passives in the supply.  Depends on switching losses.

(I once blew up a full set of 6 MOSFETs due to using a 50 MHz probe and not seeing a big 70 MHz oscillation.  They went with a bang and sprayed some chunks of epoxy around the place.)

The new CT you're thinking of is rated to 500V, but that means tested at 500V RMS for 1 second.  Insulation ages, so I would be a bit worried about that lasting for 10 - 20 years with 380V DC across the insulation.  You need to look at not just isolation voltage, but also operating voltage.
 

Offline prasimix

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I suggest you also measure the drain-source voltage on the other MOSFETs, with the following questions in mind: is the signal I'm measuring within the bandwidth of my equipment and am I seeing nasty spikes / oscillation?

The following screenshots were taken on lo-side MOSFET. Yes, I'm still on 70 MHz Rigol. I have an old analog 100 MHz Tek, but taking screenshots is not so simple (I need to call someone to take it while I'm probing signal on the PCB).







... and without load:



I didn't manage to destroy any MOSFET (that can be an explosive event) so far in normal operation. But I had two incident (in the same day thanks to lack of discipline mentioned in one of previous posts!) when I've touched, actually shorted two pins directly on the LM5041B instead of probing on neighborhood parts :phew:. End results was failure of multiple parts (LM5041B, Si8233, SiC MOSFETs), but fortunately without explosion.

Offline prasimix

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Tried yesterday 1:100 Murata 53100C on buck input with unsatisfactory results as I expected (at least in comparison with current solution). Output waveform looks like this:



... or "zoomed out":



Even if that is acceptable, it is not attractive solution for wide input voltage range. If I found current limit for 230 Vac range it will be too small for 115 Vac and vice-versa, proper threshold for 115 Vac will be way too high for 230 Vac.

I found yesterday Pulse Electronics P0582NL with 3 kVrms margin that is reportedly UL-C/UL recognized component, but it is too large for my current PCB. Therefore I have to rearrange/resize PCB layout. Other possibility is to reinforce current CT margin using opto-coupler circuit.



Offline prasimix

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I'll try to do something with existing CT by enforcing its isolation by introducing an opto-coupler and TL431. That could be still cheaper and smaller solution and provide even higher margin than any off-the-shelf CT alone. This is a first simulation that can be used as starting point for real testing:





« Last Edit: June 30, 2018, 03:35:39 pm by prasimix »
 
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Online jbb

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That seems like a lot of bits, and I think it’s the wrong approach.

Firstly, the LM5041 is a peak current mode controller (with slope compensation) and needs a high speed analog current measurement to work properly. Your circuit doesn’t provide that.

Secondly, that’s a lot of extra components. If one of them fails you loose all current control and things get very risky.

Have you considered putting a CT in series with the transformer primary? It should be voltage clamped by the secondary output voltage.

Alternatively, you could place a 0.1R (approx) current sense resistor in series with the return current from the push-pull FET source pins. This effectively measures the total inductor current for you. Losses would be quite small.

Also, the C3M280090D is in a big TO247 package which is good for cooling and bad for parasitic inductance. If you look at the C3M280090J, it’s in an SMT package with less leakage inductance and a Kelvin Source pin for improved gate drive. The switching losses are halved for the SMT version.
 

Offline prasimix

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That seems like a lot of bits, and I think it’s the wrong approach.

Firstly, the LM5041 is a peak current mode controller (with slope compensation) and needs a high speed analog current measurement to work properly. Your circuit doesn’t provide that.

Secondly, that’s a lot of extra components. If one of them fails you loose all current control and things get very risky.

It's wrong approach rightly in a order as you said: this circuit doesn't provide correct (pulsed) signal that can be used for slope compensation, and require much more components that is not so bad if its sum is cheaper then CT on secondary side with reinforced insulation.

Have you considered putting a CT in series with the transformer primary? It should be voltage clamped by the secondary output voltage.

Alternatively, you could place a 0.1R (approx) current sense resistor in series with the return current from the push-pull FET source pins. This effectively measures the total inductor current for you. Losses would be quite small.

Neither of that looks promising to me, especially adding anything in series with the source pins. Maybe with ordinary MOSFETs but not with SiC. Therefore I'll proceed with testing what is possible to do with adding CT at the buck input as started in post #20. I believe that better results can be achieved.

Also, the C3M280090D is in a big TO247 package which is good for cooling and bad for parasitic inductance. If you look at the C3M280090J, it’s in an SMT package with less leakage inductance and a Kelvin Source pin for improved gate drive. The switching losses are halved for the SMT version.

I'm aware of SMT package but also that it has much higher Rds, on (385 instead of 280 mOhms). If THT pins are inserted as much as possible (as I have now) I think that Llk is acceptable (anyway oscillograms looks fine). Also organizing cooling of THT is a way simpler then SMT. With min. heatsink it can provide half of output current without need to start fan. With bigger heatsink (e.g. if enclosed in chassis that is used for cooling) I belive that no fan will be required at all.

Offline Giaime

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About CT insulation requirements: why don't you use a CT without a primary coil and use a suitably insulated wire (or wire + silicon sleeve) to reach the required insulation rating?

I know CT w/o primary are bigger, usually for larger currents etc... but you still can find something small enough I think.
As an alternative that I tried in the past, very good in terms of speed and accuracy, are open loop Hall effect sensors (LEM, Tamura...). They came also w/o primary and I managed to get my required 4kVdc insulation rating by using a wire + silicon sleeve.
 

Offline prasimix

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About CT insulation requirements: why don't you use a CT without a primary coil and use a suitably insulated wire (or wire + silicon sleeve) to reach the required insulation rating?

I know CT w/o primary are bigger, usually for larger currents etc... but you still can find something small enough I think.

Yes, the main reason why I don't want to use such packaging is their dimensions. So far I didn't find anything that can fit within e.g. 10 x 10 mm. They can by default offer reinforced insulation that is important if CT is on the secondary side as @jbb warned me, but if I succeed to manage measurement on the primary side then functional insulation should be enough. Also I already find few single primary CT in small package the can withstand 1000 or 1500 Vrms, if Murata 53100C with its 500 Vrms is not suitable.

Offline prasimix

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Current measurment for LM5041B on primary side
« Reply #26 on: July 06, 2018, 08:17:48 am »
The problem with my first attempt to measure current on the primary side was that existing PCB wasn't designed to include CT and distance between Cbulk and hi-side MOSFET is very short. Without lots of thinking I was cut Vin trace before Cbulk instead of cutting that short trace between Cbulk and MOSFET! When I realized that I've managed in the second attempt to insert Murata 53100C (1:100) as shown below:



New schematic for current measurement is now looks like this:



Output from CT is measured directly on the CS pin of LM5041B, PCB looks now even more messy but still everything works just fine :)



Measurement for Vin=120 Vac (170 Vdc) and Iout=2,5 A:



... or Iout=5 A and compare it with previous measurement reported in #20:



Offline prasimix

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LM5041B soft-start
« Reply #27 on: July 06, 2018, 09:03:35 am »
Now with current measurement in place it's good to check how stressful is start-up. LM5041B as many other controllers has SS (soft-start) pin for limiting duty-cycle on power up. Soft-start sequence is also initiated every time when fault condition (e.g. Vcc under-voltage or Vin under-voltage) is no longer present. First I've tested it with SS capacitor with 10 nF that is apparently too low. Start-up current with 110 W load connected (Vout=44 V, Iout=2.5 A) looks like this:



Much better result can be achieved with considerably higher value (e.g. 100 nF):




 


Offline prasimix

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A clarification/correction is needed about SR controller that is presented in #6. Infineon IR1168 min. operating voltage is set to 8.1 V (typ.) by ULVO protection therefore +7 V rail shown in that schematic does not work. Actually, if you try to power up the circuit, sync MOSFETs (Q6, Q7) will be disabled, but rectification will be in place using MOSFET's body diodes giving an impression that everything is working fine! But it is not a case and that can be easily proven by checking MOSFETs dissipation and of course gate drive signal that does not exist.

In my first prototype I had about +9 V for driving IR1168 but in latest prototype QR flyback offers just  about +6.5 V (that is step-down with LDO to +5 V). Therefore in the final PCB I'll use IR11688, a similar model which working voltage goes down to 4.5 V.

Anyway, that IR1168/IR11688 is a great controller that withstand up to 200 V (Vds) without any extra circuits (like e.g. SRK2001). So far I didn't find anything even closer to it in the same price range. Also don't look for IR1163 as lower operating voltage IR1168 version announced for 2014. It seems that it is branded/labeled as mentioned IR11688.

Offline prasimix

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QR flyback based on VIPer35
« Reply #29 on: July 11, 2018, 08:43:13 am »
Finally I'll present aux/bias power supply section that is required to power on primary side LM5041B (and indirectly Si8233 A-side through LM5041B) and on secondary side NFB control/tracker, Sync. rectification (SR) controller and provide all required voltages for connecting post-regulator similar to one used in EEZ H24005 Power board.
Coming to the final solution was an expectedly long journey caused with lots of presumptions and lack of experience. On the first CF-DIC PCB prototype I tried to use PI's TNY266GN flyback controller with few off-the-shelf transformers that has enough secondaries (four in total, or 3 + 1 AUX if you like). I was especially eager to see how Feryster's 2399 transformer will behave but end result was unacceptable, I suspect because of its primary inductance that is too low.
Mentioned controller is well packed and integrated (e.g. does need external switch and protection circuitry) with reasonable price.
In the meantime I found few interesting Quasi-resonant (QR) flyback controllers also well integrated and for even better price. I've decide to give a try to the latest (5th generation) ICE5QR4770A controller. Once again I found that mentioned Feryster is not a solution, and I tried another off-the-shelf transformer this time from WE (750811914). This time I found another issue, ICE5 for unknown reason cannot start with been "kicking off" by applying shortly required bias supply. I tried to solve that with assistance of Infineon support but for unknown reason it didn't want to start, possibly because some of its protection mechanism is triggered.
Finally I found ST's VIPer family of QR controllers and decide to use VIPer35 in my latest prototype. In parallel I've arranged with people from Feryster to design a custom transformer in accordance with my specification.
That was a wining combination: nice flyback with broad input voltage range that works in QR mode with all needed output voltages. The latest schematic for that part of the CF-DIC is shown below. AC input section will be shared with CF-DIC power section.



Measurement on VIPer35 Drain pin without load (Vin=230 Vac):



... or with moderate load applied:



It's clearly visible that VIPer35's internal MOSFET is switching on at the lowest point. That can be adjusted for the used transformer by changing the value of Rlim (R19).
Usual way of providing precise enough and cheap control loop with TL431/TL432 is not used since all critical outputs are additionally regulated by BJT or LDOs. Therefore just zener diode (ZD3) is used to set a main secondary output voltage.
Perhaps "double" rectification of AUX secondary shared between powering VIPer35 (D8, ZD2) and LM5041B (D1, Q1, ZD1) is not needed and can be reduced to single circuit. I have to test that further.

Your suggestions and comments are welcomed as usual.

Offline prasimix

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Current-fed dual inductor converter source code
« Reply #30 on: July 22, 2018, 09:08:33 am »
I've decide to make CF-DIC as a separate/stand-alone module that is within size of Mean Well LRS-150-48 module previously used in EEZ H24005 project. All files are now available on the GitHub under CF-DIC project. I'm going to order new PCB soon after some additional checking is performed since new layout is quite different from previous one but I believe that it should work nicely.






« Last Edit: October 25, 2018, 09:05:58 am by prasimix »
 

Online jbb

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Would you like some review help with it?  I can see a couple of points that are quite close (and could still be fine, given the scale involved...)
 

Offline prasimix

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Of course, just go ahead! I can provide separate images of only top and bottom layer traces for better visibility if you cannot open Eagle file.

Offline prasimix

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AC mains insulation sheet
« Reply #33 on: July 28, 2018, 02:10:24 pm »
In case that converter is housed in metal chassis I'd like to insert insulation sheet between bottom PCB layer components and metal plate.
I'd like to know what is a trade name for such insulation when ordering from suppliers. Here is how it looks like in Mean well module:


Offline prasimix

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I've added in latest revision an optional temperature alarm based on simple LM211 (IC10) comparator and NTC (see Sheet 3of3). It is intended to pull-down PWRGOOD signal when temperature near one of sync mosfet become very high (currently set about 85 oC). NTC is SMT and it's located near Q8. Maybe that is not the best way how to accomplish temperature monitoring neither the best component: we can expect that some of SiC MOSFETs will be much hotter during the operation but my logic is that sync mosfet heating will increase proportionally.
Also instead of controlling PWRGOOD signal that require external agency for turn-off input voltage or remove connected load, another possibility is to block NFB optocoupler (OK2) or even LM5041B by inhibiting ULVO input while error state is reached. Former should be simpler while later asks for another optocoupler or moving a whole temperature monitoring circuit to primary side and power it from +12 V that is just fine for the LM211.

Offline prasimix

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Thermal protection with latch
« Reply #35 on: August 01, 2018, 11:30:28 am »
Thermal protection on the primary side of the converter could be something like this:



LM211 comparator is monitoring voltage on non-inverting input that comes from voltage divider with NTC (e.g. 10K/3570K). Reference voltage (that is stable enough) comes from LM5041B (REF pin) via R56/R59 divider. When temperature becomes critically high (and NTC value will decrease), LM211 will trigger Q5 that will pull to ground ULVO input until new power recycle. I've selected this method over comparator with hysteresis since it should be used only when something went terribly wrong.

Offline Giaime

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #36 on: August 01, 2018, 12:32:10 pm »
Are you sure you can guarantee the minimum holding current of the SCR, with such high value resistors?
 

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #37 on: August 01, 2018, 01:02:44 pm »
I've tested the circuit with a little bit larger SCR (MCR08) instead of specified "baby" NYC0102BLT1G (SOT-23 case), and triggering and holding is working fine repetitively.

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #38 on: August 01, 2018, 01:38:19 pm »
What I see as a possible issue here is unwanted triggering due to some glitch in AC line that is picked-up by LM211. I've tested it on the breadboard and can simulate such situation with powering on ancient Weller soldering station that is on the same power line. I believe that situation when everything is on the PCB will be better, or suggested comparator/SCR circuit has to be improved?

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #39 on: August 01, 2018, 02:45:42 pm »
Ok, it seems that quick remedy is to simply reverse a whole circuit and move up threshold level that will add extra immunity:



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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #40 on: August 02, 2018, 07:39:48 am »
Just to be sure, I would place some capacitors to ground on both LM211 inputs, to aid immunity. You don't need us triggering speeds for temperature protection. And maybe a cap in parallel to ZD5?


I've tested the circuit with a little bit larger SCR (MCR08) instead of specified "baby" NYC0102BLT1G (SOT-23 case), and triggering and holding is working fine repetitively.

Hopefully you never come across a "right by the limit outlier" component  ;D Usually for extremely low currents, an SCR made up of standard bipolar transistors works better, it has very low holding current.
 

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #41 on: August 02, 2018, 08:30:20 am »
And maybe a cap in parallel to ZD5?

Perhaps I can just move existing C42 to other side of R45, but I think that its current placement in combination with ZD5 that I must added to not exceed abs. max. ratings of ULVO (i.e. +7 V) for upper Vin give us a robust enough solution against glitches.

Offline Giaime

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #42 on: August 02, 2018, 01:04:02 pm »
That's ok as well. It's just that I don't like fast switches discharging capacitors with no current limitation. That as well can cause glitches. Putting C42 directly on IC pin limits its discharge current.

That's really nitpicking on my side, of course  :D
 

Offline Rerouter

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #43 on: September 10, 2018, 08:33:22 pm »
You mention on your website that the QR flyback is routed poorly, might I ask what parts in particular you feel need to be rerouted (its in the name :p), I figured out a nicer way of packing the LP2951, but I believe your referring to the viper35 side?
 

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #44 on: September 10, 2018, 10:07:33 pm »
Have you considered putting a CT in series with the transformer primary? It should be voltage clamped by the secondary output voltage.

Alternatively, you could place a 0.1R (approx) current sense resistor in series with the return current from the push-pull FET source pins. This effectively measures the total inductor current for you. Losses would be quite small.

Neither of that looks promising to me, especially adding anything in series with the source pins. Maybe with ordinary MOSFETs but not with SiC. Therefore I'll proceed with testing what is possible to do with adding CT at the buck input as started in post #20. I believe that better results can be achieved.

Most likely I am out of my league here, but IMHO shunt and isolation amplifier, like Si8920 could be solution... perhaps. It's Up to 5000 Vrms for 1 minute after all.  Just two cents obviously
 

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #45 on: September 11, 2018, 03:15:42 pm »
You mention on your website that the QR flyback is routed poorly, might I ask what parts in particular you feel need to be rerouted (its in the name :p), I figured out a nicer way of packing the LP2951, but I believe your referring to the viper35 side?

You mean on the GitHub not website? The latest PCB that was an attempt to clean up a jungle that grew up over the time (and shown on #10 and #26) and to separate pre-regulation from post-regulation stage since that gives at the end much more flexibility.
CF-DIC (for pre-regulation) works on that PCB almost suspiciously good :-/O, but during the reorganization of the whole PCB layout I made a fatal mistake by putting LM5041B beneath power inductors :palm:. The result is a sort of "over-synchronization" when RT input pin (used also for ext. sync) obviously is picking up noise when load is connected (or a sort of positive feedback loop is created) and working frequency jump into the sky (more then 20x higher then set frequency defined with RT resistor!). That alone make a whole PCB completely unusable.
Another issue is connected with QR feedback that is not so problematic to rectify: I tried to supply both VIPer and LM5041B from the same rectified AUX voltage, but it seems that VIPer don't like that. Therefore two separate diode + cap is required. But, it's also possible that such weirdness is connected to the first issue and that LM5041B starts to sink too much power trying to drive MOSFETs (PP stage in the first place) with insane frequency. I'm working on new PCB, not r3B8 that is on the GitHub but currently r4B4 :).

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #46 on: September 11, 2018, 03:22:06 pm »
Have you considered putting a CT in series with the transformer primary? It should be voltage clamped by the secondary output voltage.

Alternatively, you could place a 0.1R (approx) current sense resistor in series with the return current from the push-pull FET source pins. This effectively measures the total inductor current for you. Losses would be quite small.

Neither of that looks promising to me, especially adding anything in series with the source pins. Maybe with ordinary MOSFETs but not with SiC. Therefore I'll proceed with testing what is possible to do with adding CT at the buck input as started in post #20. I believe that better results can be achieved.

Most likely I am out of my league here, but IMHO shunt and isolation amplifier, like Si8920 could be solution... perhaps. It's Up to 5000 Vrms for 1 minute after all.  Just two cents obviously

Thanks for that, but I don't like to put anything in series with source pins. Solution with CT properly connected in series on the input side looks good, and cheap transformers with functional isolation exists (i.e. 500 V), and for one who wants better isolation it's possible to use with the same footprint with Hi-pot of 1 kV (possibly even 2 kV).

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #47 on: September 11, 2018, 03:50:24 pm »
... I figured out a nicer way of packing the LP2951

I forgot to mention that I'll probably move LDO's to the post-regulator board to have them closer to the load (i.e. control circuits).

Offline ogden

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #48 on: September 11, 2018, 06:13:38 pm »
shunt and isolation amplifier, like Si8920 could be solution

Thanks for that, but I don't like to put anything in series with source pins.

I said nothing about source pins, just mentioned shunt+Si8920. Put shunt where CT was originally planned, not on source pins :)
 

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #49 on: September 11, 2018, 08:12:10 pm »
Sorry, didn't got it at first.

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #50 on: September 14, 2018, 09:52:23 am »
I just finished new PCB layout and commited it at the GitHub. I'd going to send it to ALLPCB for manufacturing in the course of next week. If someone possibly have any comment on it please let me know.

Offline prasimix

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STM32F7 MCU board first prototype
« Reply #51 on: September 25, 2018, 04:46:43 pm »
While waiting for new PCB for CF-DIC I've managed to assembly the first prototype for new MCU board based on STM32F769IGT6 in LQFP176 package. This board is intended to be mounted perpendicular to the chassis front panel with exposed sockets and connectors for Ethernet, I/O port, Micro SD card, USB, encoder and user switch (LCD TFT connector will be hidden behind front panel).
Project files are available in the new repository on GitHub. Currently MCU board take care about the following peripherals and functionality:
  • Digital I/O: 2 x protected inputs, 2 x protected outputs
  • Rotary encoder with switch
  • 1 x user switch
  • 3 x SPI channels (2 x Chip selects per channel)
  • Battery backup (CR2032 button cell type)
  • USB 2.0 OTG
  • Micro SD card
  • Ethernet PHY (10/100 Mbit/s)
  • I2C EEPROM
  • JTAG IDC 20-pin connector
  • SDRAM (e.g. IS42S16400J)
  • TFT LCD with 0.5 mm FFC 40-pin connector (e.g. RFE43BH-AIW-DNS or RFE430Y-AIW-DNS)
  • TFT backlight brightness control
  • Resistive touch controller
  • Soft-start/stand-by AC power control
  • Audio amplifier with small on-board speaker
Selected MCU is capable of driving directly TFT LCD with SDRAM used as frame buffer (one or more). I also include 100 Mbit Ethernet and still have enough pins for up to 3 SPI channels and various other I/O. PCB is 4-layer and despite that I didn't manage to provide optimal connectivity between MCU and SDRAM chip, but it seems that everything works as shown on picture that follows (Nucleo board on picture is used just as debugger with SWD interface). I have to leave it overnight and make additional memory tests to check if existing layout is usable or a new revision is required.
The MCU board has 40-pin connector on the right side where 3 SPI channels are available to communicate with up to 3 peripheral module using additional "backplane" PCB that will be introduced in coming weeks.

So far we tested TFT LCD, SDRAM and USB (we acquired USB VID:PID for free thanks to pid.codes).

We found one issue that is I'd like to believe due to our inexperience with STM32: we cannot generate 25 MHz clock from PLLI2SR that is exposed on MCO2 output that is reported here. Without that Ethernet cannot be tested. If we failed to run it with 10 MHz as master clock, it is still possible to change master clock (HSE) to something else and use that HSE as input for the MCO2 MUX to get required 25 MHz.

I'll continue to report about progress of running up this prototype PCB (r1B1) and about migration of EEZ H24005 firmware to STM32 platform. Your comments and suggestions are welcomed as usual.




Offline Rerouter

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #52 on: September 26, 2018, 09:15:32 am »
I should point out your timing margins for your gerbers where on the edge of the margin, but still a smidge inside them when calculated from the setup and hold times, it only violates the manufacturers requested trace matching,

I suspect it would only really kill your memory access reliability in very humid air when the velocity of the signals reduce a little.
 

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MCU board status and AUX PS r1B1 prototype
« Reply #53 on: October 05, 2018, 03:51:44 pm »
We continued to test MCU board and found few small issues on the PCB that is reported on the GitHub's issue tracker. Situation with using MCO2 output for generating 25 MHz clock from 10 MHz master clock input is still unclear, I didn't receive so far any answer is that possible or not. Therefore I've changed master clock xtal to 25 MHz and use HSE as input for MCO2 mux and Ethernet is now functional.

The new AUX PS board is also finished and ready for testing. It include soft-start/stand-by as previous version but for up to 3 power boards. NTC instead of power resistor is used for soft-start due to smaller profile (has to be below 30 mm vertically). I have to test if it can survive charging of up to 6 x 120 uF.
Instead of Vigortronix AC/DC dual output module (5/12W, max. 5W) a VIPer35 QR flyback is employed with off-the-shelf transformer (Feryster or WE). The PCB is intentionally much wider (210 mm) since it include power AC inlet and power switch to reduce required wiring even more. It also carry standby LED and PE 4 mm banana binding post (not mounted on the picture below) that will be exposed on the enclosure's front panel.
Finally, a dedicated fan controller IC with I2C bus is used to assist MCU with driving fan with PWM and measure fan speed and ambient temperature.



Its schematics looks like this (linked from GitHub repository where BOM, Eagle and Gerbers files are also available):




« Last Edit: February 15, 2019, 07:17:02 am by prasimix »
 

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EEZ DIB DCP505 power module 0-50V/5A with 3-range current auto-ranging circuit
« Reply #54 on: December 31, 2018, 08:56:44 am »
Yesterday, I finalized PCB layout for the new Power module that is successor of the Power board used in the EEZ H24005 power supply. The working name of this module is EEZ DIB DCP505 and its design files is now available on the GitHub (the BOM section is still missing). Its PCB form factor (160 x 95 mm) is modified in line with new EEZ DIB chassis that I'll announce soon, and comes with few new features. The major and most interesting new feature is 3-range current auto-ranging circuit. It is proposed by my friend Macola after I struggling for some time with another approach that require presettable up/down counter and require more digital I/O lines for both set and read selected range.
This one require a little bit more parts but from other side it offer simple and elegant way how to set max. output current (I_SET) and read actual current (I_MON) both with information about active range (CURR_50MA, CURR_500MA, CURR_5A outputs).

The auto-ranger is designed to cover current from 0 to 5 A with automatic switching between measurement current sense resistors to achieve max. reading resolution that will be in our case 15-bit for each range, that is theoretically 0.152 mA for 5A, 15.2 uA for 500 mA and 1.52 uA for 50 mA range. That give us enough room to provide resolution of 1 mA, 100 uA and 10 uA respectively.The simulation files are attached.
Setting output current is simple: on the I_SET input one has to apply control voltage from 0-2.5 V. The control voltage range is divided in three equal parts i.e. 0-0.833 V, 0.833-1.666 V and 1.666-2.5 V. In our case with 16-bit DAC that give us possibility to define max. current for the selected range in 21845 steps (2^16 / 3) that is approx. 0.228 mA for 5 A (5 / 2^15), 2.28 uA for 500 mA and 2.28 uA for 50 mA range.
The schematic and LTspice simulation is shown below. Simulation tested the circuit with output current (Iload) that rise over the whole range (0-5 A) and with output current set with 1.5 V that put it somewhere in the middle range (500 mA) that can be seen on the latest graph (Ictrl) when error amplifier change its output state. As output current rise range indication outputs state are sequentially changed from 50 mA over 500 mA to 5 A.

The interesting detail is using of the D1 Schottky diode that is connected in parallel with range switching MOSFETs (M1, M2, M3). Thanks to that diode we have more freedom to choose MOSFETs with extra low Rds,on (i.e. below 5 mOhm) that is much cheaper and comes in much smaller package for Vds,max that shouldn't be larger then 1 V :). A prerequirement that everything works fine is that voltage over D1 never exceed ~200 mV when it starts conducting and influence measurement. That shouldn't be a problem since selected current sense resistors value gives max. 50 mV of voltage drop for the full range (e.g. 5A * 0.01R = 50 mV).

The current measurement op-amp (for ADC) in this circuit is U5, that together with U6 inverter should be precise, low-offset and wired with precise resistor to achieve high precision. I'm going to use OPA4197 for testing. A small offset (above zero) is intentionally introduced to U5 scale using R47 for calibration purposes, i.e. that DAC don't need to deliver negative output for 0 A value. Also the selected gain of U5 give us full-range value below 2.5 V, again that is intentionally done for the calibration purposes that DAC don't need to deliver "overflow" value above 2.5 V for calibrated output. 
Another important op-amp that should be precise is U3 that provide measure current value to U2 and U10 that are in charge to switch between ranges.

The simulation files are attached. Please note that parts used in the simulation differs to some degree with one that I'm going to use and test on the prototype PCB.



« Last Edit: December 31, 2018, 08:59:32 am by prasimix »
 

Offline prasimix

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Re: EEZ DIB DCP505 power module 0-50V/5A with 3-range current auto-ranging
« Reply #55 on: December 31, 2018, 10:09:59 am »
Other new feature on the Power module is "heavy-duty" OVP with triac and two fuses that should offer over-voltage protection in both direction: for the power supply and connected load. Theoretically it should manage and survive few hundreds of Amps, e.g. when 10000 uF charged to 50 V is connected on the output and discharging. How nasty such load could be is presented in the following spice simulation (zip file attached down below):



The max. current peak (440 A !) and its shape is defined with R2 and L1 and their value should be selected in accordance with what chosen triac could survive. The on-board OVP circuit looks like this:



Note that L1 inductance from the simulation is implemented directly on the PCB as spiral trace (see PCB bottom layer below). Its designed in accordance with the following calculation for number of turns and trace width:





The R2 from simulation that is R110 on the schematics is THT and could survive huge current peak (See AC01000001007JA100 datasheet).

OVP triggering threshold is set to 10% above programmed output voltage (U_SET). When triggered, triac will short power output lines and stay shorted until power is recycled or voltage above its A1/A2 pins drops down. If we presume that OVP is not triggered by Power module internal failure, we can reset it by simply set 0 V as new output voltage or by disabling OE (Output enable) circuit.

The new Power module also comes now with on-board SPI temperature sensor mounted beneath heatsink for main pass MOSFET and down-programmer MOSFET. It is thermally coupled with 5 mm thick thermal pad.
Module specific information such as calibration data or number of working hours, etc. can be now stored into on-board I2C EEPROM and makes them completely portable. Therefore, for example, it is not needed any more to recalibrate a module when it change its position inside the EEZ DIB chassis or when its moved into another chassis.   
Finally this Power module is intended to be powered with CF-DIC power pre-regulator and bias power supply that is mentioned at the beginning of this thread and its recent progress is covered here.
A whole Power module is packaged on the PCB shown on the following two pictures (thanks to the OSHpark PCB preview feature):





 
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Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #56 on: December 31, 2018, 02:19:13 pm »
This is reply to the question asked by one forum member which PM box is full, and I cannot reach him :)

The DCP505 is part of the new power supply that has to be completed in the coming months and I have to order first batch of board in coming days. It also require CF-DIC as pre-regulator and does not use Discovery but our new MCU board (STM32F7 based with larger 4.3 TFT) that is powered by new AUX PS board. The latest files can be found on the GitHub repository (currently backplane and new chassis design is missing). Feel free to subscribe on it to stay informed about progress. Please also note that when we finished with development and testing that is highly probable that a new group buy or crowdfunding will be organized.

EDIT: Nucleo board shown in post #51 is used only as debugger/firmware downloader, our MCU board is beneath TFT display. USB and/or SD card firmware downloader will be used in the final release, instead.
« Last Edit: December 31, 2018, 02:25:00 pm by prasimix »
 
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Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #57 on: February 15, 2019, 07:53:17 am »
A small update of what's going on here. The power module (DCP505) PCB has been arrived and I found instantly a stupid error on it: the power inputs on one of quad op-amp was swapped :(. Fortunately that wasn't a big deal to fix and I was focused on testing two new features: on-board OVP and three range current auto-ranging circuit.

The OVP behave more or less as expected, but main reason why I am going to replace it is lack of proper latching. When I've designing its PCB I still didn't know that Maxim has some interesting comparators equipped with latch functionality and which does not in the same time cost a fortune. Therefore I'd like to try their MAX9141 in the next PCB revision.

The auto-ranging circuit is first tested in CV mode, and it works as expected. Possibly the switching between ranges could be further improved by decreasing Rgate value for switching MOSFETs.
Unfortunately it doesn't works correctly when change in current range is happen in CC mode when current value is somewhere in-between two ranges. It is especially obvious on lower two ranges (50 mA and 500 mA). The problem lies in part of the circuit that is in charge for setting control voltage range (U11, U12, U13, U7 in schematic posted in #54) and which directly affect the CC control loop and switch back and forth I_SET value when output current is just in-between two ranges resulting in output current oscillations. That section was added to increase precision of I_SET (i.e. that output current can be set in 21845 steps for each range). Currently I don't have any idea how to make auto-ranging circuit stable in CC mode then to remove that section and use ~76.3 uA (5 / 2^16) as the smallest step in all ranges. That means that resolution of defining current in middle range (0-500 mA) will be 10 times worse, and 100 times worse in the low range (0-50 mA) then in high range (0-5 A). Perhaps that is still acceptable since auto-ranging circuit is primarily of interest to improve precision of measured current value.
The new auto-ranging circuit should now looks like this (available also in attachment):


« Last Edit: February 15, 2019, 07:57:26 am by prasimix »
 

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Bench box 3, a new three module/channel enclosure proposal
« Reply #58 on: February 15, 2019, 10:55:04 am »
Since I have now all PCBs/modules defined for completing a new power supply, I can present a new chassis/enclosure that I'm discussing with enclosure manufacturer (again Varisom from Portugal) which can house up to three modules (i.e. channels). While designing it I was struggling with lots of dilemmas mainly generated by effort to make it as compact as possible that it doesn't occupy to much space it it is going to be placed on the benchtop. I spent some time trying to organize everything inside it that it can be placed in two ways: horizontally and vertically when all content on the TFT display have to be rotated for 90 (or 270) degrees. I gave up for the moment of that concept because it will require introducing of new (soft?) material for making “feet” all around, on all four sides not just one, and that will additionally prolonged firmware development.
The new enclosure should house the following items:
  • MCU board
  • AUX PS board (for powering MCU board, 12 V DC fans, and “non-isolated” devices on the peripheral modules that are DCP505 power module for now)
  • DCP505 power module (up to three)
  • BP3C backplane for connecting MCU board with peripheral modules
  • Up to three power pre-regulators (presented here) for powering DCP505
  • 4.3 TFT touch-screen display and
  • Two 12 V DC fans
To get an idea how parts mentioned above are related to each other, I'll post first pictures of the working prototype that is currently used for firmware development:





The MCU board is placed horizontally just as backplane connected using the 40-pin (2x20) 0.1” connector. Such separation lowering the cost of PCBs production since backplane can be now 2-layers, while 4-layers can be used for more demanding MCU board. I've gave up from idea that backplane has to be mounted on the enclosure's rear panel, and decide to mount it on the bottom plate where modules have to be inserted as in a same manner as in PC (i.e. that require that top/cover plate has to be removed before module is inserted/removed).
The backplane allows connection of control lines between MCU and peripheral module using the 26-pin (2x13) 0.1” connector (black receptacles visible on the rear part of the backplane). I have also decide to keep possibility for coupling power outputs in series or parallel for modules on first two slots. Hence 20-pin (2x10) 0.1” connectors and place for two power relays on the backplane (currently jumpers are used instead of them). That will allow MCU controlled coupling for up to 100 V (in series) or up to 10 A (in parallel) that will be available on the output terminals on the module inserted into first slot. OE (Output Enable) LED is now bi-color for indicating that output is active and not coupled (Green) or active and coupled (Red). That 20-pin connector on the third slot is “dummy” used just to short post-regulator power outputs with output terminals on the PCB front side (4 mm, 19.05 mm spaced red/black connectors).

The power module (DCP505) has exposed all LEDs and connectors on its PCB front edge where front panel metal plate will be mounted with two M3 bolts to the PCBs and another two to the enclosure front panel. The cooling of power (pass) MOSFET and down-programmer MOSFET is achieved with mounting heatsink directly on the PCB fixed with three M3 bolts. Heatsink on the picture is “off-the-shelf” SK 624 50 AL. I expect that will be enough for up to 2 A of output current (~ 5W of dissipation) without need to turn on fans at all. An “issue” with this heatsink is that one has to make five M3 threaded holes that is more challenging than expected since fins are very dense (I was ruined one heatsink because drill tip broke while drilling and remain blocked in the hole). Therefore I have to check with Varisom if they can offer similar solution as one used for EEZ H24005 power modules).

The AUX PS module as shown on pictures are not on the right position. It will be mounted (vertically) on left from TFT display (and MCU board). Hence the 16-pin cable can be much shorter. Its PCB width is as wide as enclosure inside depth (230 mm) and that will reduce needed wiring since power (AC mains) switch, standby LED and PE 4 mm connector are exposed on the enclosure's front panel and IEC inlet (with two 20x5 fuses) on the rear panel.

Now we can see that the final width for three modules/channels enclosure is defined, starting from the left, with thickness of the AUX PS module, TFT display/MCU board width and 3 x 35 mm peripheral modules. That give us 290 mm in total. The height of the enclosure will be 119 mm (that is within 3U height). Enclosure can be carry around using 3248.1001 handle mounted on the top.

The first proposal for enclosure's front and rear panels looks like this:





The following items mounted on the MCU board will be exposed on the enclosure's front panel (its working name is Bench Box 3):
  • RJ-45 for 10/100 Ethernet (this is not optimal, a rear panel is perhaps better place for it but that would require additional wiring)
  • 2x digital inputs i 2x outputs (protected) used for external triggering and syncing
  • Micro SD card 
  • Mini USB OTG
  • Encoder with Ø31x16mm knob
  • User SW (programmable for various purposes)

I'll continue commiting changes about all parts of the project on GitHub repo here and your comments and ideas are welcomed as usual.
« Last Edit: February 15, 2019, 10:58:47 am by prasimix »
 

Offline alex-sh

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #59 on: February 15, 2019, 11:07:43 am »
@prasimix Very nice layout! I like it.
What touch screen are you using please?
 

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #60 on: February 15, 2019, 12:05:41 pm »
The idea is that various (any?) display with 40-pin 0.5mm connector (RGB interface, 12 o'clock viewing angle) can be used. Currently I've tested Raystar Optronic's RFE43BH-AIW-DNS. Display on the picture is Riverdi's RVT4.3ATFWR00 but unfortunately that is a 6 o'clock viewing angle display and cannot be used in final product.
I got good recommendation for EastRising displays available on buydisplay.com and eBay. The price is fantastic, and sufficient reason to test some of them like ER-TFT043-8 or ER-TFT043-3.

It is important to mention that most manufacturers offers the same TFT displays with both resistive and capacitive touchscreen. Currently we are using resistive that is only supported by selected TSC2007 controller.

Offline alex-sh

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #61 on: February 15, 2019, 12:43:40 pm »
The idea is that various (any?) display with 40-pin 0.5mm connector (RGB interface, 12 o'clock viewing angle) can be used. Currently I've tested Raystar Optronic's RFE43BH-AIW-DNS. Display on the picture is Riverdi's RVT4.3ATFWR00 but unfortunately that is a 6 o'clock viewing angle display and cannot be used in final product.
I got good recommendation for EastRising displays available on buydisplay.com and eBay. The price is fantastic, and sufficient reason to test some of them like ER-TFT043-8 or ER-TFT043-3.

It is important to mention that most manufacturers offers the same TFT displays with both resistive and capacitive touchscreen. Currently we are using resistive that is only supported by selected TSC2007 controller.

Raystar or Riverdi are not cheap. At this price level, Nextion (Serial interface) maybe a good alternative.
The other displays you mentioned (EastRising?) are really well priced. At < $10 for 4.3" display is no brainer.

 

Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #62 on: February 15, 2019, 01:16:33 pm »
At this price level, Nextion (Serial interface) maybe a good alternative.

Right, if its interface/controller works flawlessly, but still that approach make a whole thing less open source :).

Offline alex-sh

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #63 on: February 15, 2019, 01:23:59 pm »
Yes, Nextion does work flawlessly and extremely fast (has got its own processor)
 

Offline bloguetronica

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #64 on: February 17, 2019, 07:29:17 pm »
That is very nice! Thanks for sharing!

Kind regards, Samuel Lourenço
 
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Offline LapTop006

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Re: Bench box 3, a new three module/channel enclosure proposal
« Reply #65 on: February 18, 2019, 10:03:27 am »
The first proposal for enclosure's front and rear panels looks like this:

Neat. My initial response is "can you make it a touch shorter and do a full rack width case", but then I thought again. On my home bench at the moment is a gap where a HP E3631 used to be until it died. I actually have an Agilent N6705A sitting under the bunch to be a replacement, but haven't put it in place, in part because it's so big.

Looking forward to when I can put money down, your UI is better than the N6705A.
 
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Offline prasimix

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Re: EEZ H25005, a possible successor of EEZ H24005 programmable power supply
« Reply #66 on: February 18, 2019, 03:52:19 pm »
Thanks, I believe that with new MCU and bigger display we'll make UI even better. We also learn something about usability of the existing PSU (i.e. EEZ H24005) that can be further improved.

Offline prasimix

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Multiple fixed outputs module
« Reply #67 on: March 08, 2019, 10:56:22 am »
A long time ago a request for multiple fixed outputs for digital design was posted on EEZ H24005 GitHub repo. I'm wondering how much outputs and what voltages/current such power supply module should provide? Does some of them should be variable to some extent? Does current auto-ranging for stand-by consumption measurement makes sense?
The newly proposed chassis could carry up to three modules. I believe that two fully featured (DCP505) modules is enough and that leave one place vacant for a multiple outputs module.

Thanks in advance for your valuable inputs.

Offline prasimix

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The 3D model for new chassis is more or less finished and a couple of screenshots is shown below (top cover is set as transparent). A 3D PDF file can be found in attachment (Adobe reader, as far as I know is still the only one who can display 3D drawings):




« Last Edit: March 20, 2019, 01:52:28 pm by prasimix »
 

Offline Aigor

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Cool! Fusion360?
 

Offline prasimix

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No, SolidWorks made by great guy Mario from Varisom, Portugal (based on my basic DXF drawing made in Eagle). Hopefully they'll make it right in the first try, there is so many details that we tried to check via Skype :).

Offline nimish

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A long time ago a request for multiple fixed outputs for digital design was posted on EEZ H24005 GitHub repo. I'm wondering how much outputs and what voltages/current such power supply module should provide? Does some of them should be variable to some extent? Does current auto-ranging for stand-by consumption measurement makes sense?
The newly proposed chassis could carry up to three modules. I believe that two fully featured (DCP505) modules is enough and that leave one place vacant for a multiple outputs module.

Thanks in advance for your valuable inputs.
Make it a usb 5v / 3.3v and or type c pd


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Offline prasimix

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Thanks, I know nothing about USB type C, just information that it can be used also for "high power" supply, and have to investigate that further.
For 3.3/5 V outputs what current could be appropriate: up to 2-3 A?

Offline LapTop006

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Thanks, I know nothing about USB type C, just information that it can be used also for "high power" supply, and have to investigate that further.
For 3.3/5 V outputs what current could be appropriate: up to 2-3 A?

Whilst I would absolutely love a type-c USB-PD output, they might be a bit of a pain for an early module.

USB-PD rules say up to 3A at anywhere from 5-20v (with 5, 9, 15 & 20 being the standard voltages that should be supported), and 5A at 20v only if connected to a cable that declares itself safe for 5A.
 

Offline prasimix

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I found that the USB 3 PD functionality can be provided using MCU from STM32F0 family for which ST offers USB-PD stack. I believe that could speed up a whole development of something that looks rather complex.

Offline krho

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I found that the USB 3 PD functionality can be provided using MCU from STM32F0 family for which ST offers USB-PD stack. I believe that could speed up a whole development of something that looks rather complex.
You probably mean G0, as this are the CPUs that have CC pins.. however they don't provide protection on those pins.. so you have to somehow get the voltage which can go up to 25V down to safe levels e.g somewhere between 3.3 and 5V.
 

Offline prasimix

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No, I did not. I'm referring on what ST specified. There is few possibilities with F0, but also more broader support for F0/F4 families. MCU is just a part of solution and seems that it replaces Type-Port Manager (TCPM) with hard-coded protocol. ST is mentioning that their solution is tested with ONsemi's FUSB307B Type-C Port Controller (TCPC). PD looks like a science for itself, but promise flexible bidirectional power distribution.

Offline krho

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Ah ok. Well they also provide the PD libraries for G0 and L5, but G0 is way cheaper as it's m0+
 

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Hi prasimix

I’m a bit behind on the thread and just caught up to the range switching CC issue. When I looked at the schematics with the three slope current setting I thought “that looks complicated, there might be ‘bumps’ moving between ranges for CC mode.”  Then I saw your post where you discussed the issue.

I think the simplest solution is what you’ve done already: just have one CC range and call it a day.

 But there may be a useful compromise between simplicity and performance. How does the following sound?
- CC split into 2 ranges (3 is too complicated)
- coarse range is 45mA - 5A
- fine range is 0 - 50mA
- the 45mA vs 50mA is for hysteresis and fewer surprises.
- when using fine range, just force the range switching circuit to 50mA range, because you already know what the current range should be.
- for improved accuracy, you could use the signal out of the switched current sense amplifier for feedback (but you may need different current control gains for stability)
 
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Offline prasimix

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Thanks for suggestion. Splitting CC in two ranges could include some guess work in operation, i.e. if load in sleep mode drawn few mA, and few hundreds of mA when wake up, then setting lower CC range will affect load operation. Anyway, I have to rethink auto-ranger design together with complete new proposed power module (DCP505).

Offline Rerouter

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It seems some other designs rely on overkill DACC resolution in combination with a log amplifier for the input current to make the current control work over the full range. I imagine mainly it would just make it harder to calibrate at the trade off only needing 1 range.
 

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So I had a go at implementing a similar circuit in LTSpice.  Hopefully some of the concepts will be helpful.

Basic concepts:
  • Have a 5A shunt resistor always in circuit.  As you pointed out a while ago, this makes it much easier to manage the range switching.  It's also used for Constant Current (CC) control.
  • Use a separate amplifier for 500mA and 50mA range.  No need to measure the 5A range again.  Also allows the use of a different gain which can improve Vos drift sensitivity.
  • Use simplest comparator chain to select gain.  Some hysteresis will be required, because switching the range FETs injects a bit of current into the system (due to gate charge).
  • Separate CC ranges from ADC range.  We don't want automatic switching of CC range, because switching glitches could disturb the main control loop and jam pulses into delicate loads.  But we do want the current sensing to autorange.
  • Provide 2 CC ranges with 'manual' switching.  This will avoid automatic switching bouncing around, because the main control system controls the CC range override and the CC DAC.

Note: I'd expect to use a quad analog mux chip of some description.

In terms of devices with widely varying current limits, there are 3 approaches we could take:
  • The user just selects the CC range before turning the supply on.  If the 50mA CC range was selected, then the supply could only go to 50mA.  If the 5A CC range was selected then current limit steps would be coarse.  Note that current sense would still autorange.
  • Basic CC range switching during operation.  This would probably cause some kind of bump in CC mode because the CC DAC and the ForceLow signal might not be perfectly synchronised.
  • Seamless CC range switching during operation.  Add a second CC DAC&EA so that there is a 5A range CC DAC + EA and a low range CC DAC + EA.  Preset the DAC (and allow it to settle) before flipping between ranges.
 

Offline electromotive

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I just stumbled across this today. I like the wide input, wide output. I'm working on familiarizing myself with github and getting myself up to speed. I think you're really onto something great here.
 

Offline alex-sh

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I found that the USB 3 PD functionality can be provided using MCU from STM32F0 family for which ST offers USB-PD stack. I believe that could speed up a whole development of something that looks rather complex.

I have one of these PD Buddy boards with USB-C PD (5-20V 3A max).
I think it is based on STM chip. Please check it out:
https://www.tindie.com/products/clarahobbs/pd-buddy-sink/

 

Offline alex-sh

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@prasimix

Where are you going to print out your front panel please?
I did use Schaeffer AG in the past, but they are expensive.

Thanks
Alex

 

Offline prasimix

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@prasimix

Where are you going to print out your front panel please?
I did use Schaeffer AG in the past, but they are expensive.

Thanks
Alex

Yes, Schaeffer is very nice but expensive, if I remember correctly only front panel would cost almost as twice as much as complete custom made enclosure (painted and with printed front and rear) for EEZ H24005 made by Varisom. I've ordered first prototypes from Varisom again (see #68) that is going to paint and print out front and rear panels, too. I'll post some picture when it arrives.

Offline prasimix

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I found that the USB 3 PD functionality can be provided using MCU from STM32F0 family for which ST offers USB-PD stack. I believe that could speed up a whole development of something that looks rather complex.

I have one of these PD Buddy boards with USB-C PD (5-20V 3A max).
I think it is based on STM chip. Please check it out:
https://www.tindie.com/products/clarahobbs/pd-buddy-sink/

I'll try to build a capable buck stage with CV and CC control, first. Next step could be addition of STM based PD control. The buck should accept 48 Vdc on input and I'm looking to give a try to LT3763 controller. It seems that it has all what is needed even some extra stuff such as PWM dimming that could be useful for powering/testing power LEDs and laser diodes.

Offline blakme

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I came across this project while searching for open source Bench power-supply. I am interested in contributing to this work. I have background in FPGA/Digital HW and software design. Thanks! Lakshmi Aiyer
 
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Offline prasimix

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Many thanks Lakshmi for your interest. Yes, FPGA is something that is definitely coming into picture (after I failed to make something with XMOS xCORE ;)). Since development team of ULX3S project (based on Lattice ECP5) is in Zagreb, Croatia and I met them in person, we'd like to use it as a core for some new modules. Perhaps you should take a look on it, and we can continue discussion via PM, email or discord.

Offline prasimix

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New backplane
« Reply #89 on: June 01, 2019, 09:16:37 am »
A small update regarding backplane. A new prototype now can host up to four power relays for combining output terminals on the first two slots (i.e. without external wiring) in the one of the following ways:



Power relays are now controlled with 4-port I2C I/O expander. The populated PCB (except LEDs for indication which coupling is active) looks like this:



Backplane pin mappings can be found in attached PDF.
 
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Offline alex-sh

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You are really making it modular.
How many main modules do you intend having and do you foresee any add-on (optional) modules please?
 

Offline prasimix

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The number of modules could be up to 7 with current addressing of the shared I2C (#0 is reserved for MCU board) that is intended to be used for module identification and module specific info (e.g. calibration params, working hours counters, etc.).
This backplane (BP3C) obliviously can carry up to three peripheral modules, and its dimensions are defined with Bench Box 3 enclosure presented in #68. For larger module counts you'll need a bigger enclosure, and on the backplane you have to decide which of SPI channels you'd like to share since currently each of three slot has dedicated SPI channel which is not really necessary at least when we talk about power board functionality.
So far, I've made two power modules: DCP505 (0-50V/0-5A max. 250 W) that works in combination with CF-DIC, and DCP405 (0-40V/0-5A max. 155 W limited by Mean Well AC/DC module). I'm now playing another module which should offer two simplified, more "crude" DC outputs i.e. without linear post-regulator stage based on LT3763 controller as announced recently.

Offline prasimix

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EEZ Bench Box 3 enclosure first prototype
« Reply #92 on: June 20, 2019, 01:27:52 pm »
Finally, after many months of waiting the first enclosure prototype arrived few days ago. Unfortunately with more issues that I expected, but all of them are really minor and related to the front panel. The biggest and obvious one is that hole for encoder's know is not positioned correctly :)







View inside the enclosure reveals that number of wires are minimum that will simplify assembly and servicing:



Area allocated to AC/DC modules are huge enough to host a toroidal transformer of respectable size:



Feet that I found in Turkey (Altinkaya) looks pretty convenient and give us possibility to position the enclosure with an angle that will improve viewing angle on the TFT touchscreen display:



I'd like to hear your opinion about carrying handle mounted on the top cover. Some of my friends ridiculed it on the first sight as something extremely ugly. I was put it there to avoid increasing enclosure width and because with it one can conveniently and safely carry BB3 around using only one hand (another question is how often that could be a case).

Finally, here is a short overview of the first prototype:



The project also got its web pages: https://www.envox.hr/eez/eez-bench-box-3/introduction.html
 
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Offline Sparky49

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Re: EEZ Bench Box 3 (BB3)
« Reply #93 on: June 20, 2019, 01:48:10 pm »
Your attention to detail is astounding as it is inspirational. Than you for your impeccably detailed posts, I've enjoyed reading the backlog over years across all your projects.
 
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Offline alex-sh

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Re: EEZ Bench Box 3 (BB3)
« Reply #94 on: June 20, 2019, 06:59:56 pm »
This looks very good and professional!
The handle - some people like it some people not. Personally I think it’s ok. Alternatively you can do a handle on the side, but this means the handle has to come off first before the cover????
 

Online jbb

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Re: EEZ Bench Box 3 (BB3)
« Reply #95 on: June 21, 2019, 07:32:04 pm »
It’s good to see this project coming along nicely! Things like enclosures always take a lot of work to get right.

I have some questions on the enclosure:
- what are the dimensions of the current prototype?
- which way does the air flow? Is the box normally at positive or negative pressure?
- with the carry handle in place, can you stack two units on top of each other?
 
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Offline nimish

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Re: EEZ Bench Box 3 (BB3)
« Reply #96 on: June 21, 2019, 08:18:44 pm »
Is this rack mountable?


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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #97 on: June 22, 2019, 06:07:05 am »
It’s good to see this project coming along nicely! Things like enclosures always take a lot of work to get right.

I have some questions on the enclosure:
- what are the dimensions of the current prototype?

290 (W) x 123 (H) x 240 (D) mm without feet mounted. Feet are 15 mm high.
Talking about width, that is more then a half of 19" rack. If we'd like to reach a full width, additional four modules could be added (seven in total).

- which way does the air flow? Is the box normally at positive or negative pressure?

That's the good question, the fan is currently mounted to provide positive pressure, but I presume it could be also negative. As far as I know each option has its pro's and con's. What would you like to suggest?

- with the carry handle in place, can you stack two units on top of each other?

Yes, stacking is possible:

« Last Edit: June 22, 2019, 06:09:59 am by prasimix »
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #98 on: June 22, 2019, 06:08:53 am »
Is this rack mountable?

It could be, but we should make some sort of mounting brackets (and few additional holes on the sides, too), and probably in that case feet have to be removed.

Offline nimish

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Re: EEZ Bench Box 3 (BB3)
« Reply #99 on: June 23, 2019, 05:00:43 pm »
Hmm for a "pro" version something that could reuse a 4u server case and pcie style expansions to save costs would be cool...

Looks good for a compact half-width thing


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Offline prasimix

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DCM220 module prototype
« Reply #100 on: June 26, 2019, 12:56:50 pm »
I've started to test a first prototype of "aux" power module based on LT3763 as announced in #86. I've managed to put two channels that could deliver 0-20 V up to 4 A each, and has output voltage and current control. It also comes with on-board MCU for few reasons:
  • It will help us to define DIB protocol between master MCU and peripheral module with its own MCU
  • The selected STM32F373 comes with multichannel 16-bit ADC for very attractive price that is below "standalone" 4-ch ADCs with the same resolution
  • It should be cost attractive alternative to DCP405 module, when more power outputs are required on the bench: up to six channels with BB3 chassis.
The module name is DCM220, built on a 2-layer PCB. All selected components, as usual, are with exposed pins that I can solder it without need for stencil and reflow oven. OK, such requirement narrows the list of possible components, and perhaps more attractive controller then LT3763 exists on the market. Anyway, so far I'm satisfied with preliminary results made by testing only first channel. The first PCB prototype (r1B1) asked for some improvements, and it now doesn't look so nice (see below) but it will do the job.



The schematics follows below and your comments are welcomed.

Bias power supply and DIB interface



DC power input is +48 V that comes from Mean Well AC/DC module (max. 155 W), the same one used to powering the DCP405 module. TPS54060DGQ (IC2) is used as step-down converter which power inductor is replaced with coupled inductor that provide both positive and negative voltage. The negative one is used solely for diff. op-amp used for set output current. Since it cannot provide (RRO) rail-to-rail output, it is not possible to goes down to zero without slightly negative power rail. Firstly, I was thinking about deploying LM7705 but it's unnecessary expensive (with all that needed capacitors around it). Buck positive output is step-down once again with LDO (IC5) to provide +3.3 V for MCU, DAC and digital isolators.
Although power channels on this modules are not isolated (i.e. share the same Vout-), I've decide to isolate it from the MCU GND, to provide more flexibility to combine its outputs with other modules. Therefore DIB interface used for communication with the MCU board has to be isolated. A low speed variant (1 Mbit/s instead of 150Mbit/s) of IC1 and IC3 is selected that I believe will be sufficient for responsive communication. Module parameters are stored into I2C EEPROM (IC4).

DAC, temp. sensors and MCU



I have (and still have) some doubts what is the most efficient way of controlling power buck controllers voltage and current: dedicated 4-ch DAC, MCU's built-in DAC and PWM output or combination of both (e.g. 2-ch external DAC, and 2-ch MCU DAC or PWM outputs). In the first prototype MAX5715 is used, a 4-ch, 12-bit I2C DAC with pretty good price. The good thing about selected DAC is that 8- and 10-bit variants are also available that give us possibility to scale it down reducing the cost further.
It is already mention what was the idea behind selecting STM32F373 as on-board MCU: its 16-bit (SAR) ADCs. ADC inputs are used to monitor output voltage and current on both channel. To keep cost low, I've marked xtal as an option, since MCU could use internal resonator, which is not so accurate as external xtal but should do the job. We have to test that in practice. MCU flash programming is intended to be accomplish over JTAG/SWD connector, but afterward I decide to add possibility to use UART. That will require control of BOOT0 input and UART lines are also added into the latest revision of BP3C backplane (r3B1).

Power channel #1



Design of the power channel is based on the typical application of the selected LT3763 which is high voltage sync buck controller that features current monitoring and control among many other things. It is powered from bias power supply to reduce its dissipation as in case that it is supplied directly from DC power input (+48 V). The +8 V that comes from bias supply is slightly above min. Vin that is +6 V. In fact, I didn't test that yet due to inconvenient tracing on the existing PCB but that is now included in the r1B2 revision.
As current control CTRL1 input is used that accept 0 to 1.5 V for current limit programming. Since DAC output goes up to 2.5 V its output is attenuated using the diff. op-amp IC9B that full DAC scale can be used. Max. output current is defined with Rsense (R27) that generate 50 mV drop for max. output current. With selected 12 mOhm that is about 4 A. Selected switching MOSFETs are IRFR7546TRPBF with low R(ds, on) and V(ds, max) of 60 V. The lo-side MOSFET could be assisted with diode (D4) that is marked as optional but I'm using SK55 on the prototype and have to test if it will stay or not. To further reduce output ripple and noise an additional LC filtering is added (L3, C52+C56) and I have to test how it affect transient response.
Voltage is programmed by bringing another DAC channel output to the FB voltage divider (R33, R39) via R41 that are calculated to give 0 to about 20 V on the output. Output voltage is monitored by bringing it to the MCU's ADC input using the separate voltage divider (R34, R40) that gives +2.5 V for max. output voltage.
The main obstacle with LT3763 is that no CC mode of operation indication is available. Therefore I tried to derived it from CV mode of operation when voltage on the FB input pin is constant and should be about 1.2 V. Op-amp IC11B works as comparator that compares ref. voltage that divider R43, R44 set to 1.119 V just a little bit bellow mentioned CV mode voltage. First I forgot to isolate FB from the op-amp but IC11C is added later that FB pin is not affected with connected comparator. No resistor is needed on the input of IC11C since selected MC33274ADR2G has not input diodes.
Comparator's output is used as CC indicator that goes to MCU and that can indirectly set on and off CC_LED. CV mode indication does not exist per se and OE (output enable) is used instead. To avoid simultaneous activation of CC and OE LEDs, Q4 disable OE_LED (green) when CC_LED is active. Ok, other possibility is to drive OE_LED as in case of CC_LED directly from MCU, a change that I'll probably add, since four pins remain unassigned on the MCU.
Finally, the power Vout- is exposed that can be coupled under firmware control with other module's grounds using only the half of DIB power sourcing connector (X4).

Power channel #2



Nothing more can be said about second power channel that is identical to the first one.
Module's latest design files are now available on the GitHub as part of the BB3 project, and PDF schematic of the presented r1B2 is also attached here for the download.
 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #101 on: July 12, 2019, 01:43:21 am »
Well the Crowd Supply news is out. I must say I'm looking forward to this as I did with the H24005.

I wonder what the priority of additional plug-in modules is? Higher voltages, Electronic Load.

Will there be a minimum configuration? Blanking panels?

Keep up the good work - and the outstanding documentation!
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #102 on: July 12, 2019, 07:45:07 am »
I'd like to supplement BB3 over the time in a way that it became a useful "benchtop station" for testing low power (up to 400-500 W) AC/DC and DC/DC converters. Therefore, a high voltage DC power source module with all protections is needed (For DC/DC converters, 40 V / 10 A or 80 V / 5 A should be sufficient for a time being).

Other one is power analyzer that could simultaneously measure DUT (i.e. DC/DC converter) input and output power and calculate all power related figures in real time. The electronic load looks like another important module for such purposes but, as time pass, I'm thinking more about 2-quadrant (bidirectional) power source that can return power back to AC mains. In that way "sinking" few hundreds of W shouldn't be an issue.
Another interesting function is a Bode plotter, entry level network analyzer, that should help to finding out in practice what is a stability of the DUT. That functionality perhaps could be included on the power analyzer module.

That type of applications probably will require introduction of FPGA, and I've started to follow ULX3S project, and hopefully with help of some other good-willing people we'll succeed.

Finally, we have to see what time will brings to us, and perhaps some other people will find this "form factor" and accompanied (I believe not non-sense) software/firmware suite attractive for their needs, that we can work together to brings new modules to general public.
 
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Offline timgiles

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Re: EEZ Bench Box 3 (BB3)
« Reply #103 on: July 12, 2019, 06:11:30 pm »
Great  job Prasimix. Ive been following along and not had much chance to comment but its really exciting to see the move from a single product to a modular platform :-)
 
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Re: EEZ Bench Box 3 (BB3)
« Reply #104 on: July 15, 2019, 08:14:30 pm »
Great to see you're gearing up for a release! I'm going to keep an eye out.

I have a question on the dual output module... just to clarify, will the two outputs share a common ground?
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #105 on: July 15, 2019, 08:24:50 pm »
Great to see you're gearing up for a release! I'm going to keep an eye out.

I have a question on the dual output module... just to clarify, will the two outputs share a common ground?

That's right, since they also share the same power input (48 Vdc). For more details you can check the latest version of the DCM220 module on the GitHub here (where is also PDF version or in #100). I believe that is not a great obstacle. And yes, it's floating in regards to other power modules, but if needed, its ground can be connected to other grounds under firmware control (e.g. that you don't have to do that with extra wires from the outside what I found myself to do so many times with H24005 :)).

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #106 on: July 15, 2019, 10:21:44 pm »
I wonder if having a module to control an environmental factor (like temperature) would be attractive to others as well to as me? For example, one module could be measuring performance of a DUT, while another is ramping temperature up and down.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #107 on: July 16, 2019, 05:09:34 am »
What kind of functionalities you have in mind? Perhaps we can combine more then one thing on the single module: e.g. if we are concern about temperature, we could have one or more temp sensor inputs with ADC, PID, also few digital inputs/outputs for triggering, control of heaters (AC or DC relays, triac/dimmer)?

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #108 on: July 16, 2019, 06:35:18 am »
What I had in mind was the ability to combine a series of environmental tests with a DUT's parametric tests.

Example:
   Whilst stepping up and down supply voltage on a DUT, measure supply current for say x hours, or y cycles
   Once x or y have completed, step say temperature over a range z
   Complete all cycles until you get back to the original values for x,y,z and see if the DUT performs the same

Another example could be monitoring the same data as above - but the environmental changes are the frequency and magnitude of physical vibration. The issue is one of tying the DUT's performance to the environmental condition and having a common timestamp supplied by your CPU and fed to the memory card.

I suppose it's a crude data acquisition system - but the basics will all be there. A common time stamp for stored data, parametric measurement and environmental control in cycles. It reduces the effort made for field testing of devices likely to be subjected to harsh environments.

I'm keen on your Bode plotter too.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #109 on: July 16, 2019, 06:59:10 am »
Good, described "testing automation" is already in place to the great extent if we are talking strictly about DC power source (PSU) functionality: we can continuously measuring all output params (voltage, current and power, energy counter will be also added), and have a great flexibility to program (change) output parameters via SCPI commands (e.g. you can also execute LIST of parameters, initiate data logging into internal SDcard and conveniently transfer it to the PC thanks to EEZ Studio). Currently, output params changes could be synchronized with external processes via two buffered digital inputs and two outputs.
But, we have all freedom to build a new module where we can "integrate" some of external devices functionalities (to clean up benchtop a little bit :)). Especially because we can include its management to the existing "SCPI engine" on the BB3 chasis side, that could simplify user interactions locally (via TFT touchscreen+encoder) or remotely (via PC).
I presume that making an general purpose multi-channel data acquisition module should make sense. Perhaps with few outputs (for signaling, but also for power control). The module front panel is big enough that reasonable number of I/O terminals can be exposed on it.

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #110 on: July 16, 2019, 07:04:32 am »
I can see your creative juices flowing. Thank you for enabling the input.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #111 on: July 16, 2019, 07:08:21 am »
Yes, and I do believe that existing H24005 and especially new BB3 project has a real potential to be used in testing automation processes saving time and money at least for various entry level tasks. Thanks for initiate such discussion and looking forward also for more inputs from you and other forum members.
 
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Offline mrpackethead

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Re: EEZ Bench Box 3 (BB3)
« Reply #112 on: July 16, 2019, 07:48:51 am »
Looking forward to this.
On a quest to find increasingly complicated ways to blink things
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #113 on: July 16, 2019, 08:00:58 am »
Yes, and first thing first. I have to make BB3 happen (initiated with crowdfunding): to organize everything that its production can started and can be delivered smoothly that more people could get it for development and evaluation purposes, too (apart from use its existing modules for daily power delivering requirements on our benchtops ;) ).

Offline Rerouter

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Re: EEZ Bench Box 3 (BB3)
« Reply #114 on: July 16, 2019, 08:24:40 am »
I'm definatly on the hope for an SMU type plugin, And I'm trying to consolidate how it could could be approached, even If it ended up being a 3rd slot module of my own design (As long as the price is not too insane, I should be a first hand backer this time around)
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #115 on: July 16, 2019, 08:58:27 am »
(As long as the price is not too insane, I should be a first hand backer this time around)

A good thing this time is that, thanks to real modular approach (something that also existed in H24005 project but not executed properly), the "entry-level" solution starts to makes sense, too. It will include BB3 chassis, AUX-PS (+5 V, 10 or 20 W, and +12 V/10W, softstart, fan speed control), MCU board (STM32F7, 4.3" TFT touchscreen, encoder, Ethernet, USB, etc.) and three slot backplane (with power coupling). Any you can start adding new modules, that are not necessarily just single quadrant DC sources.

But, the two-channel kit, comparable with H24005, should be in the same price range with H24005. I'm working on that, and hopefully that will become reality (even that BB3 is more capable).

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Re: EEZ Bench Box 3 (BB3)
« Reply #116 on: July 16, 2019, 08:30:04 pm »
I wonder if having a module to control an environmental factor (like temperature) would be attractive to others as well to as me?

I'm definatly on the hope for an SMU type plugin...

I think there are a lot of opportunities for modules - that was Prasimixes whole concept  :).

For example, I have been doing some battery evaluation stuff at work, and there is a massive gap in the market between the <$500 hobby battery charger (they're quite good but not precision) and the >$10,000 professional battery analysers.  Maybe a BB3 with an SMU card, a Peltier control card, and an external thermal chamber (which could be bolted to the side of the BB3 to make a 19" rack payload) would do the trick?

Possibilities (and idea source):
  • Precision power meters (Prasimix)
  • Temperature controller (AlanS). A cut-down version could also function as precision RTD thermometer or strain gauge receiver
  • SMU (Rerouter)
  • Multi-channel data acquisition card (HP, Keithley et al)
  • Precision battery cycler (me)
  • Bidirectional DC supplies (me) for loop-back power testing
  • Tiny thermal chamber inside a card (me) for component and small battery characterisation
  • Battery backup module (behind LCD) for reliability or in-field usage (me).  This would make power supplies and shipping very complicated.

There are heaps of things people could build...
 
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It is important to mention that most manufacturers offers the same TFT displays with both resistive and capacitive touchscreen. Currently we are using resistive that is only supported by selected TSC2007 controller.

Capacitive would be nice I would guess, resistive touch seems to stop working/malfunctioning after some time.
 

Offline mrpackethead

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Re: EEZ Bench Box 3 (BB3)
« Reply #118 on: July 17, 2019, 08:51:37 pm »
I'm guessing it would be possible to create custom modules if you so desired given its modular form factor.

Something i'd like to do, would be a POE PSE port, as i do a lot of Powered devices.  It would be handy to be able to measure/control the PSE end.

On a quest to find increasingly complicated ways to blink things
 

Offline LapTop006

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Re: EEZ Bench Box 3 (BB3)
« Reply #119 on: July 18, 2019, 02:06:39 am »
Something i'd like to do, would be a POE PSE port, as i do a lot of Powered devices.  It would be handy to be able to measure/control the PSE end.

Oh that's a cute idea, I love that. Ability to source 30-55v (to simulate cable drops), reporting of what class the device asks for.
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #120 on: July 18, 2019, 07:49:27 am »

For example, I have been doing some battery evaluation stuff at work, and there is a massive gap in the market between the <$500 hobby battery charger (they're quite good but not precision) and the >$10,000 professional battery analysers.  Maybe a BB3 with an SMU card, a Peltier control card, and an external thermal chamber (which could be bolted to the side of the BB3 to make a 19" rack payload) would do the trick?

Could you please elaborate this a little bit more. What thermal chamber and Peltier elements are used for? To test battery behavior under different temperature? I presume then that Peltier control card should include multiple thermocouple sensor inputs that will be used to set output for powering Peltiers?

Possibilities (and idea source):
  • Precision power meters (Prasimix)
  • Temperature controller (AlanS). A cut-down version could also function as precision RTD thermometer or strain gauge receiver
  • SMU (Rerouter)
  • Multi-channel data acquisition card (HP, Keithley et al)
  • Precision battery cycler (me)
  • Bidirectional DC supplies (me) for loop-back power testing
  • Tiny thermal chamber inside a card (me) for component and small battery characterisation
  • Battery backup module (behind LCD) for reliability or in-field usage (me).  This would make power supplies and shipping very complicated.

There are heaps of things people could build...

Yes, and all that is mentioned could be integrated and benefit from the "software suite" that is already in place: to manage modules locally (TFT touchscreen + encoder) or remotely (via SCPI commands to EEZ Studio or similar application).

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #121 on: July 18, 2019, 07:52:51 am »
I'm guessing it would be possible to create custom modules if you so desired given its modular form factor.

Something i'd like to do, would be a POE PSE port, as i do a lot of Powered devices.  It would be handy to be able to measure/control the PSE end.

Ok, but I don't known anything about PSE port. Do you have any useful links to some intro/beginners content?

Offline ogden

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Re: EEZ Bench Box 3 (BB3)
« Reply #122 on: July 18, 2019, 09:29:56 am »
I'm guessing it would be possible to create custom modules if you so desired given its modular form factor.

Something i'd like to do, would be a POE PSE port, as i do a lot of Powered devices.  It would be handy to be able to measure/control the PSE end.

Ok, but I don't known anything about PSE port. Do you have any useful links to some intro/beginners content?

I am not sure why PoE needs to be integrated into power supply because there are different kinds of power PoE sourcing (standards) and to cover them all, provide all features needed for testing of PoE devices, module needs to be quite complex thus expensive. Those who are ready pay significant money most likely will buy something from SiFos (or similar) anyway.

If you are going to implement PoE module, more or less it shall contain main components of this board:
http://www.ti.com/tool/tps2372-4evm-006

[edit] If it is about popular < 30W Type2 PoE, then this much simpler board a module: http://www.ti.com/tool/tida-00465
« Last Edit: July 18, 2019, 09:40:46 am by ogden »
 
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Re: EEZ Bench Box 3 (BB3)
« Reply #123 on: July 19, 2019, 01:24:26 am »
Could you please elaborate this a little bit more. What thermal chamber and Peltier elements are used for? To test battery behavior under different temperature? I presume then that Peltier control card should include multiple thermocouple sensor inputs that will be used to set output for powering Peltiers?

Yes, for precision work it’s common for people to test at different temperatures, eg 0C, 20C and 40C. This is because cell Open Circuit Voltage is a bit temperature sensitive and cell resistance is very sensitive to temperature and state of charge.

(I’ve also found that stable control of the cell voltage and current is important. A bit of voltage ripple can make quite a big difference to when exactly the cell is “fully charged,” which leads to a random spread of capacity measurements. To get around that you then need to average more test cycles and everything takes longer...)

For a small cell, a small thermal chamber could probably be done with Peltier elements. Both heating and cooling modes would be required, which suits a Peltier well. I guess that a ‘proper’ setup would have 2 basic sensors on the Peltier elements for protection and coarse control, and at least one more precise (eg RTD) sensor for the chamber temperature. Ideally I would tape 1 more sensor to the cell itself for a grand total of 4. (But what if I want to test several cells at a time :D?)

My idea of a tiny thermal chamber which bolts on the side of a BB3 is cute but probably impractical.
 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #124 on: July 19, 2019, 02:19:04 am »
I like this idea (jbb) of being able to control a peltier based chamber from within the BB3.

When not being used for important stuff we could use it to keep our wine in good condition (I'm joking). :-DD
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #125 on: July 19, 2019, 02:34:37 am »
Wine bottles are quite long... maybe a can of beer ;)?
 

Offline mrpackethead

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Re: EEZ Bench Box 3 (BB3)
« Reply #126 on: July 19, 2019, 07:22:52 am »
I'm guessing it would be possible to create custom modules if you so desired given its modular form factor.

Something i'd like to do, would be a POE PSE port, as i do a lot of Powered devices.  It would be handy to be able to measure/control the PSE end.

Ok, but I don't known anything about PSE port. Do you have any useful links to some intro/beginners content?

I am not sure why PoE needs to be integrated into power supply because there are different kinds of power PoE sourcing (standards) and to cover them all, provide all features needed for testing of PoE devices, module needs to be quite complex thus expensive. Those who are ready pay significant money most likely will buy something from SiFos (or similar) anyway.

If you are going to implement PoE module, more or less it shall contain main components of this board:
http://www.ti.com/tool/tps2372-4evm-006

[edit] If it is about popular < 30W Type2 PoE, then this much simpler board a module: http://www.ti.com/tool/tida-00465


you may not see the need for it, and i may not see the need for other types of modules to do various differnet jobs.   Thats not really the point.  The point is that if the interface to be able to plug your module into is stadnard, and its easy enough to add code to it, then it makes it increadibly flexible for people to create things to their own needs.   of course there will be things that will be common for a lot of people, but tehre will be lots of odd ball things that people would make for themself.
On a quest to find increasingly complicated ways to blink things
 
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Offline Rerouter

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Re: EEZ Bench Box 3 (BB3)
« Reply #127 on: July 19, 2019, 07:54:34 am »
Also there is a lot in 1 given power supply module that can be mostly reused  for other purposes. Even for my SMU thoughts, most of it will be just giving it a bidirectional output stage and current shunt. apart from the level of ideal output stability its just set current with voltage compliance limit or set voltage with current source limit. the smarts come from how you use that, the feedback chain is still analog, the sampling is technically independent,

As such I'm beginning by trying to make a more flexible ADC, then once that is covered, figure out how the output stage could get away with the current tracking approach to keep the output stage regulating with very low dissipation.

The keysight level SMU's seem to have a step response bandwidth close to 50KHz, so nothing too extreme,

Technically with a multi-slope ADC like I'm trying to help work out, you could have as many analog inputs as you can mux in, so having say 6 external ADC inputs would not be expensive to add to things, just slow down how many data points you can pull off a second for a given resolution.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #128 on: July 19, 2019, 05:11:30 pm »
Thats not really the point.

That was exactly my point - that this particular function (especially 1-channel), can live it's own life w/o being irreversibly married with power supply.

Quote
The point is that if the interface to be able to plug your module into is stadnard, and its easy enough to add code to it

Yes, good point. Nobody can forbid you to make module *you* want to make and use. Perhaps I missed something - are there any obstacles that are not allowing you to make PoE module or what?
 

Offline mrpackethead

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Re: EEZ Bench Box 3 (BB3)
« Reply #129 on: July 19, 2019, 09:36:07 pm »
That was exactly my point - that this particular function (especially 1-channel), can live it's own life w/o being irreversibly married with power supply.
Quote

90% of what you need to provide the functionality of a PSE, ( that has all the measurement / control that you want ) is already there.  'Marrying' it with the unit on your desk, is not a problem at all.



Quote
The point is that if the interface to be able to plug your module into is stadnard, and its easy enough to add code to it

Quote
Yes, good point. Nobody can forbid you to make module *you* want to make and use. Perhaps I missed something - are there any obstacles that are not allowing you to make PoE module or what?

I was'nt asking any one to make it for me. It was an example. I was enquiring as the open-ness of the interface that it will connect to. 
There will be no end of special use-cases that people want to build for themselves.




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Offline ogden

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Re: EEZ Bench Box 3 (BB3)
« Reply #130 on: July 20, 2019, 10:36:33 am »
90% of what you need to provide the functionality of a PSE, ( that has all the measurement / control that you want ) is already there.  'Marrying' it with the unit on your desk, is not a problem at all.

If all what's needed is functionality of PSE, then yes I agree. On the other hand many tests are better done using standalone adapter. Such as lightning surge immunity (if apply), Ethernet signal integrity, looking for transformer core saturation current - all will benefit from standalone PSE board/adapter. If adapter for testing is needed anyway, for me there is no point to have PoE-enabled supply. Disclaimer: I do not require for everybody to agree my point of view obviously [lol].
 

Offline prasimix

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DCM220 latest prototype
« Reply #131 on: August 17, 2019, 06:07:19 pm »
I've just finished the latest DCM220 dual power module. A brief info for newcomers: it is built around LT3763 sync buck that offers current programming and monitoring. Unfortunately it does not provide CC mode of operation indication. Therefore I derived it from FB signal. A 4-channel 12-bit DAC (MAX5715) is used for set output voltage and current (times two for two channels). Instead of using dedicated ADC for measuring output voltage and current a STM32F373 MCU is used which comes with attractive multichannel 16-bit ADC! Output terminals are for 4 mm banana plugs and bi-color LED indicator is used to indicate OE (Output Enable) and CC mode of operation. Output voltage is limited to 20 V (but can be much more since Vin is 48 Vdc) and output current to approx. 4 A. Power outputs are "floated" in regard to other module's GND, but two channels share the same GND on board.



Output ripple is pretty good, if we take into account that is SMPS, and e.g. for Iout = 2 A it's below 5 mVpp or 1 mVrms (measured on the output capacitor):



So, with three DCM220 one could count on up to 6 programmable power sources packed into EEZ BB3.

Two yellow wires are correction after so far unsuccessful attempt to use on-board bias supply (+7.5 V) to power LT3763 instead of full +48 Vdc used for powering this module. Idea was to reduce dissipation of its internal regulator, but it seems that in that case output voltage cannot goes beyond voltage that is applied on its Vin (i.e. 7.5 V), at least not without damage (I've lost two of them together with few MOSFETs).

Offline ogden

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Re: EEZ Bench Box 3 (BB3)
« Reply #132 on: August 17, 2019, 08:43:14 pm »
Very nice looking module. Congrats! You did not populate RC snubbers (R31+C52, R54+C75). Why? Do you have switching waveform with/without showing difference or lack of it?
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #133 on: August 17, 2019, 09:24:21 pm »
Actually didn't finished all testing. There is also place for diode in parallel for lo-side MOSFET assistance. I was pretty satisfied with existing results, and something that really bother me is that inability to power the LT3763 with lower voltage (e.g. something that I find possible on many TI/LM controllers).

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Re: EEZ Bench Box 3 (BB3)
« Reply #134 on: August 17, 2019, 10:17:01 pm »
Maybe a zener down from your 7.5V rail to the auxiliary Vin pin? (I think those are often around 5V for LT chips.)
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #135 on: August 17, 2019, 10:20:49 pm »
Actually didn't finished all testing.

Sure. Testing alone can take lot of effort and time. BTW would be nice to see load regulation step response, like 0.1A -> 2A -> 0.1A

Quote
There is also place for diode in parallel for lo-side MOSFET assistance. I was pretty satisfied with existing results

Hard to see at this time/div, but it seems that there is some ringing. If you have time and option to test with/without snubber - why not.

Quote
something that really bother me is that inability to power the LT3763 with lower voltage (e.g. something that I find possible on many TI/LM controllers).

LT3763 is LED driver controller - it may have limitations & design compromises compared to "proper" power supply IC's. I am afraid that block diagram is not telling whole picture and you can't do anything about this "problem".
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #136 on: August 18, 2019, 06:05:24 am »
Here is transient response with compensation as it is (check schematics on GitHub, Pg. 3).
A Jim William AN104 transient load tester is used, and step response is 1 A.



Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #137 on: August 18, 2019, 06:13:38 am »
Maybe a zener down from your 7.5V rail to the auxiliary Vin pin? (I think those are often around 5V for LT chips.)

Thanks, but I'm not really sure what you mean, and don't know if Vin is "auxiliary" to LT3763 or not. Please find below correction that I had to made that LT3763 behave properly again:


Offline ogden

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Re: EEZ Bench Box 3 (BB3)
« Reply #138 on: August 18, 2019, 06:41:54 am »
I see that you tied IVINP and IVINN (inputs of amplifier) directly to power rail. Could be reason why you lost IC while you powered it with low voltage, thus creating big difference between IVINP/N inputs and VIN. I know this is speculation - because block diagram does not show how particular amplifier is powered, nor say - it is "over the top input" type or not. [edit] Better idea would be to tie them to VIN pin, through resistor like 1K or so. [edit1] There could be similar problem with output current sense amplifier as well.
« Last Edit: August 18, 2019, 06:45:30 am by ogden »
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #139 on: August 18, 2019, 06:45:28 am »
Hm, that's a good point! Perhaps they should be also tied now to bias power just as Vin. I have to order a few more LT3763 for further testing.

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Re: EEZ Bench Box 3 (BB3)
« Reply #140 on: August 18, 2019, 06:49:43 am »
For testing purposes I would replace output current sense series R51 & R52 with bigger resistors, like mentioned 1k. It may cause sense error, but could protect amplifier and let you do some testing and tinkering.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #141 on: August 18, 2019, 07:14:16 am »
I'll definitely spend some time to explore this possibility. It would be a shame not to use lower Vin, if possible, when we have on disposal that +7.5 V.
 
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LT3763 Vin modeling
« Reply #142 on: August 19, 2019, 08:00:47 pm »
Hm, I don't know why I didn't try it before, but here it is. The LTspice model (in attachment) is clearly shows what I've found in practice (with great difference that nothing is damaged). The voltage applied on the Vin pin is set to 8 and 48 V, and with former output voltage cannot reach set value:



 
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Re: EEZ Bench Box 3 (BB3)
« Reply #143 on: August 21, 2019, 06:02:53 am »
I'll try the different approach here and that is Vout "tracking". LT3763 Vin,min is 6 V therefore we need offset of at least 6 V, i.e. for Vout, Vin has to be 6 V or higher. With tracking a considerable part of total dissipation is moved to external BJT that can be easier to cool. Number of extra parts are minimal and simulation results are promising. Now I have to check that in practice.



Simulation above give us around 250 mW of dissipation for Vout of 5.5 V. That is almost 4 times lower then in case that +48 V is applied to Vin pin.
 
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Offline prasimix

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DCM220 Vin hack
« Reply #144 on: August 24, 2019, 08:15:49 am »
I've tested previously mentioned proposal to decrease Vin voltage (and consequently LT3763 power dissipation) and it looks promising. If +48 Vdc is applied to Vin input with Vout=10.5 V and Iout=1.2 A the LT3763 easily goes over 100 oC in a matter of minute (I didn't try to push it to the thermal shutdown):



After that I've added simple regulator as in picture below:



The LT3763's power dissipation drops significantly measured over many minutes (and without forced cooling) and even with higher output current (2 A). On the picture is also visible that temperature of the MOSFET is higher, but in SOT-223 it will be much easier to cool it then LT3763.
In summary, I think that simple hack is a more cheaper then switching from 2- to 4-layer PCB to eventually provide better cooling of LT3763.



EDIT: check important notice in #152
« Last Edit: September 07, 2019, 03:16:46 pm by prasimix »
 
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Re: EEZ Bench Box 3 (BB3)
« Reply #145 on: August 24, 2019, 10:30:18 pm »
I'm following along here, and I thoroughly recommend getting some of that linear dissipation out of the driver chip.  But I have a couple of questions:
  • Is having IVINP and ININN greater than VIN OK?
  • What happens when the output voltage is at a maximum?  It looks like you'll still have considerable dissipation across the internal regulator.

It's a shame that you can't feed 5V straight into INTVCC, but the data sheet says "Do not force any voltage on this pin."

If the situation is bad with high output voltage, can you measure the DC supply current into Vin?  I wonder how much of it is gate drive current, which you might be able to get around using an external gate drive supply and BJT buffer pairs to isolate the gate drive power from the on-chip regulator. Or just use MOSFETs with smaller Qg...

 
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #146 on: August 25, 2019, 06:00:49 am »
Is having IVINP and ININN greater than VIN OK?

Yes, that question still remains, it seems that leaving them tied to +48 Vdc does affect regular operations, but there is still two more options: to connect them together with Vin pin or to leave them connected together but floating. I've asked that question on Analog forum and maybe someone reply.

What happens when the output voltage is at a maximum?  It looks like you'll still have considerable dissipation across the internal regulator.

Obviously that produce max. dissipation, but I'll test that and see if it is still acceptable or not (testing mentioned above was for the middle of the range).

If the situation is bad with high output voltage, can you measure the DC supply current into Vin?  I wonder how much of it is gate drive current, which you might be able to get around using an external gate drive supply and BJT buffer pairs to isolate the gate drive power from the on-chip regulator.

I believe I could and that will be something in line with simulation (i.e. about 20 mA).

Or just use MOSFETs with smaller Qg...

Yup, it still better to move dissipation to MOSFETs (with smaller Qg and consequently higher Rds,on) then to have it on the controller. I'll check what I have on the stock, or I can order something new. If you have any good candidate to suggest that is in DPAK package, let me know.

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Re: EEZ Bench Box 3 (BB3)
« Reply #147 on: August 25, 2019, 07:20:43 am »
Hm, IRFR7546 really doesn't seems light with its 58 nC (typ) of total gate charge. I'm definitely give chance to some others like NTD5867NLT4G, IPD400N06NG or FDD5612.

I've tried with max. Vout (i.e. 20 V) and for Iout of 2 A and little assistance of cooling fan (which is a part of the deal, together with onboard NTC for measuring temperature) the LT3763 temperature is around 60 oC, that is not bad at all:


Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #148 on: August 28, 2019, 02:14:00 pm »
This starts to looks better and better. I got today NTD5867NLT4G and replace initially selected IRFR7546TRPBF MOSFETs. Former is twice as much cheaper has Total Qg of only 15 nC (typ.), but also very low QRR (Reverse Recovery charge) of only 12 nC. The results is obvious, now without fan assistance, for Vout=20 V, and Iout=2 A I have the same results as previous with fan cooling:



... with fan cooling its go below 50 oC. Oh, and currently the ambient temperature is 30 oC!

« Last Edit: August 28, 2019, 02:15:34 pm by prasimix »
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #149 on: August 29, 2019, 12:39:43 am »
Now we’re cooking! (Or, rather, not cooking.) Looks like you got a temperature rise of of 32 K down to 18K, which is a big improvement.

Perhaps a quick test at minimum output voltage would be in order to check the temperature rise of your linear dropper MOSFET?

It looks like the MOSFETs run cooler too. It’s easy to get caught up in the on resistance / conduction losses and lose sight of the switching losses.

I would like to clarify one thing: given a maximum output of 20V (which will be totally fine for many applications), why are you using a 48V input rail? Is it for common parts? With a 24V input I think you can get lower Qg MOSFETs again and drive the control chip directly from 24V.
 
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Offline Rerouter

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Re: EEZ Bench Box 3 (BB3)
« Reply #150 on: August 29, 2019, 08:15:42 am »
48V is because the same slot has to support the higher voltage single channel modules.
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #151 on: August 29, 2019, 08:18:54 am »
48V is because the same slot has to support the higher voltage single channel modules.

Exactly, that will run cost down, and with unified DCbus, we can in the next step starts to think about AC/DC converter with multiple isolated outputs, and after that about bidirectional one when 2Q and 4Q power modules come into picture!
 
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Offline prasimix

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DCM220 hack (cont.)
« Reply #152 on: September 07, 2019, 03:14:25 pm »
A small update regarding the DCM220 Vin hack (see #144): I found that when LT3763 is disabled full DCbus voltage appears on that pin (that should be input)! Therefore the voltage difference between added regulator MOSFET source and gate is 36 V, that is not good. To fix that issue a diode in series with MOSFET source to LT3763's Vin is added.

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DCP405 power module
« Reply #153 on: September 07, 2019, 05:26:53 pm »
The latest version of DCP405, a single output power module, is more or less finished and ready for planned forthcoming crowdfunding. It includes a few modifications (thanks to my friend Macola) from the previous revisions that were used the same design as the power module from the EEZ H24005 project. First, how it looks like:



Here is the list of changes:
  • The main change is that N-channel MOSFET as pass element in the post-regulator section is replaced with 2 x PNP BJTs (D45H11).
  • Changing of pass element driver section also asked for different type of down-programming. Therefore that circuit is completely redesigned.
  • The CV/CC mode of operation detection is now much simpler.
  • The bias power supply that was use not so efficient combination of linear step-down regulator (TL783) and LTC3260 capacitive switcher is replaced with low power buck (TPS54060) that is using coupled inductor to generate positive and negative voltage.
  • The good thing about replacing MOSFET (that is in TO247 package) and TL783 is that now I can use "off-the-shelf" L-profile heatsink, that will greatly simplify assembling, and no custom heatsink is needed anymore.
  • More precise (and still very cost attractive!) MC33272ADR2G op-amps are used instead of TL072. The CV loop compensation network is also cleaned up and adjusted to work properly with new op-amps.

Schematics of the post-regulator is shown below (mentioned new bias supply and CV/CC detection is not shown), and complete design is available on the GitHub as usual.



LTspice simulation of the new post-regulator is also available on the GitHub, but it is also attached to this post. Please note that it assume that input voltage is fixed, not regulated by pre-regulator circuit.
 
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Offline prasimix

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DCP405 measurements
« Reply #154 on: September 07, 2019, 05:28:51 pm »
Oh yes, I forgot to mention that I've made some measurements for the DCP405 module that can be found on: https://www.envox.hr/eez/eez-bench-box-3/eez-bb3-measurements/dcp405-power-module.html
 
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Offline prasimix

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EEZ Bench Box 3 online firmware simulator
« Reply #155 on: October 16, 2019, 09:23:44 am »
The firmware is now pretty completed regarding the new GUI, and it can be test even without having physical device thanks to the Web simulator. It includes almost all functionality of the real device and gives even possibility to attach load, and mouse wheel can be used to simulate incremental encoder. I'm attaching a few pages below and your feedback about look and feel, usability, etc. is highly appreciated.







 
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Re: EEZ Bench Box 3 (BB3)
« Reply #156 on: October 17, 2019, 09:06:42 pm »
Wow, this is great! I used it a little bit, the confusing part that by default max current was set to zero. So, it was in CC mode, but voltage and current were 0. Sort of what it should, but in real world zero is not exactly zero, so there are some numbers jumping around.

I quickly used it, was a bit difficuilt in the beginning. There are many options. I'd prefer some dedicated knobs, but this design with several modules just doesn't support it. Nonetheless, I hope it would be possible to bind the rotary knob to quickly change voltage. Motivation: sometimes I characterize elements like diodes by slowly manually changing current/voltage and observe how it reacts. Sort of poor man's SMU. I understand that it supports programming, but I found a dedicated controls to be useful.

Anyway, great job!
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #157 on: October 17, 2019, 09:29:36 pm »
Yes, it's possible to "dedicate" encoder knob to any of output values (U, I or P). On the simulator you just need to position mouse on it, click, and use mouse middle wheel to increase/decrease current value. On the real device you just need to select output value with your finger thanks to touchscreen and engage knob. If you click "user sw" you can change knob step value (e.g. auto, 500 mV, 1 V, 2 V or 5 V when voltage is changing).

Offline mrpackethead

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Re: EEZ Bench Box 3 (BB3)
« Reply #158 on: October 22, 2019, 08:06:02 am »
cant' wait to buy one!
On a quest to find increasingly complicated ways to blink things
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #159 on: October 22, 2019, 08:11:59 am »
Don't know if you possibly have the previous H24005 unit, but if you have one I can say that BB3's bigger display, better rendering (fonts are now antialiased) and responsiveness makes a huge difference, probably similar to one experienced between H24005 and regular PSU with LED/LCD displays, keypad/knobs. You cannot feel that on the simulator.
 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #160 on: October 22, 2019, 10:01:04 pm »
Yep. I thought the previous simulator was great and then realised that using the real thing would mean I was better using a rubber topped pencil than my stubby fingers. STILL it was better then my other supplies.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #161 on: November 18, 2019, 08:38:34 am »
For those who are not aware that there is a topic for the upcoming crowdfunding campaign, here is the link:
https://www.eevblog.com/forum/crowd-funded-projects/eez-bench-box-3-sequel-to-eez-h24005/msg2786804/#msg2786804
The campaign should start this week and I want to thank you in advance for your support and I believe BB3 will live up to your expectations.

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Re: EEZ Bench Box 3 (BB3)
« Reply #162 on: November 22, 2019, 12:30:34 am »
The campaign is now up.

I hope that I’ll be able to work with the DIB spec to produce custom modules, and I am looking forward to (hypothetical) extra modules for things like 2Q supplies and precision power meters.

I have a couple of technical questions:
  • How are you doing on testing and assembly? I’ve found with my products that there can be quite a lot of design for testing work...

    Eg, the connectors that were fine for dev work may wear out surprisingly fast when you’re testing a production batch and cause intermittent test failures :-(

[li]If you get a good number of orders and the cost per unit comes down a bit, would you consider doing an IEC 60950 (or similar) safety evaluation in a test lab?[/li][/list]
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #163 on: November 22, 2019, 08:07:54 am »
I hope that I’ll be able to work with the DIB spec to produce custom modules, and I am looking forward to (hypothetical) extra modules for things like 2Q supplies and precision power meters.

Many people are asking for 2Q module, and I wonder what is the best way to gather information on what people need and create an initial specification that should be used as a design guide. Perhaps we could start a discussion here and then create a new public repo on GitHub and transfer useful information there to make it accessible in a more structured way.

I have a couple of technical questions:
  • How are you doing on testing and assembly? I’ve found with my products that there can be quite a lot of design for testing work... Eg, the connectors that were fine for dev work may wear out surprisingly fast when you’re testing a production batch and cause intermittent test failures :-(
  • If you get a good number of orders and the cost per unit comes down a bit, would you consider doing an IEC 60950 (or similar) safety evaluation in a test lab?

Basic PCB testing and module assembly will be done by a PCBA contractor, functional testing will be done on my side when firmware will be downloaded and the functionality of the entire system will be tested. The self-test itself gives a good picture of what's is good or wrong, this was the case with the H24005 testing so I'll do the same for BB3.
I'm not in a position to invest in any testing automation yet, but I believe this will change if the number of units increases over time.
Having in-house safety (and EMC) evaluation could be a great plus, but it's also out of my current budget. So far, I've secured funding for entering EU-accredited lab for EMC and safety CE compliance certification for the current BB3 configuration. I'll see when testing starts if I can arrange with them some pre-compliance testing for future modules/configurations with some discounts.

Offline Rerouter

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Re: EEZ Bench Box 3 (BB3)
« Reply #164 on: November 22, 2019, 09:48:04 am »
for the 2Q, If I recall correctly it kind of needed your fancier mains supply, as you where planning on dumping the excess power back to mains, I suppose it would not be hard to take the current thermal power budget to know how much you could dissipate using the existing modules.
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #165 on: November 22, 2019, 10:07:44 am »
...
Many people are asking for 2Q module, and I wonder what is the best way to gather information on what people need and create an initial specification that should be used as a design guide.
...

I'll bet a quality 2Q module turns out to be quite complicated... for example, working out the voltage and current loop priorities in a sensible fashion.

...
Having in-house safety (and EMC) evaluation could be a great plus, but it's also out of my current budget. So far, I've secured funding for entering EU-accredited lab for EMC and safety CE compliance certification for the current BB3 configuration. I'll see when testing starts if I can arrange with them some pre-compliance testing for future modules/configurations with some discounts.

Yeah, gear gets expensive real fast.  And EMC testing sometimes requires large and specific setups (Faraday cage room, anyone?).  You probably know this already, but it's good to get in for compliance testing quite early - issues get more expensive to fix as you get further through the design process.  This might apply double for safety testing...

for the 2Q, If I recall correctly it kind of needed your fancier mains supply, as you where planning on dumping the excess power back to mains, I suppose it would not be hard to take the current thermal power budget to know how much you could dissipate using the existing modules.

While it might seem attractive to dump power to the mains side, you could get an islanding problem, and may require quite elaborate anti-islanding systems.  I think you're right that a good start would be to rate the unit to suit available power dissipation.

I guess you could have an external power resistor which plugs in for expanded range.  Getting a bit complicated at that point...
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #166 on: November 22, 2019, 10:19:20 am »
It really depends. Lets start with presumption that 2Q should substitute electronic load. Electronic loads comes in all shapes and sizes depending of the use case. My idea is to start with "dissipative" 2Q module. If we want to dissipate e.g. 100 W or even more its obvious that such dissipation will be an overkill if everything has to be done inside BB3 chassis. If the main scenario is to test another power supply, DC-DC module or huge battery discharge then we cannot do that in that way.

But, if we'd like for start to address people how is willing to test their battery operated or low power devices (e.g. various IoT gadgets) that is operated with small battery and low voltage then it seems that 2Q with e.g. 20-25 W of sinking power could be more then enough, or not?

In the next step for bigger power e.g. up to 200 W we could provide connection for external power resistor, that has to be safely caged against the accidental touch, and dissipate excess power outside BB3 chassis. Not so elegant but could be cost effective.

After this stage all others should include bidirectional AC/DC power stage.

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #167 on: November 22, 2019, 10:22:59 am »
Hi jbb, it seems that we're replying in the same time. I'm agree, making a quality (and reliable) 2Q could be quite complicated. Another mission impossible for me, but with assistance from here and there I'm now quite confident that it is doable.

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Re: EEZ Bench Box 3 (BB3)
« Reply #168 on: November 22, 2019, 04:10:50 pm »
Why not make the power supply battery powered and use the big battery to absorb the power instead of dissipating it. Or use super capacitors to store the power. If you keep an almost empty battery in the supply under normal conditions and only charge it that way and if it is charged beyond a certain point power other channels with the stored energy. Then instead of dissipating the power you store it.
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #169 on: November 22, 2019, 04:36:08 pm »
Why not make the power supply battery powered and use the big battery to absorb the power instead of dissipating it. Or use super capacitors to store the power. If you keep an almost empty battery in the supply under normal conditions and only charge it that way and if it is charged beyond a certain point power other channels with the stored energy. Then instead of dissipating the power you store it.

Hm, sounds interesting, perhaps supercap could be more suitable for such job since it should offer more freedom for charging i.e. when sinking is active. In that case a possible option could be a connector for connecting external battery/supercap?

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Re: EEZ Bench Box 3 (BB3)
« Reply #170 on: November 23, 2019, 05:44:56 am »
Why not make the power supply battery powered and use the big battery to absorb the power instead of dissipating it. Or use super capacitors to store the power. ...

The downside of a battery or capacitor bank is that it has finite energy capacity.  It could be very annoying to have the load stop working in the middle of a test because the battery is full...

One thing to look out for: it can get really hard to ship lithium batteries (whether non rechargeable coin cells, LiIon, LiPo, LiFePO4...)
 
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Re: EEZ Bench Box 3 (BB3)
« Reply #171 on: November 25, 2019, 11:05:13 pm »
I've backed your CrowdSupply thing. I can't wait, as this supply looks excellent - your attention to details is highly commendable.

However: It's currently 62% funded.
Am I right in assuming if it doesn't hit 100% funding, no one gets their PSU kits?

I really hope this isn't the case.
Is there a plan B if it fails to get there?

All the best,
Dan
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #172 on: November 26, 2019, 07:27:40 am »
Yes, if it doesn't hit 100% no one gets BB3. The plan is to finally try to find a way to launch a campaign at leading crowdfunding sites such as Kickstarter and Indiegogo. It will take extra time to do this. In the case of Kickstarter, I also need an intermediary agency, since it is still not possible to start a campaign directly from Croatia.

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Re: EEZ Bench Box 3 (BB3)
« Reply #173 on: November 26, 2019, 09:03:47 am »
I do not have that much personal experience with crowdfunders, but I made some observations.
I also was put off by the sharp drop of progress, but since then it grew steadily, if slowly. The initial surge were the early birds, which must have gone fast. Surprising, seeing that the discount wasn't *that* high.
Generally most campaigns see a surge near the end as well, at least if the situation is not hopeless.

Maybe we can get Dave to cover the BB3 in a Video? Does he have a H24005?
 

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Re: EEZ Bench Box 3 (BB3)
« Reply #174 on: November 26, 2019, 09:29:50 am »
I do not have that much personal experience with crowdfunders, but I made some observations.
I also was put off by the sharp drop of progress, but since then it grew steadily, if slowly. The initial surge were the early birds, which must have gone fast. Surprising, seeing that the discount wasn't *that* high.
Generally most campaigns see a surge near the end as well, at least if the situation is not hopeless.

Yes, nothing is finished yet. We've entered the most challenging phase now to make it visible to "outsiders" and I don't have a marketing team nor agency specialized in crowdfunding campaign promotions :). I also didn't check how visible was Crowd Supply site two years ago (in time of H24005 funding) but I can imagine that its visibility is deteriorating (I was recently warned about that from owner of other campaign who has some "metrics" available).

Maybe we can get Dave to cover the BB3 in a Video? Does he have a H24005?

As far as I know, he doesn't. I failed to send him H24005 and that was happened again with BB3. This time I didn't manage to ensure funds for test run of modules that I can complete a few units and send them around. There was a promise from a guy who visited me this summer from Middle East willing to invest in EEZ project and get 10 units for university on which he is supposedly works but he simply disappeared, and I've lost time waiting for nothing.

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #175 on: November 26, 2019, 08:55:11 pm »
Don't stress about the guy going missing. There are mongrels everywhere - I hope he got nothing from you.  :box:

I'd suggest that you keep the updates happening (on the Crowd Funding page). Some of the stuff you have been talking about with jbb may be a good starting point - he drinks, so he can't be all bad. The updates will show that this is a product for the future and not a dead end.

What other modules are you looking at - other than power supplies? A self contained generator/meter for complete frequency responses - or other module combinations for designer/maker small production runs would keep interest going.

And then there are your early birds. It appears that as most of your clients want "one with the lot" and are prepared to pay for it. You have 80-odd potential product ambassadors who should promote the unit in order to ensure that they get theirs. Best of luck.

 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #176 on: November 26, 2019, 09:01:49 pm »
One more thought. How about a demo of a computer controlled test scenario/s where information is fed back to the operator for decision making?

I used a H24005 to test some Chinese vibration motors to destruction before I committed to buy more. I'm not aware of any other power supply family that can do the work of the products in the Envox family AT THEIR PRICE POINT.
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #177 on: November 27, 2019, 08:24:26 am »
Don't stress about the guy going missing. There are mongrels everywhere - I hope he got nothing from you.  :box:

I'd suggest that you keep the updates happening (on the Crowd Funding page). Some of the stuff you have been talking about with jbb may be a good starting point - he drinks, so he can't be all bad. The updates will show that this is a product for the future and not a dead end.

Project/product is all but dead! The first update should be ready in 2-3 days and it covers in more details data logging that can be start with one (two :)) clicks. Logged data can be displayed immediately during a logging and when logging is finished. It is also possible to transfer logged data now to PC with one click action! Taking screenshots, and SD card file manager will be also presented in the first update.

We're also preparing presentation of MicroPython scripting, which is, I believe, another unique feature of the device in its price category (if anyone at all has the ability to run Python scripts directly on the device, not its PC control application). As first scripts example I'd like to make a diode tester and simple transistor curve tracer. Therefore your suggestions about curve tracer "feature set" is welcome. I have a basic understanding what is needed to draw U-I plot, but still if someone knows where to find a sort of flow diagram that would be nice.

What other modules are you looking at - other than power supplies? A self contained generator/meter for complete frequency responses - or other module combinations for designer/maker small production runs would keep interest going.

If we put aside 2Q and 4Q power modules, then DC power analyzer is high on the priority list (mentioned also here). Simple multi-line/channel digital and analog I/O board could be added rather quickly as a good showcase for potential builders of the other modules. I'm also interesting in building a simple Bode plotter that will require signal generator and decent A/D stage.

And then there are your early birds. It appears that as most of your clients want "one with the lot" and are prepared to pay for it. You have 80-odd potential product ambassadors who should promote the unit in order to ensure that they get theirs. Best of luck.

That's right and I want to thank you for your support. I do believe that other backers also will find a time to spread a word about BB3.

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #178 on: November 27, 2019, 08:28:41 am »
One more thought. How about a demo of a computer controlled test scenario/s where information is fed back to the operator for decision making?

I used a H24005 to test some Chinese vibration motors to destruction before I committed to buy more. I'm not aware of any other power supply family that can do the work of the products in the Envox family AT THEIR PRICE POINT.

Huh, that is something that I need badly: a "use case" how EEZ PSU helps one in everyday work and what is not easily achievable with basic PSU. May I contact you via PM for more details? That could be a great story for the next newsletter!

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #179 on: November 28, 2019, 07:56:25 am »
Of course!
 
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Re: EEZ Bench Box 3 (BB3)
« Reply #180 on: November 28, 2019, 10:57:07 am »
I have had quite some time now to think around your project. I was not sure where to post this, but I think it fits a bit better here than in the announcement post.

The points I am going to outline all are related to the mechanical design. I am also aware that, for the running campaign, not much (if anything) can be changed. Also, I am referencing the open box picture on Crowdsupply.

  • 1. The wiring harness.
    Is the harness routed as it is in the picture, or is that pic more of a showcase of the harness? I would be afraid if the harness could be pinched between the divider and the lid when something heavy is placed on top of the BB3. I would prefer the harness to be routed through the divider. Also, a minor point, looking at the lowest module, it seems that the harness is a tad too short, flexing the board.
  • 2. The Aux Power Board.
    Actually my biggest critique of the design. By the looks of it, I would have to open the BB3 to unplug it. Would it not make much more sense to have a power jack on the back panel and run wires to the AUX board, instead of having that deeply recessed power jack? In the process I would also make the fuse accessible without opening the box
  • 3. The Ethernet port.
    I have read you explaining somewhere here that the ethernet port is where it is, mainly for routing issues. I get that, looking at the gerbers, moving the port to the other side may be a major issue. One suggestion that should be possible without major changes: Use a "top loading" RJ45 jack. Maybe even keep the LED indicators on the front panel. Then use a small patch cord with a clip-in coupling to route the network to the back of the unit.
  • 4. The backplane.
    Last point, and the biggest. I'm sure you have explained it somewhere: Why not an actual, well, backplane?
    That would of course be a major change. Something that would require a re-spin of almost everything. But the ability of changing modules without opening the box would be a major benefit in my opinion, especially once more modules become available. And I'm sure a backplane could be designed to allow enough airflow.
    But of course proper backplane connectors are expensive, and additional mechanical features like guide rails and stable mounting of the backplane would also increase cost.

Nothing of this will be stopping my pledge (which I may still upgrade). Some of these (the harness, Aux board and maybe the network) will be things that I will try to implement with the kit.
I just wanted to present my ideas. I'm sure you had good reasons to design the BB3 as you did.
Maybe some of that can be used for an eventual BB4 ;)


   
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #181 on: November 28, 2019, 11:43:57 am »
Thanks for your feedback and support!

I have had quite some time now to think around your project. I was not sure where to post this, but I think it fits a bit better here than in the announcement post.

The points I am going to outline all are related to the mechanical design. I am also aware that, for the running campaign, not much (if anything) can be changed. Also, I am referencing the open box picture on Crowdsupply.

1. The wiring harness.
Is the harness routed as it is in the picture, or is that pic more of a showcase of the harness? I would be afraid if the harness could be pinched between the divider and the lid when something heavy is placed on top of the BB3. I would prefer the harness to be routed through the divider. Also, a minor point, looking at the lowest module, it seems that the harness is a tad too short, flexing the board.

Wiring to the modules are little too short, final version will be longer. I probably didn't fully understand this, but I see no way that the cables inside could be compromised by placing anything on top of BB3. Mean Well modules are mounted on the top cover (from "below"), and cables according to the modules stand between Mean Well modules and the back panel. Care should be taken to ensure that the cables are inserted under the fan.

2. The Aux Power Board.
Actually my biggest critique of the design. By the looks of it, I would have to open the BB3 to unplug it. Would it not make much more sense to have a power jack on the back panel and run wires to the AUX board, instead of having that deeply recessed power jack? In the process I would also make the fuse accessible without opening the box

If your major concern is fuse replacement, then here we go:



3. The Ethernet port.
I have read you explaining somewhere here that the ethernet port is where it is, mainly for routing issues. I get that, looking at the gerbers, moving the port to the other side may be a major issue. One suggestion that should be possible without major changes: Use a "top loading" RJ45 jack. Maybe even keep the LED indicators on the front panel. Then use a small patch cord with a clip-in coupling to route the network to the back of the unit.

Okay, it looks like some people really have a problem with this heretical approach and some don't :)
It looks like this to me, and so far I have had no problem working with it:



Yes, one option would be to place the RJ-45 on the opposite side of the PCB (where the LDO is now), add an extra patch cable and open a hole in the back panel.

4. The backplane.
Last point, and the biggest. I'm sure you have explained it somewhere: Why not an actual, well, backplane?
That would of course be a major change. Something that would require a re-spin of almost everything. But the ability of changing modules without opening the box would be a major benefit in my opinion, especially once more modules become available. And I'm sure a backplane could be designed to allow enough airflow.
But of course proper backplane connectors are expensive, and additional mechanical features like guide rails and stable mounting of the backplane would also increase cost.

Nothing of this will be stopping my pledge (which I may still upgrade). Some of these (the harness, Aux board and maybe the network) will be things that I will try to implement with the kit.
I just wanted to present my ideas. I'm sure you had good reasons to design the BB3 as you did.
Maybe some of that can be used for an eventual BB4 ;) 

Yes, this could be done in another way, i.e. how classic multi module enclosure where each module must be the same size. This has the advantage you already mentioned: if someone has more than three modules and wants to exchange them, they will need to remove 4 more screws. The current principle is just like with a PC, but everything happens on the front and not the back side and the modules can be of different sizes.

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Re: EEZ Bench Box 3 (BB3)
« Reply #182 on: November 28, 2019, 12:17:53 pm »
Thanks for the reply :)

I have only looked at the pictures on the crowdsupply page.

1. It was not visible on the top-down open box shot that the Meanwell units are higher than the divider, and if I have understood you correctly, are somewhat used as structural element. That of course eliminates possible pinching. Also I would never have thought that the modules are mounted on the top cover. Interesting concept.

2. Similar here. The picture of the populated AUX-PS board shows the soldered power connector, looking as if the power cable would have to be routed to the inside. It seems you are already doing something similar to what I described  :-+

3. That looks workable. I was not aware that the feet create a gap that large.

4. I was not aware that you could swap modules while only having access to the front.  :-+  See point 1 why I though that this was not possible ;). I can see the flexibility advantage of having less limitations for the board size.
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #183 on: November 28, 2019, 12:27:02 pm »
4. I was not aware that you could swap modules while only having access to the front.  :-+  See point 1 why I though that this was not possible ;). I can see the flexibility advantage of having less limitations for the board size.

I think I need to clarify this: "everything is happening on the front and not the back side": this does not mean that the modules can be pulled out in the front, but that the PC concept is inverted: just as with a PC the cover should be removed for accessing PC cards (that are on the back side), is the same with BB3 to access modules (that are on the front side). Sorry for confusion.


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Re: EEZ Bench Box 3 (BB3)
« Reply #184 on: November 30, 2019, 11:27:26 pm »
When I first saw the BB3, I assumed that the backplane was in back and the modules could be pulled out and swapped without taking the case apart. It seemed like a reasonable assumption for modular lab equipment. Can you highlight reasons you chose to put the backplane on the bottom instead of against the back? Easier airflow for cooling?
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #185 on: December 01, 2019, 09:27:57 am »
Yes, easier airflow for cooling is one of the reason. With backplane on the rear you have to put cooling fan on top or below modules. That adds at least 2 extra centimeters in height.
There are two other reasons: the ability to insert modules of different lengths and the ability to extend the backplane with new connectors (for additional functions and higher speeds) while maintaining backward compatibility.

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Re: EEZ Bench Box 3 (BB3)
« Reply #186 on: December 01, 2019, 06:33:26 pm »
Also, if a card can be pulled out the front then people want hot (power-on) swapping, which can open several cans of worms.

The space for custom extra backplane is nice, too.
 
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Offline prasimix

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MicroPython on EEZ BB3
« Reply #187 on: December 08, 2019, 12:54:52 pm »
The MicroPython is coming on BB3, here is few screenshots, and more stuff is coming soon :)



Scripts folder:



Debug console (output):




 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #188 on: December 09, 2019, 02:12:53 am »
Does this mean that a "Test Automation" script, written on the computer, can be sent to the BB3 where the direction/options for the test itself can be controlled by an operator from the front panel of the BB3? Can the results be sent back auto-magically to the computer (Test Manager)?

For example:

A battery charging test script:
  * The script is started
  * The script asks the operator for battery type
  * The script sets up the BB3 with appropriate limits and safeguards
  * The script asks for the time length of test or test start/stop times (or other condition)
  * The script draws data from the BB3 for analysis
  * The script allows the operator to terminate the test from the front panel
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #189 on: December 09, 2019, 07:00:44 am »
Yes, that is one of the possible scenario. Currently auto-magical transfer of data has to be initiated by selecting the data file and click upload, but we'll add more magic to skip that step :-/O
 
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Offline Andrew McNamara

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Safe to use DCP405 for battery charging?
« Reply #190 on: December 14, 2019, 03:29:01 am »
Is the DCP405 safe to use for battery charging (specifically, if the mains fails)?
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #191 on: December 14, 2019, 04:09:49 pm »
Thanks for asking that, I'll include that in one of the next video where various protections will be presented. Battery can remain connected regardless of blackouts and no extra diode connected in series is required as in case of many other PSU.
 
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Offline prasimix

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MQTT on EEZ BB3
« Reply #192 on: December 15, 2019, 10:29:05 am »
I'd like to present you a screenshot of first MQTT implementation on the BB3. It shows monitoring of output voltage and current on first two channels.
The MQTT connectivity makes BB3 an IoT client that can coexists with "fellow" IoT devices that it could power.
This first example is accomplished by setting MQTT broker on CloudMQTT and MQTT Explorer is used to make connection.



Now, we have to add possibility to receive all messages that appears in event log (e.g. protections tripped, channel fault, fan fault, etc.). I believe that could be a great feature for new modules that comes like multi channel data logging and I/O. Your inputs, ideas, comments are welcome as usual!

Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #193 on: December 16, 2019, 10:58:56 pm »
Hi Denis,
I enjoyed seeing the update you posted to the CrowdSupply page today explaining the power output coupling / tracking; something you mentioned in the original listing and one of the main reasons I joined in, but nice to see the detailed video explanation  :-+

My questions:
1. I've backed the Early Bird 2x Channel + extra DCM220 module for 4x channels... however say I wanted more channels, maybe the same again:
What options, if any, are there for tracking between multiple units? I obviously don't want to combine voltages/currents in any combination between 2x BB3's, but is it possible to turn all outputs on and off of both BB3's from one unit? Can I safely combine multiple BB3's to have one single common GND? [Say set each unit to common GND mode, and link both units with a lead?]
Many of my projects have many voltage rails, so looking for a good solution. [e.g. typically use simultaneously up to: -24V, +24V, +3.3V, +5V, +2.5V, +6.0V, +7.5V +12V], often less.
Are there any other clever features that you can think of having multiple BB3's "talk" to each other, to provide a nice scaleable solution?

2. Could a BB3 be configured with 3x DCP405 (Full) or is it limited to 2x - any other caveats running 3x DCP405 modules?

3. How future proof is the BB3 chassis? I see you made the H24005, which I'm unfamiliar with, but how long is the BB3 likely to stick around, or will there likely be a new chassis in a year or two?

4. Do you have a timeline on any new modules // roadmap?


Keep up the excellent work! I really hope you make the 100% target; the level of detail you've put in to this is really excellent.
All the best,
Dan
« Last Edit: December 16, 2019, 11:06:37 pm by danielbriggs »
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #194 on: December 17, 2019, 10:24:41 am »
1. I've backed the Early Bird 2x Channel + extra DCM220 module for 4x channels... however say I wanted more channels, maybe the same again:
What options, if any, are there for tracking between multiple units? I obviously don't want to combine voltages/currents in any combination between 2x BB3's, but is it possible to turn all outputs on and off of both BB3's from one unit? Can I safely combine multiple BB3's to have one single common GND? [Say set each unit to common GND mode, and link both units with a lead?]
Many of my projects have many voltage rails, so looking for a good solution. [e.g. typically use simultaneously up to: -24V, +24V, +3.3V, +5V, +2.5V, +6.0V, +7.5V +12V], often less.
Are there any other clever features that you can think of having multiple BB3's "talk" to each other, to provide a nice scaleable solution?

Tracking between multiple units could be accomplished from "outside" i.e. using EEZ Studio with little help of JS or by using MQTT client (we are finishing MQTT support). Anyway, we'll be more then happy to assist anyone who come with such request, that means who bought more then one BB3 unit :)
Idea is also to add into future chassis without TFT console that could house e.g. 6-7 units that do not require AC/DC converters (i.e. data loggers, I/O, switch matrix, signal generator, etc.). In that case we have to think about some "inter-chassis" communication.

2. Could a BB3 be configured with 3x DCP405 (Full) or is it limited to 2x - any other caveats running 3x DCP405 modules?

Yes, the third module could be also DCP405. Only limitation is couplings. It cannot be combined in series, parallel or as "split rails".

3. How future proof is the BB3 chassis? I see you made the H24005, which I'm unfamiliar with, but how long is the BB3 likely to stick around, or will there likely be a new chassis in a year or two?

There is two major reason why I've decided to move from H24005 to BB3: 1) limited modularity and 2) we've reached Arduino Due limits. It's conceived to last for a while and can be upgraded with new functionality. Currently, I can only think of new chassis as one mentioned above ("expansion unit"). That possibly will introduce changes on rear panel, but "real panel upgrade" could be a part of the deal in that case. Idea is to try to establish production after crowdfunding campaign.

4. Do you have a timeline on any new modules // roadmap?

There is not strict timeline but I'd do my best to complete at least two new modules in 2020: 1) 2Q DC power module with two current ranges suitable for powering and monitoring consumption of battery powered devices, and 2) simple data-logger (that "simple" is not necessary too simple :).
Please note that we are nothing even closer to smallest T&M corporation you ever heard of, and everything lasts much more time. During 2020 I'll probably need to spend more time on promotion and marketing that could seriously affect speed of development. Things is currently as it is, I don't like to inflate an illusion about something that we are not or make empty promises, but try to deliver as much as possible, aware of our limitations (our means Martin's and mine).

Keep up the excellent work! I really hope you make the 100% target; the level of detail you've put in to this is really excellent.
All the best,
Dan

Thanks Dan for your support, maybe we can make it happen.
 
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Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #195 on: December 17, 2019, 02:44:14 pm »
Thanks Denis for the detailed reply; all sounds really promising.

What does the digital I/O on the front panel currently do?
Would it be easy enough to allow the units to trigger each others "outputs enable / disable" from the state of the digital IO?

If this is, then I'd almost certainly be up to backing a 2nd unit. [Not pressuring you, just would be personally useful to me if I can turn on 6-8 outputs at once].

All the best,
Dan
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #196 on: December 17, 2019, 02:47:38 pm »
Thanks for mentioning I/O ports on the front panel. There is a serial port exposed, and you can use it as trigger in/trigger out: in essence everything is already there for simple multi-chassis communication!

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Re: EEZ Bench Box 3 (BB3)
« Reply #197 on: December 17, 2019, 02:50:02 pm »
Excellent! Is any of this triggering currently implemented in the firmware?
If not, is there any chance it will be when the units are shipping?
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #198 on: December 17, 2019, 02:53:06 pm »
Yes, triggering is already supported, if we need more "magic" we'll add it  :-/O

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Re: EEZ Bench Box 3 (BB3)
« Reply #199 on: December 18, 2019, 11:37:45 pm »
Yes, triggering is already supported, if we need more "magic" we'll add it  :-/O

Perfect - just backed a 2nd unit  :-DMM
 
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Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #200 on: December 19, 2019, 11:24:18 pm »
I love the new MicroPython update you posted @ CrowdSupply.

The diode test example got me thinking: I test a lot of laser diodes in my line of work, and characterising their PI curve is often useful. However to measure laser power I have a specialised power meter [either thermopile or calibrated photodiode depending on type of laser under test].
These meters generally output 0-2V full scale.

Using your BB3 setup like this would be tremendously helpful... to accurately meter: voltage, current and optical power (via scaled analog input voltage from power meter). And get the script to only test to certain current limits or optical power limits etc.

Question: could your system be extended to easily incorporate an analog input? (Or does it already?)
This would open up many many useful doors :)
« Last Edit: December 19, 2019, 11:25:59 pm by danielbriggs »
 

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #201 on: December 20, 2019, 03:32:21 am »
I love the new MicroPython update you posted @ CrowdSupply.

The diode test example got me thinking: I test a lot of laser diodes in my line of work, and characterising their PI curve is often useful. However to measure laser power I have a specialised power meter [either thermopile or calibrated photodiode depending on type of laser under test].
These meters generally output 0-2V full scale.

Using your BB3 setup like this would be tremendously helpful... to accurately meter: voltage, current and optical power (via scaled analog input voltage from power meter). And get the script to only test to certain current limits or optical power limits etc.

Question: could your system be extended to easily incorporate an analog input? (Or does it already?)
This would open up many many useful doors :)

There are also the doors that it will open with additional modules. It seems that a mooted multiple channel data-logger may be just what you need. The whole ecosystem that Envox is building will help a lot of us get our products to production.
 

Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #202 on: December 20, 2019, 10:05:17 am »

There are also the doors that it will open with additional modules. It seems that a mooted multiple channel data-logger may be just what you need. The whole ecosystem that Envox is building will help a lot of us get our products to production.

That's the main reason I got involved :-+
 

Offline IanJ

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Re: EEZ Bench Box 3 (BB3)
« Reply #203 on: December 20, 2019, 11:31:15 am »
Hi all,

Did I read somewhere that 3rd parties will be able to design, build and sell modules. If so, will there be a schematic/layout template be available at some point.

Ian.
Ian Johnston
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #204 on: December 20, 2019, 11:43:42 am »
Hi Ian, that is correct. Everything is provided as open source, open hardware. Therefore everyone is invited not just to make new modules but to clone and sell everything what is done so far. New module has to follow DIB v1.0 specification, and if DIB v2.0 is ever happen it will be backward compatible with v1.0.
First step toward module "template" can be found here: https://github.com/eez-open/modular-psu/tree/master/DIB%20v1.0

We'll do our best to assist one in integration with firmware and the rest of the system.

« Last Edit: December 20, 2019, 11:45:14 am by prasimix »
 

Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #205 on: December 20, 2019, 12:04:34 pm »
Question: could your system be extended to easily incorporate an analog input? (Or does it already?)
This would open up many many useful doors :)

Actually one analog input already exists but is not wisely deployed: it can be used only to control output voltage (i.e. remote programming). I've selected 4-ch ADC at the very beginning and didn't know in that time where to use all inputs. Usage of two is obvious: monitoring output voltage and current (U_MON and I_MON), but remaining two are used for monitoring DAC outputs (U_SET and I_SET).
Even with current configuration by adding another 1-to-2 mux (like SN74LVC1G3157) it could be possible to use existing Rprog input not only for controlling output voltage but as general purpose analog input. In that case U_SET or I_SET monitoring has to be disabled.
 
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Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #206 on: December 20, 2019, 01:31:55 pm »
Actually one analog input already exists but is not wisely deployed: it can be used only to control output voltage (i.e. remote programming). I've selected 4-ch ADC at the very beginning and didn't know in that time where to use all inputs. Usage of two is obvious: monitoring output voltage and current (U_MON and I_MON), but remaining two are used for monitoring DAC outputs (U_SET and I_SET).
Even with current configuration by adding another 1-to-2 mux (like SN74LVC1G3157) it could be possible to use existing Rprog input not only for controlling output voltage but as general purpose analog input. In that case U_SET or I_SET monitoring has to be disabled.

Ah nice!
Maybe I'll wait for a "ADC / AIO module" once the 2x units arrive to extend idea this further.
Good to know it's on the road map though + keep up the good work.

I really hope you reach the funding target; I'll be most disappointed for everyone involved if not.
 
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Online jbb

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Re: EEZ Bench Box 3 (BB3)
« Reply #207 on: December 24, 2019, 12:33:40 am »
Test scripts on board does look like a win, and Python is quite easy to understand and edit. No messing about trying to compile the whole thing from C source code.

This begs the question; could we write device drivers for the modules in Python? (They would be a little slower, but that would be OK for many things.) And store the device driver code inside the module I2C EEPROM?

————

Some security thoughts for nerds:
- STM32F7 doesn’t have a Memory Management Unit (MMU) (may have a Memory Protection Unit(MPU) which isn’t as good) so a Python virtual machine is a great way of separating applications
- it’s highly likely that there will be ways for malicious code to break out of the expected behaviour of the Python sandbox
- storing code on a device that you buy off the internet isn’t great
- the Python code on the modules could be signed using asymmetric cryptography (eg ECDSA) so that the code can be verified before execution
- EEZ could hold a master private key, and issue certificates to developers that let developers sign their own code
- maybe unsigned code could run if the user clicks an “OK, run it this time” button or configures their unit into some ‘developer’ mode

 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #208 on: December 25, 2019, 08:15:24 am »
This begs the question; could we write device drivers for the modules in Python? (They would be a little slower, but that would be OK for many things.) And store the device driver code inside the module I2C EEPROM?

This is an interesting question or proposal. Simplicity of Python is great feature, but overall performance is questionable. It could be fine for module that does not need a fast communication with the master MCU module (that is in charge of driving TFT touchscreen display). Peripheral module in that case needs on-board MCU by default, what is also not a big deal, but we have to add support for inter-module communication that is based on Python (what is not currently the case). Anyway, this is an idea worth of considering.

Some security thoughts for nerds:
- STM32F7 doesn’t have a Memory Management Unit (MMU) (may have a Memory Protection Unit(MPU) which isn’t as good) so a Python virtual machine is a great way of separating applications
- it’s highly likely that there will be ways for malicious code to break out of the expected behaviour of the Python sandbox
- storing code on a device that you buy off the internet isn’t great
- the Python code on the modules could be signed using asymmetric cryptography (eg ECDSA) so that the code can be verified before execution
- EEZ could hold a master private key, and issue certificates to developers that let developers sign their own code
- maybe unsigned code could run if the user clicks an “OK, run it this time” button or configures their unit into some ‘developer’ mode

Ok, "nerds" are welcomed with their comments here, and I have to discuss this with Martin, too.

Offline mcdanlj

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Re: EEZ Bench Box 3 (BB3)
« Reply #209 on: December 25, 2019, 04:05:50 pm »
Some security thoughts for nerds:
- STM32F7 doesn’t have a Memory Management Unit (MMU) (may have a Memory Protection Unit(MPU) which isn’t as good) so a Python virtual machine is a great way of separating applications
- it’s highly likely that there will be ways for malicious code to break out of the expected behaviour of the Python sandbox
- storing code on a device that you buy off the internet isn’t great
- the Python code on the modules could be signed using asymmetric cryptography (eg ECDSA) so that the code can be verified before execution
- EEZ could hold a master private key, and issue certificates to developers that let developers sign their own code
- maybe unsigned code could run if the user clicks an “OK, run it this time” button or configures their unit into some ‘developer’ mode

Ok, "nerds" are welcomed with their comments here, and I have to discuss this with Martin, too.

Nerd here. Opinionated nerd with software security experience, including design and implementation of software provisioning secured by public key encryption.

I would really rather not have to jump through hoops to run my own code on my own BB3. The target user isn't naïve.

I'd like to point out that there are currently 129 backers, with less than two weeks remaining on the campaign. This does not make the BB3 a substantial attack target. There's a joke: When you are in a group being chased by a bear, you don't have to run faster than the bear, you just have to run faster than the slowest person in the group. Are people going to spend time attacking the BB3 when they could be trying to take over npm or pypi packages with tens or hundreds of millions or more of potential targets?

If you start signing other people's code, you are asserting something about it. Let's pretend you set this up and start signing code. What precisely does that signature represent? Does it mean you have audited the code for safety, and are confident that it won't break something? If someone is writing malicious code, are you more likely to catch it than someone with expertise in the domain in which the code applies? If you sign malicious code because you missed the malicious nature, and it causes harm, have you incurred liability by explicitly signing the malicious code?

Encryption is not magic pixie dust that makes code secure.

You have to start with what the actual threat is, and then design a system to protect against that threat. I don't see a threat that this proposal actually protects against. I understand the theoretical danger of running "untrusted code" on a power supply, but sprinkling encryption over that code is not an effective protection mechanism.

I did warn that I'm an opinionated nerd here. ☺
 
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Online robson2017

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Re: EEZ Bench Box 3 (BB3)
« Reply #210 on: December 25, 2019, 05:54:18 pm »
Hello Everyone,
I want to share with you my progress with BB3 project (see photos below)
I've been very keen to do this project from the start and I've been waiting for it to be finished impatiently.
So far I have built 3 modules (MCU, AUX-PS & BP3C )
The next step is to build the DCP405 module, and I am waiting for the DCM220 to be finished.
“Prasimix” has done a great job with this project and has been very helpful, keep it up!
Robert
[][/]
 
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #211 on: December 26, 2019, 07:22:18 am »
Great job!  :-+

Offline prasimix

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BB3 is OSHWA certified hardware
« Reply #212 on: December 26, 2019, 07:28:58 am »
EEZ BB3 is now OSHWA-certified as open hardware. Its UID is HR000002.





 
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Offline IanJ

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Re: EEZ Bench Box 3 (BB3)
« Reply #213 on: December 27, 2019, 12:18:17 pm »
Hi all,

Just backed this and really hoping it goes ahead.

I am interested in building/selling a module which replicates one of my PDVS2 products, I.e. 0-10vdc, 10uV step change, 20bit DAC, LM399AH ref. Etc.
I think it would be fun albeit loaded with challenges.

Ian.
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Offline prasimix

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Re: EEZ Bench Box 3 (BB3)
« Reply #214 on: December 27, 2019, 12:22:35 pm »
Hi Ian, that sounds fantastic! :-+
You can count on all our support of adding new module (e.g. firmware wise, etc.). Just for the record: it does not need to be open source as rest of the BB3.
 
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Online jbb

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Re: EEZ Bench Box 3 (BB3)
« Reply #215 on: December 28, 2019, 06:41:51 pm »
Nerd here. Opinionated nerd with software security experience...

I'd like to point out that there are currently 129 backers, with less than two weeks remaining on the campaign. This does not make the BB3 a substantial attack target...

That's a very relevant point, thank you. "Threat modelling says don't bother, the crackers will come for your neighbour's IOT stuff first."
 
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Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #216 on: December 30, 2019, 11:49:02 pm »
100% Funded. We're on!
 
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Online jbb

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Re: EEZ Bench Box 3 (BB3)
« Reply #217 on: December 31, 2019, 02:47:08 am »
Congratulations prasimix!
 
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Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #218 on: December 31, 2019, 09:34:58 am »
Yes! It’s happening! :-DMM
Great start to 2020

All the best for the rest of the journey to get them ready and shipped out.
 
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Offline IanJ

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Re: EEZ Bench Box 3 (BB3)
« Reply #219 on: December 31, 2019, 10:38:49 am »
Oh, so looking forward to this.......
Ian Johnston
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Manufacturer of the PDVS2 & PDVS2mini
 
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Offline Sabrosa

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Re: EEZ Bench Box 3 (BB3)
« Reply #220 on: December 31, 2019, 05:13:12 pm »
Congratulations prasimix! The funding pace seems to have picked up a bit towards the end, so maybe there's a chance of hitting the $100k stretch goal. :)
 
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Offline danielbriggs

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Re: EEZ Bench Box 3 (BB3)
« Reply #221 on: December 31, 2019, 05:53:23 pm »
Congratulations prasimix! The funding pace seems to have picked up a bit towards the end, so maybe there's a chance of hitting the $100k stretch goal. :)

I guess it changes mindset post 100% from "do I want to maybe back this?" (possible 60-70% stall) vs. "I want to order this with a slightly shipping delay"  :)

I really hope this sticks around for many years and continues to evolve at close to it's current pace w.r.t. talk of extra modules / 8x way chassis? etc.
 
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Offline prasimix

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MicroPython Curve tracer script
« Reply #222 on: January 02, 2020, 01:41:22 pm »
The first video of BB3 as an automated NPN curve tracer:

https://twitter.com/envox/status/1212716344724066305
 
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Offline Rerouter

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Re: EEZ Bench Box 3 (BB3)
« Reply #223 on: January 02, 2020, 02:13:34 pm »
Would it be possible to run a similar demo in the 50mA range for the results, would then really show off its resolution,
 

Online jbb

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Re: MicroPython Curve tracer script
« Reply #224 on: January 02, 2020, 07:47:03 pm »
... BB3 as an automated NPN curve tracer ...

Nice! Should be applicable to other devices too (MOSFETs etc.). Seeing a video demo also shows the value of the nice big touch screen :).

At risk of being a little picky - I know you’re busy! - it would be really cool if the last couple of seconds of the video were a screen grab (or close up photo of whatever) of the curves to show what you got.

And now on another subject; it looks like you might make your stretch goal.  If you do move the Ethernet and USB ports, would that free up a little room on the front of the master control board? If so, I think moving the boot mode switch from the aux power board to the master control board would be nice; those traces went quite close to the main power switch and were making me nervous.
 

Offline AlanS

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Re: EEZ Bench Box 3 (BB3)
« Reply #225 on: January 03, 2020, 01:35:27 am »