Author Topic: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)  (Read 299337 times)

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Offline BFX

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Re: New mosfet pre-regulator PCB...
« Reply #175 on: October 05, 2015, 08:49:39 pm »
it's super project with lot of inspiration for next builders  :-+
thx
 

Offline Erythros

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #176 on: October 06, 2015, 11:53:59 am »
Excellent. It is starting to look mature with only the finalizing touches missing. I really admire your dedication. When I look at all the hours and money you had to put into it and no talk about production or even crown founded short supply production to mitigate costs that's something you don't see that often.

Are you still writing software for both Due and Mega? It seems like bigger source of problems than it is worth. Given that the architectures are different. I would probably go just with Due as it costs under 20 USD now ("clone", "based on Due" or whatever). But well... I a interested in how you will tackle it.

The change from 3 boards to just two (plus the Display Module) seems on one hand logical but on the other your box have to meet size criteria which previously it didn't have to. Also I have read somewhere in this thread about building more than dual channel PSU (there is no thing as too much channels). It looked simpler with modular control PCB setting. BTW, is the software side capable of dealing with more than two channels?

Next you will be building extra precision PSU  :-DD
 

Offline Liv

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #177 on: October 06, 2015, 01:28:53 pm »
When I look at all the hours and money you had to put into it

Yes, really big and hard job! When I made my PSU, it took 4 years. However, I spend a little money, I tried to use components from old boards.

Next you will be building extra precision PSU

Also there was a desire to make a precision PSU, that's just it quickly disappears when this job does not bring any money.
PSU PSL-3604 Pulse gen. PG-872 Freq. cnt. FC-510
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #178 on: October 06, 2015, 01:50:39 pm »
Excellent. It is starting to look mature with only the finalizing touches missing. I really admire your dedication. When I look at all the hours and money you had to put into it and no talk about production or even crown founded short supply production to mitigate costs that's something you don't see that often.

Are you still writing software for both Due and Mega? It seems like bigger source of problems than it is worth. Given that the architectures are different. I would probably go just with Due as it costs under 20 USD now ("clone", "based on Due" or whatever). But well... I a interested in how you will tackle it.

I can say so far so good regardless the huge difference in programming but also in capability. For instance Due don't have built-in EEPROM but have some sort of RTC what Mega don't have. Fortunately such difference is dissolved by including such devices on the Shield PCB. Also from what I can see now Arduino IDE is more mature (if that is a proper word for this context) when we talk about AVR then ARM architecture. Currently we faced (my colleague that is dedicated to the software part and me as "project manager and tester") with at least one "show stopper" on Due side: lack of support for chosen (and cheap) Ethernet controller. We'll see if something will pop up in the near future.
Due to the "DIY spirit" of the project I still think that its worth trying to support both architecture regardless of the fact that Due is in the same price range (yet more powerful) or as a clone even much cheaper then genuine Mega.

The change from 3 boards to just two (plus the Display Module) seems on one hand logical but on the other your box have to meet size criteria which previously it didn't have to. Also I have read somewhere in this thread about building more than dual channel PSU (there is no thing as too much channels). It looked simpler with modular control PCB setting. BTW, is the software side capable of dealing with more than two channels?

I have that on my mind. There is a few possible "branch" from the current Arduino Shield PCB:
  • Remove "binding post" section to decrease overall PCB dimension
  • Remove level shifting for 5V that only Due is supported
  • Add at least third channel with keeping PCB dimensions as small as possible (trying to stay withing Eagle Freeware limits of 100x80mm) since software is structured in modular fashion that not only that is possible to change channel count but also replace currently used I/O expander, ADC, DAC, RTC and Ethernet with other models.
Next you will be building extra precision PSU  :-DD
Yes, never say never :)
« Last Edit: October 09, 2015, 03:51:35 pm by prasimix »
 

Offline prasimix

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Short circuit and transient response measurement
« Reply #179 on: October 08, 2015, 10:01:59 am »
I'd like to present some measurement of short circuit and transient response. For the first measurement a simple low Rdson mosfet switch is used to short output terminal with 0R010 power resistor:





Output signal from signal generator (SIG trace) is limited in duration (SW trace) and output (Vout trace) is monitored:



Recovery time from short circuit is ~1.2ms:



Measurement of voltage drop on the Rsense (connector X10) can give some idea about current:



Zoom in on the rising edge:



... and zoom in on the falling edge (some oscillation is visible?):



To test transient response I built a Closed Loop Transient Load Tester as described in LTC's app note AN104-15. I was not able to follow procedure completely since I cannot afford any current probe. Therefore I just monitored Vout when the tester is connected and active.

Tester is housed in cute and easy to drill Hammond HM1590U enclosure (if somebody is interesting in PCB, I can publish it):





At the beginning I tried to test output voltage up to 50V and (of course!) that cost me few output transistors (D44H11) since that violate badly SOA. I noticed that PSU perform almost uniformly from 10 to 50V (below 10 and definitely below 7V tester starts to generate some bad oscillation. First I blamed my PSU but when I tested the same range with i.e. 3-pin standard regulators I realize that something is wrong with tester by design or because I made some bad mistake during assembly). Anyway I proceed staying mostly in the middle of the scale, to Vout=25V.
I also noticed that measure point is important. I tried that with both AC probe described in above mentioned LTC document and with 10x probe that comes with Rigol MSO. Also connecting some capacitor in parallel with probe can change results. My AC probe looks like this:



Tester have possibility to adjust DC bias of little above 1A. On top of the another 1A can be added depending of the input signal level that is used for switching on and off additional load current. Transient response vary in accordance with selected continuous (DC bias) and "switched" load (signal level). If we goes with "full scale": 1A DC bias and 1A switched load on the chassis binding posts I got the following results, 146mV over-/undershot (measured at the tester's binding posts):



Zoom in on the rising edge (undershoot is 78mV or 0.31% at 25V):



... and zoom in on the falling edge (overshoot is 72mV or 0.28% at 25V):



If I move probe from testers binding posts to the post-regulator PCB output terminals, results looks better when over-/undershot drops to 54mV:



Maybe is good to add what MSO capture when load tester output is switched off but signal from the signal generator is still present:


 

Offline mij59

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #180 on: October 08, 2015, 10:21:09 am »
The supply voltage of 7.5V is quite low for driving the mofset.
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #181 on: October 08, 2015, 10:25:10 am »
The supply voltage of 7.5V is quite low for driving the mofset.

It seems that MC34152 have no problem with that.
 

Offline mij59

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #182 on: October 08, 2015, 10:39:03 am »
The supply voltage of 7.5V is quite low for driving the mofset.

It seems that MC34152 have no problem with that.

Correct, but the gate source voltage of the mosfet is quite low, a higher gate source will reduce the on resistance of the mosfet.
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #183 on: October 08, 2015, 10:42:59 am »
Ok, with Vgs of ~7V and Vds=25V you think that is not enough to put IRLI540 into saturation?
 

Offline mij59

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #184 on: October 08, 2015, 10:58:29 am »
Ok, with Vgs of ~7V and Vds=25V you think that is not enough to put IRLI540 into saturation?

At 7.5V supply voltage you won't get a gate source voltage of ~7V, I would go for a gate source voltage of at least 10V, a supply voltage of 12V.
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #185 on: October 08, 2015, 11:02:32 am »
But trace SW (cyan) tells us that is ~7V on gate input.
 

Offline mij59

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #186 on: October 08, 2015, 12:12:09 pm »
But trace SW (cyan) tells us that is ~7V on gate input.

Ok, but properties will vary from mosfet to mosfet, I think there's not much margin build in.   
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #187 on: October 13, 2015, 03:09:17 pm »
Currently we faced (my colleague that is dedicated to the software part and me as "project manager and tester") with at least one "show stopper" on Due side: lack of support for chosen (and cheap) Ethernet controller. We'll see if something will pop up in the near future.

A small update here: support for the ethernet controller (ENC28J60) that works with both Mega and Due exists and preliminary tests are encouraging. Here is a fork from original UIPethernet library that also include API for selecting SS pin (originally it was hard-coded) and soon will be added some other things (i.e. hostname settings).
Anyway decision to proceed with both AVR and ARM support looks like good exercise to make a more generic code.
 

Offline prasimix

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Arduino Shield +BP r1B12a for programmable dual channel bench power supply
« Reply #188 on: October 21, 2015, 10:55:03 am »
Arduino shield is tested and we'll continue do use it for the software development where already a great progress is made and that will be presented soon in a separate post.
A one mistake is found on this shield that became visible when Arduino Due board was connected for the first time :(. No SPI bus was available (as wrongly presumed) on the same pins as Mega2560. The only way of using hardware SPI on Due is thru 6-pin CSPI connector that not exists on this shield. That required a small surgeon on the Due board: cutting lines that comes to the pim 50, 51 and 52 and connect it to the ICSP connector. That is now corrected. Also assigning LEDs for first channel CC and CV indications on pin 0 and 1 that is usually busy during uploading was not so nice. Therefore I relocate them to pin 4 and 5 (see EEZ Arduino pin mapping r1B11 document).



You can find in attachment Eagle schematic and PCB layout, Gerber files, Arduino pin mapping and Binding post controller (TLC5925) mapping. Here is also a BOM with ordering codes from Farnell and TME. Since TME is much cheaper and Farnell stocks parts that cannot be found on TME, I made third column what includes the cheapest pick from both suppliers (see below). There is only a few parts that you have to buy somewhere else: the TFT touch-screen display and few cables (references are also included into the BOM).



What is possibly interesting to do with this shield in the future? Here is some ideas:
  • Add more channel; at least one to have under control some kind of "aux" i.e. 0-8V output (there is enough free pins for additional up to four channels)
  • Replace the Ethernet with wireless
  • Add two more power relays on the "BP" (binding posts) side to allow grounding (connect minus output to the mains earth)
  • Add two more signal relays to cover remote sensing case when two channels are connected in serial.
  • Rearrange binding posts to have in one row power outputs and in another remote sense inputs using much smaller connectors
  • Somehow combine BPs LED indicators with CC/CV indicators
  • Completely remove binding posts section if that someone think that is unnecessary luxury
« Last Edit: November 01, 2015, 02:27:38 pm by prasimix »
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #189 on: October 21, 2015, 10:56:58 am »
I'm sending Eagle and Gerber files separately due to attachment length restriction ...
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #190 on: October 21, 2015, 11:04:44 am »
The idea #7 from the previous post is actually already accomplished. It wasn't too complicated and requires literally cutting existing shield into half and cleans up components that are not required anymore. Here it is:



You can find in attachment BOM ...
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #191 on: October 21, 2015, 11:06:23 am »
... and Eagle and Gerber files for the shield variant presented above (without binding posts section).
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #192 on: October 21, 2015, 11:53:01 am »
With new Arduino shield I'm hopefully just a step away from the functional and decent front panel. Just as a reminder the first attempt was presented here. Now it looks like this:







Placement of the communication ports (Ethernet and USB) is possibly not "by the book" but with this enclosure I ran out of available space on the back panel. A new PSU that I am planning to assembly shorty will go in 40mm wider enclosure (Modushop.biz/Hi-fi 2000 Economica EP1153220 L 320 x D 200).

The final step is to order two-color Acryl GS laser cutout (thanks 0xdeadbeef) to cover hand drilled alu plate.
 

Offline fuzzoli

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #193 on: October 21, 2015, 05:22:26 pm »
Hey there!

Is there a consolidated post listing all of the Eagle files for the entire PS?  I took a look, but must have missed it. 

This is one of the best projects in the forum!  I'm sure I'm not the only one who thinks each new update is like opening another present on your birthday! :-)

Keep up the great work!

-Frank
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #194 on: October 28, 2015, 10:18:33 pm »
Still working on it. The easiest way to check what is already available is to check from time to time the list of important changes at the top of the first post.
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #195 on: November 01, 2015, 04:15:49 pm »
A new thread about software support for this power supply is opened here.
« Last Edit: November 06, 2015, 05:28:37 pm by prasimix »
 

Offline timofonic

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #196 on: November 06, 2015, 05:13:42 pm »
A new thread about software support for this power supply is opened here.

I'm not sure what happened to it, but the link no longer works :(
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #197 on: November 06, 2015, 05:29:50 pm »
A new thread about software support for this power supply is opened here.

I'm not sure what happened to it, but the link no longer works :(

Hm, a slash at the end was missing. Please try once again.
 

Offline prasimix

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #198 on: November 10, 2015, 05:01:55 pm »
I'm started to commit files related to this project on the GitHub.
Please follow https://github.com/eez-open where also firmware/software part of the project will be published soon in accordance with "roadmap" introduced here. A dedicated site with more info about project is also under construction.
 

Offline timofonic

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Re: DIY programmable dual channel bench PSU 0-50V/3A
« Reply #199 on: November 14, 2015, 11:00:46 pm »
I'm started to commit files related to this project on the GitHub.
Please follow https://github.com/eez-open where also firmware/software part of the project will be published soon in accordance with "roadmap" introduced here. A dedicated site with more info about project is also under construction.
Is this part of homework? I see too many formal maneurisms :D

Congratularions, nice design ;)

 


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