Author Topic: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)  (Read 275849 times)

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Offline prasimix

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TFT display with ILI9341 follow up
« Reply #375 on: July 07, 2016, 01:29:59 am »
This is a quick follow up on issue with TFT touch-screen display mentioned in post #339 some time ago. That hack works but it's not optimal. Colors looks washed out and pretty distinctive vertical line pattern is visible on the screen. I tried to capture that with my photo camera with limited success:



Fortunately ITEAD put on GitHub a week ago a new library that seems to works directly (and correctly) with ILI9341 controller. Screen colors looks way better (possibly the best that this display can provide) and vertical line pattern disappeared completely (the background color is smooth and even):



My display does not come from ITEAD but it's pin compatible and software compatible with their ITDB02-3.2S V2 (SKU: IM160418005) model. It's pity that it does not offer holes in corners for simpler mounting on the front panel.

A new library will be distributed with the firmware.
 

Offline prasimix

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Hot summer day update...
« Reply #376 on: July 25, 2016, 12:11:22 am »
Many things happened since my latest post so I'll try to cover it chronologically.

1. Playing with bias power supply
From the beginning I was entertained with the idea to employ only one power input for power and bias. That simplify selection of main transformer (no custom multiple secondary windings is required) and allows me to replace transformer with AC/DC module.
Current design requires 3 or 4 different voltage, namely +5V analog, -5V analog, +5V digital and -9 to 12V for down programmer. Negative voltage requires some conversion that include inductive or capacitive pump and for that coupled inductor is used for bias buck pre-regulation stage (LM5574). I was thinking if such solution could be replaced with someone else and comes to LTC’s LTC3260 a low noise dual supply inverting charge pump that can provides up to 100 mA of output current. Since it can withstand no more then 32 V on input, obviously it still need some pre-regulation. I contacted LTC and they once again generously sent me evaluation boards for LTC3260 but also pre-regulation solution: LT8631. That is 1 A synchronous step-down regulator that operate with input voltage of up to 100 V! Demo board comes with fixed output to 5 V but with adding one resistor to feedback voltage divider I increase it to ~13 V to be within LTC3260 safe limits.  The LTC3260 generates three output voltages: negative that “mirror” input positive and two that is additionally regulated with internal LDOs. Demo board already offers +/-5 V that is required for bias. Adding that two boards into the picture wasn’t so difficult – I just removed small inductor that is on the LM5574 input, remove ferrite beads on LDOs outputs, shorted +5V analog and digital inputs and connect demo boards like on the following picture:



When powered with LRS-150-48 and LT8631, the +5V output on LTC3260 looks like this (take into account pollution generated with nearby Arduino Due and noise floor of used Rigol):



What to said then this combination works very well. That actually raises another question: if bias consumption is low (as it is!) why to stick to buck type pre-regulation? I didn’t get an answer from LTC regardless the fact that they have a strong candidate for that functionality: LT3013 high voltage (up to 80 V) LDO with powergood output that we also need to notify MCU to cut power off immediately if bias power is not correct. I didn’t have time to order it and test it mainly for power dissipation that shouldn’t be more than 1.5 W what is manageable with proper PCB layout.
If this approach is followed existing four ICs and one coupled inductor (as “problematic” part) can be replaced with just two IC and few capacitors and resistors. Regardless of its attractiveness I decided to leave bias section as is for time being.

2. Web site info update
I’m trying to keep web site up to date but it’s still a great challenge – I have no time nor resources to do it properly, not to mention my “English” and my desire to offer multilingual content. Anyway, I also added plug-in for comments (Disqus) and have no idea is it appropriate or not – no comments yet to draw any conclusion.

3. AC/DC module for AUX power module
I already asked for any experience with low power AC/DC modules as possible replacement for iron core PCB transformer used on AUX power module. The main idea behind this is to get "mains power agnostic" power supply. Selecting power AC/DC modules like LRS-150-48 resolves that partially for power side (it's still not the optimal one since it has 115/230VAC switch). Existing AUX power module transformer is 12V/6VA and 12V/5W AC/DC module such as Myrra 47154 or Vigortronix VTX-214-005-112 should do the job. I ordered one Myrra to test it and it seems that everything continues to works fine. On top of that with such "electronic" transformer there is not need anymore for bridge rectifier, filtering capacitor and 12V LDO used for powering the cooling fan. Even more: a complete buck (LM25575) for supplying Arduino shield with +5V become questionable since instead of 12V AC/DC module a 5V can be used instead. Of course for that you need 5V DC fan and that narrowing a little bit selection – it seems to me that 12V DC fan is still a common choice. Anyway, I decided to replace existing PCB transformer with “electronic” one and leave LM25575 section.

4. Ethernet RJ-45 jack
The power supply has Ethernet port and I put it directly on AUX power module that should be mounted on the enclosure rear panel. A vertical PCB mounted jack/module is required and I went shopping to the two for me available site: TME and Farnell. I already tested one that I found on TME as shown in post #326. My intention was to leave it in the BOM, and I put few of them for my next order when stock was 0. I checked few days ago with TME what is a status of that part and to my surprise I learned that they are not going to order new batch, and even if I put an order right now I need to wait until mid of December. I didn’t like what I heard and started to look for replacement without stock shortage. I found LMJ2138814S0L1T1C again from Amphenol. BTW, I tried to use that part number to locate it on the Amphenol official site but without success. Maybe I missed something or they have some other internal codes for search I don’t know. If anyone have any experience with Amphenol search please let me know :)
And another surprise follows soon: new part pinout does not follow the old one. Spot the difference:



Needless to say that generates another revision of the AUX power PCB.

5. Design for Manufacturing (DFM)
This is a hard one, but great lesson that I started long before I realized that it has it’s own label. I started building this power supply with clear intention to finish it, not to give up somewhere in the middle and offer everyone who decide to follow this project as much as possible information that it can not only build one but eventually started a small manufacturing :). The DFM seems to require not just a lot of will, time and material to complete a project but also some discipline to put everything in place. Intuitively I knew that something that is modular should be more appropriate for manufacturing and I tried to follow that path. Yes, in one moment I gave up from separate pre- and post-regulator boards but from other side I succeed to simplify wiring and now a complete power channel requires just one cable (power input) and one output connector. Other thing is decision to switch from THT to SMT or to reduce the number of THT parts as much as possible. From the beginning I tried to avoid parts that is hard to get or can generate some difficulty with assembling or increase the price of assembling in “mass” production. I also tried to stay with low cost two layer PCB. So far it works despite the fact that new power module that employs SMPS pre-regulator would be less noisy if 4 layer PCB is used. Anyway, that is rectified to some extend with “low ripple” mode of operation that is mentioned in some of previous post.
I tried to keep in mind mechanical aspects and that results in changing location of PCBs inside enclosure and switching from “portrait” to “landscape” size and saving of about 25% of enclosure volume for the same output power. More about enclosure will follow.
Finally we are coming to the point why I listed this topic: two very useful Dave’s videos: and .
I wish I saw it sooner because that definitely will save a lot of time doing boring job like managing BOM. I learned two important thing:
  • Sometimes is more cheaper then less – it’s better to have more parts with same value on the PCB then trying to “save” by selecting different values. For example if you need 11K use 1K and 10K in series if you already use that two values someplace else!
  • Everything has to be on reels, sorry no cut tapes!
Aftermath of not taking into account mentioned rules cost me a week of optimization. I finished with changes on PCBs (please check GitHub) and still need some time to generate a separate “DFM-friendly” BOM.

6. Enclosure redesigned and ordered!
This is a nice one. It was on hold for some time mainly because I told Varisom that I’m not in hurry with getting enclosure for this project. In one moment I started to wondering what’s happening and call them to find out if they are still interested or not. Varisom is family business in all positive way what that term means and they indeed care, and it’s different from corporate carefulness (for me as consumer, environment, world peace, etc.). I was on Skype for a couple of hours with shared desktop observing drawing of the new enclosure with all corrections and some new parts. I looks like this (you can also use Adobe Reader to open 3D model in attachment):





Their proposal include:
  • 4-part enclosure 1.5 mm from galvanized steel, drilled and painted in one color
  • Two 3-part heatsink, 2 mm Aluminum (they are mounted between top and bottom plate that improve mechanical strength and heat convection)
  • Two 5 mm Aluminum thermal bridge (between pre-regulator PCB section and main heatsink)
  • Four rubber feet
  • AC/DC modules mounting rail
  • Two front panel handles
  • Printing of front and rear arts in one color
Price for qty. of 10 (without VAT and shipping): 43 EUR  :-+
I already make an order, if someone is interesting please let me know.
 

Offline prasimix

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PCB panels for r5
« Reply #377 on: August 17, 2016, 10:54:40 pm »
The new PCB panels just arrived. Three panels left if someone is interested. Price is €19.80 (without VAT and shipping costs) or €35.40 with TFT touch screen display.



 

Offline Aigor

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #378 on: August 17, 2016, 10:57:01 pm »
i'm interested, in which way i can pay you? do you use paypal?
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #379 on: August 17, 2016, 10:59:02 pm »
PayPal is preferred.

Aigor, please check you inbox I sent you message few days ago :).
 

Offline kolesar007

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #380 on: August 18, 2016, 06:00:36 am »
NICE, cant wait to get them :) !
 

Offline Strada916

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #381 on: August 18, 2016, 06:23:59 am »
Do you have a set left? Prasimix?

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The Bone, the Off-White, the Ivory or the Beige?
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #382 on: August 18, 2016, 06:55:22 am »
Do you have a set left? Prasimix?

Sent from my SM-G925I using Tapatalk

Two remains.
 

Offline Mihkel

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #383 on: August 18, 2016, 07:17:22 am »
Hi Prasimix

Thank you for sharing your great project.  :-+
I'm interested to get one set of PCBs and one TFT Display.
I'll PM you.

Mihkel
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #384 on: August 18, 2016, 05:22:23 pm »
All PCBs gone! Thanks all for your support. Stay tunned for next batch (and more).  :popcorn:
 
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Offline Aigor

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #385 on: August 18, 2016, 05:28:49 pm »
Thank you Prax

Inviato dal mio Redmi Note 3 utilizzando Tapatalk

 

Offline Strada916

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #386 on: August 18, 2016, 08:01:33 pm »
Thanks Prasimix. ????

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Offline prasimix

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Assembled new boards and enclosure
« Reply #387 on: August 23, 2016, 04:17:42 am »
I spent some time over the weekend assembling power boards and Arduino shield. You can see the results on the following two videos:




 
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Offline minion

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #388 on: August 26, 2016, 02:30:26 am »
hey, nice project!

I only have one small question: on AUX board, why is there a diode D21 on the sense pin, going from the fan?

I was not able to figure it out.  :)

pozdrav iz slovenije!
« Last Edit: August 26, 2016, 02:32:35 am by minion »
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #389 on: August 26, 2016, 02:32:26 am »
Please check post #373.
 

Offline minion

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #390 on: August 26, 2016, 02:35:01 am »
that was fast, tnx  :)
 

Offline prasimix

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AUX PS r5B9 is assembled ...
« Reply #391 on: August 27, 2016, 01:41:57 am »
The AUX PS r5B9 is now also assembled. It looks like this:



All existing circuits from previous revision is now working fine but I made a stupid mistake when adding optional USB isolator. I don't know how it was happen but for some reason I didn't connect supply on the Arduino side. Therefore if any of you who is going to build this PSU wants also USB isolator then two extra wires will be required:

« Last Edit: August 27, 2016, 01:45:17 am by prasimix »
 
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Offline prasimix

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LED marking for different colors
« Reply #392 on: August 27, 2016, 01:55:59 am »
I found an another issue that is not so difficult to rectify and it's reminder to RTFM twice or at least study all accompanied pictures |O.
On the Arduino Shield 0805 LEDs are used in different colors (yellow, red, green and orange). For some reason manufacturer decided to swap anode and cathode on red LED:



Since the same component is used on PCB layout all red LEDs has to be rotated while soldering. Here is an example of how that marking looks link on the PCB:



Another possibility is to find some another LED that has same marking as all others.
Does anyone have an idea why red LED is so special?
 

Offline prasimix

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Shipment of PCB panel + TFT
« Reply #393 on: August 29, 2016, 07:28:31 pm »
I got today TFTs with delay of one week due to incomplete address :(.
Now I can send a set of PCBs and TFTs to all who paid for it. Enclosures departed last Friday from Portugal so I'm expecting them this week.
 

Offline Aigor

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #394 on: August 29, 2016, 07:30:12 pm »
My set was delivered today Thanks!
 
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Offline prasimix

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New custom made enclosure is arrived
« Reply #395 on: September 03, 2016, 06:02:42 am »
The custom made metal enclosure is arrived two days ago from Varisom in Portugal. It looks nice (color is RAL5022) and it's well manufactured, robust and should survive real mechanical stress. It was my first try to order a custom made mechanical part and there was few issues that I'll cover in some of the next posts. In the meantime take a look and let me know what you think:







« Last Edit: September 03, 2016, 06:08:02 am by prasimix »
 

Offline kolesar007

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #396 on: September 03, 2016, 12:50:10 pm »
Looks really nice and also color is one of my favorite :).
 

Offline timgiles

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #397 on: September 03, 2016, 05:01:24 pm »
What a fantastic job you have done. Just been looking at the design documents on github - really great.

You mention a group buy possibility. Is this done or planned for later on in the year? Any idea when?

Regards Timothy
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #398 on: September 03, 2016, 05:05:39 pm »
What a fantastic job you have done. Just been looking at the design documents on github - really great.

You mention a group buy possibility. Is this done or planned for later on in the year? Any idea when?

Regards Timothy

Hi Timothy, it's planned to the end of this year. Anyway one PCB panel and TFT display left.
 

Offline Strada916

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A
« Reply #399 on: September 03, 2016, 09:35:09 pm »
Hi Guys. To the people that have their psu built. Where did you get your parts from?

Prasimix: with the group buy planed. Is that for a complete kit?

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The Bone, the Off-White, the Ivory or the Beige?
 


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