DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)

[prasimix]

Until now I assembled three sets. Lots of soldering, but that is really relaxing. There is a few thing that require additional attention so I'll try to create something like "building instructions" page that could help in the process of assembling. In the meantime I'd like to share few things on the Arduino board that should be taken into account immediately:

1. Additional capacitor is recommended. There is no place on current PCB revision but it's simple to add it like this:



2. The Ethernet connector (X18) has to be right angled otherwise it will collide with CH1 heatsink . But, when right angled connector is used as on the picture below there is no possibility to put a screw to fix TFT display.



Fortunately that is not a big issue since TFT is fixed on all four corners because of 11 mm spacers:



3. Push-in connectors (X12, X14) are 4 mm apart from front panel surface. That does not mean that their pins are not accessible. It's more a question of visual appearance and you can fix that by modified cheap DIL16 sockets. You need to cut it since distance between pin rows in not 300 mils. You also need to adjust their height to 4 mm (my version is 5 mm). That can be done in a matter of minute using sandpaper.



X12 and X14 are not soldered on the PCB but inserted in modified sockets:



... and the end result looks like this:

[kaevee]

For anyone ordering on DigiKey

Item No 9 in consolidated BoM is

http://www.tme.eu/en/details/cl21c121jbannnp/0805-mlcc-smd-capacitors/samsung/

Where as in DigiKey it is

http://www.digikey.com/product-detail/en/samsung-electro-mechanics-america-inc/CL21C121JBANNNC/1276-1768-2-ND/3887426

Regards,

Venkat

[prasimix]

I added a new folder on GitHub called Building instructions. It's a work in progress. You can find there also images of PCB's layers with values displayed if you don't have Eagle nor want to install its free version only for this project.

To stay informed about changes in this folder simple subscribe to project's psu_hw repository.

[prasimix]

Dear all, recently few people started to work on improving initial BOM by adding new suppliers and finding mistakes. I started to receive multiple comments and suggestions via email and PM. To make a whole process more transparent I'd like to ask you to start using GitHub's Issue reporting and Pull request features. There we can discuss all issues in a more structured way and have a history of what has been done.

I'd also like to encourage all who find this project interesting to subscribe to project's repository (psu_hw).

Thanks!

[prasimix]

Hi everyone, I was thinking how to organize next group buy since people still coming and asking for it, and I decided to try to make it as a crowdfunding campaign. A Crowdsupply platform is selected, and I'd like to offer various options starting with bare PCBs. Maybe a "kit" version that include assembled modules, enclosure and other items required to get a completed unit should be a "central/highlighted pledge". Why not complete unit? Because it require CE and FCC certification that cost a lot and that could be an option only if enough backers shows interest. I'm aware that passing such certification with the current solution could be very challenging since e.g. for lowering a cost I didn't use 4-layer PCB for the Power module where is SMPS pre-regulator. It's also questionable how "noisy" are selected TFT display and Arduino Due "clone" (eBay-grade), etc.

Anyway, this campaign similar to the first experimental group buy (thanks everyone for your support!) is not profit driven, since the main idea is to promote open hardware solutions and try to decrease total cost as much as possible. Therefore if more funds will be raised, a better offer will be, and eventually we can ends up with completed and CE/FCC approved unit. Hopefully someone will jump in with review of what is already done, and what is a chance for existing design to pass EM compliance testing in the first place, or if chances are slim, what to change and prepare a next revision of the Power board with e.g. 4-layers and some extras to increase possibility to pass that testing without much hassle.

Your inputs are, as always, highly welcomed.

[timgiles]

Hi,

I would certainly like an option where the 'big' items such as the case, PCB, TFT and heatsinks can be ordered as a pack. Also include some of the more expensive components that have a reasonable 'bulk' discount, which as a single purchaser I am unlikely to use up in a reasonable time. In terms of all the passives, leave them out unless you want to produce a whole kit. Some of the connectors and other mechanical components can be hard for some to find the exact ones needed.

Good luck with everything.

[prasimix]

The "kit" version should be something like this:

1. Enclosure + heatsinks
2. Arduino Shield module assembled
3. AUX power supply module assembled
4. Power modules (x2) assembled
5. AC/DC power adapter x 2
6. TFT touchscreen display
7. Wiring harness
8. Fan, AC inlet, bolts, nuts, spacers, etc.
9. Arduino Due

That has to be accompanied with building instructions (web pages and few video tutorials). Maybe 5 should be optional for people who already have some suitable toroidal transformer (they also need to follow Hack #1 to use AC instead of DC input on Power modules).

Above mentioned list represents all required items to build a fully functional unit. Due to that it seems that such offer become subject for FCC certification. Only possibility to skip in this early stage such certification and makes a whole thing more affordable is to use "subassembly" model (see e.g. here or here). In that case few items have to be removed from the above mentioned list, for example 5 and 9.

In summary, I found that neither assembled unit nor complete kit can be publicly offered without FCC certification. Actually CE marking is even bigger issue because it seems that the cost of certified lab here in the EU is much higher then in the US for FCC marking. Therefore the campaign's first milestone fund projection has to be based on few parts (e.g. bare PCBs + TFT + enclosure). If it attract more backers we can starts with preparation for certification (that means having ready another revision of Power module with 4-layer PCB, test radiation at home using SDR, etc.).

[kolesar007]

I already have my kit .
Now I must check and sort all components, then order some missing parts from fernell and then find some time(most difficult part ) to put whole thing together.

[Aigor]

Same mine job

Inviato dal mio Redmi Note 3 utilizzando Tapatalk

[Mihkel]

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?

I think that will be impossible. Too many parts for making a kit. Maybe with THT but not SMT parts. At least that is beyond my current apprehension of electronic kit. When I think about group buy that is primarily for specific parts like PCBs, enclosure, TFT display, maybe some ICs like W5500, etc.

I really try to keep up to date BOM that can be found here. Yes, I know that choice of suppliers is not optimal. I found e.g. just recently that Farnell don't want to sell to private persons (only to companies). TME cover most of the world but I don't know what is shipping cost outside Europe where is bargain.
If anyone wants to compile e.g. Digikey/Mouser/Arrow or anyone else I can assist if some doubt arise and we can merge that BOM with existing one and make it available on the GitHub to everyone.

Hi Guys. As I plan to build one PSU for myself also, I did a "little" price comparison to find the best prices for needed components. I added 2 more suppliers to the BoM, Digi-Key and RS Components, with relevant component part numbers. I also added some parameters to the components descriptions, corrected few mistakes in BoM and suggested few other things to Prasimix. Now I have sent the revised BoM to Prasimix for checking and I hope that he will release it soon on Github.

Now in short: I added the best prices I found for every component of each supplier and found that the total cost of components listed in BoM for individual buy is currently around 255 €  (without VAT and shipping costs). The calculation does not include PCB's, TFT Display, Arduino, Meanwell PSU's, AC Input Option components and Custom Enclosure. In calculation I took into account that many components have MOQ (Minimum Order Quantity) and if you are buying components for one PSU, you have to buy some extra components. Of course Digikey and Mouser are selling all components in one piece also, but sometimes is cheaper to buy 10 pcs of the same component from another supplier.

And, as I promised (in post 411), I did also the calculation for Group Buy. So, if we are buying components for 10 sets, the price will be much "better", currently around 195 € (without VAT and shipping costs). Now, IF we go forward with the Group Buy, someone has to buy the components, repack whole this mess and send the packages to the participants. For repacking we need also a bunch (ca 1000 pcs) of ESD bags, what also cost money. I have calculated that I can handle all that mess and the final cost for one set will be 210 € (this covers all shipping costs from suppliers to me and cost of ESD bags). Shipping cost from me to you I will check later. And for people in EU country, VAT will be added also.

But first we need to get together 10 people at least to go forward. So, please let me know how many of you are interested in Group Buy.
I'm doing this because I'm personally also interested to get the components with better price. So, 9 more people please. Who's in? 
If you have any questions, please don't hesitate to ask.

Cheers,
Mihkel

[prasimix]

A new BOM is just uploaded on the GitHub. Mihkel did a great job reviewing timgiles Mouser list, and he added RS components and Digikey. Few capacitors are also changes as it's noted at the end of the document.

[prasimix]

During the assembly and testing two issues are found on the Power board that will require PCB modifications. Fortunately both can be done without considerable effort or special skills. The simpler one is related to radiated EMI. One of the PCB’s mounting holes is wired to the protective earth potential and the mounted heatsink for the Q4 become also on that potential when it’s fixed on the PCB. Our intention was to attenuate EMI in that way, but the end results is quite contrary when the Power board is mounted into metal (conductive) enclosure! It seems that in that way a whole enclosure is earthed not on one but on three different point (one close to the AC inlet and two via above mentioned wiring of the heatsink) and that generate ground loops.
If you are going to use metal enclosure, it is advisable to simply cut the earth trace that leads to the mounting hole which is near L2 power inductor. Use miniature drill with a diamond mill for that.



Another issue is connected with selection of the voltage programming source that in our case can be internal (DAC output, IC11) or external signal input (+2.5 V full scale) available via miniature push-in connectors located on the Arduino Shield (X12, X14). Due to the mistake on PCB layout only internal programming (that is default) is possible. To overcome this issue we need to cut U_SET_OUT trace that goes to R52 and connect it to R81.



A thin wire (e. g. for wire wrap) about 5 mm long is needed to be soldered (see below, pos. A) and PCB trace has to be cut (pos. B).

[prasimix]

I added a new section here about wire harness that should simplify cabling of the PSU. I don't know if specification format is satisfactory, so your feedback is welcome. A PDF document is also attached, and few pictures from it:

[prasimix]

For wire cutting, insulation removing and crimping I found very useful the following tools:

• Jokari No. 20050
• Engineer Crimper with No.12 and No.13

[prasimix]

The firmware M2 is almost finished and what is covered with it can be found on the following two videos:

[prasimix]

My initial intention was to additionally lower temperature of power pre-regulator by adding "thermal bridge" between bottom PCB side and post-regulator heatsink (for Q4 power mosfet). That will affect cooling fan operation since it could work with lower speed (and less audible noise) to manage the same temperature.

I found that use of conductive thermal pad e.g. aluminum block with PCB side insulated (that some of you got with customized enclosure) is a really bad choice since it will drastically increase switching noise!

If you'd like to improve cooling you can use a piece of 5 mm thick silicone thermal pad mounted. Channel temperature that is measured with NTC1 can be lowered in that way significantly. With e.g. 20 mm wide pad  it’s possible to achive 6-7 oC temperature drop on the max. load!



EDIT: search on eBay, AliExpress, etc. for e.g. 100mm x100mm x 5mm GPU RAM IC Chip Cooler Conductive Silicone Thermal Pad. It should be less then 10 USD.

[prasimix]

Dear all, I'd like to inform you that Firmware M2 is released. It's the first version that support local console (TFT color touchscreen display) and use new infrastructure for building all pages and menus that allows us to almost instantly change anything on the display. Therefore all GUI usability issues, mistakes and non-senses can be simple fixed and you can test what is done so far using software simulator (download here) even without having physical device on disposal (you have to use mouse instead of finger tip to navigate thru menus). Your feedback is welcomed.

[Electronix]

Hello everybody,

Im making also good progress with my psu.
I would like to ask if someone knows this software ?
http://www.aktakom.com/support/software/index.php?SECTION_ID=479&ELEMENT_ID=33438

This is looking as a software which i think has everything which is need to control a ps.
Even drawing of curves are integrated.
Has someone experience with this sw ?
I try to download it but it is only possible if you register a valid serial number of a
Aktakom power supply.

I will make some photos in the next days when I finished my display ui

Cheers

Sven

[prasimix]

Hi Sven, it looks like SCPI controller application for Windows. Don't know why you'd like to use it since:

This software is paid-for and its cost is included into device value.

That puts it in the same class with the many other commercial SCPI controller application.

[VEGETA]

Hi

I want to ask about how did you develop the GUI part of this project including the software you used and the circuit regarding the display. I see a lot of solutions but they are pricey and more oriented towards professionals.

thanks

[prasimix]

We are using EEZ Studio, a visual toolkit that is still under development but is now completed enough that we are using it actively to create all pages and menus for firmware (M2 and beyond). I promised its presentation before summer but due to lack of resource I still don't feel comfortable to make an introduction.
In short, it enables working with portrait and landscape display, has WYSIWYG editor that simplify massively arrangement of the displayed page items, support different type of bitmap fonts and symbols and generate code that can be combined/called directly with other Arduino sketches. It's cross-platform (Win, Linux, Mac). I can show you some screenshots, like:

Storyboard where you have on one screen all pages, to get a "big picture" and one click navigation to the page of interest:



... or page editor with all page items, listed Page structures, available Widgets that can be used and Properties of the selected item:



... or fonts management:



Actually, this power supply project should become a reference design to show what is possible to do with the EEZ Studio. If we found enough resources idea is to approach something similar to Itead Nextion and 4D Systems, but in this case as open hardware and open source, with possibility to support e.g. Energia, mBed, etc. in addition to Arduino code generation (if we make communication e.g. via serial interface than it will become completely platform independent).

[VEGETA]

I am surprised that you got this tool designed. The GUI designer is great really! I wanted something to work with PIC micros or some cheap ARM ones. looking forward for this to be released. thanks

[Electronix]

Hello everybody,

I'm using the itead displays and it is really simple to create difficult gui's.
Only problem from my side of view is the problem that the Fonds looking a little bit crappy.
They are really cheap and I spend to 5" displays, one for each channel on my psu 32volts 10 amps. 👍
Tomorrow I will post some screenshots from my power supply display.

Cheers

Sven

[Electronix]

Hello everybody,

a Little later, but here are some screenshots.

cheers

Sven

[Strada916]

Hello everybody,

a Little later, but here are some screenshots.

cheers

Sven

Wow Electronix
Nice GUI.


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