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

[Strada916]

Just tried to use the BOM upload feature in Digi-Key and 3/4 of the parts wants you to order a whole reel. Comes up with Note and asking to select a different option. Also trying to get the E14 BOM uploader to work. keeps timing out. Any one else have any issues or is it just me?

[Strada916]

OK. I give up. If there is a parts group bye please let me know. Thanks. I thought there a post about it. Not sure if it has gone ahead yet. Cheers

[Electronix]

Hi strada,

thanks. I know the pictures are not the best. I will make some new ones, also when the ps is in action so that you and the others can see a little bit more on the pictures

Cheers

Sven

[Dwaine]

Those screenshots of the firmware look really good.   I would love to start building a unit.  I guess I'll head over to GIT and start the reading.

[prasimix]

Those screenshots of the firmware look really good.   I would love to start building a unit.  I guess I'll head over to GIT and start the reading.

If this comment is related to the screenshots presented by Electronix take into account that he is selected different approach and you cannot find that in the Firmware M2. Hopefully he'll share his project soon on GitHub or someplace else.

[Strada916]

A fork perhaps?

Sent from my SM-G925I using Tapatalk

[prasimix]

Maybe, but hardly . Electronix is using Nextion 5" display that comes with 800x480 resolution and dedicated MCU/GPU. That gives you incomparable performance over Arduino Due which we pushed to the limits since it has to take care of all PSU control and drive 320x240 display with touchscreen input. Possible issue with Nextion is that is not open source and you are depending on the manufacturer's imagination and speed of adding new features in the Nextion Editor. But, Electronix shows that many things is already there and that it looks like solid foundation for project like programmable power supply. Mentioned Editor is in fact a proprietary/closed source equivalent of the open source EEZ Studio that I announced recently.

[Strada916]

Maybe, but hardly . Electronix is using Nextion 5" display that comes with 800x480 resolution and dedicated MCU/GPU. That gives you incomparable performance over Arduino Due which we pushed to the limits since it has to take care of all PSU control and drive 320x240 display with touchscreen input. Possible issue with Nextion is that is not open source and you are depending on the manufacturer's imagination and speed of adding new features in the Nextion Editor. But, Electronix shows that many things is already there and that it looks like solid foundation for project like programmable power supply. Mentioned Editor is in fact a proprietary/closed source equivalent of the open source EEZ Studio that I announced recently.

Well as far i can see. The display from Nextion is no different to a FET or linear voltage reg?

So you are saying EEZ Studio is a competitor to said editor?

Sent from my SM-G925I using Tapatalk

[prasimix]

It's only a nice "presentation layer" and what will be displayed depends of firmware. Nextion has no clue what kind of circuit has to be controlled. Also if you need remote control (e.g. via SCPI) that has to be written in firmware.

[prasimix]

So you are saying EEZ Studio is a competitor to said editor?

Cannot talk about competition since we're not going to play that game. Nextion is a proprietary solution that support their own family of TFT displays with HMI. The EEZ Studio is currently support one TFT display that is used in power supply project and can be extended over time with many others. It's also cross-platform with multi-language capability, not limited to Windows only.

[Strada916]

So you are saying EEZ Studio is a competitor to said editor?

Cannot talk about competition since we're not going to play that game. Nextion is a proprietary solution that support their own family of TFT displays with HMI. The EEZ Studio is currently support one TFT display that is used in power supply project and can be extended over time with many others. It's also cross-platform with multi-language capability, not limited to Windows only.

Sounds good

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[Electronix]

Hi guys,

of course. When I have more time I will present more pictures and more details of this Project.
Regarding on the picture it is no fork, it the display protection foil on the display which have some bubbles .
This week I was lucky cause a make a good deal to get an enclosure from metcase.
It is the unimet 6 I will use.
Some rare details of the project.
Two 5" nextion displays, each for one channel.
Two rotary encoders for mechanical enter of values.
Two cosel pba 300f-36 which can provide up to 36 volts at 10 amps.
These switching power supply's where controlled directly from my circuit so that the difference between in- and output voltage is max 1.5 volts.
Regulation of the entered voltage and current is analog and digital, cause this elaminates teparature drifts.
I want to have an exactly voltage 3 digits after decimal point. Even under load.
Using a 16 bit dac from analog devices it is the ad5689.
Using 24 adc from it it the ads 1256 for read back.
This components are all on one board.
Two of them where needed.
I must build the controller board with atmega25xx.
At the moment I use development board with atmega 16.
for the 5 volts of the controller board and power supply for the nextion displays I will use a small switching supply from meanwell 5 volts with 3 amps. The nextion consumes 500mA so.

Hope you have better overview what I'm working on. 

Cheers

Sven

[voltsandjolts]

Hi Electronix / Sven,
You have an interesting project. Could you please start a new thread/topic about it and post updates there. Its harder to follow your (and prasimix) updates when they are mixed in the same thread. Would be great.

[prasimix]

Two 5" nextion displays, each for one channel.

Huh, that is massive!
Cannot imagine in this moment what can be done with 1600x480 screen resolution.

Regarding controlling board if you're going to use Arduino and Mega, I'd like to suggest to not waste money on it since Due is in same price range and many times faster! Where that could count? Definitely in OVP and OCP if no dedicated protection circuits exists and you have to accomplish that in firmware (with so fast ADC you can possibly manage to go well bellow 1 ms reaction time). Another benefit is that you can continuously send much more data over USB (and/or Ethernet if it's planned) to some remote place (if necessary).

[prasimix]

Sven, did you forgot to mention isolation between channels and control board? Or this is a default and there is no need to be highlighted?

[Electronix]

Hi prasimix,

no of course, the isolation is standard  so mentioned it not extra.

I will have a look at the due.

Thanks prasimix

[VEGETA]

Will your eez-studio gui software support creating modern-looking guis for say PIC MCUs?

Anyway, what is the generally used (free) choice for generic gui designs using PIC\STM32\... with traditional tft screens (not third-party ones)? I think of using a normal character LCD for my psu design but maybe use a tft for a v2 of it later on.

thanks!

[prasimix]

I will have a look at the due.

I forgot to mention one huge advantage of Due over Mega: SRAM and flash RAM capacity. Mega has really pathetic 8KB of SRAM. That seems a lot at the start, but when things starts to be complicated you can run out of memory pretty soon.

[prasimix]

Will your eez-studio gui software support creating modern-looking guis for say PIC MCUs?

The EEZ Studio can support any type of GUI. The Nextion looks "modern" in comparison with what is currently implemented on the PSU for two simple reason:

• display resolution that is five times smaller then on Nextion 5" display (so you can use more detailed screen items) and
• limited total available MCU processing power (Nextion has more power to just handle display then Due that need to take care of display and all other PSU functionality.

EEZ Studio's project file is generic (for example open one used for M2 GUI generation, link) and is not related to Arduino. It's used to generate final code for the targeted platform (currently Arduino only). So it has potential to support many other IDE/platform including PIC, STM32, etc.. The "only" issue is our limited resources: if someone jump in who wants to add support for mentioned platforms that will speed up a whole process (we are still pretty busy with Arduino).

Anyway, what is the generally used (free) choice for generic gui designs using PIC\STM32\... with traditional tft screens (not third-party ones)? I think of using a normal character LCD for my psu design but maybe use a tft for a v2 of it later on.

I'm not aware of anything that is free or open-source (Nextion is free but works only with their displays). Maybe someone identified a solution that can recommend. I didn't check recently if e.g. Mikroelektronika offer anything for free.

[prasimix]

A small update that can be useful for people who already started to build their own PSU or are planing to do that.

• The PCB panel version r5B9 is tagged as version 2.0 on the GitHub. All new changes that are made, including mistakes found in r5B9, are published in Master branch as r5B10 (that include Arduino shield r3B5). Issues and new features can be now tracked using Issues section.
• Building instructions that is still work in progress can be found on the project web site or on the GitHub. Please also take into consideration Hack #2 and #8 that are updated today.
• We continue to work on Firmware M3, and you can check project status here, or discuss new features or report bugs in Issues section.

[VEGETA]

I want to build my supply with the same method as yours without the use of LT3083 or any similar devices, I wanna use a mostfet as a switch but I also don't want to use a heatsink. My supply will be limited to 2A maximum but I wanna ask you how much is the drop voltage of your design?

I get the idea of using a pre-regulator to set the voltage at a level enough to regulate while being efficient enough. How much is the drop voltage that you are maintaining?

Plus, how does this achieve 0v output?

thanks

[prasimix]

It depends on which end of the scale you are (it's higher on the lower end) but in average it's about 2.5 V. It's depends of how you set post-regulator output tracking. I'm not using LT3083 and wondering how and where are you going to dissipate any significant difference between input and output power. If you have on the input e.g. 40 V and want to regulate it down to 5 V with 2A you have in worst case (pure linear design) to dissipate 70 W. If you put some switching regulator in between you can decrease that dissipation significantly (i.e. down to few watts distributed between switching and linear mosfet/bjt). If you don't like or want to avoid switching part then you could try with mag amp but for that solution you'll need bigger enclosure and custom made transformer or deployment of three transformers on the input.

[prasimix]

Plus, how does this achieve 0v output?

By setting reference voltage for the voltage control loop to zero . But, due to various offsets in that loop it's highly likely that control voltage has to go below zero otherwise you'll reach e.g. 10-40 mV at best without applying negative control voltage. That can be fixed with rising "reference ground" of the err op amp (IC6B pin 5 via R44 here) for e.g. 100 mV (see IC7B).

[VEGETA]

It depends on which end of the scale you are (it's higher on the lower end) but in average it's about 2.5 V. It's depends of how you set post-regulator output tracking. I'm not using LT3083 and wondering how and where are you going to dissipate any significant difference between input and output power. If you have on the input e.g. 40 V and want to regulate it down to 5 V with 2A you have in worst case (pure linear design) to dissipate 70 W. If you put some switching regulator in between you can decrease that dissipation significantly (i.e. down to few watts distributed between switching and linear mosfet/bjt). If you don't like or want to avoid switching part then you could try with mag amp but for that solution you'll need bigger enclosure and custom made transformer or deployment of three transformers on the input.

I think you misunderstood me, I like the pre-regulator part and willing to use it, but I am asking about how much the pre-voltage gonna be regarding to your regulated linear voltage?

Like having a 5v output will require 7.5v input to the MOSFET, is that your case (2.5v dropout)? If so then I ask why didn't you make it like 0.5v only, by setting the pre-regulator to provide 5.5v to the MOSFET?

Also, will this give you true 0v operation?

I gave the example of LT3083 because it is the best IC to do so while achieving 0v without the use of any negative supply. I saw some ICs like this one (http://www.linear.com/product/LT3150) which has another idea, but I won't be using it (don't know how xD).

Your design is based on the basic op-amp configuration, so you can achieve 0v with it as long as you don't use any reference voltage. But the question is the drop voltage. I assume the type of the MOSFET is the answer, especially the Rdson parameter of it. Or maybe the minimum Vgs it needs.

So how did you deal with all that in your design?

thanks

[prasimix]

Lower voltage on the post-regulator is possible but with more difference you should get better performance with dynamic load.
Going down to zero is possible as I just described. Since in PCB version r5B9 offset of 100 mV is not added (IC7B) you can go down to 10-40 mV. Regardless of that you'll get zero when output is switched off (POST_OE is 0).