Author Topic: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)  (Read 276372 times)

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Offline T3sl4co1l

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1075 on: October 06, 2018, 04:29:53 am »
Ethernet has a 1nF 1.5kV from cable (center tap on the transformer) to GND for ESD protection.  Note that that's a consistent value (i.e., figure 8kV contact discharge from 300pF), but only for single shots (there's no leakage to drain accumulated charge!).

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Offline VEGETA

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1076 on: October 09, 2018, 09:46:30 pm »
Just a quick question, can you achieve isolation of 2 channels with only one AC-DC module (or any DC source)? I thought about it and my answer was no. I just wanted to read your opinion.

However, there is the floating regulator design so does it allow for example connecting the 2 channels in series or parallel assuming both of them has only one power source (a battery pack for example).

 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1077 on: October 10, 2018, 01:21:47 am »
As far as I know the answer to the first question is no, and yes to the second one as you suggested.
 

Offline VEGETA

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1078 on: October 10, 2018, 04:27:00 pm »
As far as I know the answer to the first question is no, and yes to the second one as you suggested.

Good, looks like I got it correctly.

However, for the floating regulator.. I kinda have a problem of understanding how it would be 2 channels in series while both of them returns to battery negative terminal.

I will ask someone here since he know a lot about them.

 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1079 on: October 10, 2018, 04:36:16 pm »
For two channels in series you cannot expect that both of them provide a full range but just half, e.g. 2 x 20 V for single power input that can provide up to 40 V on output. You still have to make a "floating" control logic for at least "upper" channel.
 

Offline VEGETA

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1080 on: October 10, 2018, 05:13:22 pm »
For two channels in series you cannot expect that both of them provide a full range but just half, e.g. 2 x 20 V for single power input that can provide up to 40 V on output. You still have to make a "floating" control logic for at least "upper" channel.

If both 20v 2A then two in series will be 40v 2A and in parallel 20v 4A, I know that already since it is what all PSUs are.

but what is the floating control logic for the upper channel? In my design, we used an isolated DC-DC module to get the control logic working and so on as I remember. Now we have to get 1 per channel so we have to get 2? what if I plan to use a microcontroller with external ADC + DAC to control both channels...? how will all that fit?
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1081 on: October 10, 2018, 05:40:42 pm »
If both 20v 2A then two in series will be 40v 2A and in parallel 20v 4A, I know that already since it is what all PSUs are.

Yes, but in parallel you could go up to 40V if their single power input provide enough voltage and power.

but what is the floating control logic for the upper channel? In my design, we used an isolated DC-DC module to get the control logic working and so on as I remember. Now we have to get 1 per channel so we have to get 2? what if I plan to use a microcontroller with external ADC + DAC to control both channels...? how will all that fit?

Yes, you should deploy two isolated bias power supply for control logic each referenced to positive power channel output. If MCU/digital control is required you have to isolate it on digital (before DAC/ADC looking from digital to analog section) or analog side (after the DAC/ADC section). Digital isolation is easier and cheaper to achieve without compromising linearity/precision. SiLabs has great isolators for attractive price.
Some sort of isolation between MCU and more then one power channels is required anyway if you'd like to have two separated floating power output.
 

Offline VEGETA

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1082 on: October 10, 2018, 07:48:32 pm »
Quote
Yes, but in parallel you could go up to 40V if their single power input provide enough voltage and power.

Yes, assuming the source is powerful.

A side question: can this be achieved by 4 parallel 18650 li-ion batteries (using buck-boost converter)?

Quote
If MCU/digital control is required you have to isolate it on digital (before DAC/ADC looking from digital to analog section) or analog side (after the DAC/ADC section)

You mean powering the arduino by an isolated dc-dc converter? as well as DAC and ADC?

Quote
SiLabs has great isolators for attractive price

I only buy stuff from Aliexpress, thus I searched and found this one: ADUM1201 and ADUM1400 which is 4 channels (2 for each supply channel). Looks like it has this one from Silabs too: SI8660BA.

 Looks like it is just up to 5v but I guess this is suitable since ADC\DAC won't go above. So now I can just power the MCU via any means then get the signal (SPI,I2C) from it to this IC then to DAC. The same for ADC too. Is this method correct?

However, I guess you could use one IC per channel since you don't want to mix the voltages between them, is it correct?


Quote
Some sort of isolation between MCU and more then one power channels is required anyway if you'd like to have two separated floating power output.

Isn't this achieved already by using digital isolators between ADC\DAC and MCU for each channel? while MCU itself could be powered directly from the battery pack.

I have a design that is working in LTSPICE here in the forum, with cooperation with kelinstein if you would like to take a look.


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EDIT: I have attached the design image quickly.
« Last Edit: October 10, 2018, 09:29:04 pm by VEGETA »
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1083 on: October 11, 2018, 04:38:20 am »
A side question: can this be achieved by 4 parallel 18650 li-ion batteries (using buck-boost converter)?

I have no experience with 18650 batteries. Possibly yes to some extent since such batteries are used in Dave's uSupply.

Quote
If MCU/digital control is required you have to isolate it on digital (before DAC/ADC looking from digital to analog section) or analog side (after the DAC/ADC section)

You mean powering the arduino by an isolated dc-dc converter? as well as DAC and ADC?

Yes, your digital control (MCU+peripherals) need separated power rail, that can be floating or e.g. PE referenced.

I only buy stuff from Aliexpress, thus I searched and found this one: ADUM1201 and ADUM1400 which is 4 channels (2 for each supply channel). Looks like it has this one from Silabs too: SI8660BA.

 Looks like it is just up to 5v but I guess this is suitable since ADC\DAC won't go above. So now I can just power the MCU via any means then get the signal (SPI,I2C) from it to this IC then to DAC. The same for ADC too. Is this method correct?

However, I guess you could use one IC per channel since you don't want to mix the voltages between them, is it correct?

That's correct.

Quote
Some sort of isolation between MCU and more then one power channels is required anyway if you'd like to have two separated floating power output.

Isn't this achieved already by using digital isolators between ADC\DAC and MCU for each channel? while MCU itself could be powered directly from the battery pack.

I have a design that is working in LTSPICE here in the forum, with cooperation with kelinstein if you would like to take a look.

You have to provide isolation in all sections: analog/linear and digital. No common ground is allowed if you want two separated isolated channels or their coupling in series. That doesn't matter for parallel coupling.
 

Offline morris6

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1084 on: January 29, 2019, 07:57:40 am »
It's a bit silent here.. let's give this thread a bump. The EEZ H24005 is a great project FWIW and I have build three pieces so far.


@prasimix:

I feel a bit like the sorcerers apprentice digging into this. The possibility to open the psu-firmware project file was not presented and discussed yet, nevertheless.. 

It all started with trying to correct some typo's in the screen texts. It looked like this could be done using EEZ-Studio after opening the psu.eez-project file. I felt a bit uncertain about what I was doing, but it worked out fine. After correcting some typo's in the texts of the pages just "Build" and "Save". Several files are updated auto-magically... Then start the Arduino environment, compile and load the corrected firmware. Nice!

Next was cleaning up the small text font characters, pixel editing character by character. Same procedure.. Nice!

And then.. the degree symbol. It shows on screen as "oC" while "°C" is intended. Of course this is a "minor" issue, but a device wherein so many hours of development are invested deserves better, I think. For this a simple text correction didn't work, for several different reasons I think. Ascii code page problems, 'char' type signed or unsigned, It proved too difficult for me, I am only apprentice remember..!
So I copied a trick that is used elsewhere in the psu firmware. Also icons are addressed as text item. I created a new icon "°C" at position 151 in the small fonts section of the psu.eez-project file. Most probably you consider this as a definite "NoNo", editing this file by hand. But it worked. After changing the text string in value.cpp from "oC" to "\u0097" the new icon "°C" shows up on the display, after compile and load of course.

I took the liberty to open an issue on Github about this and uploaded the altered files there.

Some pictures of the display "Before" and "After" are posted here to get an idea of the cleaned fonts and the "°C" symbol.

Maybe these alterations can be taken along in the next firmware update.
 
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Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1085 on: January 30, 2019, 02:21:58 am »
Glad to see that someone had a time and patience to dive into the GUI project without waiting that I eventually find a time to describe a whole process (and what I've promised a few times in the past :(). Anyway, it seems that you successfully managed what you'd like to change what is a sort of proof that working with EEZ Studio ESP module is pretty intuitive. I presume that you are already find out that M2 version of EEZ Studio is needed to edit EEZ H24005 project, and this is a note for other who is willing to follow your steps.
Thanks for adding your changes into GitHub. We'll try to include that possibly in first next firmware release.
 
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Offline morris6

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1086 on: January 30, 2019, 08:32:41 am »
Yes, I was using the M2 version. You mean M3 version cannot be used yet or anymore for this purpose?
 

Offline prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #1087 on: January 30, 2019, 09:38:55 am »
Unfortunately M3 cannot be used for H24005 project, it will support only a new STM32 MCU board. But, if any issue arise with using M2 feel free to report it on GitHub and we'll try to take care of it.
 
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