Author Topic: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)  (Read 351649 times)

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Online prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #825 on: November 03, 2017, 01:37:17 pm »
Touch screen in current design is the only way that guarantee AC softstart (due to Arduino "feature" #96).

Some brainstorming here about a possible workaround for this startup issue.

The idea is to use the voltage monitoring in IC31 TPS3705-33D to delay the control of PWR_DIRECT and PWR_SSTART and “wait out” the 10ms pulse from the Arduino.
PFO will be held low and block PWRSS and PWRDIR until R1 has charged up C to the level that input PFI goes above 1.25V.
From the datasheet (see picture), this level is calculated as: VTH=((R1+R2)/R2)x1.25

Have I missed something?

I've checked this issue once again. Don't know if that is Arduino issue or something else. Here is how it looks when front panel switch is used to power up Arduino shield board:

.

SS (blue) and DIR (magenta) traces are measured on gates of Q32 and Q33. RST (cyan) is measured directly on the Ardiuno Due pin (i.e. how MCU see RESET signal). With different time base we can see that glitch lasts 25 ms:



IC29A gate (AND) should is used to prohibit activation of softstart outputs but it seems that PWRSS and PWRDIR needs another 25 ms to be set to low state after reset condition. If we measure concurrently that two signals and outputs to Q32 and Q33 we will get this:



... and schematic with trace descriptions:



Therefore your suggestion with power-up delay should work only if it's somehow added to end of RESET pulse (e.g. additional 30 or more milliseconds).

Offline texaspyro

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #826 on: November 03, 2017, 03:47:35 pm »
Ha, ha, you can but don't expect precision in ppm :).

Well, I do expect ppm level precision,  but life seldom meets expectations.    :-DD
 
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Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #827 on: November 03, 2017, 08:32:55 pm »
Some questions here about CC in serial mode and the power limit warning.
Coupling: Serial
Voltage: 80V
Load: Resistor ~3Ohm

Current limit=1A Both channels are in CC mode
Vout=2,79V
Vset=80,00V
P=2,78W

CL=1,5A - CH1 in CC mode, CH2 in CV. Why?
Vout=4,17V
Vset=42,09V - Why?
P=6,26W

CL=3,9A - CH1 in CC mode, CH2 in CV.
Vout=10,02V
Vset=80,00V
P=36,06W
Warning: Power limit exceeded. - Why?


I can see that the theoretical power will exceed 310W @ 80V 3,9A, but in CC mode in this case we are far away from that.

Why does CH2 go into CV and Vset drops down from 80V?

 

Online prasimix

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #828 on: November 03, 2017, 08:39:38 pm »
Upper power limit is checking when you set new value, not in "runtime". So, if you don't need/expect more then e.g. 40 W then you don't to set 310 W, or not?
Regarding channels coupling did you have a chance to watch this video?


Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #829 on: November 03, 2017, 09:22:09 pm »
Thanks!  :-+
I have seen that video, but it was about then you released it, so obviously I didn’t remember it all correctly... 

Another observersion:
With the output On I am able to go “over” the 310W limit (e.g. over 4A@80V) if I use the steps. It is also possible with the rotary encoder if it’s done slowly, about max one step per second.
If it has been set “too high”, the keypad is the only way to go back down again if the output is Off. Step, slide and rotary encoder are all blocked by the “Power limit exceeded” warning.
If the output is On it is possible to go back down the same way it is possible to go up over the limit.
 
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #830 on: November 03, 2017, 10:34:47 pm »
Therefore your suggestion with power-up delay should work only if it's somehow added to end of RESET pulse (e.g. additional 30 or more milliseconds).

It looks like there is ~200ms from 3V3 is live to RST=1 and after that we need another 25ms delay of the and gate. Right?

A quick test on the bench with 100k for R1 and R2 and 1uF for C gave a delay of about 60ms until 1.25V was reached.

If R1 is feed from RST out on IC31 (pin.7) instead of the 3V3 rail, the 60ms delay will not start until RST goes high.
 
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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #831 on: November 04, 2017, 09:22:35 am »
Thanks!  :-+
I have seen that video, but it was about then you released it, so obviously I didn’t remember it all correctly... 

Another observersion:
With the output On I am able to go “over” the 310W limit (e.g. over 4A@80V) if I use the steps. It is also possible with the rotary encoder if it’s done slowly, about max one step per second.
If it has been set “too high”, the keypad is the only way to go back down again if the output is Off. Step, slide and rotary encoder are all blocked by the “Power limit exceeded” warning.
If the output is On it is possible to go back down the same way it is possible to go up over the limit.

Hm, this is interesting. I tried it just now, outputs are coupled in series, current is set to 4 A and, output is on, and with slowly increasing output voltage I'm repeatedly get error message on attempt to go over 77.50 V that is right (77.5 x 4 = 310). I need more input here.

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #832 on: November 04, 2017, 09:39:58 am »
Thanks!  :-+
I have seen that video, but it was about then you released it, so obviously I didn’t remember it all correctly... 

Another observersion:
With the output On I am able to go “over” the 310W limit (e.g. over 4A@80V) if I use the steps. It is also possible with the rotary encoder if it’s done slowly, about max one step per second.
If it has been set “too high”, the keypad is the only way to go back down again if the output is Off. Step, slide and rotary encoder are all blocked by the “Power limit exceeded” warning.
If the output is On it is possible to go back down the same way it is possible to go up over the limit.

Hm, this is interesting. I tried it just now, outputs are coupled in series, current is set to 4 A and, output is on, and with slowly increasing output voltage I'm repeatedly get error message on attempt to go over 77.50 V that is right (77.5 x 4 = 310). I need more input here.
Try to increase current instead of voltage in cc mode.

Skickat från min Nexus 6 via Tapatalk

 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #833 on: November 04, 2017, 10:01:09 am »
Therefore your suggestion with power-up delay should work only if it's somehow added to end of RESET pulse (e.g. additional 30 or more milliseconds).

It looks like there is ~200ms from 3V3 is live to RST=1 and after that we need another 25ms delay of the and gate. Right?

A quick test on the bench with 100k for R1 and R2 and 1uF for C gave a delay of about 60ms until 1.25V was reached.

If R1 is feed from RST out on IC31 (pin.7) instead of the 3V3 rail, the 60ms delay will not start until RST goes high.

We are almost there. Only what is missing is AND-ing instead of OR-ing PFO and WDO outputs.

EDIT: without introducing more components maybe we should tied permanently WDO to MR input (JP8 is out) and connect PFO to IC29A input.
« Last Edit: November 04, 2017, 10:09:47 am by prasimix »
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #834 on: November 04, 2017, 10:19:01 am »
Therefore your suggestion with power-up delay should work only if it's somehow added to end of RESET pulse (e.g. additional 30 or more milliseconds).

It looks like there is ~200ms from 3V3 is live to RST=1 and after that we need another 25ms delay of the and gate. Right?

A quick test on the bench with 100k for R1 and R2 and 1uF for C gave a delay of about 60ms until 1.25V was reached.

If R1 is feed from RST out on IC31 (pin.7) instead of the 3V3 rail, the 60ms delay will not start until RST goes high.

We are almost there. Only what is missing is AND-ing instead of OR-ing PFO and WDO outputs.

EDIT: without introducing more components maybe we should tied permanently WDO to MR input (JP8 is out) and connect PFO to IC29A input.
Why AND-ing PFO and WDO? Anyone should be able to shut off the power independently, or?
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #835 on: November 04, 2017, 10:22:33 am »
Yes but, WDO is on the power-up high and in that way cancels effect of delayed PFO. With minimum additional components it should looks like this:



WDO will now generate reset if watchdog failed (i.e. firmware stuck).

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #836 on: November 04, 2017, 11:22:49 am »
Yes but, WDO is on the power-up high and in that way cancels effect of delayed PFO. With minimum additional components it should looks like this:
WDO will now generate reset if watchdog failed (i.e. firmware stuck).

The two diodes on PFO and WDO are in the wrong way in my last sketch. See new one below.
With the diodes in the opposite way PFO and WDO should be able to pull the AND-gate (pin 2 on IC29A) low independently of each other.
Am I missing something?

Your solution will work, but is a little harder to hack in on an existing board, and will not be able to shut down the power in case of stuck firmware (WDT).

 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #837 on: November 04, 2017, 11:28:43 am »
You're right, but I'll stay with solution in my previous post. No need to introduce two more components. I think that we also we don't need 100K on previous R160 position (if diode are not using). PFO and WDO are not open collector outputs.

I'll try to modify my Arduino shield and let you know how it looks like.
« Last Edit: November 04, 2017, 11:31:35 am by prasimix »
 

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #838 on: November 04, 2017, 11:47:01 am »
You're right, but I'll stay with solution in my previous post. No need to introduce two more components. I think that we also we don't need 100K on previous R160 position (if diode are not using). PFO and WDO are not open collector outputs.

I'll try to modify my Arduino shield and let you know how it looks like.
Right, R160 pollup is not needed in your version.
What is D21 needed for?
Do we have a strong high level on the anode to charge up the cap?
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #839 on: November 04, 2017, 12:11:06 pm »
D21 is added that IC31 output not interfere with reset generating by Arduino IDE during before firmware upload is begin. I'll check if that side of diode is appropriate to charge capacitor.

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #840 on: November 04, 2017, 01:56:46 pm »
D21 is added that IC31 output not interfere with reset generating by Arduino IDE during before firmware upload is begin. I'll check if that side of diode is appropriate to charge capacitor.
It looks like IC31 is capable to drive several mA.
That will be enough to charge the cap directly from pin2 (reset) on IC31.
What was your thought then getting the charging from outside (anode) D21?
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #841 on: November 04, 2017, 02:35:44 pm »
What was your thought then getting the charging from outside (anode) D21?

To cover last possible but unlikely scenario: that someone use Arduino Due on-oboard reset switch instead of SW3 (when. e.g. when top cover is open) :D. I just finished modification and on the power up you can see that SS and DIR are free of glitch:



If I'm using Arduino reset instead of SW with PFI voltage divider connected to D21 cathode glitch is still there:



... but with connection to D21 anode we have clean situation like in power up scenario:



Here is how modification looks like if someone is interesting to add this improvement:

1. IC31 is removed and pin 4 is disconnected from the GND:



2. JP8 position is changed:



3. Pin 5 is connected to other side of the JP8 (yellow wire), combination of  2 x 100K and 1uF is soldered to pin 4 (one leg to GND on supercap, another on D21 anode):



Thanks Pjoms once again for your assistance.


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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #842 on: November 04, 2017, 02:58:46 pm »
Thanks!  :-+
I have seen that video, but it was about then you released it, so obviously I didn’t remember it all correctly... 

Another observersion:
With the output On I am able to go “over” the 310W limit (e.g. over 4A@80V) if I use the steps. It is also possible with the rotary encoder if it’s done slowly, about max one step per second.
If it has been set “too high”, the keypad is the only way to go back down again if the output is Off. Step, slide and rotary encoder are all blocked by the “Power limit exceeded” warning.
If the output is On it is possible to go back down the same way it is possible to go up over the limit.

Hm, this is interesting. I tried it just now, outputs are coupled in series, current is set to 4 A and, output is on, and with slowly increasing output voltage I'm repeatedly get error message on attempt to go over 77.50 V that is right (77.5 x 4 = 310). I need more input here.
Try to increase current instead of voltage in cc mode.

Skickat från min Nexus 6 via Tapatalk

Tried but still without success. I set voltage to 80 V, connect 16R4 load to be in CC mode and starts to change current and cannot go over 3.87 A.

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #843 on: November 04, 2017, 03:30:06 pm »
Tried but still without success. I set voltage to 80 V, connect 16R4 load to be in CC mode and starts to change current and cannot go over 3.87 A.

This phenomenon seems to rise with lower load resistance.
At 15 ohm I also got a stable behaviour, but under ~10 ohm it went easier and easier.
With a 3 ohm load I have no problem to reproduce it.
 
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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #844 on: November 05, 2017, 07:28:11 am »
Tried but still without success. I set voltage to 80 V, connect 16R4 load to be in CC mode and starts to change current and cannot go over 3.87 A.

This phenomenon seems to rise with lower load resistance.
At 15 ohm I also got a stable behaviour, but under ~10 ohm it went easier and easier.
With a 3 ohm load I have no problem to reproduce it.

I can confirm this with smaller load: tested with 2R, voltage set to 80 V, in CC mode I can slowly increase current up to 5 A (i.e. 400 W). Do you mind to open this as new issue in GitHub for firmware?

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #845 on: November 05, 2017, 10:15:55 am »
I can confirm this with smaller load: tested with 2R, voltage set to 80 V, in CC mode I can slowly increase current up to 5 A (i.e. 400 W). Do you mind to open this as new issue in GitHub for firmware?

Ok. #183
 
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Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #846 on: November 05, 2017, 01:15:01 pm »
I can confirm this with smaller load: tested with 2R, voltage set to 80 V, in CC mode I can slowly increase current up to 5 A (i.e. 400 W). Do you mind to open this as new issue in GitHub for firmware?
Ok. #183

More observersions, setup same as described above:
Coupling: Serial
Volt: 80V
Enable output and increase the current in cc-mode.


Load 0-4.7 Ohm.
Keypad or SCPI-command can be used to go back under power limit level with no load or output off.

Current can be set from about 1.5-3A to anything up to 5A using keypad or SCPI-command without power limit warning.
If current is set to something below 1-1.5A power limit warning occur as expected. This limit does not seem to be fixed. Sometimes I was able to jump directly from 1.1A to 5A without any warning, but sometimes I have to go from something like 2-3A. From 3A to 5A seems to always work.


Load 10 ohm.
PSU shut down due to “CH2 fault detected” then jumping from 3A to 5A using keypad.

Log:
**ERROR: -243,"CH2 fault detected"
**ERROR: -350,"Queue overflow"
**ERROR: -243,"CH2 fault detected"
**ERROR: -350,"Queue overflow"
**ERROR: -243,"CH2 fault detected"
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #847 on: November 05, 2017, 01:17:32 pm »
Are you receiving **ERROR: -243,"CH2 fault detected" also in CV mode?

Offline Pjoms

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #848 on: November 05, 2017, 01:23:41 pm »
Are you receiving **ERROR: -243,"CH2 fault detected" also in CV mode?
CH1 is in CC and CH2 in CV, but CH2 also goes into CC when changing current to 5A just before the PSU shut down.
 

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Re: DIY SCPI programmable dual channel bench PSU 0-50V/3A (now EEZ H24005)
« Reply #849 on: November 05, 2017, 01:25:20 pm »
OK, it seems that we need to improve "balancing algorithm" for channels coupled in series.


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