I need a little technical help with a power supply ,Please

[24 track]

​

I built a specific use power supply based on An ATX computer Power supply it works beautifully ,but I need to modify my design for future consideration I do have a question for you,
I have a COOLER MASTER RS-500-PSAR-J3 power supply it reads Input 120 VAC, output DCV { +3.3V (22A) /+5V (20A) =130Watts} , { +12V1(20A) /+12V2 (20A)=360 watts} , { -12V (0.8A)=9.6Watts} , {+5VSB (2.5A) = 12.5 W} .Question is it possible to step up the -12 Volts to a higher Amperage , if I can or need to remove the +3.3 volt , 22A and modify that part of the circuit to match the -12 V circuit ?
please and thank you, ,
the difference from this pic to my unit is -12V is 0.8A,@ 9.6 Watts

 

[24 track]

I came across this article how to take +12Vdc and covert it to -12VDC , the issue I am confronted with is how much amperage will it supply . the actual on board -12VDC is 0.8 Amps @9.6 watts
The ATX PS has 12 X 12 volt runs and 12 X Ground wire so I have enough potential to do what I need to do with this circuit.

https://electronicsarea.com/12v-to-12v-dc-converter/#:~:text=This 12V to -12V DC converter circuit, gives,IC timer configured as astable multivibrator is used.

I will have to see what the 555 timer can take to give a decent amperage out put using a +12vdc source @20 amps
I may have to search out more info as the out put will be a small amperage. from the 555 timer

 

[24 track]

I found this on AliExpress for 7.69 CDN each I bought 3. I think it may work!

1.Description: It is a Dual Output Step Down Power Supply Module with input DC 13V~36V and output DC -12V and +12V.It can provide stable +/-12V output. It can maximum output 2.5A.
2.Feature: A>.Low ripple B>.High efficiency C>.Low power consumption D>.Ultra small volume E>.Fixed output voltage F>.Dual voltage output
3.Parameter: A>.Converter IC:TPS5430 B>.Input voltage DC 13V~36V C>.Output voltage DC -12V and +12V
4.Output power:30W(Need heat sink when more than 10W)
5.Conversion efficiency:>88%
6.Output ripple:<80mV
7.Work frequency:500KHz
8.Stand-by current:10mA
9.Operating Temperature:-20℃~85℃
10.Operating Humidity:5%~95%RH
11.PCB Size:50*50*18mm 4.Package: 1pcs DC-DC -12V 12V Dual Buck Step Down Power Supply Module

 

[guitar_paul1]

I'd take the rating seriously and it looks like it needs 13 in not 12. I'm not sure it would work as designed if it only receives 12v in. You need the headroom even if it is only 1 volt.
PS I wouldn't even think of modifying a switcher, so there's that.
If you have a different DC supply to feed the Ali express board AND if you can tolerate 80mV ripple, then it looks like it could work. I wouldn't run anything from Ali express anywhere near its rated amperage, though.

 

[24 track]

I'd take the rating seriously and it looks like it needs 13 in not 12. I'm not sure it would work as designed if it only receives 12v in. You need the headroom even if it is only 1 volt.
PS I wouldn't even think of modifying a switcher, so there's that.
If you have a different DC supply to feed the Ali express board AND if you can tolerate 80mV ripple, then it looks like it could work. I wouldn't run anything from Ali express anywhere near its rated amperage, though.

What I am building is a PS for euro rack , I have built one that works and supplies power to at least 30+ modules , I just want to strengthen the -12 volt rail to at least 2.0A , not a weak point in my original PS but I want to beef that up as -12 is used for digital modules.

the +12 V1 reads @ 13.09 Volts output not 12 Volts

All of the buss boards I use for the modules create the +5 volts using the +12V input and a 7805 VR and 2 caps (1uf) and diodes (n 4007) included on the Bus board so I dont have to use the +5 from the PS ( 20A worth) and can dedicate this rail to USB powered devices, but I will see if it is noisy when I apply the switcher for the -12V . I wont need the +12V from the switcher as I have enough from the PS it's self so the only tap I will use is the -12V output ,
Q: if the Ripple from the power supply is filtered and goes into the switcher that shouldn't it clean up any excess ripple ?

no I do quadruple the wires from the PS to ensure current is applied


I have bought several Ali Express units that out perform most things on the market effectively, and to be honest most aftermarket devices are the Ali Express units ( so I found out while researching this, Amazon, Ebay , Temu nothing from mouser, or Digikey) with stupid markups and tariffs/taxes applied . plus take forever to get here, I get these with in 7 days usually.

if you have a better solution I am all in as this aspect is new to me and who knows I may luck out LOL

 

[guitar_paul1]

Sounds like you've got it covered. Let us know how it all works.

 

[24 track]

Sounds like you've got it covered. Let us know how it all works.

I will, Its the only solution I can find that makes sense. If i could find a schematic to fill the gap I would try that as well. I wish I took electronic engineering in school!
thank you

 

[Peegoo]

@24 track

Years ago when I upgraded my workshop I wanted to install a simple music system that played FM radio and MP3s via BT and USB connection. I needed something small and rugged enough to survive a dusty environment. The easy and affordable answer was an automotive radio.

I needed a 12vDC power supply that could provide at least 15A to drive the four speakers mounted to the ceiling, so I worked up a plan to make one myself...and the parts cost was about the same as a ready-made PS, so I punted and got one of THESE <--Click Here




..

 

[24 track]

@24 track

Years ago when I upgraded my workshop I wanted to install a simple music system that played FM radio and MP3s via BT and USB connection. I needed something small and rugged enough to survive a dusty environment. The easy and affordable answer was an automotive radio.

I needed a 12vDC power supply that could provide at least 15A to drive the four speakers mounted to the ceiling, so I worked up a plan to make one myself...and the parts cost was about the same as a ready-made PS, so I punted and got one of THESE <--Click Here




..

I have one of those, Meanwell units, great for Skiff cases . I designed and built a 24Volt A/C powered unit for my test Case but too small for what I am going build, you can tell by the amperage I'm using. So far 21.00 CDN is the only cost .

 

[24 track]

I'm going to investigate if this series / Parallel circuit may give me what I need as well , I am just unsure if shorting a 12vdc to ground is going to give me issues , or kill the supply , this is a simplified diagram of the principal not exactly what I will do , but I will figure it out
maybe a couple of well placed heavy duty diodes will do the trick, I will get it!

 

[24 track]

I got the bucking circuits in today I tested them at 13V input on the power supply the BC out put was neg 12.08 V @ 0.035W at 1amp no load , I can adjust up to 3.5 amps for 7.00 CDN well worth it for my purposes. I can integrate this into my ATX power supply to give up to 3.5 amps more than the 0.8 amps supplied by the ATX PS alone. for a total of 4.3 amps @ neg 12volts. much more than I need to create a Euro-rack High power supply to run lots of modules in larger systems. this may work!

 

[NickK_chugchug]

I got the bucking circuits in today I tested them at 13V input on the power supply the BC out put was neg 12.08 V @ 0.035W at 1amp no load , I can adjust up to 3.5 amps for 7.00 CDN well worth it for my purposes. I can integrate this into my ATX power supply to give up to 3.5 amps more than the 0.8 amps supplied by the ATX PS alone. for a total of 4.3 amps @ neg 12volts. much more than I need to create a Euro-rack High power supply to run lots of modules in larger systems. this may work!

View attachment 1385113

What you have, as a design, is quite standard. Wall AC -> SMPS -> DC bus -> number of smaller switchers that then customise voltage and load.

As long as you have adequate switching filtering it will be relatively quiet. Low loads may result in some switchers altering the switching speed to be more efficient, that can lead to noise appearing further down the frequency range and it makes simple noise filtering inefficient.

The only issue you may find is that some SMPS designs have problems operating with zero load. Same with the small DC-DC converters. So just check what the minimum load that it can safely regulate is.

I opened up my Tone City 5 independent pedal supply - it basically has the same as your design:

Wall wart 12V dc switcher -> internal switcher drives a small transformer with taps for each pedal supply -> independent supply section then has buck converter to reduce the voltage down to 9V and it passes through inductor filtering etc.

I couldn't see if it had a LDO voltage regulator but that's an option for this sort of thing as it reduces the switching noise up to about 1MHz (although best <100Khz) and can cope with variable switching speeds, after that you're into ferrites.

I've used a number of LDOs and voltage regulators you could then use to drop the 12V to 9V and lower the noise (power supply rejection, PSRR):
3042 LDO - lower current at 200mA each, you'll get about -90dB PSRR at 500KHz
3080 LDO - higher current capacity into the 1A IIRC, you'll see around -30dB PSRR at 500KHz
LM317 - trusty old school voltage regulator, 1A IIRC current capability but only -10dB PSRR at 500KHz.

Just be careful of the layout for the 3042 it should have positive voltage guard shielding around the SET pin to keep the noise down.

 

[24 track]

What you have, as a design, is quite standard. Wall AC -> SMPS -> DC bus -> number of smaller switchers that then customise voltage and load.

As long as you have adequate switching filtering it will be relatively quiet. Low loads may result in some switchers altering the switching speed to be more efficient, that can lead to noise appearing further down the frequency range and it makes simple noise filtering inefficient.

The only issue you may find is that some SMPS designs have problems operating with zero load. Same with the small DC-DC converters. So just check what the minimum load that it can safely regulate is.

I opened up my Tone City 5 independent pedal supply - it basically has the same as your design:

Wall wart 12V dc switcher -> internal switcher drives a small transformer with taps for each pedal supply -> independent supply section then has buck converter to reduce the voltage down to 9V and it passes through inductor filtering etc.

I couldn't see if it had a LDO voltage regulator but that's an option for this sort of thing as it reduces the switching noise up to about 1MHz (although best <100Khz) and can cope with variable switching speeds, after that you're into ferrites.

I've used a number of LDOs and voltage regulators you could then use to drop the 12V to 9V and lower the noise (power supply rejection, PSRR):
3042 LDO - lower current at 200mA each, you'll get about -90dB PSRR at 500KHz
3080 LDO - higher current capacity into the 1A IIRC, you'll see around -30dB PSRR at 500KHz
LM317 - trusty old school voltage regulator, 1A IIRC current capability but only -10dB PSRR at 500KHz.

Just be careful of the layout for the 3042 it should have positive voltage guard shielding around the SET pin to keep the noise down.

Thank you for your reply

On the redesign of the ATX units I place a 50 watt 8ohm resister across the pos 5 volt rail to ground to ensure a proper load at all times. this worked very well with my first build unit and no issues at all , but is precautionary .

I do not need the pos 3 volt rail so i will remove all the tags for that which is too bad because it is 22watts output.

For the digital parts of the euro rack modules I need both positive and neg 12volts , the positive portions are fine at 40 amps total @360 watts total for the +12volt (1) and +12volt (2) output busses ( both read at 13.08 volts DC out enough to drive the bucking circuit).
Now the negative 12volt rail is only 0.8 amps off the internal power rail (the single blue wire in the bundle) so by adding the Bucking circuit I can get another 3.5 amps of power to the negative 12volts for a total of a potential 4.3 amps which is more than enough to run about 40 digital modules with op amps etc. ( I also build my own modules and buss boards for this)

The Meanwell option power supplies that are standard in euro rack can get costly when building a large system because it may take several units to do the job, so by using an ATX supply that you can get for next to nothing in old tower PCs , with a little ingenuity, a resister and a 7.00 bucking circuit , problem solved, and power to spare.

 

[NickK_chugchug]

Thank you for your reply

On the redesign of the ATX units I place a 50 watt 8ohm resister across the pos 5 volt rail to ground to ensure a proper load at all times. this worked very well with my first build unit and no issues at all , but is precautionary .

I do not need the pos 3 volt rail so i will remove all the tags for that which is too bad because it is 22watts output.

For the digital parts of the euro rack modules I need both positive and neg 12volts , the positive portions are fine at 40 amps total @360 watts total for the +12volt (1) and +12volt (2) output busses ( both read at 13.08 volts DC out enough to drive the bucking circuit).
Now the negative 12volt rail is only 0.8 amps off the internal power rail (the single blue wire in the bundle) so by adding the Bucking circuit I can get another 3.5 amps of power to the negative 12volts for a total of a potential 4.3 amps which is more than enough to run about 40 digital modules with op amps etc. ( I also build my own modules and buss boards for this)

The Meanwell option power supplies that are standard in euro rack can get costly when building a large system because it may take several units to do the job, so by using an ATX supply that you can get for next to nothing in old tower PCs , with a little ingenuity, a resister and a 7.00 bucking circuit , problem solved, and power to spare.

Just on the ATX power supply.

On the input side of the ATX you'll have power factor correction (PTC), thus smooths the power draw over the full input sine wave of input wall AC. This is needed to prevent a sharp spike of power draw, it also requires the ATX to have a minimum amount of harmonics generated back into the power (the power companies start having power failures due to damage caused by harmonics).
The PTC is like a switcher in that it switches to limit the current draw within the sine wave, but it will switch off if the DC link bus inside is at full capacity (ie the caps are charged an the voltage is at it's maximum).
So you may need a minimal draw from the non-utilised output power rails to ensure that the PTC has enough work todo. If it doesn't it could switch off causing more noise on the wall power inlet which then transfers to your other audio equipment.

Meanwell are pretty decent. I have a couple of SMPS supplies (one runs 24/7 on the pond filter) and the other is a medical grade 19Vdc supply that I used for audio which provides both low ripple and low noise due to the additional filtering.

I'm tempted to create a 19Vdc->12Vdc regulated supply to remove the 50Hz hum I noted on my pedals but the majority of this is through the air interference. Shielding should help that (I know it sounds odd shielding power supply wires!) but this is the hump of noise that my pedals add and you'll note that 50Hz hum and the harmonic:

Note: this is dead silent on the low gain of my marshall, in the cranked high gain the amp and this are relatively noisy with the tube screamer increasing gain too.

It's worth connecting your audio output of your pedal board to a USB interface with 192KHz and 24bit resolution (like the minifuse1 or scarlet etc), then remove the guitar input into the first pedal. I'd probably remove the high gain dirt pedal just for the measurements.
Measure the noise using something like the RTA setting in Room EQ Wizard (REW). 192Khz means 192,000 samples/sec which means from sampling theory gives a range of 0-96KHz and relatively sensitive to give a low noise floor of the measurements.
It won't be fast enough to detect some of the switcher noise for some buck converters that operate at 500KHz but you will spot some noise your PSU adds in the audio band if there's any.

To spot the 500KHz noise you'd need to use a scope but the issue is a scope is low resolution (ie not as sensitive to detecting noise) but would allow you to spot really noisy output up to the bandwidth of the scope. My little Siglent will do up to 200MHz but as it's only 8 bit and relatively noisy, it will only spot noise at around -80dB, although you can use the scope front end to amplify that and go lower it will start adding it's own noise and you'll not have accurate peak measurements (we only have 8bits of dynamic range) and that may get you down to around -120dB.
Just a safety point - don't plug a scope into the mains side or the switching element - even if the front end can tolerate 400Vpp. There's no guarantee you'll experience any transients and those can be well above the front end of the scope.

 

[24 track]

Just on the ATX power supply.

On the input side of the ATX you'll have power factor correction (PTC), thus smooths the power draw over the full input sine wave of input wall AC. This is needed to prevent a sharp spike of power draw, it also requires the ATX to have a minimum amount of harmonics generated back into the power (the power companies start having power failures due to damage caused by harmonics).
The PTC is like a switcher in that it switches to limit the current draw within the sine wave, but it will switch off if the DC link bus inside is at full capacity (ie the caps are charged an the voltage is at it's maximum).
So you may need a minimal draw from the non-utilised output power rails to ensure that the PTC has enough work todo. If it doesn't it could switch off causing more noise on the wall power inlet which then transfers to your other audio equipment.

Meanwell are pretty decent. I have a couple of SMPS supplies (one runs 24/7 on the pond filter) and the other is a medical grade 19Vdc supply that I used for audio which provides both low ripple and low noise due to the additional filtering.

I'm tempted to create a 19Vdc->12Vdc regulated supply to remove the 50Hz hum I noted on my pedals but the majority of this is through the air interference. Shielding should help that (I know it sounds odd shielding power supply wires!) but this is the hump of noise that my pedals add and you'll note that 50Hz hum and the harmonic:
View attachment 1389589
Note: this is dead silent on the low gain of my marshall, in the cranked high gain the amp and this are relatively noisy with the tube screamer increasing gain too.

It's worth connecting your audio output of your pedal board to a USB interface with 192KHz and 24bit resolution (like the minifuse1 or scarlet etc), then remove the guitar input into the first pedal. I'd probably remove the high gain dirt pedal just for the measurements.
Measure the noise using something like the RTA setting in Room EQ Wizard (REW). 192Khz means 192,000 samples/sec which means from sampling theory gives a range of 0-96KHz and relatively sensitive to give a low noise floor of the measurements.
It won't be fast enough to detect some of the switcher noise for some buck converters that operate at 500KHz but you will spot some noise your PSU adds in the audio band if there's any.

To spot the 500KHz noise you'd need to use a scope but the issue is a scope is low resolution (ie not as sensitive to detecting noise) but would allow you to spot really noisy output up to the bandwidth of the scope. My little Siglent will do up to 200MHz but as it's only 8 bit and relatively noisy, it will only spot noise at around -80dB, although you can use the scope front end to amplify that and go lower it will start adding it's own noise and you'll not have accurate peak measurements (we only have 8bits of dynamic range) and that may get you down to around -120dB.
Just a safety point - don't plug a scope into the mains side or the switching element - even if the front end can tolerate 400Vpp. There's no guarantee you'll experience any transients and those can be well above the front end of the scope.

So you may need a minimal draw from the non-utilised output power rails to ensure that the PTC has enough work todo. If it doesn't it could switch off causing more noise on the wall power inlet which then transfers to your other audio equipment.

I have 2 mean well supplies for my smaller racks , the ATX has tons more power

As I mentioned I placed a 50 watt 8 ohm resister across the +5 volt rail to ground to ensure there is load on that rail as needed.
The purpose of this project is to use a single power source to handle up to 30-40 Euro-Rack modules , I have an ATX unit I made in operation now and it has tons of power and current. the Issue i want to address is the ATX only has 0.8 Amps at -12volts (at 10Watts) when the +12 volt rail is 23.0 Amps and 23.0 Amps on the +5 Volts. The Buss boards I created for the modules all have specific filter caps to filter ripple specifically to the digital modules and can produce an additional +5 volt with a 7805 regulator. What I would like to do is enhance the -12 volt rail. The bucking unit will do that, and as tested was right on the money , giving me another 3.5 amps of current on the -12volt rail for a total of approximately 40 watts of power.

I am open to alternatives to creating an enhanced -12 volts from the ATX directly , the largest I have seen for ATX is 1 amp but I have not been able to find a specific Schematic on the circuit to look at all my options .

 

[NickK_chugchug]

So you may need a minimal draw from the non-utilised output power rails to ensure that the PTC has enough work todo. If it doesn't it could switch off causing more noise on the wall power inlet which then transfers to your other audio equipment.

I have 2 mean well supplies for my smaller racks , the ATX has tons more power

As I mentioned I placed a 50 watt 8 ohm resister across the +5 volt rail to ground to ensure there is load on that rail as needed.
The purpose of this project is to use a single power source to handle up to 30-40 Euro-Rack modules , I have an ATX unit I made in operation now and it has tons of power and current. the Issue i want to address is the ATX only has 0.8 Amps at -12volts (at 10Watts) when the +12 volt rail is 23.0 Amps and 23.0 Amps on the +5 Volts. The Buss boards I created for the modules all have specific filter caps to filter ripple specifically to the digital modules and can produce an additional +5 volt with a 7805 regulator. What I would like to do is enhance the -12 volt rail. The bucking unit will do that, and as tested was right on the money , giving me another 3.5 amps of current on the -12volt rail for a total of approximately 40 watts of power.

I am open to alternatives to creating an enhanced -12 volts from the ATX directly , the largest I have seen for ATX is 1 amp but I have not been able to find a specific Schematic on the circuit to look at all my options .

Ok, I had envisaged a small amount of power draw.. Now I understand..

 

[24 track]

Ok, I had envisaged a small amount of power draw.. Now I understand..

Thank you for your input, i do appreciate it . It's one of those questions where I wish I had some one in the know bounce the ideas off of.
I tried Mr. Carlson's Lab on you tube but was directed to his Pay-tron, LOL , you know you give me money and I may answer your inquiry some what. LOL.

the ATX I have ear marked for this has 12 X +12 volt runs and 12 X ground rails , and 12 X +5 volt runs but only 1X -12 volt runs
so you can see my concern . the +5 volts I can supply from the bus boards , so that leaves me with 20 Amps of +5 volts to power USB devices externally ..............so close so far away, LOL ( I will remove all the 12 X 3.3 Volt runs as they are not being used.)

 

[NickK_chugchug]

Thank you for your input, i do appreciate it . It's one of those questions where I wish I had some one in the know bounce the ideas off of.
I tried Mr. Carlson's Lab on you tube but was directed to his Pay-tron, LOL , you know you give me money and I may answer your inquiry some what. LOL.

the ATX I have ear marked for this has 12 X +12 volt runs and 12 X ground rails , and 12 X +5 volt runs but only 1X -12 volt runs
so you can see my concern . the +5 volts I can supply from the bus boards , so that leaves me with 20 Amps of +5 volts to power USB devices externally ..............so close so far away, LOL ( I will remove all the 12 X 3.3 Volt runs as they are not being used.)

On the redesign of the ATX units I place a 50 watt 8ohm resister across the pos 5 volt rail to ground to ensure a proper load at all times. this worked very well with my first build unit and no issues at all , but is precautionary .

I do not need the pos 3 volt rail so i will remove all the tags for that which is too bad because it is 22watts output.

Boost converter will (reducing current) drive 5V with that 3v3 rail. However .. you may need a constant load or the chain of switchers ends up as a problem.

Without a picture I'm finding it difficult to visually what your need I and how the supplies fit. I'll point some things out:

For the digital parts of the euro rack modules I need both positive and neg 12volts , the positive portions are fine at 40 amps total @360 watts total for the +12volt (1) and +12volt (2) output busses ( both read at 13.08 volts DC out enough to drive the bucking circuit).

Ok here we may have an issue.

The ±5V from the TPS54x0 board work because the switchers are configured in such a way (buck/boost) to drop the voltage negative on one side. TI's data sheet has detail of both the buck positive and the buck/boost negative reference examples - it look like they've just implemented that.

I take it you're running a second switcher with the 12V line into a second board for 12V output. Issue here is that you're measuring low/no load at 13.08V? This means under full load that will drop and you may find you're not getting 12V unless your buck/boosting both positive and negative sides to get +12V and -12V.

Now the negative 12volt rail is only 0.8 amps off the internal power rail (the single blue wire in the bundle) so by adding the Bucking circuit I can get another 3.5 amps of power to the negative 12volts for a total of a potential 4.3 amps which is more than enough to run about 40 digital modules with op amps etc. ( I also build my own modules and buss boards for this)

So you want to connect the negative switcher and negative 12V power rail together?

This I would not do. We don't know enough about the design or control circuits to say if this is feasible.

Switcher in parallel with each other need correct current loop designs (ie output and return) and that their respective control circuits work together to prevent overloading one area of the system.

I know Meanwell have SMPS power supplies that explicitly have control lines that are tied together so the SMPSs can work in parallel correctly. The power load is then balanced correctly over the SMPS modules. If one is taken out of service, the other SMPS then increase their output, and vice versa when it's brought back on line the SMPS balance automatically.

I have not seen the capability in the ATX supply, let alone working with external simple switcher boards.

Short answer is - I wouldn't do this.

The more devices you have in parallel, or series, the more you're going to find you'll have noise on the power. When I did my ADC power supply for the clock, clock buffer and I2C isolation, I used inductor and caps to minimise the 24MHz noise and keep that noise as close to the source as possible (it also means less current loops). Your opamps etc should have local supplies to reduce the current loops for the signal coming through the power supply pins to the respective chip ground pins.

 

[24 track]

I hope this may give you an idea of what I am doing here , I used this video as a template for my first power supply tons of info here
I hope it's not too long but he does explain in great detail , and my first attempt works flawlessly . The ATX I have for this project has been tested to spec and exceeds the what the label reads.

one thing I added that is not in the video My ground ,+12, -12 Volt lines I used up 3-4 +12 volts leads to combined together to ensure proper currents , same with the Ground but I only had 1 line for the -12 Volts ( Blue wire) . the wire harness I built is heavier wire to accommodate the current draw.

I take it you're running a second switcher with the 12V line into a second board for 12V output. Issue here is that you're measuring low/no load at 13.08V? This means under full load that will drop and you may find you're not getting 12V unless your buck/boosting both positive and negative sides to get +12V and -12V.

negative, I was thinking on just beefing up the -12volts if I need to , I have a ton of +12volts but with the additional potential 2.5 amps on the negative output from the board , it will supplement the 0.8amps on the ATX - 12v output. later today I will show you the buss board I built it has provisions for 18 more modules and I can daisy chain the for another 18 to 36 at least .



this an older pic of the system I built you can see the ATX PS on the right hand side (Red and Green LEDs) , this is much bigger now hence the expansion at least 20-40 more modules .

the first post in this thread has the specs for the ATX I plan to use on the label of the unit

here are the pics of power buss boards i am using , I do not need the +5volt rail as it is produced from the +12volts through the 7805 regulator on the board, I can drive about 3 of these boards 18 outputs each with no issues on the ATX , but I wish I had access to more -12Volts

 

[Skyhook]

I wouldn't run anything from Ali express anywhere near its rated amperage, though.

This!