Combining PSU rails for lab power supply? Answered

I recently received 2 old computers from friends for tinkering purposes. I'd like to take their PSUs and create a power supply for projects. However, they only have max outputs of 110W. So, I have a few questions: 1.) Is it possible to combine rails? 2.) Is it safe? 3.) What kind of power increase would I be seeing? Please try to answer all 3 individually.

Question by General Eggs   |  last reply


Turning on an old Psu

Hey there, I got this old PSU, a Delta DPS-350EB-3 from an HP NetServer. I'm trying to make a lab power supply out of it, i just can't get it to power on. There's a blue wire bundled with a ground that when shorted will power the psu for a second then shut it back off.  I tried to put a load on the 5v & 12v with no success. Anyone got an idea? Thanks

Topic by wbzial   |  last reply


Is it possible to wire computer PSU's in series to achieve a higher voltage? If so, how can it be done?

I want to make bench top PSU's out of old computer power supplies and I want a 24v output as well as the typical outputs, but I don't want to put a transformer on it that could only handle so much current (I might want to run some bigger motors off it)

Question by The Ideanator   |  last reply


Computer PSU wire question? Answered

Hi all, I want to turn an old computer PSU into a lab bench PSU.  After cutting all the connectors at the end of the cables, I've noticed that some of the common (black) wires were made of copper, while some of them were made of nickel \ aluminum (Silverish). The same is true for the +5V (red) cables. It's not the first PSU I noticed that had the different materials, and I was wondering: 1) Why are there two different kinds of wire? 2) Is it OK to ignore the wire material and just splice all the blacks together, and all the reds together? Thanks!

Question by Morgantao   |  last reply


ATX PSU to Work Bench PS - Adjustable Voltage and Current question

I am working on converting an old 600W ATX PSU to a bench power supply for me to use for some lab work.  Not everything that I will be plugging into it will have built in current limiting capabilities.  The guide/setup i found on here that I will most likely be following are:  https://www.instructables.com/id/DIY-PSU-into-Bench-Power-supply/  &  http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply The first link is how I would like mine to end up looking. My PSU is rated as: +3.3V @ 32A +5v @ 50A +12v @ 24A -12v @ 1A -5v @ .5A My end goal is to be able to control the voltage and current output from each binding post.  I will be hooking up a multimeter to this as well and am thinking that i could control what it monitors by some dipswitch setup or switching setup(as far as to which binding posts it's monitoring). I do understand that V = IR.  So keeping 5v but only wanting 3A, i would increase the resistance which is why at first i thought i could play a POT in the circuit.  However after seeing how the voltage regulation was hooked up, I am confused how to do so now since it was connected in the fashion i thought i would need to control the current.  (https://www.instructables.com/files/orig/F2D/LMFU/FYYNECNH/F2DLMFUFYYNECNH.jpg) I would probably use a LM338 since it would allow for more current but again, i would love to be able to have the full 50A available all at one shot but i don't think those IC's allow for that. I am extremely new to all of this and am still learning as well, so if i was able to communicate what i am looking to do correctly and you have a way of explaining it to me, a picture would be awesome if you have the time to create one. :D TYIA for any suggestions.

Topic by agentc0re   |  last reply


24v power supply out of computer psus?

So i watched a video a while ago, it was about turning a psu into a lab bench psu. The guy said you can run 2 of them together making 24v, having to cut the (earth)ground on one of them and have them running to the same outlet. So i can have the 24v but what about 3.3v and the 5v? im not really sure how those would work, wouldnt they just stay at their normal voltage levels?

Question by knexsuperbuilderfreak   |  last reply


Broken PSU? Answered

 I recently seen an instructable on converting an old computer PSU into a lab power supply. I followed it correctly, connecting the orange wire to the brown, the green to black and a 10W Wirebound resistor across red and black. The PSU turns on and all of the voltage rails work (although some are out by +-.75V sometimes), but I can hear a faint screeching noise and the fan doesn't spin.  I though the screeching may be normal because all I normally hear is the fan, is this okay. The fan is rated at 12V 0.3A, but when I measured the voltage over it, it was only 3.4V, why is this and how do I fix it. Any help appreciated, Thanks. 

Question by R055_28   |  last reply


Can I make these projects to sell?

I want to offer an instructable building service (through the instructables forum) for people who want a project but can't build it. I am going to have a list of projects that I am comfortable building and will build for people. These are the instructables I am going to start with: https://www.instructables.com/id/Make-a-Joule-Thief/ https://www.instructables.com/id/ATX--%3E-Lab-Bench-Power-Supply-Conversion/ https://www.instructables.com/id/Music-LED-Light-Box/ Can someone tell me which of these I can use. Also how to tell on any instructable whether or not I can use it. Also if anybody has any other sugestion for this endeavour I would apreciate it. Thanks

Question by nurdee1   |  last reply


Having trouble measuring voltage with arduino.

I have posted this question before but I’ve made a few changes with my circuit with no luck. I’m trying to make a variable lab bench power supply with an lcd screen to read voltage and current while adjusting them. I’m using TL431 to have a 2.5v Vref and  a op amp in voltage follower configuration with 10M and 1M trimmer (Divider) on the input to finely calibrate 38v down to 2.5. The op amp is acting like a buffer. This is the code I've come up with: float volt; int sum = 0;                   unsigned char sample_count = 0; #define NUM_SAMPLES 10 void setup() {   analogReference(EXTERNAL);   Serial.begin(9600); } void loop() {   while (sample_count < NUM_SAMPLES) {    sum += analogRead(A0);    sample_count++;    delay(10);     }    volt = ((float)sum / (float)NUM_SAMPLES * 2.5) / 1023.0;     Serial.println(volt * 15.2 ,3);     sample_count = 0;     sum = 0; } Parts list: LM358 (for now, will upgrade to a unity gain stable op amp) 10M 5% resistor 1M trimmer Arduino Mega (Will use a pro mini in the final circuit) Breadboard (Will this effect my readings?) TL431 (2.5v Vref) Yes I now the LM358 is not suited for this application but I don’t think this will affect my readings by much, about 5% maybe. Will it? This code is gives me OK values at start but when I start to decrease/Increase the voltage. It lags behind and offsets by 1-2 volts on the reading. My goal with this project is to read (LIVE, meaning while changing voltage with buttons and see it change without any offset/lag) Voltage with a resolution of +-5/10mv accuracy and also read current (But thats for a later day). One last thing, I’m 16 so a lot of electronic terms tend to go over my head so please while giving an answer keep it simple if possible. Thanks :D

Question by faraz ahmed khan   |  last reply


Raspberry pi 2 processing capability?

Hearing the announcement of the new latest and greatest Raspberry Pi 2, now a backwards compatible computer with a 0.9GHz ARM Cortex-A7 quad core processor and 1GB of LPDDR2 SDRAM, I was wondering of the feasibility of using it as a very cheap and basic solution for a simple computer for my lab. Currently, I am using a compaq presario C700 Pentium Dual-Core laptop, that has been maxed out with 2GB 800MHz kingston RAM, and is running Kubuntu. I should also not the HDD has been replaced with a 120GB one from an old and broken Xbox. I do not like it much anymore, because although the performance of it is acceptable, the screen is a bit low res, at 1280x800, it's pretty dark (or at least until it 'warms up' to full brightness), it had a major scratch on the screen, (no idea how it got there) and after buffing it out with many methods, including with an eraser, the area has became discolored, like a portion of the screen has higher gamut and brightness, and lower black levels. :( Oh well. The main killer for it is that it's form factor. It is too big, heavy, the screen is too small, and it is very cumbersome to use far away in the corner of my workbench. Of course being a laptop, the 'base' of it is fixed to the screen, and to move it closer to me takes away lots of valuable space on my really messy bench. I mostly use it to research part numbers, get schematics off of google, watch YT videos, log data from serial ports (including my UNI-T multimeter with basic data-logging capabilities), and stuff like that. I may have as many as 20 tabs open at a time, which did tax my old compaq C700 when it had 1GB of RAM, but that was likely due to a memory leak issue with chrome, since I have the SAME issue with my main desktop, with 8GB of DDR3 RAM. If the video by MAKE is anything to judge, it looks just as powerful, as this embedded video is large! https://www.youtube.com/watch?v=pZz8MW3DSqA My hope is to replace it with a raspberry pi, and be able to use it for these basic operations w/ a old LCD monitor which can be picked up off of craigslist for cheap. Maybe I can even find one in the dump :P. Maybe I can configure the GPIO pins to be COM and parallel ports, w/ clock, Tx, Rx, and everything else! That way an external FTDI chip and using the limited number of USBs is not an issue. Is that possible?

Question by -max-   |  last reply


Raspberry pi 2 processing capability?

Hearing the announcement of the new latest and greatest Raspberry Pi 2, now a backwards compatible computer with a 0.9GHz ARM Cortex-A7 quad core processor and 1GB of LPDDR2 SDRAM, I was wondering of the feasibility of using it as a very cheap and basic solution for a simple computer for my lab. Currently, I am using a compaq presario C700 Pentium Dual-Core laptop, that has been maxed out with 2GB 800MHz kingston RAM, and is running Kubuntu. I should also not the HDD has been replaced with a 120GB one from an old and broken Xbox. I do not like it much anymore, because although the performance of it is acceptable, the screen is a bit low res, at 1280x800, it's pretty dark (or at least until it 'warms up' to full brightness), it had a major scratch on the screen, (no idea how it got there) and after buffing it out with many methods, including with an eraser, the area has became discolored, like a portion of the screen has higher gamut and brightness, and lower black levels. :( Oh well. The main killer for it is that it's form factor. It is too big, heavy, the screen is too small, and it is very cumbersome to use far away in the corner of my workbench. Of course being a laptop, the 'base' of it is fixed to the screen, and to move it closer to me takes away lots of valuable space on my really messy bench. I mostly use it to research part numbers, get schematics off of google, watch YT videos, log data from serial ports (including my UNI-T multimeter with basic data-logging capabilities), and stuff like that. I may have as many as 20 tabs open at a time, which did tax my old compaq C700 when it had 1GB of RAM, but that was likely due to a memory leak issue with chrome, since I have the SAME issue with my main desktop, with 8GB of DDR3 RAM. If the video by MAKE is anything to judge, it looks just as powerful, as this embedded video is large! https://www.youtube.com/watch?v=pZz8MW3DSqA My hope is to replace it with a raspberry pi, and be able to use it for these basic operations w/ a old cheap LCD monitor which can be picked up off of craigslist for cheap. Generally old 4:3 monitors go for next to nothing. Maybe I can even find one in the dump :P. Maybe I can configure the GPIO pins to be COM ports, w/ clock and everything else! That way an external FTDI chip and using the limited number of USBs is not an issue. Is that possible?

Question by -max-   |  last reply