Introduction: DIY PSU Into Bench Power Supply

Picture of DIY PSU Into Bench Power Supply
This is my bench power supply made out of an PSU. Any questions....? I'll be glad to help.

And here is the schematic.. (in the schematic there is a mistake, the USB should be connected to ground an +5 instead of -5)

And here you can see a graphic schematic.


denojorim (author)2017-09-26

how did you manage to connect both the multimeter wth the PSU, realy cool idea. kindly explain.

rubens74 made it! (author)2017-03-30

I tried it the same way as schematic but t only gives output of 13.3v maximum

ccronkhite (author)2015-10-22

So... I put together the variable voltage circuit on my breadboard, hooked it up to the pos and neg 12V of my power supply. Turned it on and it was putting out about 22V at first, then as I started to turn the potentiometer, the pot went up in smoke. The pot that I got was rated at 5k with a power rating of 0.5watts. I'm assuming the 0.5w is not high enough. Anyone know the minimum rating that is needed for this? My initial guess would be to calculate the watts coming out of the -12V lead on the power supply and use that as a bare minimum.

russ_hensel (author)2015-01-09

Just a note to let you know I have added this instructable to the collection:
Encyclopedia of ATX to Bench Power Supply Conversion
Take a look at about 70 different approaches to this project.

Drillbit (author)2014-03-01

Any plans on posting a step by step for this instructable? I do hope you do, I would like to build one just like yours to test with Halloween props.

newtonn2 (author)Drillbit2014-03-01

Hi there! I don't have this power supply anymore. Did you check my other power supply instructable?

Drillbit (author)newtonn22014-03-01

I have, I still like this one the best for the ideas I have for it. If you do make another I would love a step by step. Working on a low voltage haunt and these would be great.

laiskasmariui (author)2012-12-07

Hi, I've build a similar unit, but when i try to draw more current it shuts down. The most current i saw om my meter was around 500mA, on the PSU itself it says: 16A at 12V, 13A at 5V and so on. Have you any idea where the problem could be?

Hatredman (author)laiskasmariui2013-12-01

Maybe the load resistor you're using is too low, so it drains more current than it's needed.

imonfyre (author)2013-02-25

Hi there, I have was just poking around for some power supplies conversions, and yours looks very nice. A question, though... Is it possible to get 15v out of your set up by combining the -12v and the +3.3v?

tariqshan (author)2013-02-04

Nice work, i have a question about this psu from dell NPS-330CB C well i did some search on net for pinout it turned out that grey wire is for PWR-ON ok short it with which wire to switch it on. yes switching is main problem help needed.

The Dragonborn (author)2012-06-03

This thing is sweet....must build it!

hmorton1 (author)2012-04-27

Hey there, very nice writeup.. please tell us when will you update your new instructable for the new Bench Power supply?

newtonn2 (author)hmorton12012-04-28

Hi there! The instructable of my new bench power supply is on line an running, see it here

seanksg (author)2011-12-12

Is there a specific type of relay you used for this?

jkotecki (author)2011-09-28

Great project!! I have one question though. You show the connections for the USB charger port connected to -5v and GND. Should that be +5v instead?

newtonn2 (author)jkotecki2011-09-28

Ups! Thank you for pointing that out, it is a mistake of course. You need to connect the usb to Ground and +5. Sorry about that.

jkotecki (author)newtonn22011-09-29

I have one more question. On your schematic what is the switch actually connected to other than ground?

newtonn2 (author)jkotecki2011-09-29

It's connected to the green wire. That switch will turn the PSU on.

brusho150 (author)newtonn22011-11-17

I donot have green wire on my atx power supply. What to do please help!

Kandeman (author)2011-10-07

Thanks for this circuit, I've had fun putting it together but have a small problem. I can only get a touch over 12.3v across the regulated output (LM350K). I've double checked the circuit and confirmed that I have 23v across the input (ceramic capacitor). Can't quite work out what I've done wrong?

Kandeman (author)Kandeman2011-10-09

Must have something wrong or the PSU is not right but I can't put my finger on the problem. Getting 12.3v instead of 22+ and the PSU shuts off pretty much anytime there is a load on it. Have checked the datasheet of the LM350K to make sure I identified the pins correctly and according to my PCB design they are correct, will need to check the wiring to make sure that I soldered it according to the design.

Kandeman (author)Kandeman2011-10-15

Changed the negative rail from -12 to ground and everything now works fiine, just only get 10.6v max. Must be the PSU so will look out for a higher rated PSU but this will do for now.

crf250rider14 (author)2011-09-18

I hope you are still checking this, I have a quick question. If I add a voltage regulator will the 5v, 12v and so on rails still put out the same amount of amps it says it will on the box? Or Are they limited by the LM317?
Hope you can help.

ReCreate (author)2009-04-08

Looks pretty nifty,but could you post a picture of the circuit boards (excludes the psu's ) with maybe a label on all of the components? i don't quite understand schematics,but i do clearly understand pictures a picture is worth a million words,said some person...

newtonn2 (author)ReCreate2009-04-09

Hi there! i'm glad you like my bench power unit.

For the voltage regulator i just use this very helpfull instructable ....

But insted of using the LM317 I used the LM350 becouse its a bit more powerfull, and i used the 24V exit from the PSU with is the +12 as positive and -12 for negative.

i'm afraid its not possible for me to take any picture, couse i don't have any, and i would have to take the psu a part. beside that, my circuit was really messy so i don't really thing a picture will help LOL.

If you need any extra help, just let me know.

axdsqzwer (author)newtonn22011-06-15

pls help me!how to connect the v controller?ty

ReCreate (author)newtonn22009-04-09

I got a question,that thing outputted like 22V right?(according to the video) Did that thing multiply the voltage or was it getting an input of aboove 20something volts prom the PSU Also,i have a power supply from an old computer,it has the orange cable but it measures 0.16V(it being positive on the multimeter and the negative connected to ground) On another old PSU that i have it measures 10v so i don't get it,whats going on?

newtonn2 (author)ReCreate2009-04-10

Most PSU have a sticker on one side, telling you the color of the cables and the voltages of each. Normally they are:
Yellow = +12V
Red = +5V
Orange = +3.3v
Black= 0V
Blue = -12v
White = -5V

From this outputs you can get... 3.3v, 5v, 7v, 10v, 12v, 17v and 24v
3.3v= Orange (+), Ground (-)
5v= Red (+), Ground (-)
7v= Yellow (+), Red (-)
10v= Red (+), White (-)
12v= Yellow (+), Ground (-)
17v= Red (+), Blue (-)
24v= Yellow (+), Blue (-)

So i took the Yellow and Blue (24v) to the voltage regulator circuit. and there is always a drop of 3v more or less when you use a voltage regulator, so that's why you see a reading of 22.5V more or less.

All PSU i ever touch had the same color coding so, i don't really know why you have 0.16v on the orange and 10v on another, it may be that they are not working 100%. or maybe they are too old and i never came across one like that.

ReCreate (author)newtonn22009-07-20

Hey, How much current does the 24V one output?

ReCreate (author)newtonn22009-04-10

Ah,its much clearer now. Thanks Apparently My PSU outputs 3V from the white wire and ground,it sometimes reaches 4V Also i tested yellow with blue and it is at 24V,gee thanks! This is quite nice,i will build this whenever i get a chance to buy all the parts.

ReCreate (author)newtonn22009-04-10

hmm...interesting. Thanks for your reply!

ReCreate (author)newtonn22009-04-09

Oh thanks

ReCreate (author)ReCreate2009-04-08

And also can you post links to some website where we can buy all of the parts?

ReCreate (author)ReCreate2009-04-08

And also estimate the total cost?

newtonn2 (author)ReCreate2009-04-09

As i did recycle most parts, I don't really know how much would it be. but if you have the PSU i think u could get all the parts for less than 15 bucks. U don't really need to buy a really good voltage meter, couse the one i installed on top of the PSU was like 5 bucks and it reads the same voltage as my expensive voltage meter. For the potentiometer i used a volume potentiometer from an amplifier. The Led i used was taken from the front panel of an old computer, and the USB connectors as well. The connector for the regulated voltage came from a subwoofer. The capacitor and diodes were recycled as well from an old circuit (with i don't really know where came from, i just have lots of recyclable "rubbish", LOL) I love to recycle part from old stuff i don't use anymore. Maybe if u look around you home, u could find electronic thins that don't work or not in use..... go ahead and take apart, u'll find lots of parts. Hope that helps.

ReCreate (author)newtonn22009-04-09

Ha yeah,i found tons of electronics in the past year,you just gotta look,and you'll find

newtonn2 (author)ReCreate2009-04-09

I did recycle almost all the parts, the only thin i did bought was the voltage regulator LM317, and i bought it from ebay. I bought 5 and payed about a dollar each.

axdsqzwer (author)2011-06-15

can u pls help me?how can i connect a V Controller on a PSU?

gullfunk (author)2011-06-06

where can i get the LM350

crf250rider14 (author)2011-04-25

Hey there and awsome project! I have one question, how did you take the USB out of the computer? Mine seems to be attached to the motherboard, if i do take it out though which line would I connect it to? I just want to charge my cell phone via USB.
The cell phone charger already has a usb attachment.
Have a good one.

matroska (author)2011-04-23

Hm, the PDF schematic file doesn't seem to work...

mkasp (author)2011-01-28

There are 3 terminals to the pot, you only show connecting two terminals (in both your pdf schematic and jpg). The way i understand a pot to work is pins 1 and 3 are power (usually +Vdd and Gnd), and 2 is output. Am I missing something in you schematic?

newtonn2 (author)mkasp2011-01-28

Hi there! I'm using the pot as a variable resistor, that's why you only need to use two pins.

mkasp (author)mkasp2011-01-28

I also dont understand why nothing in that circuit is grounded. Doesnt there have to be some type of common ground in there?

kasta96 (author)2011-01-22

ho much A you can get from the voltage regulated connectors?

p.s. very good work! =)

agentc0re (author)2010-11-21

Is it possible to also have a POT that will control the current output without affecting the voltage WHILE at the same time still being able to control the voltage output like you have done?

jcWiz (author)2010-03-16

What potentiometer type did you use? Mine (5k) burned to a crisp in no time :(

newtonn2 (author)jcWiz2010-03-18

 I use a normal potentiometer, not a power resistor. Did you check that the wiring is correct?

jcWiz (author)newtonn22010-03-18

I used your Graphical Diagram matching everything. without the potentiometer attached the output is around 22v (the potentiometer i used is a normal coal strip one... at this voltages i was told it would most certainly burn. now I'm going to use wirewound i think (in Portugal we call this type "Bobinated" - freely translating) 5k 5w or above. 

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Bio: Always loved electronics. I like to reuse parts or componets and I Love to be part of the Instructable community.
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