Introduction: Bench Top Power Supply

Picture of Bench Top Power Supply

I finally found the time to make my own bench top power supply from and old computer power supply. This has been done many times before and this is my take on it.

What you need

  • Computer Power Supply
  • Screw drivers
  • Wire cutter/Strippers
  • Ring terminals
  • Soldering Iron (If your right terminals aren't crimp type)
  • 4 screw terminal posts (I made my own, Instructable here)
  • Heat shrink Tubing
  • Switch
  • Drill

And as always be careful around power supply's. They contain capacitors that can cause serious harm to yourself if not handled properly.

Step 1: Identifying Wires

Picture of Identifying Wires

For the first step we need to take the case off from around the power supply.

Now you need to identify the wires

  • YELLOW = 12 Volts
  • RED = 5 Volts
  • ORANGE = 3.3 Volts
  • BLACK = Ground
  • Green = Power On

I cut all the other wires back down to the board and wrapped the ends with black tape to prevent them from accidentally touching anything else.

I then sorted the yellow, red, orange and black wires into separate groups.

I set the green wire and one black wire aside for the switch to turn on the power supply.

Step 2: Adding Terminals

Picture of Adding Terminals

Now i selected around 6 wires from each color and trimmed the rest down close to the board and covered with black tape.

The six wires from each color were then soldered into a ring terminal and then covered with heat shrink tubing.

The green wire and the one black wire were wired into the switch.

I then attached my screw post terminals to the ring terminals.

Step 3: Drilling Holes

Picture of Drilling Holes

Mark out on your power supply case where you want your terminals and switch to be. (Since my power supply was smaller and more compact I didn't have much choice where they would fit)

Drill out your holes and test fit your terminals and switch.

Step 4: Button Everything Up

Picture of Button Everything Up

Put your post terminals and switch in there holes and reassemble the case. Now plug in power and test your voltages. You now have a cheap desktop power supply.

I would of liked to have added an led to signal when the power supply was turned on and this could easily be done with an led in series with a resistor connected to one of the voltages.

Thank you for taking the time to read my instructable, have a nice day!


chrisb1111 (author)2016-06-11

thanks for all the details - like color code of the wires etc. This let me build a DC power this afternoon. Plus I added two DC-DC step down adjustable modules with LCD display, so I can get variable voltages apart from the ones provided.

Lockheed95 (author)2016-01-06

sorry for my poor english but why do you need a load?

Gelfling6 (author)Lockheed952016-04-11

It's dependant on the supply.. Most switching supplies, will shut-down if there is no load across the +5V rail to GND.. I think a lot of the newer ATX supplies have this already covered, but a lot of the older ones, (right back to the original IBM-PC 5150), if there was no load, would simply stop working within seconds if there was none. (something about the feedback circuit that regulates the voltages.. If no load or overload, the supply simply shuts-down.)

Gelfling6 (author)Gelfling62016-04-11

BTW Joshmt2012, Love the "DefCon" switch application! (flip cover toggle)

Mesut.DD (author)2015-10-18

good power supply

dstmartinmaker (author)2015-09-08

Excellent. One of the cleanest designs i've seen!

yysmart (author)2015-07-23

is col

teaMJPx made it! (author)2015-05-31

Thank you for this. Ive always wanted to make one for myself and with your ible I went ahead and did it. I added little feet around the sides and the bottom so I can use anywhere and not worry about scratching stuff... jejeje


ferjanyen (author)2015-03-31

Hi, is the power supply limiting current? and if so by how much from each voltage? And it would not be better to take off all the wires and just put one of each of thicker diameter to reduce cluster arround posts?

ktzalas (author)ferjanyen2015-04-02

How much current is allocated for each rail (voltage) should be written somewhere on your psu. I believe (correct me if im wrong) you should use more wires than one since with one wire you would be using a specific rail and put load only on that while psu are designed to share the load.

ktzalas made it! (author)2015-03-30

I also used an old ATX supply but i had to call forth the power of grayskull to fit the cables inside. For the record my psu use the GRAY wire + Ground to power up but that is probably because it is quite old. Also very clear instructions indeed.

jpmorgan34 made it! (author)2015-03-25

I used an ATX power supply and I didn't have enough room inside the case so I used parts from an old erector set and hot glued everything together. Works great would recomend this build for anyone who uses lo voltages often. Great clear instructions thanks for the awsome page

RobertsBooks (author)2015-03-25

I made one. love it. I used color coded terminals though. I don't want to forget or permanent marker to wear off so that's the only change I made. good job.

joshmt2012 (author)RobertsBooks2015-03-25

awesome! You have some pictures of it? And I printed a new base plate for the terminals with the voltages on it I just haven't gotten around to installing it

EvolvedAwesome (author)2015-03-15

Great idea! I will suggest two things though. First, I would love to see this mounted into your desk, that would be awesome! Secondly, I want to warn anyone who attempts this that capacitors in the PSU can kill if your not careful. Please use the appropriate safety equipment or you could get badly injured or even killed!

nerd7473 (author)EvolvedAwesome2015-03-23

same point I made capacitors in PSU and in old TVs arent safe to mess with and that includes old monitors

argyre (author)2015-03-23

Might I suggest that you go old school, and instead of adding an LED and extra wires, you select a power switch with a built-in light up indicator.

joshmt2012 (author)argyre2015-03-23

This is a possibility depending on how the switch is wired. Since you arent actually running 12v through the switch to turn the power supply on you have to add the power into the switch. The switch i used has a built in light but its wired to use the incoming voltage to power it, this doesnt work because if you add one of the 12v wires you are basically creating a short. I hope that makes sense how i explaned it

cptdragn (author)2015-03-22

A simple high quality 12Volt 100Amp Power Supply thread starts here

look around. there are ways to run power supplies in series as well.

Ralphxyz (author)2015-03-17

What do you do with the Green wire?

kallum.strachan (author)Ralphxyz2015-03-20

Green should be your ground so you can add another terminal to give you the option to ground some projects

The green wire is what tells the power supply to turn on, so it has to be connected to a "black" ground. So the green and a black are wired into the switch to do that.

oh ok, I also had an earth wire in mine which was connected to the metal frame

joshmt2012 (author)Ralphxyz2015-03-17

It get connected to the switch with one of the grounds

Ralphxyz (author)2015-03-21

My PSU has a on/off switch can I just jumper the green wire to any black?

joshmt2012 (author)Ralphxyz2015-03-21

Yeah you can do that, and just use the psu on/off to turn on it on

Ralphxyz (author)joshmt20122015-03-21

I see other projects use a load resistor, apparently some psu don turn on unless they see a load! Would a LED generate enough load?

joshmt2012 (author)Ralphxyz2015-03-21

you will have to use a resister in series with the led, and yes i believe that would create a large enough load. My power supply was older so it doesnt need the load to be able to operate

Ralphxyz (author)2015-03-21

Are all of the black wires Ground? I just pulled a power supply out of old computer there are so many wires.

joshmt2012 (author)Ralphxyz2015-03-21

yeah all the black wires are ground

roger.k.mathers (author)2015-03-19

I wish some one would do instruction on how to run multiple supplies in order to increase amps

SIRJAMES09 (author)2015-03-17

and I expected this to be extremely complicated.....

How cool! 8-)

I have everything but the terminals & the circuit tester....

this is awesome!!

Thank you for sharing SIr!

joshmt2012 (author)SIRJAMES092015-03-17

Thank You!! glad you like it

roberthellier37 (author)2015-03-17

I like this Idea.... a good way top re cycle old PC PSU.... well done. I will have my PSU in a metal and plasic case for good earthing bond. and put the terminals on an plastic board to prevent any shorting out.... great idea tho

Orngrimm (author)2015-03-16

I always connect my green wire (ATX pwr ON) to GND. This is because all my PSU's seem to have a primary-switch i use for powering ON and OFF.

That said, i wanted to stress out something: NEVER ever EVER (!!) relocate, rewire or mess with this primary-side-switch (Located near the mains-Plug pf the PSU) except switching it on and off (Intended use).
If you want a easy and save means to switch the PSU on and off, you should use the method provided here in this instructable and use a switch to connect the green to GND (PSU = ON) or leave it unconnected (PSU = OFF).

nerd7473 (author)2015-03-15

I don't know if anyone is aware but this project can be deadly due to high-voltage capacitors found in PSUs (power supply units) I hope that those who attempt this stay safe... and careful

-sincerely: nerd7473

daniellozysko (author)2015-03-15


chelseabun (author)2015-03-15

You make a same mistake that I have made in my ATX power supply. It's should have at least 2 ground posts. And you might want to add some filter capacitors

joshmt2012 (author)chelseabun2015-03-15

My original plan was to have a ground post for each voltage terminal, but limited space inside only allowed me to have one. Im planning on building my next one out of a full size atx and add variable voltage to it. Thank you for the suggestions!

monkeyracing (author)2015-03-15

Can you describe how you made the posts? That would save me a lot of frustration at my local, poorly stocked supplier. Thanks!

joshmt2012 (author)monkeyracing2015-03-15

Sorry i forgot to add the link for the instructables on it, here it is

russ_hensel (author)2015-03-14

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.

joshmt2012 (author)russ_hensel2015-03-14

Awesome! thank you

About This Instructable




Bio: I am a Senior in college studying Mechanical Engineering. My interests include woodworking, 3D printing, electronics and building computers
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