Convert an ATX Power Supply Into a Regular DC Power Supply!

A DC power supply can be hard to find and expensive. With features that are more or less hit or miss for what you need.

In this Instructable, I will show you how to convert a computer power supply into a regular DC power supply with 12, 5 and 3.3 volt outputs. For about $10!

Why use a computer (ATX) power supply? Well, they're available everywhere, and they can output tremendous amounts of power in a small form factor. They have overload protection built right in, and even a 500W model can be reasonably priced with high efficiency. The voltage rails are incredibly stable. Giving nice, clean DC current even at high loads.

Plus, it's likely that many of you simply have an extra one lying around doing nothing. Might as well get the most value for your investment.
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Step 1: Getting Started

The first order of business is that of safety. While I'm reasonably sure that there isn't enough residual energy to stop your heart, those capacitors can still bite, and that can cause significant pain and maybe even burns. So be paranoid when getting close to the internal circuitry. It would probably be a good idea to put on some insulating gloves. Also (obviously) make sure the thing is unplugged. You are responsible for your own safety!

Here are the tools/parts needed:

Needle-nose pliers
Soldering iron
3 x "Banana Jack" Insulated Binding Post sets
1 x bag of "#6" Ring Tongue Terminals (16-14 gauge)
Rubber feet
Small bit of heat shrink.
Wire strippers

Ok, let's get to voiding some warranties!

Step 2: Opening Up

Open the PSU and make an assessment of the space you have to work with. Make sure that there won't be any clearance issues for the binding posts or wires.

Once you have decided how your PSU will be configured, mark with pencil where you want to drill the holes later on. This will help you in cutting the wires to the appropriate length.
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selfiboy4 days ago

but how can i get 5v and 1a?

I made it but problem is that I received 14.3 volts

Is there a way to run a few of these together to increase the amps/volts?

No I don't believe so..each one is independent of each other... Want more power get a bigger transformer

yes if you put each wire color relative to its voltage the more wires together will give you more amperage

what I meant actually was running multiple power supplies together
russ_hensel21 days ago

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.

BarryTrodd3 months ago


I have just finished converting a 400watt ATX power supply but unfortunately it does not work. When I switch on the fan turns over a couple of times and then stops. The only signs of any voltages are the lit up Green LED that I have connected between the purple wire and black ground wire. I have tried having a 10 ohm 10 watt resister between the red wire and ground but that does not help, in fact it appears to make it worse as the fan then only turns about 180 degrees and the. Stops. Any suggestions please

I have had the same problem with my power supply. The problem is that there is a shortage somewhere which results in the system shutting down. Try to find the shortage and everything should be allright. Mine was located at the added resistor, it touched the housing of the power supply when closing it. After having added heat shrinking tube, the problem was solved. Good luck


I don't mean to butt in but if you have a newer ATX supply (that is one that has most of the current on the 12V rails or one lacking a white wire which IS found on older PSUs) then you will need to put the load resistor between the 12V (usually yellow wire) and Gnd (the black wire). Before you do that though, you might want to test if your PSU is still working.

If you've still have a purple wire, then that usually has a +5 volt continuous output even with the supply off (it's the PSU's standby good switch). Measure the voltage drop of that across a resistor (connect the purple wire to one end of a resistor, connect a black wire to the other end, and measure the voltage across the resistor). If that's about +5volts then that's working and so's your PSU.

Hope that fixes your problem.

You must have a load on the supply, or it will shut itself off. It's a safety feature in power supplies.

I had a 10 ohm 10 watt resister between the red wire and ground. Is that not a LOAD on the supply?
Sorry. I didn't see that part.
Misael Saenz Flores made it!1 month ago
From when I wanted to make one, thank you very much for the tutorial has been my great and works perfectly, proven to 12V, 5V and 3.3V, thank you very much
Buildkhahh1 month ago

I have a more basic question concerning how a power supply would be used to power a device.

If I have a device that requires 12 volts@3.33 amps (40 watts) and I have a power supply that produces 12 volts@15 amps (180 watts) is it safe to use the larger power supply?

Also is there any way to figure out how a power supply with a larger voltage would impact a device that requires a smaller one?

As an example, I have a device that requires 5 volts at 1 amp, I have an 18 volt power supply rated at 0.5 amp. Is there any way to make the 18 volt power supply fit the requirements of the 5 volt device.


imdiko242 months ago

Hi! If I'm using a 20W, 12V Halogen Bulb as my dummy load, would this also serve as a current limit of 1.6Amps for my circuit?

imdiko24 imdiko242 months ago

whelp that was a stupid question :p But I did it! I used it to power my 8A solar tracker system. Power resistors were a bit too difficult to find around my area so I used a 12V 20W halogen lamp instead. Nice light to help you while soldering

sarathsama2 months ago

can i use stand by purple wire to connect to usb to charge a mobile while in stand by mode

rhendric5 months ago

The fan inside the power supply is inside the power supply for a reason, to help to cool off those giant heatsinks, you shouldn't run it without one, else you run a higher risk of over-heating.

kjoanisse5 months ago

Sweet tutorial , i just have one question , if i take all my yellow and black wire and i just take one of each color (ex: Black n Yellow together x10) can i plug like 3 , 12v pc fan on it w/ one 12v Peltier module ?

So what i wanna know is can i have more than one 12v output? Can i have like 4 , 12v output on a single PSU?

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Davlof made it!5 months ago

Thanks for the info! I made this to power a guitar string foam cutter and charge my phone and MP3 player. My wires were a bit different but figured it out with a meter. As you can see I added two USB chargers and a car accessory plug. I figured why not! My local store had a very limited selection of banana terminals so I have a black one that is actually voltage, I will need to make labels later for the different voltages :)


Great tutorial, thanks. Just a comment: I do not believe it is necessary to group all of the cables together, since they are connected internally (you can check that with a multimeter).

So you should be able to extract the whole power through one wire, and considering the powers of ATX power supplies are relatively reduced, the cross-section won't be an issue either.

Hi there, thanks for the great instructable!

A question for you... my dad and I made this according to your instructions, but with the wires connected to bolts (see photo below). We tested the voltage with our meter (photo below). Our results for the yellow wire were:

black pole on black wire & red poll on yellow wire (would have thought it should be positive) = negative 12 volts!

black pole on yellow wire & red pole on black wire (you would have thought this would give positive 12 volts) = positive 2.85 volts!

Neither of us understood why we got this result. Any suggestions much appreciated.

Also, now I'm using the power supply to electroform a piece of stick (coated in varnish, dried, sprayed with waterproof glue, covered with graphite powder as a conductive medium). It's been in there for more than 24 hours, but I don't see any plating happening (lots of bubbles though!).

If you have any thoughts as to what we could be doing wrong in either part of the procedure, they would be great to know!

Thanks for your help :-)

2014-05-08 11.44.32.jpg2014-05-10 17.09.32.jpg2014-05-10 17.16.07.jpg2014-05-11 13.43.39.jpg2014-05-11 13.44.23.jpg

PS and the copper wire connecting the graphite-coated stick to the red alligator clip keeps breaking off. There is something not right here! (louise)

cecil2299 months ago

If you hook the +12v too the +3.3v would that give me +15.3v ? And would it make it 41amps ?

en_rov cecil2299 months ago
No, by connecting those wires in series you will get 17+ volts, but the amperage that can be drawn safely is the lowest of the two outputs. 23 amps, in this case.
cecil229 en_rov9 months ago

ok, thanks for the help :)

triesna10 months ago

hi, my name is triesna.

I am very interested to make a main power supply for powering the led circuit. My current need is 12 volts by using a power suplly unit from the computer say that unused.

I have a SAMSUNG power supply unit type PSD-300 DAG3.

I have been doing is, cut the cable from the current 220 volts then I plug in the switch. Then I installed the 2 LEDs for indicator. The first sets I Led in series with a resistor and connect to it with purple and black wires. The second Led I connect in series as well and my sets with cable red + gray and black.

I posted a small switch with a connecting cable between the Green and black wires.

I also put 2 pieces resistor 27 ohm in parallel and I connect the resistor-kai's feet with the red and black wires cable.

The problem I faced, when both my switch is on, the fan spins only once and the indicator light flashes once and then only to die again.

For 12 volt output I am trying to install flexible led lights and also just flashes once and then don't want to flame back.

Please help me, where my error lies in constructing the power supply to make the dc adapter 12 volt?

Thanks for the help.

en_rov triesna9 months ago
Look for shorts.
longp200010 months ago
Mine sis not work. It came on for about 5 seconds and now will not come back on at all.
I put all of the red, orange and yellow wires together by colors and split the black/ground to a ground post with each of three colors. I added a 10ohm x1watt resistor from one red and one black. I have the green and a black/ground. I have the fan plugged in to the power supply board (the fan came on for those 5 seconds too). While it was on I did get measureable voltage in from the 12v post. I have a pink wire which I have hooked up to the red wires and orange wires with no luck. I have a brown wire that I hooked up to the orange and them to the green and black, no luck. I have a gray wire I have hooked to the green and black as well as all the others with no luck. I have a purple and blue also which I have not done anything with. The LED that is in the power supply board blinked while it was on for the 5 seconds.

Any one have ideas?
en_rov longp20009 months ago
Double check the green cable is properly hooked to ground. Else, look for shorts. I had accidentally shorted two wires, and the thing seemed dead. I unplugged it from the socket for about two hours and it worked again.
claws110 months ago

Didn't work for me... just made a slight hissing noise and that was it.

Ah well i now have spare wire so all is good.

Mister DO11 months ago
I made a version of your instructable. Modifications to design:

I kept it at 12 volt. I don't have any other voltage needs right now.

I kept the fan and mounted it on the outside of the case.

I added a 12v auto accessory socket to charge my cell phone and my handheld transceiver.

I also used Anderson powerpole connectors. Our ham clubs in the area have standardized on that connector type.

One interesting note. I had the thing all wired up and it would just shut off. I went back to the 20 pin connector and noticed that a brown and orange wire were connected and a pink and red wire were connected. Once I put then together I was getting a steady 11.83 volts.

Thanks for posting the 'ible.


Mister DO
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SarCrisu12 months ago


I have a question about the ground connector.

Is it safe to use devices with different volt requirements on the same ground connector?

roachburn SarCrisu11 months ago

Yes. The psu uses the same ground for all its different voltages. I build alot of circuitry and do it all the time. I think there may be some instances where you would not use a common ground but I have never ran into this issue. You can always use a volt meter to see if a circuit is shorting out. Generally DC voltage is pretty safe and wont cause a big fire or or kill you. Always assume that it is dangerous though and take precautions. If I am really unsure about a circuit, I will take it outside and plug it into a power strip with a switch and turn it off if I see the magic smoke hehe.

agr00m4 years ago
 The tutorial you posted a link to as a more comprehensive how-to, has you putting a power resistor in it.  What's that for?  It sounds like something you either have to have or completely don't need.
It's useful for charging well-spent car battery. That heavy usage may draw too much power, invoking shutdown.
Megahurtz4 years ago
Excellent instructable! Will this thing run a 12v cordless dril? I have a brass tumbler I am using with a cordless drill but it's a pain having to switch out the batteries every hour or 2. If so, what posts would you use?
Check the amperage--you can't use an average block rectifier. (Note that LCD/LED monitors, etc. which use blocks don't use many watts--they achieve extraordinary energy efficiency.) Note how much larger block rectifiers are for laptops and their sophisticated batteries.

A related issue: DC power supplies actually prove available which feature 20-pin connectors intended for low-power PC motherboards. Such SFF solutions are intended mainly for 12V batteries from vehicles. (Conceivably, DIYs may achieve terabytes in autos.) These low-power boards can't offer much in the way of video performance, though.
12v cordless drill would be powered (duh) by 12v and the ground rail. just hook it up to your drill, mind the polarity
it *might* run the drill, but if it uses too much power, it *might* not
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