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.
cecil2296 days ago

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

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.

ok, thanks for the help :)

triesna26 days 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 triesna3 days ago
Look for shorts.
longp200010 days 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?
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.
claws11 month 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 DO1 month 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
14, 18:46.jpg
SarCrisu2 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?

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.
gsnoorky agr00m3 months ago
It's useful for charging well-spent car battery. That heavy usage may draw too much power, invoking shutdown.
Megahurtz3 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
I have a 12 v dc output power adapter for what I do not know and I stripped the wires and connected it but it did not have enough power
Look at the current rating on your 12 V DC power adapter. Most of the wall brick type adapters I've seen only supply 1–2 amps at most. Probably your drill needs more than that. The ATX supply probably will work since it can supply more than 200 watts of 12 V power.
JetBlack4 months ago
I'm planning on doind this one for 12V LED lighting, but I'm not sure if it is indeed necessity of this resistor for the load. I mean, I maybe very wrong, but what I'll do is light my place all with 12V/0.7W power LED. What do you think is right for me to do?
Does anyone know if its possible to get over 20amps DC (hopefully 25)at at least 12 volts from a homemade DC converter made from a computer supply?(and how many watts of a supply is needed from the computer) Trying to save some $ buying a 12volt DC power supply for a charger to charge batteries for my cars and airplanes.THANKS!
fety banzaichibi8 months ago
This might help. I'm doing the same thing, I want to power my Quattro 4x6 charger.

jasshopper10 months ago
how can i get(or can you?)24v at a minimum of 8-15A? (the modifications)?
JTreehorn3 years ago
Thought I would post these pics of my finished product. Give your supply a name, take some measurements, and with a little photoshop you can give your power supply a professional look. (Sorry about the poor quality images. Cell phones were not made for photography)
Sitnalta (author)  JTreehorn2 years ago
That is awesome! How did you make the labels?
JTreehorn Sitnalta10 months ago
2 years later... with a ruler and Photoshop.
That looks fantastic!
that looks delicious
P.S. Almost forgot to say thanks for the instructable. So... thank you very much. If it wasn't for people like you who post these things, I wouldn't know the first place to begin. Keep 'em coming.
tandrel2 years ago
I can do this, and it all runs fine and can even power some other 12v sources I have, but when using this for a car amplifier as soon as I plug in the REM wire the powersupply turns off and wont turn back on for about 3 minutes... is there a way around this. It happened even when I was using a separate power supply for my remote wire too.
i dont know much anything about this, but they did say it has a built in overload protection. i think that's what this is.... so you're overloading it? i dunno, just a suggestion, from someone who can only guess since they dont have one XP
I am trying to convert a new 1200W PSU and have found that in addition to the expected wire colors there are Yellow & Green wires as well. I looked around online and found that they are "Protective Ground" wires.

What do I do with them?

Any help would be great.

I'm guessing you can you use this to charge 12V motorcycle batteries? Am I right? I have a 350W PSU lying around in the house, was planning to convert it to a 12V only charger.

No a 12v battery needs for than 12 volts to charge. Around 13.5 or 14. :)
needs more than*
very good idea! i love it! was just getting ready to buy a 12v supply, but ive got at least a dozen of these laying around.
Jugfet1 year ago
I'm a spelunker here in the UK, involved with exploring old metal mines. To charge my miners lamps I needed a 5V supply. I used an old PC PSU and can charge 10 lamps from it. The equivalent commercial unit costs in excess of £200 or close on $300 US.
The unit charges Lead Acid batteries with ease. Batteries do present a fairly passive load on the PSU and I'm not sure how switch mode PSU's would respond to inductive loads especially fluctuating ones; I wonder about the effects of back EMF.
thank you bud , my mind is clear now, I got the right inspiration on what I have to do with that stuff

It's possible to add more power supplies in series to get 24V, and all the mixes possible that a second, third, etc supply will allow.

For example, 3V correctly modified (as discussed briefly below) would produce a 15V line. Care is needed - of course - in the assembly.

You must isolate any additional supplies (I've cut the GND pin at plug, so only power cable need modification.) This is termed 'floating' ground.

Parallel arrangements would not need this modification to any of the voltages on the based standard. Some in parallel and some in series are still possible at once with the understanding that ANY supply added to the base voltages will (or will not) need GND modification based on there individual function.

If they explode when power applied - you haven't done it correctly,lol. So understanding and care is needed.

I am tempted to consider the function and safety of putting the floating grounds attached to a 'base' voltage, with the realization that it may greatly reduce the possible amperage in those lines - as the floating supply grounds (if connected) may draw power from it's use. I also wonder what would happen if floating supply is GNDed to .. say the base 3V line. And then used in series in other lines would start at 3V. Don't know and would be interested in learning this. I would guess that all would be fine as long as loads are below the lowest max amp rating on a voltage.

One note already discussed is that older supplies must have a small load on 5V section before power up is possible. A simple resister between 5V to it's PS's GND (isolated or not) is needed in that case.. look to comments here for more info - if desired.

"May the (electric) Force be with you",

PS. Any 'floating' supply should be physically isolated, for safety of people and pets, and to prevent accidentally grounding. Watch for fire, as I've seen in my travels, a power supply melt isolation if incorrectly connected. (before floppy cable connecters were keyed, reversal will connect 5V to GND and supply will contently deliver at least the rated amperage for that voltage) .. poor cables, but eye opening, as most natural disasters are.

PPS. Great and useful Instructable!
jadi9291 year ago
actually I am going to try a 100 ohm 1 watt resistor like someone mentioned and see where that gets me

right now i had a10 ohm 10 watt resistor
jadi9291 year ago
Hi guys, I need some help. I followed all the steps and but my PS does not turn on, the fan doesn't turn on either.

Mine seems to have a brown "Sense" wire which I connected to 3.3v (orange) wires, but that didn't do anything.

I also tried connecting the brown wire to the black and green wires but that didn't do anything.



a side question, the heatsinks inside the PS aren't supposed to have any voltages in them right? but when mine is plugged in my voltmeter reads 157v between the two heat sinks? WTF?

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