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.

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:

Drill
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.
Screwdriver
Wire strippers

Ok, let's get to voiding some warranties!

Comments

[Shawn112270]

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.

Thanks,
E

[banzaichibi]

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!

[frozenkamote]

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.

Thanks

[Jakob2803]

No a 12v battery needs for than 12 volts to charge. Around 13.5 or 14. :)

[Jakob2803]

needs more than*

[god.favored]

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.

[Jugfet]

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.

[aristide202]

thank you bud , my mind is clear now, I got the right inspiration on what I have to do with that stuff

[Steven.Work]

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",
Steve

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!

[jadi929]

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

[jadi929]

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.

Also, BE VERY CAREFUL!! I GOT SHOCKED DOING THIS! MAKE SURE YOUR CAPACITORS ARE NOT CHARGED WHILE HANDLING!

I GOT SHOCKED PRETTY BAD LOL

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?

[alahamm]

I have a COMPAC PS-5201-4T2; Here is the pinout:

1. Brown 3.3 Volts
2. Brown 3 VRS
3. Black Ground
4. Red 5 Volts
5. Black Ground
6. Red 5 Volts
7. Gray Aux Ground
8. Purple Fan Off
9. Green 5VA
10. Orange 12 Volts

11. Brown 3.3 Volts
12. Blue -12 Volts
13. Black Ground
14. White OS
15. Black Ground
16. Black Ground
17. Black Ground
18. Yellow -5 Volts
19. Red 5 Volts
20. Red 5 Volts


When I power it the fan doesnt runand the only pin with voltage is 5vA.
Can somebody explain exactly how to get it to work, please. Thanks.

[mlinhart]

Hi,
I have an AT power supply, it was creating 11.43v from the yellow 12v wire. I wired a 12v globe to one of the black wires and one of the red (5v) wires. I put the multimeter on the 12v and ground wire while the globe was on. it read -12.21 I was wondering why it said negative? and also my lipo charger can handle 12v-17v, would it be ok if I put another globe on the 5v rail? or is one enough already?
cheers

[houdini0118]

you probably had it backwards if you touch the multi meter with the leads reversed is should be fine

[benji.abrams]

this is my atx build

[FireCGun]

can some one explain to me how can i get efferent voltages from the power suppler

[sun_ray2050]

here i made ;)

[tandrel]

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.

[Thundagere]

Hey, if I want to power two items (a computer fan and a peltier cooler) with this device, and both are twelve volts, then how should I do it? I would also want to power a 5V peltier cooler, so what connections would I make/ Would I need to add extra binding posts?

[junbata]

Good day !
Can Anybody Please
help me to Idfentified the pin out of my ATX COMPAQ
model PS 5201 4T2.
I like to make power supply also. from that Model.
The position of the green or Power ON is not in Position 14.
Please help me to solve this.
and do I need sense wire also. to be able to run it.
I have 20 pins out.

GOD BLESS.

Thanks

[altricious]

Depending on your PS, there may be "Power Sensing" wires that also need to be connected. You can tell because there will be two wires to a single terminal on the 2x10 or 2x12 plug. Mine had a brown wire that needed to be tied to the orange otherwise it would not run.

[Surg]

Hi guys.

Thanks for this great info. I just converted my first ATX 600w PSU model ULT-VX600 yesterday. It is working good thus far, and is so much quieter then the marine battery charger that I was previously running. I use it to power a Hyperion LiPo battery charger for my RC hobbie. My charger is capable of accepting 12-28 volts on the DC input side. I did some test charging pulling 25 amps from the PSU and am noticing the output voltage of the PSU drop to close to 11 volts and as a result my charger stops charging one leg. I have 10g wire soldered to the power bus on the inside to provide power to my charger. It shouldn't be a voltage drop issue.

Is there a way to tweak it to make it put out over 12 volts?

I was also considering wiring two ATX's in series to get 24 volts, but the problem would be that they share case ground with - DC. If I put the + from one the ATX to the - of the other it would short out since they are using a common AC source for power. The -12v line is only rated at less then one amp, so that is worthless to me.

Any suggestions?

[techxpert]

lesson for everyone don't put your hand on the big yellow transformer while pushing the power cord into the socket or big jolt tingling up your arm before jumping back just in time to save your life and live to type this up on another computer!

[Blacklight [HUN]]

Nice job.
My problem is that I can't run a zvs driver (pulls around 5A at 24V), a plasma speaker either.
It just simply turns off.
What could be the problem? :S

[louige99]

well you have 24V at 5A which is 120W, i assume your PSU is rated above that but that doesnt really mean much at all. most PSU's only allow certain max power for a combination of rails. For instance, a PSU with a 12V, 5V, and 3.3V rail might be rated at 250W, but the combined wattage of the 5V and 3.3V rails might only be 110W.

In short, check what specific ratings are on the stickers on the PSU and search the internet for the data sheet if you can find it. If you cant, i would say thats your problem and you can really only fix it by getting a new PSU that has a 25V 5A rating on it

[soshimo]

Do you have any problems with arcing on the low voltage terminals? Most ATX PSU's put out over 30A on the +5v line. That could cause arcing or smoke your circuit. Have you had much trouble with this? I'm wondering if it's not better to just pony up another $100 for a lab PSU. The potential loss of some high priced IC's I have (and some of which are not available anymore) is not worth saving a few bucks IMO. Good tut anyway. One last point, those caps inside the PSU can hold a SIGNIFICANT charge. They will do more than bite, they could kill you. I've blasted molten pieces off a screwdriver when trying to discharge them. FYI.

[shussain13]

Hi I want to use an Esc to control a motor. Instead of providing power to Esc through Lipos, can I use regulated Dc power supply?

Actually I want to make a test bench and I want to do series of experiments relating to my project, for which I cannot wait to charge the Lipo again and again

Any guidance in this will be much appreciated

Regards

[diy_bloke]

great stuff. I used something similar to feed a bunch of flashes during a photoshoot

[nsharma11]

can i take 24volt output from a normal atx computer smps...can any body help me for this

[bwdane]

Thank you for the instructable. I used this as a basis for a slightly different project. I am using a 500W power supply to power a radio in my garage consisting of old car audio bits. It is able to power a 500W amplifier that is pushing two 4.5" component speakers and a 12" subwoofer as well as an Alpine head unit. Now I just have to figure out how to add a small battery to hold the radio's settings.

[trosa3]

Great instructable! I am a R.C. enthusiast and I have had many problems finding a reliable 12v dc supply for my battery chargers. This really worked out great for me, It only costs a few bucks and like you said almost everyone has a pc power supply laying around.

[AntonMadness]

I would like to share a rule of thumb we use at my company concerning maximum current vs. wire thickness:
1mm^2 10A
1.5mm^2 16A
2,5mm^2 25A
4mm^2 32A
6mm^2 40A
My PSU is rated:
-12V 0,8A
-5V 0,5A
+3.3V 26A
+5V 35A
+12V 15A

I'm not thinking of using the negative voltages. The wires are AWG16 = 1.310mm^2. Because I don't think I will go to the max, 2 wires will give me enough room to pull 25A per channel(NOT simultaneously!).

So using two wires will give you 200% current without melting your wires and it will save you some room and time grouping ALL the wires.

[JTreehorn]

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]

That is awesome! How did you make the labels?

[ninjatails]

That looks fantastic!

[emitsorrels]

that looks delicious

[JTreehorn]

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.

[rcarter5]

hi, this is grate, i fly rc helicopters that run on 12s lipo batries, (44.4v) my battery charger needs a 400 w power suply
http://www.hobbyking.com/hobbyking/store/__17753__Turnigy_Mega_200Wx2_Battery_charger_discharger_400w_.html
i will be charging at 10 amps x 2

i have a 600w psu, will it handle wot i need?

thanx, wuld apriciate it if some one culd email me direct, i dont get mutch time to get on line at the mo
[e-mail]

[LasVegas]

If you start that supply without a minimum load of a few amps on the +5 volt line, your going to simply burn out the supply. Also, why didn't you make the -12v line available? While limited, it's still very useful.

[Gelfling6]

most of the time, these pans usually include a 10-33 Ohm wire-wound 10W or 5W resistor across the +5V supply wires, to maintain an ample load, with minimal load to detract from the +5V voltage. (Though, a 33-Ohm looks more like a 5-Watt film resistor, in my 400-Watt supply, looks pretty small, but appears to provide this load.) I've noticed some of these supplies have the load resistor already soldered right to the board, across both the +5 & +3.3 voltages. I agree on the -12V line.. there are still plenty of projects that requires even the old EIA RS-232 voltages (+12V & -12V)

When I look for supplies to convert, I'll actually scrap supplies that don't have the -5V live, for parts.. those with everything, get converted.