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

Step 9 Updates

Originality

This project is not necessarily original and has been done by many people.

The most "together" project is that of this guy: http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

There are a multitude of other projects, but I feel mine and his are the best I've seen so far.

Issue of the Resistor

Power supplies need a certain minimum load to work properly. The min. load for mine is around 0.8 amps. Thus if you plan on powering LED's or other such low-power device exclusively, you'll need a resistor to provide a load. Otherwise you will damage the PSU.

A meaty 10-Ohm, 10 watt resistor from Radio Shack is a good choice. Wire it across 12 volt and ground.

-12V and -5V lines

It has been brought to my attention that the -12V and -5 lines are pretty handy for diversifying the voltages this thing can produce. These are the white and blue wires I told you to cut earlier.

Of course, adding them is simple, it's just a matter of getting two extra binding posts and connecting the wires to them. It's just a question of "Do I need these?"

I didn't, all I really needed was the 12V line. But as I said, if you need them, they're easy to install.

UPDATE 12-1-11

Still going strong! This little PSU has been super handy. 

Comments

[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.

[StCanna]

This is a great instructable and just happen to be trying to figure out how to power a peltier to cool a network cabinet. i was going to buy a 12v 105w transformer for about $8 then, i remembered that i have and old 230w psu that has been sitting under my house for a several years that i can use. i've got lots of Nord TM-127-1.4-8.5mx peltiers (5-15v, up to 8.5a) and picked up some surplus heatsinks with fans to put on both sides. the fans are rated 12v @ 1w and since i'm new to this adhoc engineering i want to ask if you know, should i just hook everything to the 12v posts and see how they run or maybe i need some capacitors/resistors. I'm planning on making this project my first 'ible and any help would be great.

[sschoemann]

Peltiers are poor choices for cooling any computer system. They are excessively dependent on temperature differentials. so if the room temp gets close to 80 F the cooling will pretty much stop. My daughter has a dorm fridge that uses peltiers. works great in the wintertime, but once the ambient temps rise above 75 the temp inside the fridge starts to rise at 80 it starts to get warm inside the fridge at 85 its heating food without changing the polarity of the coupling... to keep it working it would have to be used in conjunction with an evaporative liquid cooling system on the exterior... For your network cabinet, if this is a serious endeavor, pick up a portable (read Interior compact, rollabout) airconditioner and plumb it into the cabinet. These use standard airconditioner compressors and refridgerants and do the job quite nicely, in addition to keeping dust out of the cabinet.

[StCanna]

correction it's actually a 185w max power supply. +5v/25a, +12w/4a, +3.3v 16a.

[Jomasdf]

Great job!

I'm a newb, so yeah,,

I was wondering is its possible to power
http://www.alibaba.com/product-gs/325940621/sound_control_led_light/showimage.html
For example with this, and how would I connect it?

Thanks!

[Megahurtz]

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?

[beehard44]

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

[Megahurtz]

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

[skylen]

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.

[agr00m]

 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.

[darmic]

where would you get the output from? im sorry, but im not much of an expert. thanks a lot. Regards. darmic

[cheeto4493]

What do you mean? "where get the output from" The power supply? Ask around, some offices and computer repair places have a bunch of old computer cases laying around, or even thrift stores sometimes have old computers for nearly nothing.

[darmic]

thanks for your answer. i'm sorry...i didn't explain myself well. Where do you get the Output DC? i mean..from which part of the transformed PSU? from which "wire"? And another question, what is the function of the ground knob? Thanks darmic

[cheeto4493]

Go back to step 3 and 4. You are basically cutting the quick connectors off of the wires, and then pulling them back inside the case. Bundling groups of wires together by color. Yellow for 12vlt, red for 5vlts black for common. The black "knob" looking thing labeled ground is a binding post with a banana plug socket in the middle (it's the same for the red ones too). They are commonly found at electronics stores, and make connecting wires easy. If you have a volt/ohm meter with removable leads, they are most likely banana plugs

[darmic]

do you mean that the DC can be taken out from the "knobs" (binding the banana plugs) to any external circuit by means of soldering a wire to the inside of the knobs (where there is the metal)? i'm sorry for the inconvenience. as i said, i'm not much of an expert..in fact i'm just a beginner. thanks

[cheeto4493]

Close, you can connect Banana plugs to the ends of wires that you would use often, or if you just want to use the wire, you unscrew the binding post, stick the wire through the hole in the side, and then tighten the post back down.

[omnibot]

I note on your pic there seems to be no insulation between the chassis and the connectors. Out of curiosity, how do you keep the current from grounding into the chassis?

[cheeto4493]

couldn't remember, I've slept since then ;-) Had a guess though, but took it apart to be sure. Took some pictures while I was at it. The binding posts come with 2 black insulating washers. I made a third by using a hole punch that punches 1/8" holes and heavy cardboard (like what is on the back of a pad of paper). Centered those holes under a standard 1/4" hole punch, and ended up with washers. I suppose I could have found some nylon washers that size at the hardware store, but I had the smaller hole punch, so it was easier to make, than to drive. Drill 1/4" holes for the posts instead of 1/8", and the new cardboard washers center in the larger hole. Another option would be to go to Radio Sh.... and buy an insulator kit for a T0-220 transistor. This is used to keep some tranistors from grounding against their heatsinks. Same Idea. ~Travis

[cheeto4493]

(removed by author or community request)

[cheeto4493]

I mounted mine to the top half. I also installed a couple of panel mount fuse holders. Actually came in handy once. Was soldering up a wire that had pulled loose on a circuit I was working on, and forgot the power supply was on. Also forgot the new soldering iron was grounded. "Pop"...... 2 disadvantages of mounting to top: Extra length of wire needed inside to allow room to work with the top off, and you have to make sure everything clears when you reassemble it. One of my fuse holders came real close to a heat sink. I left a couple of the standard cables coming out to plug stuff into, and only used 2 of each color going to the binding posts. I clipped the extra wires off at the board level, and this freed up some extra space inside. Try to find a power supply that has 3.3v coming out. Mine didn't, or at least I can't find a cut-off wire or label that said it did. I'm always having to hook up a couple batteries to test stuff, if I only had that 3vlt line....... One other thing I plan on adding to mine is a cigarette lighter outlet (probably on one of the cables that I left on. That way I can plug in car accessories to it, like my phone charger