I know there is already a bunch of these on here, but I didn't see any quite like this so I thought I would post it, so here it is.

This power supply has 3 12v lines, 3 5v lines, 3 3.3v lines, 1 -12v line, & 2 USB ports.
It uses a 480 Watt ATX power supply and puts out enough power to run most projects.
It cost about $35 for everything including the ATX power supply.
This is also a good way to make those ATX power supplys that most people have sitting around gathering dust useful again.


This project involves electricity and sharp tools.
however this power supply only puts out 24v max You should not open the case, when plugged in there is a deadly amount of power inside and the capacitors inside will store a large amount of power for days even when unplugged.
This power supply puts out enough current to start a fire. Make sure to use wire that is heavy enough to handle the current and make sure that there are no shorts.
I am not responsible if you electrocute yourself or anyone else, if you blow something up, or if you burn your house down so be careful.

Step 1: Parts & Tools


  • ATX Power Supply
  • Binding Posts With Banana Jacks
  • Butt Splices
  • Eye Connectors
  • Type A USB Jacks
  • 12 Way Terminal Block
  • Small Piece Of Strip board
  • Miniature SPST Toggle Switch
  • NC Momentary Pushbutton Switch
  • Panel Mount Indicator LED (Mine has a built in resistor for 12v use)
  • High Power Resistors
  • Heat sinks For Resistors
  • Wire For Connecting Everything
  • Super Glue
  • Electrical Tape
  • Zip Ties
  • Craft Plywood Or Other Material To Make Case Out Of


  • Wire Strippers
  • Wire Cutters
  • Crimpers
  • Utility Knife
  • Pliers
  • Hot Glue Gun
  • Soldering Iron & Solder
  • Drill & Drill Bits
  • Screw Driver
  • Volt Meter
<p>very nice</p>
is this downloadable ?
Would it be wrong if I connected +5 and +12 outputs in series, to get 17V? That's because I'm trying to charge car battery using ATX, and connecting it to -12V is not the option, due to it's poor current rating.
You can't connect the outputs in series.<br> The negative connections are connected to ground so you can't connect two different power supplies in series either.<br>
It seems obvious to me now, what was I thinking :)<br>Any other suggestions how to get 17V and some decent current?
<p>-5v and 12v make 17volts. Just think of it like thermometer readings. -12v and +12v is a 24v swing</p>
<p>No!!! Be careful of this. Different power lines are rated at different amperage - so while you could use -12 and +12 for a 24 volt differential, the -12 volt line does NOT sink the same amperage as the positive one does. You would be better to use something like a LM2596S DC-DC Constant Current and Voltage Adjustable Module, which gives you something like 1.2v-30volts adjustable and up to 5 amps output with an input of between 7-15 volts I believe. There are similar products out there that allow you to get to what you want without breaking the rules. So depending on your amperage requirements, you could use it connected to the +12v line. Remember that the amperage you use for the adjustable line will reduce the available output from the +12 line.<br></p>
<br> You could look for an old laptop power supply. Some of them will be around 17 volts and the usually supply 2 - 4 amps. I have gotten them cheaply at yard sales and swap meets.<br> I have a 16v one that works well for charging batteries.<br>
Hi everyone i'am new to instructable I'm looking to build a power supply out of a computer power supply i need 12v 4amp but the power supply says 12v 12amp for a amplifier please help me thank you
<p>Your device will only use as many amps as it needs. Using a power supply that has a higher current rating is fine.</p>
Thank You
<p>how can I wire this for 24v?</p>
<p>Just a note to let you know I have added this instructable to the collection: <br>Encyclopedia of ATX to Bench Power Supply Conversion <br>&gt;&gt; <a href="http://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/" rel="nofollow">http://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/</a><br>Take a look at about 70 different approaches to this project.<br> </p>
Very nice job. The only suggestion I have is to make it have molex and motherboard connectors in the back so you can just plug in any power supply withought taking anything apart. You could put the resistors with heat sinks in the wooden case and add a fan and air vent. Then it would be completely modular.
Me to thats what i`m making
<p>how did yours go? i found attaching the ATX plug to the terminals a waste of time scrapped the idea. its only a $38 PSU</p>
I was going to do this project, but then the power supply decided to die. Some of the ground rails didn't work. In the end, I trashed the power supply, and the parts are sitting in my closet. So yeah, that comment was from four years ago. Sorry I couldn't be more useful.<br><br>-Eric
I was going to do this project, but then the power supply decided to die. Some of the ground rails didn't work. In the end, I trashed the power supply, and the parts are sitting in my closet. So yeah, that comment was from four years ago. Sorry I couldn't be more useful.<br><br>-Eric
<p>Made This: Substituted minium load resistors for cooling fans and a the LED in a light up magnifying glass that i jerry rigged </p><p>yes they are always on but so is the PSU fan, its of little consequence </p>
did you wire the atx power on switch like so: http://ubuntuone.com/p/155G/
No, I've never seen it wired like that before. The green wire (ps_on) is connected to ground.
i have had it wired like this and had no problems but when i wired another power supply with ps-on wire to the ground it burned the power supply immediately. i read about &quot;ps-on to ground&quot; on wikipedia. i figured out the right way (ps-on to pwr-ok) by my self.
i just tried ps-on to ground on two power supplies. i gues we now have two ways to turn a power supply on: ps-on to ground or ps-on to pwr-ok. i probably short circuted that other supply that burned. :)<br>
Some old dell power supplies used a different pinout even though the connector is identical.
all i know is i had it wired my way and it's been working for years and it still works.<br>no additional loads needed. it's not a dell but generic atx.
<p>ps-on to ground has never failed me </p>
Additional safety notice: <br> <br>WARNING <br> <br>Due to their inner workings, these power supplies work with very high voltage inside, up to 500V (and more depending on the topology). Unless you seriously know what you're doing, don't open open the case, don't touch the components, don't replace anything inside. <br> <br>It sound boring, but it's much better than a call to the EMS for defibrillation.
I believe USB ports are limited to 500mA. Are the two USB ports current limited in any way?
The USB standard specifies 500mA for compliance. However due to the popularity of devices charged by USB and their power requirements, manufacturers choose to make USB ports capable of outputting over 500mA, which is not covered by the standard - it's up to each manufacturer to decide. This allows you to charge your power hungry devices faster using the same convenient port. <br> <br>The iPad charger for example is limited at 2.1A. In this project, there is no additional limiter so it would fall back to the current capacity of the ATX line used - in this case 2A as rocketman221 said. <br> <br>Ideally, to make things just a little safer, you could add a current regulator set to a reasonable value. <br> <br>The good thing about ATX PSUs is that their 5V lines can supply much more current than normal USB ports or hub (which often share a total capacity). You could be assured to have the current you want on each port (eg. 2A on each ports, charge at maximum rate iPads with no time compromise).
my laptop usb allows up to a 1000mA or 1A per port It all realy has to do with the Motherboard and what the psu can handle I have seen some that can supply 2A per port with all the hubs and other stuff out there most computer companies realized the 500mA was not enough and the keep breaking and burning out
In most cases, it would be wise to use a regulating circuit that will only output 500mA. I believe in this case however, it's VERY useful the way he set it up. I know personally that when I want to charge more then two things off my USB hub.... they both charge slower! I think in this case, it's fine. Cell phones, IPOD's, Blackberries.... all charge at over 500mA current draw. If you want to know why they limit it to 500mA......... there is no reason! There are downsides however: - USB cords stop responding after 16 feet - USB hubs which split one port into 4, only gets 125mA PER PORT!!! USB is nice, wireless is better!
usb 3.0 increases power to 900mA.
The usb ports on the power supply are connected to the 5V standby line which is limited to 2 amps.
24 volt by using +12 v and -12v if want higher current should change diode-12v to a bigger one
Do know that the maximum current available on the -12V is usually very low, less than 1A (often &lt;500mA).
There is nothing easy you can do to increase the current from -12v.<br>
oooh... I have an extra 750 watt power supply from a dual (redundant back up)power supply server that I got for free from work (they were throwing out old server racks, and I got to swipe an old hp DL360 g4P for free.) I think I will be using it for some mad science...
On the specifications of my computer power supply it says &quot;+5 VDC minimum load is 0.2 A when there is a minimum load of 0.3 A on the +12 VDC and 0.42 A on the +3.3 VDC outputs simultaneously. +5 V minimum load is 1 A for load transient tests.&quot; After reading this I still have no clue if I need a Power resistor. How do I know what I need?
3.3V - 5 ohm - .66A - 2.2W<br> 5V - 5 ohm - 1A - 5W<br> 12V - 20 ohm - .6A - 7.2W<br> <br> The 12V resistor will get very hot. It should be a 20W resistor or two 10 ohm 10W resistors in series. The 5v resistor should be 10W and the 3.3v should be a 5W.<br> Using a resistor rated for twice the power dissipated keeps them from getting burning hot.<br>
wouldn't the -12 volt line just be the same as the 12 volt line, just with the terminals switched?
Yes but you can get 24 volts from the +12v to the -12v line. The -12v can be used just like the +12v though.
oh, so using the -12v as a second groundish thing, but lower? and also, when you say the -12v can be used just like the +12v, do you mean that the -12v can be used with the ground, so that, like before, the -12 acts like a more negative terminal than the ground?
Here I home this diagram helps.
on the top line it says24 volts. which is positive and negetive? im still learning about dual rail power supplies
The -12v is negative. That would be the blue wire on an atx power supply.<br>The +12v is positive.
well it certainly helps me :D <br>i have a powerbook 190 that uses 24v and has no 24v adapter. <br>
Make sure the -12v line can supply enough current. The -12v on my power supply only puts out 800mA.
What exactly is this for?
It's a handy power supply that outputs a few different standard voltages so you can bench-test circuits you make, or use it to power devices.

About This Instructable


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Bio: I enjoy building electronics &amp; robots. I like building computers as well as writing programs &amp; web sites. I like to build and launch rockets. I especially ... More »
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