Tag Archives: ATX

DIY Bench Power Supply

For any electronics hobbyist, one of the most crucial tools while testing/prototyping circuits on a breadboard/perfboard is a good standard power supply. But buying a typical bench power supply might not be an option for everyone.

One of the easiest (and perhaps the most useful) hardware hacks I’ve ever done is to re-use a really old PC CPU’s ATX power supply as my own bench power supply. Earlier I used to keep leeching 5V or 3.3V DC off of Arduino Uno boards powered through DC 9 V Adapters and I’d always have to use DC jack to molex or other such types of connectors in conjunction with a plethora of DC adapters to power my breadboard prototypes.

Now, I can easily use this setup to have easy access to 3.3V, 5V and 12V each capable of sourcing 3 A of current too! 🙂
The best part is, there’s really not much that you need to do to get it up and running!

Here’s what an ATX power supply looks like:
http://www.ebay.in/itm/like/intex-450w-smps-atx-power-supply-sata-connectors-/271505046206?pt=in_computer_components

You can get one for around INR 800 (13 USD) easily from a local computer hardware store or online.

Here’s the pinout of the connectors on such an ATX supply:

atx-psu-pinouts
(http://www.helpwithpcs.com/courses/power-supply/atx-psu-pinouts.gif)

As you can see on the main ATX 20 pin connector, most of the standard operating voltages that we need for any electronics projects are right there! The only hitch is, you can’t just plug it in, flip the switch on the back, and make it run.

Remember how your PC CPU powers up? You have to push the power button right? The connection responsible for the powering up is the PS_ON pin shown there. For our purposes, we simply have to short that with GND to get the power supply up and running. So you could simply snip, strip and twist them together, or as I’ve done in my case, connect it to a small slider switch.

DSC_0675     DSC_0678

As for the other supply voltages, I’ve stripped them and connected the wires into this small “distribution circuit” which is essentially just screw terminals for the 3.3V, 12V, 5V, GND wires along with rows of male headers for the same along with a “Power On” green LED and the slider switch. You could even use the ATX 20 pin connector as is, but the molex connector on that has sockets that are larger than the usual breadboard hole sized male headers and that is why I went in for such a setup. ….and we’re done!

I found plenty of instructables online for setting this up and I thought that I could just help add to the list of resources out there so that more people starting off into DIY electronics or budding “Makers” could maybe have some easy access to these common voltages with very little effort, time and/or money.

TL;DR:

Step1: Get the ATX power supply
Step2: Short the Green wire with any one of the black wires on the 20 pin header
Step3: Solder a small perfboard distribution setup if you want
Step4: Plug it in, and DONE! Hookup your breadboard circuit and enjoy!

P.S. Be safe while dealing with the power supply and handling AC voltage and do leave room for the cooling fan at the back of the ATX power supply box

Some more pictures of my setup :

I even hooked up a push button switch and 2 wires to a small DC motor that I can drive with this supply. I intend to fix standard PCB Drill bits with it by gluing the chuck that I can take out from a normal hand press PCB drill in order to have a neat automatic PCB Drill for any prototype PCB’s I make at home with the toner transfer method. I’ll post that as soon as I’m done with it.
Cheers!