ATX PSU: from junkyard to working bench


Please note that this blog has been moved.

Now it has its own domain: mynixworld.info🙂

If you want to read the latest version of this article (recommended) please click here and I open the page for you.

I had few old computers that I had to recycle. Because I’m a sentimental guy (or just stingy?) I didn’t wanted to throw them out through the window so I began to collect everything that I could use later in some DIY projects.

Today I found that it would be nice to have a variable bench power supply. One could get one for twenty bucks plus shipping from eBay or if you want something fancy you could pay like one hundred bucks for something like this.

Another option would be to use one of your scrap computer from the junkyard, take out its power supply unit, do some minor adjustments and Voilà!, you have got a bench power supply for free:
atxpsu

Question: is it complicated to convert an ATX power supply to a bench variable PSU?

Answer: No. I’m not an electrician nor I’m working on electronics branch, in fact I started with small projects just few months ago. With proper tools and patient this task is a breeze.

Requirements

  1. an (old) working ATX PSU
  2. heat shrinking tubes (preferably different colours and sizes)
  3. 1 x main switch (rocker power switch 4-pins)
  4. 1 x load current switch (toggle switch 6-pins)
  5. 6 x binding posts (1 black for ground and 3/5 red for loads)
  6. 2 x dummy load resistor (5W 10Ω ceramic resistor)
  7. 2 x 330Ω resistors
  8. 2 x light emitting diode 5mm LED (1 red, 1 green)
  9. 1 x prototype paper PCB

atxreqOf course, you will need some tools like multimeter, soldering gun and  solder and soldering paste, a drill, pliers, etc.

Instructions

I followed this tutorial so I’m not going to duplicate the story. Please check that video and even the project’s page. Another good tutorial could be found here.

Final notes

Although I followed the video tutorial step by step I wasn’t able to succeed replicating that project. The problem was that the ATX PSU  started for 1-2 seconds than stopped unexpectedly. By checking the circuit diagram from the other tutorial I made a small change in the project’s design by adapting its circuit diagram (excepting the fuses which by the way are a very good idea):

Project gallery

I have taken few photos so that you can see how things works:

atxpsu_1atxpsu_2atxpsu_3atxpsu_4atxpsu_5atxpsu_6

About Eugen Mihailescu

Always looking to learn more about *nix world, about the fundamental concepts of arithmetic, algebra and geometry. I am also passionate about programming, database and systems administration.
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