Saturday, March 10, 2012

ATX Bench Power Supply v2.0


I have been quite satisfied with the desktop power supply I made from an old PC power supply. My only problem with is that it takes up a lot of space on my desk. I have been long thinking how I could reduce its size and finally I realized that I don’t need an extra box around the power supply, I can mount the connectors on its original enclosure.

The finished item


In this minimalistic version I don’t use a display to show the voltage, since the different values are constant. They are what are available in a standard ATX PSU. So the list of materials I used:

  • 1 * used ATX power supply
  • 18 * banana post bindings – 5 different colours to colour code the outputs
  • 1 * on/off switch
  • 1 * blue LED and matching current limiting resistor for power on indication
  • 4 * self-adhesive rubber feet (from an old laptop)
  • Some pieces of heat shrinking tube
Most of the banana sockets in place. You can see I originally planned them in a different location, but then I realized (luckily, before drilling the holes) that the PCB has some huge heat sinks that prevent me to put the banana sockets where I planned. So I moved them a bit.

This is how it is going to look at the end. You can see the fake/dummy socket at the bottom right.


These are the steps I followed to create my new bench power supply:
  1. Decided which of the available power lines I wanted to use. I will use +5V, +12V, -12V, +3.3V, GND.
  2. Decided how many copies of each I want to use. I will use +5V – 3*, +12V – 3*, -12V – 2*, +3.3V – 3*, GND – 6*. These are the voltages I usually need for my projects.
  3. Planned and marked where all the banana sockets, the on/off switch and the power LED should go. Unfortunately, I overlooked the vent of the power supply and found out too late that one of the -12V sockets will not fit. I left the outlines of the socket though but it's fake :)
  4. Drilled all the holes with an appropriate sized drill bit.
  5. Sanded the front surface with a relatively coarse sanding paper to give the box a new look.
  6. Mounted all the banana sockets, and the switch.
  7. Used some hot glue to fix the LED in place.
  8. Cut the ATX power cables to a manageable length so that they are long enough to work with but not too long to block air circulation. Good air circulation has to be kept.
  9. Soldered all the cables to the appropriate banana socket, switch and LED. For the LED I used the POWER_OK signal (grey cable) with a current limiting resistor.
  10. I put some heat shrinking tube on the end of any unused cable and I tied them together with a zip lock tie.
  11. Stuck a piece of sticky rubber pads (salvaged from an old laptop) to each corner of the bottom side to prevent it to scratch my desk.
  12. Left the floppy/HDD power cables intact and mounted them on the side with some zip lock tie. Sometimes I use them, too.
All the above steps are very easy, you just have to make sure all cables go where they should and avoid any short circuits.

After putting back the cover, the power supply is ready to be used.

Some more pictures

For some experiments this cables might come handy.

These rubber pads were salvaged from an old laptop.

All the "UI" mounted in place and all the cables soldered.

The finished product from the angle I see it on my desk.