Desktop Power Supply

A fairly standard project for electronic beginners is to build a desktop power supply from an old computer power supply.  I know some of you are thinking “Huh?  Why on Earth would you do that?”  When you are playing with a new circuit, you always need a DC power source and it isn’t convenient to keep digging out batteries and a battery case to get the voltage you want.  Instead, you would like an easy way to get different voltages that you can use to power different circuits.  The answer is a desktop power supply like this one:

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A “Real” power supply that costs “Real” money

This one would be great but it costs $331.  When you’ve already spent far too much on your new hobby, the quest for continued marital harmony suggests that you forgo spending hundreds of dollars on a new piece of equipment and build one yourself.  That’s how I ended up with this:

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It isn’t as pretty and doesn’t have as many features but it was far cheaper than a store-bought unit.  (To be honest, there are cheaper store-bought power supplies but comparing mine to one that costs $79 would make you wonder why in the heck I made my own.)

To build this, I used an old computer power supply from a computer that I bought back in 2000, a stereo speaker that we got at the Arc for $4.00 and various bits and pieces that *should* have cost me about $20.  Of course, I ordered some wrong parts mistakenly and then wasted a board with some ham-fisted soldering but, in theory, I built this for less than the cost of buying one new.  I’m happy with the functionality but the craftsmanship isn’t where I want it.  One of the LEDs is misaligned with the others and the hole I cut for the digital display is too big on one side.  Even though it isn’t pretty, it has features that one wouldn’t find in a cheaper unit:

  • 12, 5 and 3.3 volt rails
  • Adjustable rail that goes from 1.2 to 10.5 volts
  • Digital display of the output voltage
  • USB port for devices that use USB power
  • Genuine BradLab© construction

Here are pictures from construction:

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