A DIY Adjustable Voltage Power Supply

By Paul Marossy
Last updated 08/23/04

If you build / breadboard electronic circuits a lot, an adjustable power supply really is a great help. I built one from a kit, made by KitsRUs.com , Kit No 68.

It's a very easy circuit to build, and it provides up to 30 volts DC at up to 1.5 amps of current. It's a textbook adjustable voltage circuit, and can accept either AC or DC inputs due to an on-board rectifier. I added a few things to make it a very useful tool. Below are some more details.

	Here is the view from above. The board on the right is the adjustable power supply. The three blue jacks to the left are for my digital multi-meter probes. Everything is mounted to a 3/8" thick piece of plywood which measures 8"x5". The black surface is 1/16" thick self-adhesive neoprene rubber.
	This is the front. I used slip-on wire terminals for easy removal of the wires going to the DMM probe jacks.
	Here is a close-up of the power supply board. There is a point-to-point style terminal strip behind it.
	Here it is with my DMM plugged in. The middle plug is a common ground. The one on the right measures the input voltage. The one on the left measures the output voltage.
	About a year after I built this circuit, I decided that I wanted it to be in an enclosure. I recycled another computer A/B switch box for my enclosure.
	Here is a picture of the inside of the enclosure.

A practical and very inexpensive way to power your circuits in the R&D phase. Most of the parts for this project could be found at your local RadioShack if you wanted to build it from scratch.

Here is an example of a scratch built adjustable power supply using a LM317 regulator.