Belgian engineering student Gert-Jan built a great looking, and functional, linear regulated power supply for a test bench from an old radio transformer and a handful of supporting parts. This is a pretty nice looking adaptation of the common LM317-based power supply project. It only has a few parts and can make a nice, workable bench supply.
The supply uses an LM317 linear regulator. It can offer an adjustable voltage from 1.2-20V, since that’s the maximum output of the transformer, even though the LM317 itself is rated up to 37V. The case and meters came from eBay.
I do like what looks like a precision pot he’s chosen for the adjustment. I’d love to see a version of this build with a complimentary negative supply built around the LM337 as well. There’s plenty of room on that main piece of perfboard!
Making your own version of this supply would be pretty easy. Gert-Jan goes over the math of LM317’s adjustment range and includes schematics for each part of the system (rectifier and regulator). It’s up to you to string those two together, but that shouldn’t be very difficult. Transformers like that are pretty common, too. This would be a fun afternoon project. I might end up building one myself, I could use another adjustable supply. Maybe I’ll add a negative side to my version, too.
RETROVOLTAGE 