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For my next electronics project I wanted to do something useful for the lab. I have been looking at picking up an adjustable power supply for my bench, but was inspired to build one myself. I searched the Internet for a good tutorial, but had a little trouble finding one that I liked. It was ultimately my brother who came through and sent me a link to www.jumperone.com. Phil provides a great video tutorial explaining the theory and construction of an adjustable linear power supply, using the LM317 voltage regulator.

http://jumperone.com/2011/08/lm317-adjustable-psu/

This turned out to be a great learning project and I would recommend it to anyone. I followed Phil’s design fairly close only making a few changes based on his lessons learned. I am using screw post terminals for all the connections to the circuit board and I have also put in a second 5 volt regulator to provide power to the volt meter and load switch relay. Another big difference was the volt meter I used supported a common ground, so I didn’t need a second transformer.

The biggest challenge for this project was designing and etching the circuit board. It took a couple tries to get a product I was proud of. I used the eagle file provided by Phil as a starting place. I then made the modifications I wanted for my design and laid the board out from scratch. Once etched, I used a Dremel with the drill press stand to drill the holes.

Overall I am happy with the outcome of this supply. Some things I will consider next time are:

  1. Add a 15 turn potentiometer in series with the voltmeter. The meter I’m using has a small potentiometer on it for calibration, but a 15 turn one would give me a little more control. Phil’s original design did incorporate this as well.
  2. I would like some kind of silk screen/markings on the front panel to indicate the function of all the controls.
  3. An amp meter would be a great feature to include in the future.

Download Eagle Files Here: LM317_Linear_Power_Supply

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