Variable Voltage Power Supply using a LM317


A classic afternoon project. I was in need of a variable voltage and didn’t have a proper lab power supply available. But I did have a solid 12 volts from an old computer PSU. So I built myself this little thing.


It’s really nothing more than a LM317 in a TO220 package with a pot, two capacitors and banana jacks. It measures about 65x55mm and has rubber feet so it sits nicely on the bench. All the parts I found laying around here. The little heat sink can handle 5 to 10 watts without getting overly hot.


Over a short period of time you can burn quite a bit more so you can draw up to 1.5 Amps (the LM317’s internal current limit) from anywhere between 1.25 and 10 volts when connecting it to a 12V supply.


4 thoughts on “Variable Voltage Power Supply using a LM317”

  1. Hi. I came across your blog from the MPPT solar charger post. I realised your PCB all look very nice and clean. Can you share with me your method of making those pretty boards?

    1. Hi John. Thanks for your comment. All my boards here are milled, not etched. I’m using a LPKF Protomat S62 that I happen to have access to. Getting started with this machine and all the CAD/CAM stuff was kind of hard but now it’s quite quick and easy for me to make a prototyping board like this one. The process is not suitable for more than a few pieces as it almost doesn’t scale with quantity but really nice for prototyping. I’m planning to do a post on how I make these boards once I get to it.

  2. Hello Lukas
    Nice project ! Would be possible please to share schematic and PCB layout of your Variable Voltage Power Supply?

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