Variable Voltage Power Supply using a LM317

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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.

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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.

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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.

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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?

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    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.

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