So I required a little breadboard PSU to prototype some 3.3V units that I’m working with. I had some LM317 units lying around so I’ve decided to make a little breadboard PSU. I’ve made it to be switchable between 5V and 3.3V by means of switching a jumper between two positions. If you do decide to make this circuit, please don’t remove the jumper whilst powered up since the voltage will then spike to the input voltage whilst the jumper is removed. This is due to the adjustment leg going open loop. Other than that there shouldn’t be any issues.
I’ve decided to make it a set voltage module by using fixed resistors instead of variable potentiometers or trimmer resistors. Obviously the same circuit can be achieved by using a 3.3V linear regulator and a 5V linear regulator on one board and then just switching between which regulator will be active. But as I said, I already had the LM317 lying around from the previous battery charger project that I did.
If your interested in building this circuit then you can find the Github repository over here. Drop me a comment if you have any questions.
Paladin Enabling Technologies 
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