Tuesday, April 19, 2011

Variable DC Voltage Source

I wanted to have a DC voltage source for home projects and I decided to make one. I cheated and used a "wall wart" transformer which I picked up at the Goodwill. This takes care of AC step down transformer and rectification, I ended up adding a number of components though to protect from voltage spikes, smooth out the voltage, reduce noise and buffer the output so the load impedance has minimal effect on the voltage setting. The 100k pot sets the voltage output but there is a switch which can select between a 0 to 20V output range and a 0 to 10V output range which gives a little more control in the lower voltages.
I breadboarded most of the circuit before soldering to perf board, it seems to be working well so far but I am waiting for the analog panel meter (one of those old ones with a needle indicator) and I still need to find a nice little box to enclose it in.
This is a low current supply, I may build another one very similar but with a heavy duty 25V transformer that I have sitting around. We'll see how this Goodwill special holds up. 

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