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make bench power supply Adjustable Voltage Control? Answered

Ok so i have a atx bench power supply i made and now i need to be able to put a Adjustable Voltage Control dial on it so i can go from 0v to 12v how do i do so? And can i use any spare parts from around the house?

2 Replies

frollard (author)2010-07-07

You need to convert the atx supply as you have already done, and then add another circuit to create a variable voltage. This is easy enough with an adjustable voltage regulator. It works like a 7805 or 7812 regulator but instead of just having in and regulated out, it has in, reference, and regulated adjustable out. The LM317 is a great cheap example: But be advised, it has some drawbacks.  Regulating the voltage drops it from anywhere around .3v (high quality digital alternatives) to 2 volts, so the most you can regulate out of 12 volts is 0-10 adjustable.

Search for LM317 circuit to get a schematic -- there are a hundred here on instructables alone.

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schwendigo (author)frollard2018-02-07

what if you use the -12 and +12 to get 24v, for a max of 22v after the drop?

however, i heard the +12v is rated different amperage than the -12v - do you know how to determine the max current draw?

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