Shop made bench power supply.


I have an atx dual sata 550 watt power supply... I have seen a bunch of instructables on here that allow just a few different voltage selections.. I have also seen a few with potentiometers to allow it to be more adjustable (dial up or down the voltage).
That is what i want, i dont want to be limited to just three different options. S my question to you is, what type of potentiometer do i need to buy for this? And will a regular autostore purchased dashboard voltage meter window work?
Also, what type of fuse/or breaker should i use?. Do i even need one? I also head i need some kind of "switch" for this as well. I found circut diagrams, i found list of items needed, but most of the instructables ihave found arent very specific on the specs of these extra items needed... Any help or direction would greatly help. Im going out to radio shack today and would love to grab the items needed to finish this priject.
Thanks all...

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pfred24 years ago
I would be interested in seeing the circuit diagrams you have found. There are ways to make some switch mode power supplies adjustable but they are a bit tricky to accomplish. You have to break into the feedback, or reference voltage of the comparator and adjust that.
SlickSqueegie (author)  pfred24 years ago
finding a single diagram is the tough part....they all look different... I just found another one that requires a lm338... soo lost. :-/
SlickSqueegie (author)  pfred24 years ago
I thought this would be a somewhat simple project... I have seen many different ways to do this, im confused as to specifics on the materials... I just learned that a "pot" is a potentiometer. I now what a cap is as well. But there are so many variables.. Maybe im in over my head and have no business doing this... I went to radio shack to find a pot, which one do i need? And then i stumbled upon a reostat? Whats that for? I have a few lm317s....
Like you said there are several instructables on here that cover this topic. So start reading up on them and see how its done.

But to directly answer your question you will need more that just a pot to vary the voltage on the 12V rail. You will need to use an LM317 in conjunction with the pot to vary the voltage output. More is needed if you don't want to be limited to only 1A on the variable output. But these things are covered in there instructables.
SlickSqueegie (author) 4 years ago
Here is the label on the power supply