Computer power supply

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Reply to
JeffM
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Can I use a OLD computers power supply box as a power supply unit for my circuits? I don't have a motherboard or anything for the power supply so id it possible to jus hook up the power supply to the wall and use the 5V, 12V and grounds?

Reply to
Mountain Dwe

ok.. That sounds more trouble than convenience.. so let me ask this simple question..... Is the step down transformer in the power supply just a normal step down transformer??? I mean can I salvage it and make my own general propose bench power supply? I would assume I could use the rectifier diodes on the board too??

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Reply to
Mountain Dwe

Absolutely.

As a minimum, buy some terminal boards and build yourself a proper interface to the voltages, maybe mount everything on a spare piece of wood. Understand the current and power limits of the supply. Fuse the outputs appropriately, and realize that you will not have an indicator of the status of the voltage and current without building your own displays. You might want to integrate some switches for better control. It all depends on the scope of what you want to do.

-- Al Brennan

Reply to
Kitchen Man

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Reply to
Art

supply?

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The stepdown transformer is a switched mode power supply (switched primary, rectified secondary, usually pulse width modulated circuit)

You *can* make a general 5V supply out of it, but beware of the "power good" line If using it, just use it "as is" since many of them are rather critical in layout and used components (especially if resonant-mode types) I personally wouldn't dream of disassembling it to build another, I'd just design another then

Reply to
peterken

Also ... I think all the computer supplies need some sort of load on the 5V line to power up. A 6v automotive bulb will work.

Reply to
JeB

Is it worth the trouble, how expensive are the power supplies your looking at. If you are a novice, do you really want to be playing about with 240V AC?

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Reply to
Richard Harris

Yeah, there's more to it than just plugging it in, I kinda overlooked some of the finer details when I posted. But, where there's a will, there's a way. It's a handy, pre-built switcher with common voltages ready to go. 5V and 12V will let you build some interesting projects, fun with op amps and low power auto stuff. Looks like there's plenty of info on the web about how to get the thing running, and there must be a gazillion of them laying around in junk piles.

-- Al Brennan

Reply to
Kitchen Man

But it's also tremendous overkill for a small bench supply. The fact that the supply likely needs a minimum mode should be a giveaway, you will be wasting more current on the load than you use on the op-amps.

The only time such supplies are really useful is if you have a need for high current.

They do make nice cases for small projects, though. You can pull out the circuit board, strip some of the parts, and then build a linear power supply inside. Grab a suitable transformer out of a junked consumer device, use the bridge from the switching supply, get some electrolytics from somewhere (since switching supplies work by generating a signal at a much higher frequency than 60Hz, they don't need as much capacitance at the output and thus they'll be too small for a 60Hz supply), and likely pull a 3terminal regulator out of the same consumer device, or another.

Such a supply will not supply nearly as much current as the switching supply, but you won't be wasting power on a load to keep the supply running, and it won't be as noisy for those analog devices, and the regulation may be better.

Michael

Reply to
Michael Black

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