power supply

[Gordon WParticipant @gordonw]

This will be a simple question for a lot of you– I have a couple of ex-computer power supply "boxes". Label states +12 V 12amp max, -12V 1amp max. Max continuous DC power 200W. If I use this to drive a DC motor do I connect to + and – and then can use the full 12 amps if need be ?, Or connect to + and ground ( the case )? Could I use two supplies in parallel and get 24 Amps ? OK that's two questions.

[Gordon WParticipant @gordonw]

[Martin KyteParticipant @martinkyte99762]

You have in each box 2 supplies one at +12V @ 12A and one at -12V @ 1A.

To use the +12V connect between +12V and 0V. Not a good idea to connect the two boxes in parallel.

You may have to fiddle about a bit. Computer supplies are usually power managed from the mother board or at least some remote on/off switching device.

regards Martin

[Neil WyattModerator @neilwyatt]

There will be a wire (green or purple from memory) that has to be shorted to ground to get it to work. Check the net.

Some PSUs used to require a modest load on the +5v line to allow the higher voltages to work as well. Not sure if this still applies.

A bit of filtering between output and load might make it live longer if using with a motor.

Neil

[Gordon WParticipant @gordonw]

Thanks for the quick replies. Have been looking on the net and more or less what you are saying, can't think why I never tried the net first ! Seems green wire is the start wire and may need a push switch, but will have to try it and see. What sort of filter might be needed ? Will have to get going with the old meter. Not sure how old these are but not modern. I can see what looks like a choke or small toroidal transformer inside.

[Ed DuffnerParticipant @edduffner79357]

With a negative 12 volts I think that's an old AT PSU as opposed to the later ATX versions.

Connect the green wire to any black wire to make the PSU work, needs to be a constant connection, not just a push-to-connect.

Ed.

[Martin KyteParticipant @martinkyte99762]

It's undoubtedly a switch mode supply and will have high frequency chokes and toroids.

Martin

[Speedy Builder5Participant @speedybuilder5]

Just a "heads up" If you like a bit of electronics dabbling, it may be time to grab hold of a few desk top computer power supplies. A lot of the market is going / gone to laptops and old desktop computers are two a penny when out of date. Grab a few before its too late ??

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