[cjchands]

Hi guys,
I am working on a delta tau motion controller that requires power supply on the board to 4 terminals:
G, +5, +12, -12V
I have been told that I can use the power source from the PC p/s directly.
Problem is that I can get +5, +12 from the reference Ground.
But how on earth can you get -12 V from the same G??????

Or if you have other solution, where can you find powersupply that support
-12V?
Thanks.
J.

[Al_The_Man]

Pin 12 (blue) of the ATX supply on the older style XT mother board with two connectors it is the blue wire, next to the two ground wires on the 6 pin connector.
Al.

[JFettig]

its not always blue.

and you mean AT not XT power supply.

Jon

[kreutz]

On the ATX power supplies, at least the ones with the 20 pin motherboard connectors, it is still the blue wire. Read the rating for -12 volt source on the power supply sticker (typically 0.2 to 0.5 Amp depending on the power supply)

[jkeyser14]

yep, these guys are right, ATX power supplies have a -12v. I suggest using a multimeter to figure out which wire(s) is -12, just to be on the safe side.

[cjchands]

Thanks guys for your knowledge.
If you look on the sticker, it sure says: +12V (10A), +5V (15A)....
BUT -12V (1A)..?
Why is it that -12V gets only 1A? Not using very much or what? And if you use analog signal +/-10V, I thought you need current equally between the positive and negative 10 V. Am I wrong?

[Al_The_Man]

Is this a stand-alone card or plug into PC MB, if so the mother board usually provides the voltages, the PC -12v is only used for things like RS232 which requires little current.
Also if the analogue ±10vdc is for servo command signal, the current required is very small.
Al.

[cjchands]

It is a standalone Al.
Thanks for the explanation.