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Topic: ATX Power Supply, power on and constant supply (Read 247 times) previous topic - next topic

INTP

Let's suppose I want to use an ATX power supply to power some LED strips, and a microcontroller to control this setup (likely a Wemos D1 Mini).

The ATX PSU has its power-on green wire that needs to be pulled to ground to turn on the PSU. Sounds like throwing in a MOSFET there would allow the MCU to turn the PSU on and off.

But the MCU needs power, of course. I read that there's a 5V line somewhere in the ATX 24-pin that is always on. Is it possible to power the MCU with this constant power source while the PSU is off? Is there an ATX-standard current rating on this wire? Are the grounds still active when the PSU is off?

Southpark

I read that there's a 5V line somewhere in the ATX 24-pin that is always on. Is it possible to power the MCU with this constant power source while the PSU is off? Is there an ATX-standard current rating on this wire? Are the grounds still active when the PSU is off?
There are various kinds of atx supplies....various ratings.

Your question about grounds still being active needs to be clarified. What do you mean about grounds still being active? If unsure.... use a multimeter to test for continuity.

INTP

In case anyone is interested in the answer, it seems the +5v constant/standby purple wire is rated for 500mA, so plenty to run an MCU that in turn controls the PSU on/off as a whole.

JohnLincoln

#3
Jun 05, 2017, 01:36 pm Last Edit: Jun 05, 2017, 01:42 pm by JohnLincoln
Have a look at this ATX Power Supply Design Guide. It should tell you everything you need to know.

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