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Topic: Trying to start a PC with an Arduino (Read 721 times) previous topic - next topic

alexandrutoki

Hello,

I located the two pins that are responsible for powering up the PC. The are connected to the `Power On` button and one pin has an output of `5V` while the other is the `ground`.

So far so good, the problem is when I connect the `5V` one to the Ardunio `VIN` and a ground cable from the PC power source to the Arduino `GND`, instead of powering my board, the PC starts and then promptly stops, as if I pressed the `power button` and did not release it.

It seems that electricity passes through the Arduino without powering it. I tested the `VIN` and `GND` pins with a normal breadboard power source and they are not broken, as the board starts up with no problem.

My plan was to power the Arduino with the `5V` pin and send a `digitalWrite(somePin, HIGH)` for a short amount of time to the ground pin from the PC that would normally be connected to the power button, thus "closing" the circuit like the normal case button would.

Zapro

I'm a bit confused by your explanation.

It /sounds/ like you want to power the Arduino from the power-signal-pin - that won't work.

To power the Arduino, connect 5V from the PC's standby-supply to 5V-pin on the Arduino - not VIN - VIN Needs approximately 7.5V or higher to work properly.

To "press" the power button, alternate the pin between being an input (not 'pressing' the button) and then an output and low, then 'pressing' the button.

The super awesome way to do this would to be using an optoisolator (look it up!) and use that for "pressing" the button - it's a safe way and you don't end up destroying anything by accident.

// Per.

alexandrutoki

Ok, I understand that I can not power the Arduino from the signal pin.

I connected it to the 5v and GND of a on-board USB set of pins.

But if I connect the POWER ON pin which does not have voltage to the USB 5V pin, the computer will still not start. I'm guessing connecting it to an Arduino pin and using digitalWrite(HIGH) would be similar.

MorganS

Do you know that that particular USB pin has 5V when the computer is off?
"The problem is in the code you didn't post."


Zapro

You need to read what i wrote. You need to connect the power-on -signal to GND to turn on the computer, not +5V!

// Per.

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