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How to shut down / wake up a computer from a PLC

Posted on 2014-11-05
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Last Modified: 2014-11-05
Hello everyone,

I'm laying out a project that involves both a PLC system and a computer. What it will do is fetch the signal from some analog sensors, display all the necessary info in a 10.1" HMI screen and mirror that screen on a big screen LED TV using the HDMI port on the PC and a Windows based software.

All the PLC/HMI part will be powered through a custom built UPS system but the PC/TV part won't. I really don't care if that part shuts down during a power failure (which almost doesn't occour).

What I need is a way to turn on and shut down the PC using the PLC. For example, tu turn on when I power up the PLC system and shut down when I press a button either on the touchscreen (HMI screen) or phisically on the side of my enclosure. This is to avoid Windows/disk errors in later uses.

There won't be a keyboard or mouse attached to the PC so shutting down the computer the usual way is out of the question.

Is it possible to electronically send a wake up or shut down signal to the computer?

The HMI will be conected to the computer using an 10/100 Ethernet port but I could easily attach a serial (RS-232 or RS-485) connection between them. Or just from the PLC analog ports to the PC's serial port.

Thanks in advance!
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Question by:Caracena
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Dr. Klahn earned 500 total points
ID: 40424745
Turning the system on is easy.  Short the appropriate pin on the power supply to ground (simulates pressing the power switch) and the system starts up.

Shutting down requires the assistance of Windows.  Configure the power switch handling to turn the system off when the power switch is pressed (see image below).  Then short the start pin on the power supply again, and in a few minutes the system will shut down.

XP power handling
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by:Caracena
ID: 40424933
Hmmm... I'd thought that but didn't think it would work, specially for the shutdown part. I'm used to do that to test my water cooling each time I change it. Gonna try and configure it with the PLC.

Thanks!!
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Expert Comment

by:Dr. Klahn
ID: 40425053
Side note:  Ground the start pin only briefly.  Once the system is up and running, holding the start pin at ground for some length of time (usually 4 seconds, sometimes longer) will drop-dead-halt the motherboard.  Windows doesn't like this, so don't use it as a shutdown method unless all else fails.
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