Building a device to power on/off computers

Posted on 2006-04-11
Last Modified: 2010-04-26
I want to build a device that will interface with a computer via USB or RS232 that will power a different computer on or off.  I'm envisioning the device having  a lead that will connect directly to the power leads on the target computer's motherboard, and a USB/serial cable heading to the "controller" computer's USB/serial port.

I know there are a million retail solultions out there -- I won't bore you with the details, but none of them work for me.  I need to build one.  

My question is simple:  can anyone point me to readily available electronic components that would allow me to build this?  Again, I don't want a packaged retail solution.  I want the actual electronic components.  

Thanks in advance.

Reg Natarajan
Question by:regnatarajan
    LVL 70

    Accepted Solution

    Without more details (distance involved in particular) it's difficult to say what might work for sure.   But assuming the distance involved does not exceed the length constraints for an RS-232 cable run, all you need is a 12v momentary contact micro-solenoid switch, and you can simply control it with any of the control signals from an RS-232 serial port.  Check with any auto parts store -- there are quite a few 12v solenoid switches used in automotive electronics.  You need one with a very low current draw.

    Here's a simple relay already mounted on a PCB that you could use in a kit box (or mount inside of the "target" PC):

    If you would prefer to get a pre-built interface board for this project, you can get them here:

    (a) for a paralle port:

    (b) for a serial port:

    (c) for a USB port:
    LVL 70

    Expert Comment

    ... just tested the links and the last one doesn't go directly to the USB switch => but it's listed on that page.  (It does a lot more than you need; and is the most expensive of the above options)

    Author Comment

    Thanks, Gary.  That's exactly what I needed.

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