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Hello fellow Arduino users!

I am working on a project that uses an IR sensor to detect a signal from a universal remote and turns on/off a computer.  One of my concerns is activating the power switch for the computer.  I want to retain the stock functionality of the power button, but also be able to electronically activate it.

So far, I have 2 2-pin headers connected pin for pin to each other.  one being where you plug in the case switch (just a momentary pushbutton), the other header will plug into the motherboard (probably with wires, not the header itself smiley ), so when the case switch is pressed, it will connect the wires on the motherboard and voila, power!

Now, for using the arduino to connect the switch, I could use some type of relay, but that seems like overkill for such a small load (I can't imagine the motherboard uses much current to detect the power switch).  I think I can use a small signal transistor, but that would mean I would have to mind the direction that the circuit is plugged into the motherboard (because transistors can only flow current in one direction, if I'm not mistaken).  Here's a diagram:

My question: is there any way I can make a bi-directional solid state relay with basic components?  I have a bunch of transistors and diodes that will hopefully be able to do the trick.  thoughts?

Left Coast, CA (USA)
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There probably is but I would always recommend the simplest, safest solution possible. Using a very small 5vdc relay like shown here can be driven directly from a digital output pin (use a fly-back diode across the coil if you wish) with no additional components required. The coil draws no more current then a standard LED does. The relay contacts allow complete isolation and are not polarity sensitive.

« Last Edit: February 12, 2009, 03:16:59 pm by retrolefty » Logged

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