Get an Arduino to "press a button"?

Using Arduino General Electronics
1

I have a projector I'm trying to get to start up when the power gets turned on. I've added a couple wires to the pins on the tact switch for the power button. The button still works, and if I cross the wires, the projector turns on. So looking for a way to electrically "cross the wires".

I was thinking possibly an optoisolator, but it sounds like those put out a voltage, and I really just want to connect the two together.

Any ideas? Is there some device like an opto that does this, or some variation of opto maybe?

Danke, Ian

2

The amount of current flowing when the wires are "crossed" will make the difference.

I would say BJT, FET, or the best option would more than likely be a relay.

*edit: Relay examples in playground:
http://arduino.cc/playground/Main/InterfacingWithHardware#Electrical_High_Power

3

Little relay like this would work

Can drive directly with an output pin. Put a 1n4148 diode across the relay coil (cathode to 5V, anode to arduino pin).

Relay.jpg
Relay.jpg960×720 16.4 KB

4

I was thinking possibly an optoisolator, but it sounds like those put out a voltage,

No they don't.

You can get all sorts of components optically isolated, like a triac, transister, SCR, logic gate or FET.
For your case an opto isolated FET would fit the bill very well.

5

Well to use a semiconductor solution (transistor, opto, etc) you really need to know something about those two wires you 'cross'. What is the open circuit voltage, what is the polarity or is it an AC voltage, how much current flows when you 'cross the wires'? If you don't know those values then you are better off using a standard relay as the contacts will work without having to know those things, except possibly how much current is being switched on and off.

Lefty