momentary contact switch via an opto relay

We need to interface to another piece of equipment, which expects a momentary contact switch input.

I chose a Panasonic AQY212EH PhotoMos for this purpose. It's an optically isolated relay in a 4-pin DIP package.

I simply connected a BeagleBoard GPIO output to pin 1 through a 130 ohm resistor; and grounded pin 2. Then pins 3 and 4 can simulate a pushbutton. i.e., when the BeagleBoard output is driven high we have a closed circuit on pins 3-4 (about 1 ohm resistance); and when the BeagleBoard output is driven low, we've got an open circuit.

Simple, cheap, and it optically isolates the BeagleBoard from the external equipment.