DarkTherapy wrote:I did think if an even cheaper method to activate a relay remotely (I've done this to turn on a remote pc as an FTP server in the past)
Get an old Nokia 3210 - or any other old Nokia that let's you make custom ringtones along with its own pay as you go sim (free). Create a ringtone that consists of a single note for 1 second then silent for 30 seconds. Assign that tone to a contact number - your other phone. Set the phone to silent and only play that tone when you call the Nokia from your other phone.
Hook up 5v from the charger to a resistor and npn transistor, then hook up a wire from the phone speaker to a capacitor and the base of the transistor. Now attach a 5v relay to the transistor.
Now dial the Nokia's number from the other phone, the Nokia will play its 1 second tone that will be turned into a small DC current through the cap and into the transistor, which will turn the relay on for 1 second then off again.
As the Nokia never "picks up" the calls it will never cost anything to activate the relay over cellular. Just call it, then put the phone down after a couple of seconds.
I hear Hamas has a few job openings that you may be qualified for...
But in all seriousness, this is pretty cool, and has got me thinking if there's any way to integrate this with my Insteon HA system. Since the controller is networked, a Pi might not even ben eded. Hmm.