Hello, I have been thinking about making my own homemade electronic pet door for fun like one found http://www.doors4pets.com/Pet-Doors/electronic-pet-doors.asp. The dog wears a transmitter on his collar and when he gets close to the door, the receiver on the door recognizes the transmitter and the door opens the door and closes. Anyone know of what kind of kit I should buy for the transmitter/receiver? Many of these things say they use infrared. Is that what I should use? It has been a few years since school, but I was thinking of hooking up the receiver output to a 555 timer chip to regulate the door opening and closing sequence, and then hook up the output of that to a relay that would operate a 120 V power source to open the door. And I'm not sure if I would need some kind of programmable logic device to control all of this or maybe I could use a transistor or some sort like a Bipolar Junction Transistor. If I do need a PLC, I can't think of a place that I could program it. It was nice having those labs in school. Any suggestions?