I'm trying to design a simple circuit that will enable a magnet passing by an induction coil to send an IR pulse to a simple receiver plugged into a Linux box. This will be used to measure the speed of a turning wheel without having to worry about batteries or a power block of any sort. Any ideas? I have the design of a simple 555-based transmitter and a simple 38KHz receiver, all using parts from Radio Shack. My concern is powering up the capacitor and triggering the pulse with magnetic induction from a magnet attached to the wheel. Very much like a bicycle speedometer, where the magnet passes a reed switch to close a circuit, I want the magnet to pass by an induction coil to transmit an IR pulse.