We are thinking of trying to set up a kind of Hall-effect sensor for a digital input to an Arduino. My latest idea is to hook up a coil to a Zener diode. Ground one side of the zenner, with the high side tied to an Arduino digital input.

When a magnet passes near the coil, it should induce a current, which will (hopefully) create 5v over the diode, triggering a rising/falling edge interrupt. When the current goes in the other direction, the zenner will show only the typical .25v diode drop, which should read as "0" on a digital input.

Might a small coil produce enough current to avalanche a zenner? I know that they need some small number of micro/milliamps to get over the hump and show voltage. Is the current higher for reverse bias/zenner avalanche than a forward diode? Might a simple diode (to prevent negative voltage) in parallel with a resistor work better? I like the zenner since I'm worried that a voltage spike might damage the AVR digital input.

Is this worth a try? Does it sound like a good sensor for when a wheel magnet passes by?