Been working on an idea for the Bike project. (a detector that will open or close a relay if the peddler quits peddling.
I tried placing a strong magnet on the rim of the bike and can get a multi-meter (analog) to make a very small jump as the magnet passes by a coil I've got positioned close to the rim. Plan is to use the small amount of generated current to charge a capacitor that would then have enough current to pull down a relay (or transistor switch). A resister would be in place drawing current away from the capacitor so that the rider had to keep charging the capacitor faster then the resister was discharging it or it will complete/disconnect a circuit alerting the rider that he has quit peddling. Kind of a nag alarm really, (gosh, I hate to get nagged, but Hey!, I'm not the one who is going to have to ride this exercise bike)
My thoughts are that this would produce an A/C pulse so naturally I grabbed a diode and put it inline with the coil to convert it to pulsed DC. For some reason I get no signal at all now that a diode is in-line. Makes no difference which way the diode is oriented or what direction the wheel is turning.
Is the signal so low from the coil that the diode can't handle it? I don't know what sort of diode I was using, I just pulled a couple of different ones from a old board and gave it a try.
Do I need a special diode? Do I need a full wave rectifier for this to work?
Thanks in advance, Lawrence