SPEEDOMETER DRIVE

Originally I used a Hall Effect sensor to trigger the speedo head as was suggested by Classic Instruments. I have burned out about 6 of those. Some kind of voltage spike was getting to them, I think. I added a capacitor to try to eliminate those but to no avail.

I have now switched to a reed switch. This is a switch that is triggered by a magnet passing by the switch. The speedo head operates by grounding the sensor wire with pulses of grounding. The reed switch is perfect for this.
I found one that mounted where the old unit was and stuck rare earth magnets to the brake rotor, no glue, one on each spoke. This gave the same pulses as the Hall Effect unit so no new calibration was needed. So far this is working great and will no burn out since there is no voltage going to it.