Step 8Installing the Sensor / Reed Switch

The 'sensor' is just a reed switch that closes the circuit when a magnet passes in front.

The Arduino monitors when the sensor pin goes HIGH (magnet present) and sends out a pulse over serial of speed data etc.

1. Connect one wire from the sensor to Arduino +3.5v / 5v.
2. The remaining wire goes to Arduino A0 pin (acting as digital pin 14).
3. Connect a pull-down resistor between A0 and ground to make sure the pin isn't 'floating' about when we try and read it.