Embedded Lab

Check out this detailed build of Arduino-powered speedometer to monitor your bike speed on road. The project uses a reed switch to sense the rotation of one of the bike’s wheels. The Arduino reads in the reed switch closings and calculates the bike speed in mph. The calculated speed is displayed on a LCD screen. The speedometer is calibrated by defining the radious of the wheel in the firmware.

Arduino bike speedometer

Secure both the magnet and reed switch to your bike wheel with electrical tape (either wheel is fine).  As shown in the images above, the magnet connects to one of the tire spokes and the reed switch connects to the frame of the bike.  This way, each time the bike wheel turns the magnet moves past the switch. Connect the leads form the reed switch to the long wires from your protoboard (orientation does not matter here- it’s just a switch)