Normally, digital speedometers are found only in luxury cars and high-end motor-bikes. We describe here how to build a microcontroller based digital speedometer. The rotation of the wheel is sensed by the combined action of a reed switch and
a magnet fixed on the wheel. The sensor sends a pulse to the microcontroller each time a revolution is made. The circuit uses a microcontroller, an LCD display and some commonly available components. It is a better alternative to the mechanical speedometer. The features of the digital speedometer are:

1. Digital readout.
2. Speed displayed in km/hour.
3. Distance travelled displayed in kilometres.
5. Reliability due to use of the microcontroller.
6. No mechanical wear and tear.
7. Home-brewed speed transducer/sensor.
8. Self reset to zero after completion of 99,999.9 km.
9. Easy to build and fix onto the bike.