Contactless digital tachometer using 8051.

A three digit contact less digital tachometer using 8051 microcontroller which can be used for measuring the revolutions/second of a rotating wheel, disc, shaft or anything like that is introduced in this project. The tachometer can measure up to a maximum of 255 rev/sec at an accuracy of 1 rev/sec. What you just need to do is to align the sensor close to the reflective strip (aluminium foil, white paper or some thing like that) glued on the rotating surface and the meter shows the rev/sec on the display.

The basic principle involves a simple embedded system with a sensor, a controller and an actuator. The sensor used here is the one consisting of a white LED and a phototransistor, the controller used is the microcontroller loaded with a compiled code and the actuator is a display device, displaying the speed of the motor. The sensor senses the speed of the motor without actually being in contact with it by the principle of white light transmission and reflection and generates a signal. This signal is converted into an electric signal and fed to the microcontroller, which is programmed to calculate the speed in terms of number of motor revolutions in one minute. This speed is displayed on the LCD.