Tachometers are devices that are used to measure spinning speed that is expressed as RPM (revolutions per minute). You can find tachometers almost in all cars. But sometimes there is a need to find out RPM for different objects like in modeling, robotics, bicycles etc. It is better to use a contactless tachometer because there isn’t always an option to measure spinning speed directly. So here it is – a simple contactless tachometer project where RPM of rotating shaft is measured with IR sensor.
Simply you need to stick a reflective sticker on a rotating part and then place an IR opto-couple which sends IR beam and then detects reflective changes. The rest part is left for AVR ATmega microcontroller which actually rejects noise from signal and then calculates RPM value which then is displayed on LCD display. You can download all project files ready to build your own, or buy a ready preprogrammed kit to go along with less effort.