Tachometer is a device that measures the rotational speed of any shaft or disc. The unit of the measurement is usually revolutions per minute or RPM. The traditional method of measuring RPM of a rotating shaft was based on velocity feedback concept where a dc generator is hooked to the rotating shaft so that the voltage induced across the generator’s terminals is proportional to the speed of the shaft. Today, we are going to make a digital tachometer based on a PIC microcontroller that requires no physical contact with the rotating shaft to measure its rotational speed. The physical contact is avoided by using an optical detection technique that requires an infrared light emitting diode in conjunction with a photo detecting diode. StartUSB for PIC from mikroElektronika is the main controller board used in this project. To read more about this board, visit my article Getting started with PIC18F Microcontrollers. This tachometer can measure speeds up to 99960 RPM with the resolution of 60 RPM. The result is shown on a 16×2 character LCD display.
Contact-less digital tachometer using StartUSB for PIC and optical sensors