In this design we use AT89S52 microcontroller to build inexpensive revs-per-minute meter. This meter can measure speed in the range of 1 to 9999 rev/min. This design was originally developed to measure the speed of brushless motors, but it can use for any application where the speed is in above mentioned range. In the given design input pulses are generated using Allegro A1203 Hall-effect bipolar switch and it can be replaced with any other Hall-effect sensor or IR detector.
Current version of RPM counter is based on Atmel’s AT89S52 8bit MCU and control software is developed using MikroC 8051 compiler.
At the time of implementation and testing we use Allegro A1203, A3517 and A3056 (for gear-tooth sensor operations) Hall-effect bipolar switches with this system and all these sensors produce excellent results with it.
AT89S52 source code and complete circuit diagram of this project are available to download at http://elect.wikispaces.com