Back in the old days where you won’t find any LCDs and seven segment displays – thus in the past the world of electronic indicators is ruled by the infamous analog dials – the one with the arm that points to values in the back ground. Back then tachometers, which are used to measure rotational speed is made up of a DC generator, the voltage output of the generator is then used to crank up the analog dial to indicate the speed of the shaft of interest – which is given in RPM or rotations per minute. This is not portable since one must attach the DC generator to the shaft either by a coupling or any other means – not to mention the dangers when dealing with high speed mechanical entities.
This project demonstrates the use of a microcontroller and IR reflective techniques to build a non invasive tachometer – yup non invasive it doesn’t touch the rotating shaft all you need is a piece of white paper and your good to go measuring RPMs on a speeding shaft. The tachometer counts the number of times the white piece of paper passes through the infrared pair in a given time number of passes over the specific time [a fraction of 1 minute] would give us the number of rotations per minute. The timer0 module of PIC18F2550 was used to keep track of the time. microElectronika’s microC IDE was use to build the program – two more thing about this tachometer? It doesn’t come with old school analog dials, it comes with a 2×20 LCD and no contact thus less chances of getting a finger ripped off.