CONTACTLESS TACHOMETER

Abstract

Tachometer is used to measure speed of motor or shaft or propeller. This tachometer is designed using ATMega16 micro-controller. It can measure time interval varied for better accuracy. Attractive feature of this is it measures speed without any physical contact with shaft or motor. It shows RPS speed on LCD and Tachometer setting can be changed from simple push buttons. It uses low cost infrared transmitter-receiver pair for sensing propellers. It can measure RPS speed up to the depends on the speed of the motor The AVR ATmega16 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the AVR ATmega16 achieves throughputs approaching 1 MIPS per MHz allowing the system designed to optimize power consumption versus processing speed. Here timer interrupts and counter application of the microcontroller is used for frequency calculation. Because of its simple architecture and tool availability it is very popular. Most important part of the Tachometer is sensors. It uses low cost infrared sensors for sensing propellers. IR LED will transmit IR rays and receiver generates some analog voltage and when the propeller cuts the IR transmitter- receiver pair sends a zero voltage to the microcontroller. This analog voltage is sensed and generates an interrupt to micro-controller. The trains of analog voltage pulses increment the counter value. Timer will be set for one second. After one second the counter value will display on the 16x2 LCD and simultaneously counter resets. The setup is also modified by providing a LED and a buzzer to make warning or indication of some fixed rated speed of the motor. The LED and the buzzer connect to the microcontroller which monitors the speed of the motor. Such a setup needs a variable potentiometer c to be connected across the supply of the motor and thereby the speed of the motor can be varied to an extent. By varying the supply using the potentiometer, the speed of the motor varies and when the speed reaches or exceeds the fixed rated speed, the LED will glow simultaneously the buzzer beeps. The future modifications that can provide to the tachometer is by altering it for controlling the speed of any dc motor using the advanced usage of microcontroller.