Developing an Electronic Distance Meter

This electronic meter was created in order to measure distance covered by a bicycle using magnet and magnet sensor contact for proximity effect to sense the turning of the wheel.

A16-pin Motorola Nitron 68HC908QY4 microcontroller is interfaced with a 16×1 line LCD module. The LCD displays the data as the microcontroller counts pulse signals coming from the reed switch. The proximity effect detects the rolling when the magnet is close to the reed switch. An ON/OFF signal is produced as the reed switch contact closes or opens.

Since the microcontroller uses internal reset and internal oscillator, the supply to +VDD and VSS is the only thing required by using decoupling capacitors. The PTA2 are the sensor inputs for reed switch contact and PTA0 for 0/+5V optional analog input. Both sensors are using small phone jack. A battery with simple 5.1V Zener diode is used as the power supply although three 1.5V AA or 9V battery can be used. When the supply is down to +3V, the circuit still runs properly.

A universal PCB can be used to build the board as the sensor was protected using shrinkage tube when put to the wheel.

Rest of the project