Sunday, November 8, 2015

Digital LCD Speedometer and Odometer Circuit - 16F628


speedo odometer

In my previous post, I explained how to build a simple speedometer circuit using a micro-controller and seven segments. Read it from here. This is a further development of that circuit. This circuit indicates both speed and distance.

A speedometer or a speed meter is an instrument that measures and displays the instantaneous speed of a vehicle. An odometer or odograph is an instrument that indicates distance traveled by a vehicle.

speedo odometer circuit
Speedometer + Odometer Circuit

For this circuit I used PIC16F628A micro-controller and 16x2 LCD. You can able to see speed in first line and distance in second line on the LCD. Distance will update every 100 meters and speed updates every one second. Value of distance writes to Eeprom in every 1 km. I also added a button to this circuit. The purpose is, reset the distance to zero.

Same as the Speedometer Circuit, micro-controller count the signals received to RA4 pin and then calculate speed and distance, then display information on LCD. 8 MHz resonator is use to generate clock signals. However, you can always use crystal for it and make sure to add 22pf ceramic capacitors if you use crystal oscillator.

Measure the radius of the wheel and enter it to Eeprom address 0x00. Default value for radius is 30cm (0x1E). I used two magnets to operate reed switch. Please refer my previous post for more details and circuit connection.

Maximum speed is 999 kmh
Maximum distance is 9999 km
Supply voltage is 5v

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