A microcontroller based automobile digital RPM meter

Some of the smaller cars available today does not have an RPM meter on them – this would be some trouble since you wont be able to determine the actual speed of the car’s engine, thus will have an impact on the fuel consumption since engines are efficient at a certain range of shaft speed. This project makes use of an AVR microcontroller and a signal conditioning circuit that makes use of an LM324 operational amplifier (Op-Amp). The input signal was taken from the High Voltage (HV line) of the main distributor of the engine. This specific point was chosen since all (gasoline) engines have an HV line. The signal from the HV line is fed into the signal conditioning circuit before being fed to the microcontroller’s PB1 pin. The Timer/Counter1 External Counter Input mode of the PB1 pin is used as an external clocking source for the MCU’s timer1 making it able to do frequency measurements. While another timer (timer0) is used to measure the elapsed time. If you wonder whats in the HV line that makes it a good… Continue reading