RPM Meter for Automobiles Circuit Diagram
An efficient way to measure the RPM of a vehicle is through its ignition pulses. RPM of a vehicle is directly proportional to the rate of its ignition pulses. An ignition coil (also called spark coil) is an induction coil in an automobile’s ignition system that transforms the battery’s low voltage to the thousands of volts needed to create an electric spark in the spark plugs for igniting the fuel. Here we measure the rate of ignition pulses with a sensor system attached to the spark coil and thus indicate the RPM using a bar graph comprising 20 LEDs. Circuit and working Fig. 1 shows the circuit for RPM meter. The circuit is built around frequency-to-voltage converter LM2917N-8 (IC1), bar display drivers LM3914 (IC2 and IC3), 20 LEDs (LED1 through LED20) and some other components. Fig. 1: RPM meter circuit Diagram The circuit has three stages—pulse detection, frequency-to-voltage conversion and display of voltage by the LED bar graph. To sense the pulses from the ignition coil, 18SWG P...