Electronic tachometer for IC engines - has engine ignition pulses applied to monostable flip=flop to produce train of pulses of constant duration and varying frequency

摘要

The electronic rev. counter for IC engines, consists of a monostable flip flop to which the filtered engine ignition pulses are fed. This produces a train of fixed duration but variable frequency pulses to a suitable display instrument. Ignition pulses from the contact breaker in the engine ignition system are fed to a voltage divider (R4, R1, R2) and filtering circuit containing a zener diode (Z1) and capacitance (C1) the output of which triggers a monostable fixed pulse duration flip flop (2). A train of fixed duration pulses of frequency dependent on the engine speed, is fed to a suitable voltmeter display (3). The shape of the ignition pulses and the operation of the filtering circuit are described at some length.