How to Convert 1-Coil Tach Signal to 4-Coil Signal for Distributorless Ignition System?

A tachometer connected to a distributorless ignition system (DIS) receives a signal from only one of four coils, resulting in a quarter of the expected pulse frequency and thus incorrect RPM readings. To correct this, the pulse count must be multiplied by four, corresponding to the number of ignition coils or cylinders in a 4-stroke engine. Directly multiplying the voltage signal is not feasible; instead, a frequency multiplier or pulse counting method is required. One solution involves using digital logic gates, such as XOR gates in a CD4071 IC, to double pulse frequency twice, effectively quadrupling the pulses. This approach avoids microcontroller programming and operates at automotive 12V supply levels. However, pulse width and signal integrity must be considered to ensure compatibility with the tachometer input. Alternatively, a microcontroller-based frequency counter can count pulses over a time interval, multiply by four, and output a suitable signal for the tachometer display. Proper noise protection and input pin configuration are necessary for reliable operation.
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