Noise immune reset circuit for resetting the integrator of an electronic engine spark timing controller

摘要

A pickup operatively coupled with an internal combustion engine develops a train of bi-polar pulses wherein each bi-polar pulse is generated at a predetermined engine crank angle and each bi-polar pulse comprises a leading pulse portion of one polarity and a trailing pulse portion of opposite polarity. A bi-stable circuit is switched to a set condition in response to a given magnitude of the trailing pulse portion of each bi-polar pulse and is switched to a reset condition in response to a given magnitude of the leading pulse portion of each bi-polar pulse. A monostable circuit is operatively coupled with the bi-stable circuit to provide an output pulse of predetermined duration in response to the switching of the bi-stable circuit from the reset to the set condition. A transistor has its emitter-collector circuit connected across the capacitor of the engine spark timing controller integrator circuit and its base terminal connected to the output of the monostable circuit. The output pulse of the monostable circuit causes the transistor to switch into conduction to thereby short circuit the capacitor and reset the integrator. The circuit is highly immune to spurious triggering due to noise and provides rapid, accurate resetting of the integrator at the predetermined engine crank angles.