Abstract: A digital system controls ignition dwell for an internal combustion engine. Dwell time is maintained constant, thus assuring a constant high level ignition spark, over the entire active RPM range of the engine. In addition, the system compensates for temperature and aging induced changes in the ignition components.In operation, one sensor generates pulses representative of engine angular position while a second produces ignition pulses. An angle counter stores the number of position pulses generated thereby creating a count representative of engine position. A speed counter stores the number of position pulses generated for a clock interval, producing a count representative of engine speed. Dwell time is initiated at a predetermined relationship between the counter outputs which assures a constant dwell time. Feedback circuitry monitors current through the ignition coil and alters the clock interval to compensate for ignition component changes.

Abstract: An improved ignition system uses feedback techniques to maintain a constant high energy ignition spark level over the normal range of engine RPM. The feedback automatically compensates for environmental and aging effects such as increased ignition coil resistance and decreased battery voltage.A voltage controlled monostable multivibrator produces pulses determining the "on" time of an electronic switch which is in series with the coil. Current through the coil is sensed by a generator which feeds back an appropriate signal to control the monostable whereby a constant dwell time is maintained. At very high engine RPM a second feedback source servo-controls the system to a constant dwell angle condition. A constant dwell angle is also established at cranking speeds by a second pulse generator in parallel with the first.