Abstract: A rotary direction sensor used in conjunction with an engine spark ignition system is disclosed. Two sensors are used to sense the rotational position of a rotary body which is being synchronously rotated by the crankshaft of an internal combustion engine. Output signals of the sensors are compared by a logic circuit which produces ignition spark timing signals in response to the rotation of the rotary body in a predetermined direction. These spark timing signals are subsequently used to trigger SCRs which apply a high voltage across an ignition coil and thereby cause an ignition spark in a cylinder of the internal combustion engine. The sensors, the rotary body and the logic circuit are constructed so that engine spark timing signals are only produced for the internal combustion engine when the rotary body is rotated in a given rotary direction. Thus the generation of cylinder spark ignitions when the engine is being rotated in a reverse direction is inhibited.

Abstract: A selective threshold ignition circuit adaptable for use in an electronic ignition system for an engine is disclosed. A magnetic pick-up produces an AC signal about a DC reference level which has a frequency related to the rotational movement produced by the engine. A circuit receives this AC signal and produces a corresponding spark timing signal by comparing the AC signal with a DC threshold level. A selector circuit chooses a first DC threshold level for the comparing circuit which is effectively equal to the DC reference level during the period of engine start up. The selector circuit chooses a second DC threshold level which is different from the DC reference level when the engine is running and before the engine has been started. By providing a threshold level equal to the DC reference level during the engine start up mode of operation, an accurate ignition timing signal is produced during this critical period.

Abstract: A first sensor couples to an internal combustion engine and generates a first set of pulses suitable for ignition firing. A second sensor operates in synchronism to the first sensor producing a second set of multiple pulses, during the interval between a first set of pulses, whose occurrence corresponds to specified angles of engine revolution and whose time duration is inversely related to engine RPM. The second pulse set is processed through a digital-to-analog converter having a staircase output voltage which is representative of instantaneous engine position.The second pulse set is further processed through an integrator, modified to produce an output approximating an inverse, or hyperbolic, functional relationship to the input, whereby output pulses are generated whose peak amplitude is representative of instantaneous engine speed, i.e. RPM.Comparator circuitry produces a trigger signal corresponding to a predetermined relationship between the positive voltage signal and speed pulses.