Electronic Spark Control Module: Description and Operation

Digifant ECU:

PURPOSE AND LOCATION
The ignition (Hall) control unit functions as an electronic switch that opens and closes the coil primary ground connection to control the current in the ignition coil. This function is comparable to the operation of the points in a mechanical ignition system. The control unit is located inside the Digifant control unit, in the LH heater air intake cowl.

NOTE: Although the name "ignition (Hall) control unit" implies a component with processing abilities, this control unit has no such function. It is strictly a switching device.

OPERATION AND SIGNAL
The ignition (Hall) control unit consists of a power transistor and integrated circuit. It is used to make and break the primary circuit, and to regulate the current through the ignition coil. It receives a triggering signal from the ECU. The ECU applies power to the output stage, which turns it ON. In this ON state, current flows through the primary circuit of the ignition coil. When the ECU determines it's time for a spark, the power to the output stage is momentarily interrupted. The transistor turns OFF, breaking the primary circuit, and inducing a high voltage spark in the secondary circuit. The ECU regulates the duration of the interruption in the trigger signal, and thus regulates the dwell angle, and charging time. The longer the interruption, the smaller the dwell angle and the shorter the charge time.