Ignition, Basic Function

Fig. 4 Breakerless ignition system wiring circuit.:

Purpose
The electronic ignition system, Fig. 4, uses a Hall effect switch to generate a pulse signal. The Hall switch is connected to a control unit that converts and amplifies the Hall signal. The control unit controls the coil.

Fig. 3 Breakerless distributor w/Hall transmitter:

Fig. 2 Hall Transmitter & Air Gap:

Construction
The Hall transmitter, Fig. 1, replaces the induction coil transmitter found in conventional breakerless ignition systems, and consists of a semi-conductor layered on magnetic material and a permanent magnet.

The semi-conductor and magnet are mounted on a plate in the distributor and separated by an air gap, Fig. 2.


Operation
During operation, constant current flows through the semi-conductor. Exposure to a magnetic field induces voltage across the semi-conductor called a Hall effect, which is transmitted to an electronic control unit. A rotor with four slots rotates in the transmitter air gap to make and break the magnetic field, controlling ignition timing.

When the rotor cuts the magnetic field, no Hall effect is transmitted. Signal voltage in the control unit is high, charging the coil primary circuit. When a rotor slot is in front of the transmitter, Hall effect is generated and transmitted to the control unit. Control unit signal current is low, and the control unit opens the coil primary circuit, inducing secondary ignition voltage. The control unit limits system current and controls dwell time (coil saturation) depending upon battery voltage, engine RPM, and temperature.