Lesson3/Learning Event 3
the pickup unit. That is, as a tooth on the reluctor passes the pickup coil, magnetic lines of force
flow from the permanent magnet, through the pole piece, and through the reluctor back to the
magnet. Voltage is induced in the windings as these magnetic lines of force pass through the
pickup coil. This voltage is carried from the pickup coil to the control unit by the distributor leads.
When the pulse enters the control unit, it signals the control unit to interrupt the ignition primary
circuit. This causes the primary circuit to collapse and begins the induction of the magnetic lines of
force from the primary side of the coil into the secondary side of the coil. This induction provides
the required voltage to jump the spark plug gap and ignite the airfuel mixture in the combustion
chamber.
As the tooth on the reluctor moves away from the pickup unit, the primary circuit is again
completed. The magnetic field again is built up in the primary windings of the ignition coil, where
it waits for another signal from the pickup unit.
The buildup and collapse of the primary circuit takes place very rapidly. This is brought about by
transistor action and the speed of the reluctor.
The advantages of an electronic ignition system are that the transistors in the control unit can make
and break the primary circuit much faster than conventional ignition points. Higher primary
voltages can be used because this system can be made to handle higher voltages without harmful
effects, whereas ignition points cannot. The quicker switching time of this system allows longer
coil primary circuit buildup and longer induction time when the primary circuit collapses. This
increased time allows the primary circuit to build up more current and the secondary circuit to
discharge more current. The higher secondary current produces a hotter spark at the spark plug,
which allows the engine to operate more efficiently.
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