Ignition Systems Trigger Systems

1. Ignition Systems page 7Ignition Systems page 7
Trigger systemsTrigger systems

2. We have already described theWe have already described the
contact breaker points, andcontact breaker points, and
stated that the mechanicalstated that the mechanical
system has a limited life span,system has a limited life span,
doesn’t stay accurately adjusteddoesn’t stay accurately adjusted
for a long time, and that thefor a long time, and that the
secondary voltage output issecondary voltage output is
limited.limited.

3. A major improvement inA major improvement in
switching the primary circuit isswitching the primary circuit is
using transistorized system.using transistorized system.

4. A transistor is used inA transistor is used in
conjunction with some form ofconjunction with some form of
pulse generator to provide thepulse generator to provide the
timing signal.timing signal.

5. Name the three main types of pulseName the three main types of pulse
generator:generator:
• Hall Effect
• Inductive
• Optical

6. Label the inductive pulse generatorLabel the inductive pulse generator
Iron rotor trigger wheel
Path of magnetic field
Air gap (0.5mm)
Permanent magnet
Alternating current
generated

7. Describe the operation of the inductive pulseDescribe the operation of the inductive pulse
generator trigger system.generator trigger system.
As the iron rotor turns an AC voltage is
induced into the inductive winding. The
faster the rotor turns, the higher the
frequency and the voltage. The voltage
and frequency variation provides the
sensing signal.

8. Another of the main types of pulse generatorAnother of the main types of pulse generator
is the Hall Effect, label the illustration belowis the Hall Effect, label the illustration below
Rotor arm
VanesMagnet
Hall chip

9. Briefly describe its operationBriefly describe its operation
• As the vane passes between the magnet
and the hall chip, the magnetic flux is
diverted away from the chip. This causes
the chip to be turned off and on.
• Note: the spark occurs the instant the
vane leaves the air gap.

10. QuestionsQuestions
1. Name three types of pulse generator.
2. How does the inductive pulse generator
work?
3. What type of signal does an inductive
sensor produce?
4. Why should you be careful when working
on a hall effect system?
5. What happens to the signal produced by
an inductive sensor with speed?

11. AnswersAnswers
1. Inductive, Hall effect, Optical
2. An iron magnet rotor turns and induces
an AC voltage into windings wound
around a second permanent magnet.
3. AC current or alternating current.
4. A high voltage can be produced by the
coil – even when the engine is being
turned over by hand.
5. The frequency increases, the voltage
output increases