Optical Distrbutor

Optical Distributor

The optical sensor is inside the distributor. These are not so common these days as dirt gets inside the stopping the infra red diode from emitting light. 

This sensor is made up of an infra red diode, a photo electric cell and a chopper plate. The chopper plate has for vanes regarding the number of cylinders. the upper picture shows a 4 cylinder engine. This has 3 wires ,a power, signal and a ground. When the cutter plate interferes with a light we get a high voltage and wen the cutter plate moves away from the light we get a low voltage.

this is the circuit diagram for the sensor. 5v goes into the infra red led and it emits light onto the photo electric diode which grounds the circuit. and there is 0v at signal. As the chopper plate interrupts the light the photo diode doesn't receive light so it does not let the 5v to ground. therefore we have a 5v at signal. This is how we get a square wave pattern shown below.

Our distributor needed a 12v suppy so we wired up a 12v supply and a ground. We connected the oscilloscope to the signal. As we turned it we got 11.55v when the chopper plate was interupting infra red light and 0.37v  when the plate moved away.

We got this pattern on the scope. It shows how its switching on and off.

A - when the diode is receiving the infra red light, circuit is grounded and voltage is 0.3v.

B - the infrared light is interrupted by the chopper plate and voltage increases to 11.55v.

C - chopper plate is still on between the infra red light therefore the voltage is still 11,55v.

D - chopper plate moves away from the light and now thee photo diode is receiving the light infra red light, the circuit is grounded therefore the voltage drops down to 0.3v.

E - the chopper plate is not interrupting the light so the circuit is still grounded.

The difference between the the 3 sensors are that the hall effect and optical have a digital pastern but the inductive type has an analogue pattern.The hall effect and optical have the same working principal but with different components.The difference in the optical and hall effect sensors is when the chopper plate cuts the light in the optical its firing time for the coil and when the chopper plate in the hall effect is interrupting  the magnetic field its dwell for the coil.