Hi every one:


I and buddhika found some informations about the Auto dimmer headlight circuit

This is a simple circuit, using a LDR to be a sensor, LDR light dependent resistance,
This type resistance has such function:

When in the dark the resistance is increasing.

When under the light the resistance is reducing.

The LDR is used  together with the transistor, and the LDR is connect to the base, the LDR is sensor to send the current to the transistor, and let the transistor to be a switch,
When in the circuit the senor and transistor is used for the switch to control the electrical unit liking the bulb, they uses the relay to be a control.

Light changing----LDR----current----transistor base----transistor on----relay switch----bulb high beam and low beam switch.


The diode I think is a protection for the relay coil.

That is our understanding for this circuit.

Week one for the blogger Technology Projector