Hi,

I was wondering how light sensors for DRLs work in cars. I know the electronics part; when the light falls on the sensor it produces current and that can be used as a switch. My question is specific to cars.

I can see two terminals in the sensor. How does it work? Is it that one terminal has 12v input and when the light falls on the sensor it closes the circuit and allows the 12v to pass through it, or is the current generated by the sensor is fed to a circuit that amplifies the current and uses as a switch?

Please explain in detail and it would be great if anybody can provide a circuit diagram for light sensor used for DRL for Accord 2003-07 models.

I am talking about this product.

 

There is this wonderful search engine called google, you should learn to use.

Ambient Light Sensor - WikID, the Industrial Design Engineering wiki

good luck

 

7th generation Accords (2003-2007) does not use the sunlight sensor as part of the DRL circuit. With the ignition switch in on or start, battery voltage is supplied to the DRL Control Unit through fuse 21 (in the under-dash fuse/relay box). When the headlight switch is OFF, the control block in the relay control module senses that there is no voltage supplied to the control block from the low and high beam headlight relays. Voltage is supplied through the DRL control unit to the high beam headlights.

For 2003-2007 Accords, if equipped with climate control, the sunlight sensor is used in conjunction with a temperature sensor for climate control. The sunlight sensor is not used for the headlights for the 7th generation Accord.

For 8th generation Accords (2008-2012), if equipped with automatic lighting; when the Headlight Switch is in the AUTO position, the Driver’s Multiplex Integrated Control Unit (MICU) and Passenger’s MICU receive an automatic lighting signal.When the Automatic Lighting Sensor detects low ambient light, a lights-on signal is transmitted to the Driver’s MICU and the Passenger’s MICU.The Driver’s MICU and the Passenger’s MICU activate their Low Beam Control Circuits, supplying battery voltage to the Low Beam Headlights, causing them to come on. The automatic lighting sensor is not used to turn on DRL.

 

@Texashonda: Thanks a lot. That helps.

@Redbull-1: Wow, that was great. That was really helpful. But I have this question. Does this particular sensor generates current when light falls on it or does it allow the current to pass through it when it senses light?

LDR (light dependent resistors) is a variable resistor that varies with intensity of light. So just want to know if that sensor works on Photodiode sensor principle or LDR principle?

 

awesome info. can you share the 9th gen logic for the same system?

 

I don't have the logic information for the 9th gen, as there were some changes especially for the Touring trim level which had more sensors and had LED DRLs.

Actually, both 8th and 9th gen Accords, if equipped with climate control and automatic lighting control had separate sunlight sensor and auto lighting sensors incorporated into the same housing.

The 9th generation Accords for some trim levels seems to have some changes that may utilize a few more sensors. Accords in other non-domestic markets seems to even be more sophisticated.