By

Anuraag G V

Rain Light Sensor

The rain-light sensor supports the field of vision of the driver by detecting the amount of rain and the amount of light and functioning automatically.

Introduction

Circuit Diagram

Rain Light Sensor

Rain light Controller

Wiper Motor

Steering column switch

Light Control ECU

Washer Motor

Head Lamp

The rain light sensor is connected via a local interconnect network (LIN) bus to the rain & light control ECU.

The rain & light control ECU controls the wiper motor in automatic mode according to the commands of the rain sensor.

The rain & light control ECU sends the pulse width modulation (PWM) signal to body control module (BCM) to operate the parking lights & headlamps. Steering column switch (SCS) position, rain sensor sensitivity

The rain light sensor is the combination of two sensors including an infrared rain sensor and optical light sensor.

Rain Light sensor Functions

The rain-sensitive wiper function detects the rain droplets on vehicle windscreen and activates the front wipers to operate intermittently, low or high speed mode according to the raindrops size on the windshield.

This function frees driver from adjusting wipers manually in intermittent rain condition.

Functions of Auto Wipe

The sensor houses 6 infra-red light emitting diodes (LEDs) forming a segment of a circle around the receiver diode. The LEDs are divided into two branches, each containing three LEDs.

The receiver diode is irradiated alternately at each branch by the reflection from the surface of the windshield.

The circuit of the receiver element is arranged so that no signal voltage is produced when the amount of light being emitted by the two branches of LEDs are identical.

Basic Principle

Any rain drops landing on the windshield in the sensitivity area of the sensor cause spontaneous imbalance in the reflection, with the result that a voltage with the clocking frequency of the LEDs is produced.

The automatic lighting function will turn the headlamps (low beam & parking light) on when it detects the ambient light intensity reducing below desired threshold. It also switches ON headlamps when the vehicle enters in to the tunnel and switches off when vehicles in open ambient.

FUNTIONING OF AUTO LIGHT

The light/tunnel sensor is optical system. It operates with two different receiving diodes A & B, with different characteristics.

Diode A measures infrared light intensity this information is used to measure the global ambient light with the relative wide apex angle.

Diode B is an optical sensor which works with light this diode measures the global ambient light in the forward direction of the car.

WORKING PRINCIPAL OF AUTOLIGHT FUNCTION

In case of failure of light sensor, disconnection in the circuit, short circuit in the wring harness or any switch failure or ECU software failure, the basic function of the headlamp should not get affected. Hence in any of above mentioned failures, headlamps (Low beam) and parking lamps are switched on continuously.

Similar failsafe arrangement was provided for rain sensor. In case of similar failure in rain sensor, wipers will be switched on in fixed intermittent speed.

FAIL SAFE FUNCTIONALITY &DIAGNOSTIC

The rain light sensor was adapted for the existing vehicle architecture. The rain light sensor is optimized for the basic functions while considering all the Indian customer expectations. We developed a more advanced system which offered even greater comfort and safety to the customer

Conclusion

Sidharth Gupta, Dayanand Maruti Chougule and Amol Deshpande, “Development and Calibration of a Rain-Light Sensor and Controller ” SAE Technical paper series 2010-01-0296.

References