The device and principle of operation of the rain sensor in the car

Until recently, the function of automatically turning on the wipers was installed only on expensive cars, and now the rain sensor is integrated into the configuration of budget models. Such systems are designed to increase the comfort of driving and assist the driver while driving.

What is and where is the rain sensor in the car

The rain sensor in the car is used to detect rainfall and activate the wipers when needed. In a normal situation, the driver independently monitors the weather conditions and the operation of the brushes, distracting from concentration on the road, but the automatic system is able to react to the level of precipitation itself. Depending on the intensity of rain or snow, the sensor generates a control signal and regulates the modes of operation of the brushes and their speed.

As a rule, the sensor is located on the windshield, in a place that will not block the driver's view of the road. The space behind the rear-view mirror is suitable for this.

The sensor looks like a small reading device located on the back of the windshield. Depending on the design features, it can not only turn on the wipers, but also recognize the light level to turn on the headlights. The device is attached to the windshield using special compounds.

Main functions and purpose

Having figured out what a car rain sensor is, you need to understand the purpose and main functions of the device:

• identification of rain and snow;
• windshield contamination analysis;
• control of wipers, as well as adjustment of their mode of operation;
• automatic switching on of light in case of insufficient illumination (in the case of a combined sensor).

The precipitation sensor also has significant drawbacks, including false triggering when water enters the analysis area or failure when the glass is flooded with dirt or water from neighboring cars. Also, the control circuit of the car may not turn on the washers, which will lead to smearing of dirt on the glass and impairment of visibility. Any automatic system does not exclude flaws and errors. For example, the activation of the brushes usually occurs with a slight delay, and during this time the driver can independently clean the glass.

Manufacturers are constantly working to improve functionality and reduce rain sensor errors.

Device and design features

Initially, a simple scheme from American manufacturers was used to determine the degree of precipitation. Special films were installed on the windshield to conduct resistance, and the measuring system analyzed the change in parameters. If the resistance dropped, the brushes were automatically turned on. But the design had a number of drawbacks, since it was triggered by a large number of false factors, including insects stuck to the glass.

In the early 80s, designers began to develop devices consisting of LEDs and photodiodes that respond to changes in the angle of refraction of light. This made it possible to increase the measurement accuracy and reduce the number of false alarms.

The precipitation sensor is a housing with a board and optical elements inside. The main components of the device:

• photodiode;
• two LEDs;
• light sensor (if available);
• Control block.

At the moment of detecting an increased level of precipitation, the sensor generates a control signal to turn on the wipers, and also controls the intensity of their work.

The devices determine the level and strength of rain, as well as other types of precipitation and glass contamination. This allows you to increase the efficiency and sensitivity of the system.

Principle of operation

The principle of operation of the sensor is based on the operation of photosensitive semiconductor elements and the laws of light refraction. The idea is that the LED generates a beam of light and the photodiode receives it.

1. The LED sends out pulsed beams that are focused through the optical element.
2. The light signal is reflected and sent to a photodetector, which analyzes the amount of light and the degree of reflection.
3. To protect against false alarms, the light beam is directed into the photodiode by pulses. Even in the event of a third-party light flux, the system is protected from false triggering.
4. The worse the light signal is perceived by the photodetector, the higher the system determines the value of the precipitation level and regulates the operation of the wiper.

More sophisticated systems include a remote photodiode and an ambient light sensor that analyze conditions around the vehicle and turn on the headlights without driver intervention.

How to turn on the rain sensor

If the car does not have a sensor from the manufacturer, it is easy to buy and install it yourself. Companies producing such technical devices are developing detailed instructions for installing and configuring the system.

Approximate step-by-step instructions on how to turn on a standard rain sensor:

1. Find the steering column switch responsible for the operation of the wipers and washer.
2. Turn the ring of the switch from the initial position to a value from 1 to 4. The higher the value, the greater the sensitivity of the element.
3. Check the system is working.

The function can be disabled only by moving the regulator to the zero position.

How to check if it works

This requires plain water and a spray bottle. Step-by-step instructions on how to check the sensor with your own hands:

• turn on the rain sensor;
• apply water with a spray to the windshield;
• wait for the system to work for 20-30 seconds.

Before starting the test, you must put the sensor in the sensitive mode. For greater accuracy, tests are carried out in several modes of operation.

All systems are protected against false alarms, so it is necessary to evenly apply water to the windshield for 20 seconds. Otherwise, the automatic complex will not work and will not turn on the brushes. Alternatively, you can use computer diagnostics.

The precipitation sensor allows you to automatically monitor the weather conditions, and in case of rain or snow - to turn on the cleaners. Although the system has several disadvantages, it makes driving much easier.