The combined rain and light sensor performs the function of auxiliary lighting control, relieving the driver from manually switching on the headlights, as well as controlling the wiper mode depending on the degree of moisture coverage of the windshield. The developers set themselves the goal of placing these functions in one block.
Location
The rain and light sensor is located on the windshield in the interior rear-view mirror holder.
Purpose of the light sensor
- Automatic switching on and off of headlights
- Activating the Coming Home/Leaving Home function
- Day and night recognition for rain sensor
Activation conditions
The light sensor informs the onboard supply control unit that the headlights should be switched on under the following conditions:
- twilight
- darkness
- entrance to the tunnel and passage through the tunnel
- riding through the forest
The principle of operation of the light sensor
To recognize specific environmental conditions, such as driving through an alley of trees or driving through a tunnel, there are two zones for measuring the illumination of the light sensor. The global zone evaluates the direct illumination of the car, and the front zone evaluates the lighting conditions of the road section in front of the car.
Rain sensor assignment
Depending on the degree of coverage of the windshield with water, the rain sensor performs the following functions:
Automatic wiper on/off in seven speeds
- turn on headlights when it rains
How the rain sensor works
To detect moisture on the windshield, rain sensors use the physical law of light refraction. LEDs embedded in a circle in the sensor emit infrared light from the inner surface, which passes through the windshield.
If the windshield is dry, infrared light is reflected off the outer surface of the glass. As a result, the photodiode in the middle of the sensor measures the high light intensity.
If the windshield is covered with water or drops of water, then the optical properties of the glass surface change. Light due to refraction through water droplets passes through the surface of the windshield. As a result, a small part of the infrared light is reflected back and the photodiode measures the lower light intensity (principle of light scattering measurement).
Today, a car is not just a means of transportation, it is a thing to which more and more requirements are presented. The driver is no longer surprised by the presence of all kinds of devices in the car. Rather, surprise them by their absence. Some of the modern technical devices greatly simplify the life of the owner of the vehicle.
So, for example, a device that is definitely necessary for a modern motorist is a light sensor, also known as a car light sensor. It detects insufficient ambient light and corrects it without driver intervention.
The device allows you to automate the process of turning on and off the dipped beam, as well as side lights in cases where it gets too dark outside.
How does a light sensor work on a car
The device itself determines that visibility has become insufficient and, without human intervention, turns on additional lighting.
At the same time, you can not worry that too bright light will turn on and this will lead to unpleasant consequences. Each sensor in the settings has certain parameters for the lack of illumination.
So, in cases of a certain level of insufficient illumination, your car will independently light up the dimensions, and in order to turn on the low beam, other external conditions are necessary. Therefore, you can not worry that the system will confuse something and the wrong light will work that you need.
Of course, this device, at first glance, only slightly reduces the load on the driver, but it is from such small things that, in general, driving a car is formed.
It is worth noting that the car sensor works very quickly, almost instantly. So you don't have to wait for it to light up if a dark tunnel comes your way. The light, in this case, will light up after one, maximum two seconds.
Ultimately, a device as small and highly specialized as a light sensor in a car makes driving much safer because the driver does not have to be distracted. The driver's concentration while driving will remain at a higher level.
The light sensor in the car not only turns on the headlights on its own, but also turns off the extra light on its own if the street lighting has become sufficient for road safety. This means that if you suddenly leave a dark section of the road for a more illuminated section of the road, you will not accidentally leave on.
This device is especially useful for those who often travel long distances. If during your journey the sun manages to set and then rise again, and there are many tunnels on the road, then such a device will greatly simplify the driving process and make the movement easier, more enjoyable and safer.
And, if after a long journey you try to accidentally leave your car with the headlights on, the sensor will react to this and turn them off.
In addition, there are also similar light sensors, but only for the car interior. This device does not make the traffic easier, but it makes the life of the motorist more pleasant.
Automatic switching on of the light in the car interior using a light sensor
As soon as you install the light sensor on the car, you will immediately feel that your car is now taking care of you. If you have to sit in the cabin for a long time and wait for someone, then the car will turn on the light itself when it gets dark. You can calmly read your favorite book and not worry that you accidentally read it, you won’t notice how it gets dark and your eyes get tired. The car will take care of this and turn on the light itself at the right time.
In many modern cars, light sensors are installed at the factory. You are very lucky if such a device was in your configuration. However, not all packages have them. As a rule, light sensors are only in fairly expensive car models. You can easily buy it yourself if your car did not have this device installed.
The price of this nice device is not high, and installing a light sensor is not a big deal. But, having paid once for such an important and necessary device, you can later forget about constantly turning on and off the headlights and lights in the car.
After purchasing, you can customize the new device individually for yourself and your requirements.
Of course, each driver needs to decide for himself whether he specifically needs a car light switch sensor. But, if you care about safety and want to make driving more comfortable, then you should consider purchasing this device.
The machine itself will take care of you, turning on the light as soon as it really needs to. The likelihood that you will get into an accident due to the fact that you did not turn on the light on time will decrease. And your eyes will always be in comfortable lighting.
One of the options that was previously installed only on expensive cars - a rain sensor, has become quite affordable for budget cars. However, sometimes a lot of questions arise on it, so it is quite reasonable to ask - how does it work?
Why is such a device needed?
Before dealing with the operation of such a device, let's try to understand why it is needed, and in fact, what is it? The name itself predetermines the purpose of such a product - to establish the fact of rain. Although the tasks that an automobile rain and light sensor performs are much broader than those described.
Among them it is worth noting:
- establishing the fact of the beginning of rain, as well as snow;
- determination of the degree of contamination of the windshield;
- automatic switching on of the wipers during precipitation and setting their operating modes depending on the intensity of bad weather;
- turning on lights at low light levels (applies to the light sensor).
Its installation is carried out behind the rear-view mirror, for example, as shown in the photo:
Having dealt with what the rain and light sensor does, it is necessary to answer the question - why is all this needed? The answer is quite obvious - to improve traffic safety. Such a device, according to the intentions of the developers, should save the driver from unnecessary operations (turning on / off the wipers), distracting him from driving, and also automatically provide excellent visibility on the road under any conditions.
How does the rain sensor work?
The principle of operation of the rain sensor is based on a comparison of the optical properties of the windshield under different atmospheric conditions, more precisely, on the differences in the reflection of the infrared beam from a clean and wet or contaminated glass surface.
Everything is quite simple - it consists of emitting and receiving infrared LEDs. The device and operation of such a product will help to understand the photo: 
This product is located on the windshield from the inside. From the emitting LED, infrared radiation enters the outer surface, is reflected from it and captured by the photodiode. The level of the reflected signal depends on the state of the outer surface of the glass, from clean glass there will be one signal, from dirty glass - another, from wet glass - the third. By the magnitude of this signal, the control unit determines the need to turn on the wipers.
As can be seen from the above description, such a device is arranged quite simply, which predetermines fairly broad possibilities for its use.
What such a device looks like is shown, for example, in the photo: 
As can be seen from the figure, in a separate housing there is a control unit connected by a harness to a relay that controls the operation of the wiper. The control unit must be glued in the overlap area of the wiper brushes. 
How this work is done will allow you to understand the video. The data presented confirms that it is easy to glue such a device, and this work can be done by yourself.
Flaws
With all the external attractiveness of such a product, it has certain disadvantages, which cannot be ignored. These should include:
- Delayed performance. It happens that a single drop in the sensor's coverage area causes it to turn on the wipers, although the rest of the glass is clean and dry. The opposite situation is also possible, when water or dirt from an oncoming car fills the glass on the driver's side, but does not reach the sensor, and the wipers do not turn on.
- Turning on the wipers without turning on the glass washer. The work of the wipers when dirt gets on the glass leads to the fact that the dirt is simply smeared.
- Sensitivity to glass quality. The slightest bumps, cracks and chips lead to the fact that it stops working.
- Response delay. It can be up to two seconds in some cases, which gives the impression that the rain sensor is not working. Therefore, sometimes it’s not enough just to stick it, you need to get used to its presence, overcoming the desire to manually turn on the wipers.
Checking how this wiper control works is simple. It is only necessary to splash water into the area where the sensor is located. For example, the video shows how to check the operation of the wipers.
Automatic control of car windshield wipers is possible through the use of the described device. It allows you to save the driver from the need to manually control the work of the wipers, and serves to increase the comfort of driving the car and the safety of the car. How much this device will be necessary and useful for you is already a matter of personal choice.
Additional features in modern cars make driving more comfortable and safer. One of these options is the vehicle light sensor. In the article we will talk about its device and the principle of operation.
What is a light sensor in a car
Another name for this option is the light sensor. Its device is quite simple. It consists of a photocell, a control unit and a small relay. The element itself is installed in the most illuminated place of the car, not subject to pollution. Usually above or below the windshield. Indirectly, the light sensor can be attributed to security systems. The driver may simply forget or ignore the need to turn on the headlights when entering a tunnel or other dark area. The system will do it itself.
Interior light sensor
The photocell captures the change in illumination in space. If there is not enough light, then a signal is transmitted to the control unit, and then the relay turns on the dipped beam and side lights. If the system captures sufficient illumination, then the lighting equipment turns off.
Light sensor device
The design of the component and the entire system is quite simple. If such an option is present in the basic configuration of the car, then it is located in a special recess in front of the windshield. The sensor housing contains an LED and photosensitive elements. The sensor is connected to the control unit, relay and contacts for switching on dimensions and low beam.
The lighting control switch must be set to the AUTO position for the system to operate in automatic mode.
Lighting switch. AUTO position Special photodiode filters recognize daylight and electric light. It is very convenient, for example, when entering a tunnel or a covered parking lot. You can also set the time for the headlights to fade out after the ignition is turned off or under normal lighting conditions.
Types of light sensors
Conventional light sensor
If the car is not equipped with such a device, then you can easily install it yourself. The system is inexpensive. It is enough to fix the sensor, connect the relay and correctly connect the wires to the car's electrical wiring. The system will work properly.
Built-in light sensor
Built-in light control components come in more expensive car trim levels. As a rule, the set of their functions is wider. You can set the system to turn on the interior lights, turn the instrument panel lights on and off.
Combined light sensor
Often a light sensor can be combined in one device with a rain sensor. In this case, it is attached to the top of the windshield. If everything is clear with the light sensor, then the operation of the rain sensor is also based on photodiodes and photocells. If rain drops fall on the windshield, the transmitted light is refracted differently and scattered on the way back. Photocells detect this and turn on the windshield wipers. When it rains heavily, the headlights turn on automatically. Drivers note that the system works correctly and correctly. The driver does not need to turn on the windshield wipers every time the glass gets wet. The photocell detects the level of water on the glass and the intensity of the rain and adjusts the frequency of the windshield wipers on its own. In some models, when it rains, the heated glass is turned on to prevent it from fogging up.
How to check if the device is working
This option is very convenient and drivers quickly get used to it. No need to worry about turning the headlights on or off - the system does it for you. But if the system fails, then the motorist may not notice the breakdown in time.
Checking the light sensor is very simple. It is enough to cover it with dark material or rags. If everything is in order, then the system will perceive it as night and turn on the light and parking lights.
Automatic light switching is one of the active safety systems of the car. A similar function is found not only in executive class cars, but also on budget models. Consider how the headlight sensor works.
Principle of operation
The operation of the light sensor is based on the ability of some elements to change their resistance when exposed to light. Light-sensitive elements used as light sensors can be divided into 2 types:
- photodiodes. When light rays hit the sensitive area, the resistance changes at the outputs of the photodiode, which makes it possible to determine the level of illumination;
- phototransistor - an optoelectronic semiconductor, the purpose of which is no different from a conventional transistor. Recall that the transistor, like the relay, is used as an electronic key with low-current control of power outputs. In a transistor, current flows between the collector and emitter only when current is applied to the base terminal. In a phototransistor, the base terminal is exposed to light. The hit of the rays on the sensitive element generates a current at the output of the base, which makes it possible to use the phototransistor as an actuating device for automatically turning on consumers.
Features application in the car
The light sensor in the car is used not only for the convenience of the driver, but also to improve road safety. In the daytime, the driver no longer needs to be distracted by turning on the headlights when entering tunnels or darkened sections of the road. A photosensitive transistor controls the lighting in automatic mode. The function of manual switching on and off is retained.
If in the daytime everything is clear with the operation of the sensor, then what about at night when oncoming cars are moving and road lights are passing by? After all, the sensor, reacting to the appearance of light, should not turn off the headlights of the car. That is why a narrow range of reaction to light is not enough. The vector of sensitivity to light rays is located in two directions: frontal and vertical. This allows you to accurately assess the level of illumination. In some cars, the sensing element is directed into the passenger compartment, which also allows you to offset the influence of variable factors.
The light sensor in a car is often combined with the rain sensor and is located at the top of the windshield. It can also be installed in front of the windshield in the center of the dashboard.
Additional functions
Even in the simplest light sensor, you can adjust the sensitivity using a tuning resistor. The driver, at his discretion, can adjust the sensitivity level at which the headlights will automatically turn on at the border of daytime and twilight.
At the same time, the use of a smart light sensor makes it possible to realize not only the automatic switching on / off of the dipped beam, but also the adaptation of lighting devices to changing conditions. A striking example of such capabilities is high beam control. To prevent dazzling drivers, when detecting the glow of the headlights of an oncoming car, the sensor will automatically turn off the high beam. In some types of systems, you can set the side lights and low beam headlights to turn on depending on the degree of illumination. Dimensions will automatically turn on even in the daytime, but in cloudy weather. 
Flaws
It would be wrong to rank the disadvantages of automated headlight control as the disadvantages of the system itself. All of them are connected with the peculiarity of the work of human consciousness. After getting used to the work of the light sensor, drivers, changing to cars without an electronic assistant, may forget to turn on the headlights in time. The danger in this case is not so much in getting a fine, but in increasing the risk of an accident. A similar situation can happen if the sensor breakage is not noticed in time. You can check the performance of the photosensitive element even in the daytime. To do this, it is enough to turn the light switch to the Auto position, and then cover the sensor site with a rag, thereby simulating the onset of twilight.
