Optoelectronic Light and rain sensors, which transform light of different wavelengths into electrical signals, which are known as optoelectronic sensors. The light therefore causes electrons to be released from a semiconductor or metal surface, and if there is an external electric field, the free charge carriers that are produced as a consequence of this result in a photometric current that is proportional to the light’s intensity.
Rain sensors systems:
Opto electronic sensors are used in a reflective mode in rain sensor systems to detect the presence of water on the windshield so that the windshield wipers can be controlled automatically. In-vehicle safety and comfort are considerably improved thanks to the rain sensor, which relieves driver fatigue by automatically activating the windshield wiper system when it rains and thus significantly enhancing in-vehicle safety and comfort. The rain sensor first appeared in automobiles in the mid-1990s, and it has since become an indispensible component of contemporary car electronics.
An LED emits light in such a way that when the windshield is dry almost the entire amount of light is reflected onto a light sensor. When the windshield is wet, the reflective behavior changes: the more water there is on the surface, the less light is reflected. In the new rain sensors, infrared light is used instead of conventional visible light. This means that the sensor can be mounted in the black area at the edge of the windshield and cannot be seen from outside.
Working Operation of Rain sensors:
An infrared beam is reflected off the outer windshield surface back to the infrared sensor array. When moisture strikes the windshield, the system detects a reflection to its infrared beam. Advanced analogue and digital signal processing determines the intensity of rain. The sensor communicates to the wiper control module, which switches on the wiper motor and controls the wipers automatically, according to the moisture intensity detected.
Depending on the quantity of rain detected, the sensor controls the speed of the wiper system. In conjunction with electronically controlled wiper drive units, the wiping speed can be continuously adjusted in intermittent operation. In the event of splash water – as when overtaking a truck – the system switches immediately to the highest speed.
The new rain sensors offers further options. For example, it can be used to close windows and sunroofs automatically if the vehicle is parked and it starts to rain. It can even be fitted with an additional light sensor to control the headlights – at night or at the entrance to a tunnel, the lights can be switched on without any intervention by the driver.
Automatic lighting of the headlights is controlled by a passive light sensor. It measures available light using a set of photo-electric cells.
The light sensor comprises three lenses that focus the light onto three photo-electric cells. This allowed “the luminous space” surrounding the vehicle into several zones through the directivity of each basic lens cell pair.
- Lens 1: Measure total ambient light
- Lens 2: Intersect Front source of light
- Lens 3: Distinguish Road Condition (Like brighter sunny weather condition or Dark tunnel)
By comparing the information gathered by these three devices, the system computer determines the situation with which the vehicle is confronted and commands the headlights in consequence. An optoelectronic detector is used to measure the illumination conditions outside the vehicle. The sensor captures certain wavelengths using an upstream filter glass in order to differentiate between artificial light and natural light, according to the manufacturer. Two sensors, each of which operates independently of the other, are used to measure the ambient light and the front-end illumination.
In order to do this, the receiver properties of the sensor must be tailored to the specific installation scenario. In addition to using sensor data, a special algorithm incorporates information from the vehicle electronics to detect various lighting conditions (day, night, sunset or when passing through a tunnel or bridge) and turns on or off the daytime running light in response to the detected lighting conditions.