Automotive technology sensing wiper

Sensing wiper (Induction type wiper), different from the traditional wiper sensing wiper can automatically sense the size of the presence or absence of rainfall, and rainfall automatically work at different speeds, generally used in high-grade car.

The core components of the sensing wiper rain sensor, rain sensor mainstream market optical and capacitive two choices. Xiaobian introduce the works of these two sensors:

The ① optical. The Xiaobian be simple life experiments to make everyone look better.

The Xiaobian holding the light source (orange arrow), the other side is a mirror (white arrow). This is a very common phenomenon of life: refraction when the light will not be on the mirror surface is clean and dry; Once the mirror significant drops dependent on light scattering occur immediately, give people a sense of hazy. Optical rain sensor is the use of this principle, the interior mirror back with integrated rain sensor with a phototransistor and light-emitting diodes. When the weather is dry, did not occur due to the light refraction, the amount of the light received by the phototransistor is not changed, the corresponding electrical signal is also not changed. If it rains a wet (or glass), the light emitting diode generates the light is attached to the windshield of the rain barrier refraction occurs, resulting in the change of the amount of light received by the phototransistor. Once this change is beyond the the ECU set of range, the wiper will start, and to adapt to speed changes with rainfall. This rain sensor accuracy is very high, the only flaw is that is more sensitive to some non Raindrops objects, such as mud, insects, leaves.

 Capacitive rain sensor principle is relatively complex, to measure the rainfall is a huge difference in the use of glass and rain permittivity (dielectric constant of the glass 2, the dielectric constant of the rain for 80).
Was finger parallel to the metal plate mounted on the windshield between the inner and outer layers, wherein a set of metal plates interleaved, but does not touch the other metal plates, so that the windshield and the metal plate is formed between the dielectric. Capacitive sensors, each group of the dielectric are connected to the high-frequency balanced bridge similar to the Wheatstone bridge and the capacitance can be measured, thereby to monitor the capacitance of the capacitive sensor. Each group dielectric capacitance are not changed when the weather is dry, balanced bridge does not sense a change in capacitance, the wiper does not work; When it rains, the windshield outer surface due to rainwater infiltration into the metal plate, dielectric The constant change, once beyond the allowable range, the ECU can receive the signal and allow wiper work. Obviously, capacitive wiper according to the size of the rainfall automatically adjusts wiper speed. The advantage of this rain sensor do not need to detect light, and can be arranged in a dark location of the edge of the windshield, and the media (windshield) is ready, wiring and sensor placement is also more convenient, cost is not high. Disadvantageously, soon be scraped off under the long-term work of the wiper on the windshield outer surface of the finger-like metal strips, and cause the wiper work failure.

In addition, there are some models use vehicle speed sensor as a rain sensor to open the wiper, according to the vehicle speed to adjust wiper speed, the faster the speed, the faster the wiper speed. This "rain sensor" cost economy, only need to use the original vehicle speed sensor can be completed, the drawbacks of not open automatically, according to the rainfall size will not solve the problem if the rainfall is very slow speed.