Rain Sensors

Basic Description

Automotive rain sensors detect rain falling on the windshield of a vehicle. Although rain sensors first appeared on automobiles 50 years ago [1], they have only recently begun to see widespread use. One of the more common rain sensor implementations employs an infrared light that is beamed at a 45-degree angle onto the windshield from inside the car. If the glass is wet, less light makes it back to the sensor, and the wipers turn on.

Diagram by Robert Bosch GmBH illustrating the operation of a rain sensor.

Other rain sensors measure the capacitance between two metal plates. The presence of water droplets near the plates causes a change in the capacitance. Another type of rain sensor employs a piezoelectric vibrating element that responds to the frequencies produced by rain drops hitting the windshield.

Manufacturers

Bosch, Kostal, Preh, Rain Tracker, TRW, Valeo

For More Information

[1] Rain sensor, Wikipedia, Oct, 2009

[2] Rain-sensing Wipers, Karim Nice, Howstuffworks, March 23, 2001.

[3] 2008 Silverado RainSense Wipers, YouTube, Jan. 2008.

[3] Automatic Saab Windshield Wipers, YouTube, July 2009.

[4] Rain-sensing Wipers, J.D. Power web article.