A rain sensor or rain switch is a rain-activated switching device. There are two main applications for rain sensor. The first is a water conservation device connected to an automatic irrigation system that causes the system to shut down in case of rain. The second is a tool used to protect the inside of the car from rain and to support the windshield automatic wiper mode. An additional application in a professional satellite communications antenna is to trigger a rain blower in the antenna feed aperture, to remove the water droplets from the mylar cover that keeps the air pressurized and dry inside the waveguide.
Video Rain sensor
Irrigation sensor
Rain sensors for irrigation systems are available in both wireless and preprogrammed versions, mostly using hygroscopic disks that swell in the presence of rain and shrink back down when drying - electrical switches in turn are suppressed or released by hygroscopic. the disk stack, and the drying rate is usually adjusted by controlling the vents reaching the pile. However, some types of electrical sensors are also marketed using tipping buckets or conductance type probes to measure rainfall. Both wireless and wired versions use a similar mechanism to temporarily suspend watering by irrigation controllers - especially those connected to irrigation control sensor terminals, or mounted in series with common solenoid valve circuits thus preventing the opening of each valve when rain has been felt.
Some irrigation rain sensors also contain freeze sensors to keep the system operating in freezing temperatures, especially where irrigation systems are still used during the winter.
Several types of sensors are required on new grass sprinklers systems in Florida, New Jersey, Minnesota, Connecticut and most of Texas.
Maps Rain sensor
Automotive sensor
In 1958, the Cadillac Motor General Division experimented with water-sensitive switches that triggered a variety of electric motors to seal the top of the convertible and raise open windows from a specially constructed Eldorado Biarritz model, when it rains. The first such device seems to have been used for the same purpose in a Le Saber designated concept vehicle and was built around 1950-51. For Model Year 1996, Cadillac once again equips cars with automatic rain sensors; this time to automatically trigger a windshield wiper and adjust its speed to the required conditions.
The most common modern rain sensor is based on the principle of total internal reflection: infrared light is emitted at an angle of 45 degrees to the windshield of the interior - if the glass is wet, less light makes it back to the sensor, and the wiper lights up. In December 2017 Tesla began launching OTA updates (2017.52.3) that allowed their AP2.x car to take advantage of onboard cameras to detect rain passively without using special sensors - this implementation does not work in the dark.
Most vehicles with this feature have an "AUTOMATIC" position on the stem.
See also
- Sensor list
References
Source of the article : Wikipedia
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