How do automatic window wipers work?

Question

You know, the ones that only operate when it rains? how does it detect rain?

Answer 1

A rain sensor on the windscreen, here's more about it, scroll down to automotive sensors.

http://en.wikipedia.org/wiki/Rain_sensor

Answer 2

just behind the rear view mirror is a small man who has a finger sticking out to detect rain drops, Dave is his name and he's so very shy. and lonley. Ahhhh.

Answer 3

Its the on board computer but you have to push the wiper handle up on these cars like you're going to wipe the window intermittently on a normal car. Once they detect water they wipe the window to the speed and frequency they deem fit for the conditions

Answer 4

Most cars use optical rain sensors they bounce beams of light through the windscreen, and look for disturbances in the beams caused by raindrops. Typically, a rain sensor will have an emitter that emits pulses of light, coupled into the windscreen with a lens.

The beams travel through the windscreen at about 45 degrees.  The beams are totally internally reflected by the outside surface of the windscreen, so they bounce back into the sensor.  A detector picks up the beams and measures them.

If rain drops are present on the outside surface of the windscreen, some of the beams escape.  This reduces the intensity of the beams.  The detector senses this, and circuitry measures the reduction in intensity and figures out that it must be raining.  The rest of the control system then runs the wipers.

Answer 5

There is a sensor ( normally up by the rear view mirror ) that uses refraction and reflection of infared light to detect how many water droplets are on the glass. When there are too many it triggers the wipers.

see http://en.wikipedia.org/wiki/Total_inter...

Answer 6

There is a detector pad inside the car, usually behind the rear view mirror,it detects the light refractions from water droplets and away it goes.

Answer 7

sensor based. Detects moisture or rain and activates automatically

-I'm not exactly sure how the sensors themselves work, other than being specifically set up to detect water.

Probably similar to the one that gives you the outside air temp (those sensors are in the side mirrors)

Answer 8

how do they work? poorly that's how!!

When you get any drizzle or mist, and you are sat in traffic the wipers will just sit there like lemons! But if you get a slighty bigger than average drop of rain, they go like they are on drugs!

It doesn't matter how much you adjust the sensitivity, they are still as temperamental! If you are offered them steer well clear - intermittent wipers are FAR better!