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A sensor or a Swiss Army knife?

John Day

John Day

Posted Aug 27, 2010

In the world of hard things to do, turning windshield wipers on and off seems pretty far down the list. On the other hand, how many car buyers today opt for hand-crankable as opposed to pushbutton windows? I’m more aware of windshield wiping after hearing Hella Electronics describe its new rain/light sensor, which sounds like the sensor equivalent of a Swiss Army Knife. It senses more than just rain and ambient light.

The car owner advantage in linking a rain sensor to a windshield wiper controller is most apparent in on-again/off-again weather conditions, when water or slush or whatever periodically splashes up on the windshield or intermittent rain showers are present. It’s not a huge deal to keep turning the wipers on and off, but neither does doing so add to the pleasure of the driving experience. So all things being equal, which they hardly ever are, it’s better to have the feature than not.

If you are an automaker or tier one supplier designing the feature, you want the sensor to be as small as possible and still work. Hella says its newest model, which is ramping into production this summer, is less than half the size of its predecessor. The sensor can be attached directly to the windshield or embedded in the foot of the rearview mirror.

Small size is important because a growing number of applications are contending for space in the same area – forward-looking camera applications, for example, which need a clear field of view to work properly. Hella’s device senses rain, to support efficient windshield wiping, and ambient light, to turn headlamps and dashboard lights on quickly when light conditions change, as they will when the vehicle enters a tunnel. A solar sensing capability provides more precise control of dual HVAC systems, because it knows on which side of the vehicle the sun is shining more brightly, and the ability to sense humidity inside the vehicle will be especially useful when combined with start-stop technology. Don’t shut the engine off when the outside air is humid or the windshield will fog up fast.

It’s a little thing, the sensor, but all together it does a pretty big job.

Hella Electronics, humidity sensor, ambient light sensor, Swiss Army knife, rain-light sensor, start-stop

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John DayJohn Day recently launched John Day’s Automotive Electronics News ( to provide news and feature coverage of the automotive electronics industry. Earlier he wrote for Auto Electronics magazine, Auto E-lectronics, EE Times, and other business and engineering publications. Visit John Day

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