Electronics Assembly Knowledge, Vision & Wisdom
The Phantom Switch
The Phantom Switch
A flat panel switch turned on but only when a nearby door was slammed shut. What was causing the switch to activate?
Mysteries of Science
Dr. Gilleo
Mysteries of Science by Dr. Ken Gilleo
Dr. Gilleo is a chemist, inventor and general problem solver. Ken has been tracking industrial forensics and collecting case histories for decades. These cases are taken from the vast world of industry and commercial enterprise.

Check out Dr. Gilleo's eBook, 100 Mysteries Solved by Science. We hope you enjoy these case histories. You need not be an engineer or scientist to understand the problems and appreciate the solutions.
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Transcript
In the early days of flat panel appliances switches an oven manufacturer was perplexed by a problem with their product. It seemed that some of the switched were turning themselves on even when no one was near the appliance.

The switching was happening on several locations throughout the United States. The most common complaint was that the oven was turning on when someone entered or exited the house or apartment. The switch seemed to be triggered by the slamming of a door. This problem was occurring in both condos and small apartments.

An engineer investigating the mystery found that the on switch activated when the apartment door was slammed, but closing the door slowly had no effect. 

What was causing the switch to turn on? 

Here's the rest of the story.

Slamming the door in a small apartment would create a momentary pressure wave and if it was large enough the sealed membrane style switch could turn on. This was confirmed by watching the switch move inward when the apartment door was slammed.

Why did it only happen in small areas like apartments?

Larger and older houses did not trigger the switch because the room volume dissipated the pressure wave.

What was the fix?  The switch had to be redesigned; the original design was just too sensitive.

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