Wallswitch state detection by lightbulb

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Wallswitch state detection by lightbulb

Postby yusuf.khan.uct » January 28th, 2014, 12:17 pm


The bulb in the above article seems quite ordinary; rechargeable, remote control LED bulb funded by Kickstarter, but it is somehow able to detect if its wallswitch has been turned on, even if there has been a power failure.

Can anybody explain how this is done, or preferably, a way to build the sensor at home.
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Re: Wallswitch state detection by lightbulb

Postby k-ww » January 28th, 2014, 1:00 pm

A few questions to better understand the operationm of the bulb:

Firstly: will the bulb stay on if there is a 'normal' bulb wired in parallel with it and it looses power?

The second is: if you unscrew it while it is on, does it stay on?

The third is: did you look for the patent?
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Re: Wallswitch state detection by lightbulb

Postby modder_mike » January 30th, 2014, 7:55 pm

Here's my guess. If there is still power to the system, there will always be a little-bitty 50/60Hz sine wave coupled onto the other wires - an inescapable side effect of wires with nonzero resistance run in parallel for long distances. If there is no power to the entire system, presumably that little bitty signal goes away, and the bulb can sense this and turns on accordingly.
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