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Very simple proximity activated switch (several inches range)? Answered

Hello Instructables! I am looking for a simple electronic switch that will instantly turn on when it comes within a few inches (5-8) of a little beacon or antenna of some sort.

I would like to be able to have the beacon be small, and preferably flat in form factor, with the receiver/switch system being no larger than an inch square. For size constraints, watch batteries would be the most preferred power source. 

Would RFID be a good option for this? 

Preferably I don't want this to have to be hooked to a phone, and it would need to be something that I could conceivably make a PCB foror use a very small existing board like a TEENSY. 

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steveastrouk (author)2017-10-27

Yeah, RFID is a good choice here. Sparkfun et al sell suitable modules.

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ilpug (author)steveastrouk2017-10-27

That's what I was leaning towards but upon further research I have learned that RFID needs the antenna and coil to be held close to a certain orientation near each other to read. My application would have the receiver in a wrist wearable and the beacon on something else, and they would not always be oriented correctly in use. Are there omni-directionally reading RFID systems that would still fit the form factors?

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steveastrouk (author)ilpug2017-10-27

Much depends on the antenna, and the sensitivity of the system, you can get results at extreme misorientations, if your receiver is sensitive enough.

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