possible proximity sensor or switch

[DPluss]

Hey guys!

I'm trying to start a new project which involves a proximity sensor but I'm dont really have a clue how to start.
My idea basicly is, theres a small key like thing in my pocket, and when I get close to the sensor(about 3 meters) it recognizes it and turns on a switch, and when I leave it turns off the switch, how can I achieve this kind of thing? I read about rfid readers but it said they only work in really close (like 5-10cm) ranges :/ I need atleast 2-3meters. Or can I achieve this with somekind of proximity switch?

I would really appreciate the help! Thank you!

 

[barry]

Trying to detect something as small as a key at 3 meters is pretty demanding; definitely NOT a simple project. Think inverse-square law.

 

[hobbyckts]

Will PIR sensors work for you? I guess it covers more than what RFID covers. But not sure about the exact range.

 

[FvM]

"Vicinity" ISO16593 RFID can achieve several meters range under circumstances, but only using large reader coils and several watts power. UHF RFID can also achieve larger ranges.

In both cases, the requirements for the tag antenna will probably not fit the "small key" idea. But you should at least study the recent technology to know why your project can't be realized.

An active tag (a battery powered transceiver) can better achieve long range and small size.