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Some advice on an RFID idea i have? Answered

Realistically, how difficult would it be to DIY a passive RFID system where the tag simply reacts by lighting a low power LED. Catch is, i would want it to have an effective range of at least 1m. Could i build the EM emitter myself, or would i have to buy a high power reader?

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frollard (author)2012-02-05

Not difficult at all for the 'tag lighting up an led instead of responding with a code'

Somewhat difficult is the 'get it to work at a meter distance' -- without a pretty big/directional reader/transmitter or a VERY well tuned transmitter you won't get 1m distance

You could build all of the above yourself. If you just want power from A to B and not any data transfer, then you want just inductive coupled coils. Generally if you build 2 identical coils and put AC into one the other should react with some current. The frequency/voltage required will vary based on the coil and distance required.

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steveastrouk (author)frollard2012-02-06

You CAN do inductive data transfer over the same channel, while you are transferring power. Its not hard.

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frollard (author)steveastrouk2012-02-06

Indeed, it's how most-all rfid systems work - powering the iC almost as a byproduct of the data stream. I never said it was impossible or difficult to get the data across, just that if a person ONLY wanted to light an led then it simplifies things since you can ignore the data's requirements and just stick to the power coupling ;)

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R3born (author)frollard2012-02-07

Well it's solely the power coupling aspect i'm after. How could a directional emitter be designed, as i imagine this would help with the 1m requirements.

This is my first attempt at RFID, so a great amount of crash coursing going on atm :D

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frollard (author)R3born2012-02-08

http://en.wikipedia.org/wiki/Wireless_energy_transfer

http://en.wikipedia.org/wiki/Inductive_coupling

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