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I am working off an Arduino Uno with an AdaFruit PN532 NFC/RFID shield. The goal is to have a shoe box, with a false bottom. Under that false bottom would be my prototype, which I hope will be able to detect any MIFARE tag that is in the box, above the false bottom.

The range obviously for these devices is practically touching, but I was was wondering if there is anyway to extend the reach of the NFC/RFID shield, so that the entire false bottom of the box could act as that antenna.

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  • Note that NFC uses an air-coupled transformer, not an antenna proper. – Ignacio Vazquez-Abrams Sep 5 '14 at 22:12
  • Thats all greek to me.. the board i am using is the AdaFruit pn532, it looks like an antenna... can you explain the difference? – erik Sep 5 '14 at 22:15
  • adafruit.com/products/364 – erik Sep 5 '14 at 22:16
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    It's actually a wire that goes through several loops and then connects to another power connection. An actual antenna is unconnected at the end, and the charge within it vibrates to emit EM radiation. – Ignacio Vazquez-Abrams Sep 5 '14 at 22:25
  • So what's on the board linked above and is there a way to extend its reach? – erik Sep 5 '14 at 22:26
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I suspect not. NFC is designed for short range for privacy reasons. Some RFID systems have longer ranges (a few meters). They work by using an electromagnet to create a switching magnetic field. The RFID/NFC chip takes power from the magnetic field and then modulates a signal onto it, which the sensor detects. In order for it to work the chip needs to be close enough to get as strong enough field to power itself, and to modulate that field.

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  • is it possible then to build something that will increase that fields diameter? – erik Sep 5 '14 at 23:14
  • Useful answer. +1 – user2497 Aug 26 '17 at 22:34
  • @erik The board you linked has an inductive loop on it, printed in PC traces. (The loops in the image.) You could probably cut the traces that connect to those loops and connect each end to some bell wire that you wrap around the perimeter of your box's false bottom. If you did that then the whole bottom of the box should serve as an RFID "pad". The thing I'm not sure about is if the circuit could tolerate the changes in resistance and inductance from the larger coil of wire and still work. An EE would be better able to judge that. – Duncan C Sep 12 '17 at 14:45

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