Can I tell when chip/card has left vicinity of RFID sensor?

[trhaynes]

I have an idea for a little hardware project and I'm eyeing the Phidgets USB RFID reader (hooked up to a Raspberry Pi). I need to know when a RFID chip/card is in range of the sensor, which is easy to do. But the chip will stay near the sensor (for minutes or 2-3 hours), and I need to know that. And then I need to know when the chip moves out of range, so I can preform another action.

Basically, does the Phidgets USB RFID reader continuously send the chip ID via USB when the card is in range, or does it do some sort of debouncing in hardware?

If RFID isn't designed for this, can anyone suggest another inexpensive NFC-ish scheme that might work?

Thanks for your help!

-tom


ps. The idea is to make a music box ... an album starts playing when you place the "album" (block w/chip) onto a basic wooden board (w/tech inside). Then it stops when you move the block off again.

[mparadis]

There's an event called OnTagLost or TagLost depending on the language you're using. Take a look at the RFID class in the API for your language for more information.

[trhaynes]

Great, thank you. Looks like there's a setOnTagLostHandler() method in Python.

What is the "refresh rate" for the sensor? That is, how quickly will my code be alerted that the tag was lost?

Thanks.

[Patrick]

You will get the tagLost event about 200ms after the tag is removed.

-Patrick