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I am designing a hobby project where I need a small device (powered by RPi that is running an app over linux) to be able to detect when it is within, say, 2 feet of another object. I think this is a perfect use case for RFID.

I need an RFID interrogator integrated with the RPi (I have a Model B), and tags that the interrogator is compatible with. When the reader detects a tag, it needs to communicate with an app running on the RPi, probably via serial comm.

My question: What types of RFID tags and readers would be cheap/OSHW, and compatible with RPi?

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+100

Check out this tutorial on Adafruit NFC/RFID on Raspberry Pi Add RFID/NFC read and write to your Pi in an hour! . Here is the product page

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    Great link to full tutorial. Definitely worth a read. +1 – Piotr Kula Jul 15 '14 at 17:34
  • Thanks @Phil Vallone (+1) - a few quick followup questions; as after reading the product page, I'm a bit confused. (1) How do I connect the NFC chip to the RPi: UART, FTDI, SPI, other? (2) If I wanted to write software that controlled when the NFC chip scans for tags, and how to handle responses when tags are scanned, do I deploy that software on RPi or the NFC chip itself? I guess with #2, I'm asking where the RFID middleware lives. Thanks again! – zharvey Jul 15 '14 at 18:23
  • @zharvey From what it looks like, you connect the NFC/RFID (UART, TX/RX, Vc & Gnd) to the RPi GPIO pins (learn.adafruit.com/adafruit-nfc-rfid-on-raspberry-pi/…). It looks like all the info is there that you need to know. I would suggest picking it up from Adafruit. I have purchased a lot of items from Adafruit and their forum has engineers to answer your questions – PhillyNJ Jul 15 '14 at 18:34
  • You know that with those rfid readers you get a max of 15cm reading distance if you lucky more like up to 5cm, – Piotr Kula Jul 16 '14 at 11:36
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125 Kilo Hertz - Close Proximity

This is a really great way but these only work up to 15 centimetres. That is only 1/4 of what you need.

This Olimex, produced in Europe emulates a keyboard input, which the Pi can do over USB. Its cheap at 5 GBP and works with tags on 125Khz

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This site is another hackerspace shop that has some interesting custom solutions and tags that also work on the 125Khz spectrum, but still up to 15cm maximum range.

UHF ~900 Mega Hertz - Long Range

These are more pricey and need dedicated hardware and use various kinds of antennas. Short range ones for about 8USD for up to 50 centimetres (this is what you want) and long range ones up to 6 metres that costs up to 250USD. The tags them selves are very cheap in bulk about 0.10USD at 1000 units.

Here is a system that can read certain RFID UHF (~900Mhz) tags up to 4 metres. There is no price so I assume its darn expensive and it doesnt support all tags and uses some kind of proprietary SDK, over USB and is supported on Linux. These are typically used in Toll Gate systems where cars have E-Tags

This is a USB receiver for 177 USD but still needs an antenna. The initial investment might be expensive but from there on after the tags are cheap.

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