SparkFun Electronics Forum

Long time lurker, first time poster! I'm looking for a wireless/RF solution for my project, and would like to know what you guys think.

I'm looking to have a reader on a stationary device that would be able to detect when someone with a tag is within 5'-10' the reader. I only need to know whether a tag is present or not.

I immediately thought of RFID for this project, but at 5'-10' it seems like that may require UHF which can be very costly. I've looked at Zigbee, but it seems like that may be too much range, and I would prefer the tags to be economical. I am not opposed to going with an active tag, but it would have to have long battery life (years). It cannot be line of sight (LOS) as the tag would be in someone's clothing.

Is this something I can make work with HF RFID and a larger antenna? What other options are there? :think: :think:

The lowest bands RFID tags operate in are 125Khz & 13MHz. There are also 'key fob' tags for users. Lower frequency equates to greater distance. A decent antenna is also a requirement.

I am familiar with a 125Khz system in an airport which is good for interacting with tags 15+ feet away.

All RFID schema require processing, even for 'presence only' therefore your system will require a bottom end Arduino or similar - the cost should be $5 tops. Tags are around $0.75.

DuckDuckGo tells me Sparkfun has RFID in the 125Khz band. Alternatively the Rip-Off artists on E-Bay and Amazon offer systems.

`Perhaps use a beacon with an impaired antenna? That way the beacon is only detected at short range.