2-3 ft Range Activation

Hello. I have gone around in circles trying to find a low cost, simple solution for activating processes on an Arduino by having something come within a couple feet proximity of it. I require more than the couple inch range provided by passive RFIDs. and higher end RFIDs are cost prohibitive. It does not need to be a secure or unique ID connection, it does not need to send any data. I just need to be able to sense when something is in range of the Arduino. But it has to be able to know the difference between something I want to detect (something with the "beacon") and something I don't want to active it (everyone else walking by). so IR prox sensors and simple visual type systems are not the answer. any suggestions?

think high tech doggy door, though this is not my application. the dog could wear something that unlocks the door (if you ignore the security of the system).

any suggestions would help! especially if you've had luck doing something similar. thanks!

The PIXY (CMUCam5) can automatically detect and report two-color signatures on an object.

Is it to sense people carrying a transponder? How big can it be?

The door control could send interrogation continuously and when it gets a response it could open the door. What is the max distance from the door that you want it to allow?


The problem is too vaguely formulated to get a concrete answer, can you give more details? Size, weight any barking/meowing noises the "object" use to do ? Can it be trained to push a button? Can it carry batteries and circuitry? etc., etc.. as you see, we-re speculating too much.

Sorry for the vagueness, I was trying not to lead the question too much so I could hopefully get ideas I haven't already pursued, or new approaches.

let's assume it really just is a pet door. or a pet feeder. so I would ideally be able to put something small on my dog's collar that would activate it when he was within a couple feet, with no dog training required. but not activate it when across the room. and something that would not get activated by the cat walking by. functionally I want exactly what an rfid tag and reader would do. I just need more range. I could probably make it work if I could even get just 12" range or so. I am also looking in to larger reader antennas for 125khz rfid, but antennas are not my thing so my work is sloppy.

thanks for the replies and ideas so far. really appreciate it!