Radio Frequency Proximity Detector

Hello, Does anyone have an instructable for building a proximity detector based on a radio transmitter and receiver? Or some other wave based method? I've viewed the IR proximity detector here on this site, but I need a transmitter/receiver based one. Yes, this is for my pet. I have 2 cats and 1 dog. I need to keep the dog out of the same areas that the cats are allowed to go into, thus the proximity detector needs to be specifically tuned to the dog. Distance does not have to be far, anywhere from several inches to a couple feet. Appreciate any comments or instructables! Thanks, Eric

frank2608011510 years ago
Did you ever see the AM radio transmitter one? You can use a normal AM radio to listen to the signal, make 3 transmitters on different channels and find them each individually I bet with some work you can even determine direction and range by receiving stronger or weaker signals

Does anybody have any idea on how to make a very cheap proximity sensor, which could work over a distance of about 100 metres? I want to make a system where LEDs (carried by people!) change colour as they approach a certain point, i.e, white LEDs turn red as they move towards a central point. The problem is I want to have 50+ separate LEDs, and I'm on a very tight budget! Any ideas appreciated. Thanks!
offlogic10 years ago
Ricarr- thought equipping your dog's collar with strobed IR LEDs, using an IR detector to trigger a ultrasonic tweeter "blast" to give the dog some boundaries? Just a thought.