Tons of hits with google. automatic cat door. http://www.sureflap.com/products/details/1-microchip-cat-door You don't want a 'transmitter' on his collar. You want a transceiver so that it only IDents when interrogated. RF ID chip can work with a large loop (like around the door). http://www.instructables.com/id/Pet-Curfew-An-Arduino-Controlled-Pet-Door/ Why not call the local pet store and see what they have in stock. Time vs money. Turnkey vs your time. On Mon, Dec 9, 2013 at 10:53 PM, Dwayne Reid wrote= : > Good day to all. > > I have a 4-year-old cat who discovered this past summer that he > *really* liked being outdoors. He was strictly an indoor cat up > until that time but now he gets cranky if he's not allowed outside. > > That wasn't a problem during the summer months - and not even that > much problem during the fall. He spent literally weeks outside and > the only time that I saw him was when I called him every evening to > come get supper (when it got dark). > > But now its winter outside and he is spending his days inside. We've > got a foot or more of snow and the temperature plummeted down to -30C > or so this past week. He won't be a happy camper if he has to stay > outside for extended periods. > > So, several weeks ago, I installed a cat door in my bedroom > window. It took him a while to figure out how to get outside but he > sure had no problem figuring out how to come back inside . Now > he comes and goes as he pleases. > > I knew that it would only be a matter of time before some of his > neighborhood feline friends also discovered this wonderful door into > warmth, fresh water, and food. It happened today. > > So now I've locked the cat door into allowing traffic from IN to OUT > only. I have to let the cat in manually when he wants in. That's OK > when I'm here but not good during the day when I'm at work. > > I want to put a small, short-range transmitter on his collar so that > I can have a pair of RC servos un-block the 'IN' traffic > direction. I thought about using permanent magnets on his collar, > but am unhappy with the prospect of them gathering ferrous debris as > well as the very short range operation. I think that RF is my best > bet. Modulated IR would be a close second choice. > > Is anyone aware of an inexpensive, short-range RF link that has a > transmitter that will operate for several months from a single > battery change? It really only needs a foot or so of range. I don't > really care how large the receiver is but the transmitter would > ideally be in a waterproof enclosure that is suitable for attaching > to collar for a small cat. > > I'd rather purchase a ready-made transmitter if possible (and > matching receiver). Is anyone aware of something that might be suitable? > > Many thanks! > > dwayne > > -- > Dwayne Reid > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > (780) 489-3199 voice (780) 487-6397 fax > www.trinity-electronics.com > Custom Electronics Design and Manufacturing > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .