Herding cats

Unfortunately, especially if the house is kept warm and food abundant, owners will find not only their own cat taking advantage of the facilities, but other cats. These may include large, un-neutered tom cats, who are quite capable of bullying the precious feline that is supposed to be resident, taking what they want for themselves, regardless of the needs and desires of the rightful resident. One schoolteacher, we know, thought he had solved the problem by putting out additional supplies of food, but finds that he is now sharing his abode with no less than eight of the creatures, in addition to the one he originally started with. Such problems have led to the development of tags that have to be worn by cats on a collar, that only allow a cat flap to be released in the event of the proximity of the tag. The only problem is that many cats will not wear a collar, and if one is fitted, go to any lengths to get rid of it. And if they do submit to this indignity, are liable to strangle themselves in the course of their active life style, chasing birds, squirrels and other cats through trees, and doing the other things such animals are wont to do. The Challenge Our challenge this month is to come up with a means of opening a cat flap or a door, on the detection of a permitted cat, and keeping it shut to all other creatures. Cats, of course, because of the superior nature of their species, rather expect a flunky to open and close the house back door on being recognised, possibly with the accompaniment of a bow and the doffing of a hat. However, since this not practicable in other than royal palaces, other technologies need to be applied and adopted. These could be optical, recognising the cat, or even detecting the scent of a particular cat, but both solutions offer particular technical challenges. The solution offered below, on the other hand solves the problem elegantly and at very modest cost. Its development has required a minor breakthrough in electronics, which may have many other additional applications and is protected by patent. For those without access to the web, the solution will be described fully in our March edition. See if you can come up with anything better. Solution The solution to this month's challenge is the brainchild of Cambridge scientist, Dr Nick Hill, who has devised a system powered by four small batteries that can remotely read the chips with which most owned cats are implanted in order to identify them, and unlatch the cat flap on detecting that a particular cat is authorised to use it. Andy Bank, General Manager of Cambridge start-up company SureFlap, told us that if Dr Hill had had to use conventional embedded chip reading technology, it "Would have had to be a mains powered device". Without going into details, he told us that, "The breakthrough difference is in the circuit design, in that it automatically tunes and removes any upper limit antenna efficiency that may be used. This allows the use of high efficiency antennae that would otherwise require very fine setup".' An additional benefit of this automatic tuning is that it can compensate for the effects of detuning, which is a major problem with RFID systems. This is where the resonant frequency of a reader or tag changes through variations in components and/or the presence of metal and/or water in the vicinity, as in this case where it forms a large part of the cat. Dr Hill says that, "Our technology allows the system to compensate for this and can be applied both in a reader and also for the very first time in a passive RFID tag. This is set to have a major impact on RFID as a whole". The development is now available as the commercially available "SureFlap", which is sold by the Yorkshire company, Animalcare, which is the UK distributor of the "identichip" microchip. The device sells for £79.99 and runs off four standard AA batteries. An optical sensor detects the cat, and the device can be taught to permanently recognise up to 32 chipped cats and keep out the others. Dr Hill's company, Cambridge Resonant Technologies has patented the base technology, which it has called, "OnTune" and is free to license it for other uses.