About 1977 I had two cats and a 24/7 cat flap, but a stray was coming in during the night and getting food left for the residents. I breadboarded a cat discriminator. It used two telephone relay coils that could detect a small magnet passing between them, added to the cat collars and a light bulb plus detector (photoresistor). If the magnetic signal was triggered and a cat entered, it was a resident, if the non-resident entered, not wearing the magnet, it sounded an alarm. I added larger flap made from cardboard and a solenoid that allowed the large flap to fall and close off the smaller flap so no exit was possible. The no-exit flap solenoid was actually manually energized by touching two wires together on the end of a cable that ran to my bedroom. Everything was rather crude. I expected that I needed it once.
After I installed it I tested it with my cats with and without collars and it seemed to work well. That same night at around 02:00 the alarm sounded, I touched the wires together, the larger flap fell and I went out. The non-resident, hearing me stirring, made a mad dash for the door and hit the large flap covering the bidirectional flap. I tried to catch this panicking cat, and in the process the breadboard and the lamp, photoresistor and coils all came undone from their temporary mounts. It was a jumble. The non-resident had to be chased around the house, leaping up at closed windows, and eventually I caught him, and trimmed off his whiskers with a scissors. This is a very powerful yet harmless reminder since they depend on them for feeling for passages that their body can get through. (A fellow cat lover told me that once they trimmed off their cat's whiskers and the can would be ware of going from room to room in the house especially if the door was partly closed leaving a narrow gap.) They will be disoriented for some months until new whiskers grow back. A good reminder. I finally opened the door and released the non-resident, who seemed to traverse the back yard that was a least 15 meters (or 40-some feet) long in three or four leaps. He never again appeared. The damaged cat discriminator was summarily taken apart. I remember using LM324 and LM 339 in the circuit. One of the cats was a great hunter, and I lived north of the San Fernando Valley in foothill areas (Newhall, CA) where some ground squirrels lived. My hunter cat, a gentle calico, would bring home slain squirrels and leave various parts somewhere in the house as a token of her skill, for me to find and clean up when I got home. This happened on a nearly daily basis one spring. Eventually it stopped and I found that the nearby colony has been totally exterminated by my calico. For a while I had wondered what it would take to build a prey discriminator that could block her entry only when she carried a victim, but even now I suspect that that is a much greater challenge. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/YW_1WLGSTogJ. For more options, visit https://groups.google.com/groups/opt_out.
