Dear Deaf Dog Owners,
Miranda told me there are a number of people who would like to know more about the collar we made for Emma.
The basic idea is to use the guts of a radio remote controlled toy car as a means to turn on and off a vibrator fixed to the dog's collar. The car has everything you need---hand held radio transmitter/actuator, small radio receiver with antenna, and a small motor that forms the basis of the vibrator.
I bought the least expensive remote controlled toy car I could find. There is a wide variety available, each offering different styling and each offering different remote control options., but all you need is the simplest and cheapest. The one I used cost about $10. It's remote control feature was very limited. When you turned the car on (There's an on-off switch on the car.) it ran forward continuously. When you pulled the trigger on the remote control unit, the car's direction reversed.
In this particular car (and probably most others, although I'm not an expert) the battery, receiver electronics and on-off switch were all right next to each other in a plastic assembly which I 'extracted'. Basically, I broke the car apart until this was all that was left. You want these components to occupy as little space as possible because they will be hanging on your dog's collar.
I also 'extracted' the motor, and epoxied a small piece of metal to the side of its shaft. The idea is to fix something to the shaft that will cause the motor to be out of balance so that when it runs it will shake (vibrate). Anything will work, even a pebble. You can try a few things by first fixing them to the shaft with tape to get a feel for whether or not there's enough vibration. Heavier things will cause greater vibrations.
I put the motor in a plastic 35mm film canister -- you can get them free at any photo store-- and stuffed some paper in to hold it in place.
The battery/receiver/on-off switch assembly, and the vibrator, are sewn onto a collar. It's probably best to sew the antenna in too, and not have it stick up where it might get in the dog's way. That's what Miranda did and it works fine.
If the remote controlled car you started with is normally stopped, and only runs when activated, then you're finished. In my case, the car ran all the time, and reversed when activated, i.e., the motor ran all the time, only changing direction. Thus, it vibrated all the time, whether the actuator was pressed or not. In order to prevent it from running forward continuously, and only running (in this case backward, but who cares, all you want to do is have it turn) when activated, I put a diode in series with one of the leads to the motor. You can buy diodes at Radio Shack for less than a buck. Try the diode in each lead to the motor, and in each direction in each lead, until you hit upon the right lead and direction to do what you want. If this seems to hard to do, find a car that is normally stopped, and only runs when activated (either backwards or forwards, it doesn't matter).
That's it. I'm happy to try to answer any questions, or to clarify the above.
Bob & Miranda firstname.lastname@example.org