Help with sensing proximity

I would like to make a drinking fountain that turns on when my dog gets near enough, and shuts off when he leaves. I am wondering if a combination of sensor types would be the best way to go.

If I use a PIR motion detector, I am afraid that it might shut off while the dog is still drinking, since he won't be moving much, unless the movement of his head and tongue would be enough motion to cause retriggering.

I'm not sure any ultrasonic sensor would work well with a dog's hearing.

I thought about detecting the metal in his choke chain.

I also thought that using a PIR type motion sensor with a separate distance sensor to prevent false triggering. I figure I could write code to make sure that motion is detected AND something is within range before triggering, then shuts off when nothing remains in range of distance sensor.

Another thought was to measure the ambient IR level, then trigger when proximity of the dog provides an increase in heat/IR.

Can anyone suggest the best approach and/or sensors to try?
Many thanks,

How about a footpad to step on? If dog decides to lay down it, can turn it off after 120 seconds of being on or similar, wait for him to move off & back on to restart.

Ultrasonic isn't good detecting my hair or wool shirt, is your doggy long-hair furry?

You could go with beam-interrupt, which to me is funny since the smart move is to limit the detector aperture rather than play with aiming thin beams of light. An IR source and a detector on opposite sides of the bowl and you'll know when something light-blocking is between.

You could go for capacitance sensing. Those can go from touch to close to nearby.
Arduino Playground -- Capacitive sensing.

You might go with multiple sensor types.

You might want to make sure the bowl only gets so full...... and the dog.

Dogs are quite clever, most of them can learn to activate an switch or similar device for turning on the water supply. Water can be supplied as long as the switch is pressed, or for a limited time.

With a waterspout fountain you can use a light barrier on top of the fountain.

Thanks for the replies so far! Time to begin experimenting...
Bryan :slight_smile:

I like dogs, I will help you.

I would approach it this way. Some dog doors open when dog gets close. They work by using a close range signal that is in the dogs collar. Lots of collars already have this, shouldn't be hard to find one. I bet someone on here can tell you what signal they use.

The way the dog door works is it is a standard dog door with flap, but it has a garage door mechanism that prevents possums and other unwanted rodents from coming into your house through the dog door. It only opens when dog gets close to dog door. Others work by that flap being a swinging solid flat that is locked in place, therefor no garage door mechanism is needed.

I'd look into using the same technology. Ultrasonic, and stepping plate sensors seem to complicated.

Ultrasonic is out because fur makes a lousy sound reflector.

RFID, the reader for the collar device, is expen$ive and way more complicated than a step surface laid on a layer of conductive foam that you sense resistance change strongly when it compresses or a detector detecting light or not. But the capacitive proximity sensor does take work but is very satisfying and costs less than $1 to make.

One I forgot is active IR. You put the IR led and detector side by side pointing out. When anything that reflects near-IR approaches it gets detected.