Our cat, Murray, had gotten into the habit of preferring to drink from a slow trickle in the bathroom sink.  This wasn't always convenient for us, so I decided to modify a pet fountain.  After checking out several of them, I went with the Drinkwell Platinum.  It has a carbon filter, adjustable stream, large reservoir, and is pretty quiet.  I didn't see the need to have it run constantly, so I wanted to put a motion detector on it to run only when he came near.

This ws a pretty straight forward project and turned out really well.  Murray loves it.

Step 1: Motion Detector

If the fountain is the body of this project, the passive infared motion detector (PIR) is the brain.  I didn't have to search very long to find the perfect detector.  It was very small and simple to wire into a control board.  I found it at http://www.glolab.com .  The detector itself fit perfectly into a 3/8 inch hole I drilled in the front of the fountain frame.  It took me a little time to figure out the best way to hook it up since it has a dedicated relay out.  It turned out that since I was using a solid state relay to activate the pump, the standard out worked best.

The additional items necessary for this project are a small perfboard, 180 ohm resistor, 7805 voltage regulator, AQH2213 solid state relay, 0.1uF capacitor, 10uF 50V capacitor, 1000uF 25V capacitor, a bridge rectifier, 2 Molex KK connectors (male and female for each), and a 3 pin header.

Step 2: Electronic Design

So, the design was very straight forward.  The fountain's pump came with a 12 volt AC transformer.  The PIR runs on DC.  I used a bridge rectifier to convert the AC to DC after the AC has run to the pump.  The 12V DC is then converted to 5 volts and regulated through a 7805 regulator.  The pump is switched on with an AQH 2213 solid state relay. The schematic shows a 3213, but Digikey was out when I went to order.  Th only difference is the mA tollerance, 600mA for 2213, 1.2A for 3213.  The 600mA provides almost double the max draw on start up of the pump, so it worked fine.  The relay is triggered by the output from the PIR. The LED trigger in the SSR has a max forward voltage of 1.3V at 20MA and the PIR outputs 3.5V. Using Ohm's law:

(3.5-1.3)V / 20mA = 110 ohms, so I used a 180 ohm resistor. 

The red and white jumper wires on the breadboard simulate the power to the pump.

Step 3: Power Connection

In order to connect the power to the circuit, I cut off the barrel plug it came with and replaced it with a Molex KK connector.

Step 4: PIR Connection

The PIR mounts in the front of the fountain frame, so it needed 3 wires to connect to the circuit board (+V, Ground, and Output).  I termiated these in a simple 3 pin header, bent a little to fit into the tight space.  The wires tuck up nicely between the outer fountain frame and the bowl.

Step 5: Circuit Connection

Here you can see the underside of the fountain where the PIR wires come around from the front, and the female KK connector coming from the pump.  This space was able to contain the circuit board nicely once I added some one inch standoffs.  I drilled from the outside of the fountain frame to screw in the board.

Step 6: Finished!

All that was left was to fill the reservoir and plug it in.  Murray took to it right away and the PIR, though continuously re-triggered while he's moving in front of it, shuts off after 30 seconds without motion.  The sensitivity is enough for Murray to trigger it when approached, but not when we walk past, about 6 feet away.

Here's a video of it in action, where you can also see where the sensor is mounted.

<p>I just bought one of these fountains and didnt like the fact that it continously runs. Your project is a awesome modification. Would you consider putting it together as a kit to sell? I dont want to do all the electronics, I just want to have a finished kit that I just have to mount to the water fountain.</p>
Continuously running is what keeps the water from becoming stagnant and growing algae.
<p>I agree with skidoal. It would be awesome if you sold it as a kit, as I don't really have time to do this. My cat drinks mostly from the sink, which is cute but also a bit of a pain :|</p>
<p>I found a wireless motion detector that links with an outlet at Menards on clearance for $14 this weekend. I installed the wall outlet, placed the wireless motion sensor near the water fountain, and, ta-da!, motion activated pet fountain. It auto-shuts off after one minute from her walking away. Perfect. </p>
<p>This is awesome! Thanks so much for posting it. Our cat used to like her Raindrop fountain but now she just wants to splash the water everywhere. She prefers to drink from the sink if we turn it on for her. I'm thinking maybe if the fountain isn't running all the time, she will like it better. I dunno I'm ready to try anything- she's 16 and her kidneys aren't at 100% so if this gets her to drink her water and enjoy it, I will try it. I've been looking for a fountain where the cat presses a button to dispense but cant seem to find one. this seems like a nice idea or maybe i could even modify it to add use a pedal she could step on, instead of using the motion detector.</p>
Hi there - this is brilliant! I have to commend you on your great thread. Like you I can't stand the idea of wasting the energy, filter and pump by running it constantly. Would really like to build one of these. I first need to order the components. I'm trying to figure out which voltage regulator to get. I guess I need to get a better idea of what the switching voltage and current needs to be. Also, the 0.1uF capacitor - what voltage should that be rated to. Your advice would be very much appreciated.
Brian, Thanks for posting. This excellent! I understand the whole cat and sink thing very much. I look forward to studing the design so we can get our bathroom sink back also... Bob Z

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