Smart Cat Fountain: Camera Recognizes the Cat, Home Assistant Opens the Faucet

Susi (British Shorthair) and Loki (Maine Coon) don't drink from a bowl. Period. What they want is fresh, running water from the bathroom faucet. Cat fountain? Ignored. So for years I opened the tap just a little, so a thin stream would run for them. The real problem wasn't the cats — it was me. I constantly forgot to close the tap again. More than once the water ran all night. Or the entire workday while I was on shift. With water prices these days that adds up, and it's completely unnecessary. One thing was clear: the cats won't change. So the tech has to take over the forgetting part.

The obvious approach: a PIR motion sensor above the sink plus a smart valve in the water line. Cat arrives, motion detected, water on. Cat leaves, water off. And it did work. Except: a PIR sensor can't tell a cat from a human. Every morning when I stumbled into the bathroom half asleep, the tap opened. Brushing your teeth next to an automatic stream of water gets annoying faster than you'd think. What I needed wasn't motion detection, but an answer to the question: is that thing in the sink a cat — or me?

Object detection provides the answer. My server runs Frigate — an open-source NVR that analyzes camera streams in real time. A Coral USB Accelerator* handles the actual detection, so the CPU barely notices. The flow: 1. A small ESP32 camera above the sink streams the image to Frigate 2. Frigate detects whether there's a cat in the frame — not just "something is moving" 3. A zone sits exactly on the sink, so a cat lounging next to it doesn't count 4. The result goes to Home Assistant via MQTT, the rest is an automation The difference from a motion sensor: Frigate doesn't say "motion", it says "cat, 81%". And when I'm standing at the sink myself, it says "person" — and the valve stays closed. Exactly what I wanted.

I didn't want an off-the-shelf IP camera in my bathroom — too big, too expensive, and honestly, I prefer building this kind of thing myself. I ended up with a Freenove ESP32-S3 WROOM CAM board* (16 MB flash, 8 MB PSRAM) with an OV5640 sensor. The firmware is built with PlatformIO and streams MJPEG over RTSP — 1280x720 at around 10 fps. Frigate only needs 5 fps for detection anyway, so that's plenty. Updates run over OTA, so no crawling into the bathroom with a USB cable. Two things worth knowing: - The ESP32-S3 has no hardware H.264. MJPEG causes a bit more CPU load in Frigate — completely uncritical for a single camera. - The camera should look at the sink from above at an angle, so the cat is visible as a whole animal. Just a head at the edge of the frame often isn't enough for a confident detection. And yes: the board is currently mounted bare on the wall. The case is in the 3D printer queue — as is tradition for any proper maker project.

A Sonoff SWV* sits in the water line to the faucet — a Zigbee water valve switchable by Home Assistant. One thing to watch when buying: it comes as a BSP variant (G3/4 thread, EU) and as a US version with NPT thread — make sure you grab the one that matches your plumbing. The logic consists of four automations: 1. Open: Frigate reports a cat in the sink zone → valve opens 2. Run-on: Cat leaves the sink → a 45-second timer starts 3. Close: Timer expires → valve closes 4. Safety cutoff: After 3 minutes maximum, it always closes — in case Frigate decides a towel is a cat at 3 am On top of that there's a master switch (input_boolean) to disable the whole automation whenever I don't want it running. One detail I particularly like: the water runs through a countertop filter before it comes out of the tap. So the cats are drinking filtered water here. Strictly speaking, they drink better water than I do.

The funniest bug of the project: Loki is too big for the detection model to be a cat. The COCO model Frigate uses by default regularly classifies the Maine Coon as dog — at 79% confidence, so the model is quite sure about it. The pragmatic fix: since no dog lives here, Frigate simply tracks `cat` and `dog` on this camera, and the automation treats both the same. Problem solved. As for Loki's dignity, no comment. The system has been running around the clock ever since — including at half past four in the morning when Susi takes her early drink. The tap now runs exactly when a cat sits in front of it. And not a minute longer. Though Loki has started interpreting the system rather generously: he just settles into the sink and enjoys the running water as ambience — a cat in the zone is a cat in the zone, after all. At least the three-minute safety cutoff puts an end to each spa session. (The photo is real, by the way — I only had an ugly grille in the background removed via AI retouching.) Next up: the printed case for the camera, and maybe some subtle night lighting so the model detects even more reliably in the dark. All configs are on GitHub: esp32-frigate-cat-fountain — the Frigate snippet, the HA automations and the PlatformIO firmware.