Motion Sensor Concept for Light Control with Cats in Bathroom

Configuration
1

Hi everyone,

I’m currently renovating a fairly large bathroom and have the opportunity to hardwire everything. My goal is a 100% reliable presence detection for lighting (Futlight LEDs via LocalTuya) that completely ignores my cats (approx. 4-5 kg) walking on the floor.

Since traditional PIR sensors either suffer from false triggers by pets or leave you in the dark while in the bathtub/shower, I’m planning to use mmWave sensors. Since I have full access to the ceiling, I want to use flush-mounted ceiling sensors instead of wall-mounted ones like the Aqara FP2, mainly to utilize the physical Z-axis limitation to “blind out” the floor.

Here is my current technical concept:

The Hardware & Setup

  • Sensors: 3x Tuya ZY-M100-L (24GHz mmWave, 230V Ceiling Flush Mount version).
  • Integration: Zigbee2MQTT in a Dockerized Home Assistant setup.
  • Lighting: Futlight LEDs integrated via LocalTuya.

The 3-Zone Concept & Cat Immunity

Instead of relying on software algorithms to filter out pets, I plan to use the detection_distance_max parameter in Z2M to create a physical “cutoff” above the floor. Assuming a ceiling height of 2.50m (approx. 8.2 ft):

  1. Zone 1: The Shower (Brick Walls)
  • Placement: Dead center above the shower cabin.
  • Distance Config: Max range set to ~1.80m (approx. 5.9 ft).
  • Logic: The sensor dome ends roughly 50-60 cm above the shower floor. It detects my upper body instantly, but when a cat walks into the shower, it stays below the radar cone. The brick walls will act as a natural shield against interference with the other sensors.
  1. Zone 2: The Bathtub
  • Placement: Above the tub (slightly towards the head end to catch breathing).
  • Distance Config: Max range set to ~2.00m (approx. 6.5 ft) to reach into the tub.
  • Logic: The tub itself is elevated, so the radar won’t reach the floor outside the tub where the cats roam.
  1. Zone 3: Main Area (Vanity/Sink)
  • Placement: Slightly in front of the sink.
  • Distance Config: Max range set to ~1.60m (approx. 5.2 ft).
  • Logic: Detects upper body movement immediately. The floor (and thus the cats) is completely out of the radial reach.

My Questions for the Community:

  1. Interference: Has anyone run multiple Tuya ZY-M100 ceiling sensors in the same room? Since the shower is bricked, I’m mostly worried about the tub and vanity sensors interfering with each other. Does strict distance limiting prevent cross-talk, or will the 24GHz signals still bounce and mess with each other?
  2. Cat Reality Check: Has anyone successfully used this Z-axis “cutoff” method with ceiling mmWave sensors to ignore pets? Does the cone geometry work as intended in real life, or do stray reflections still cause false positives from the floor?
  3. Alternative: Would a single Aqara FP2 (wall-mounted) with configured “interference zones” for the floor be more reliable, despite its lack of true Z-axis awareness? Or would the best way be to combind the Aquara with the Tuya Sensors to have a Logic Like " if distance from top = human and precence (aquara) = on , trigger light" the best option?
2

5 minutes after you’re done setting up, at least 1 cat will jump on the toilet, vanity or bath. There goes your Z-axis cutoff.

1 Like
3

Is moisture build-up or steam clouds going to cause issues with your sensors?

4

WiFi presence

Or

5

You only need mmWave to hold the lights on while you are not moving. So place an IR beam across the door frame at waist height. Breaking this beam will turn the lights on. Turn the light off only when mmWave says the room is unoccupied.

The beam will turn on the light when you leave, but it has no effect as the lights are already on.

This does fail if the cats are in the room with you and you leave, the lights will stay on util the cats leave. But cats will never trigger the lights on

If you can’t build an IR beam, then use a PIR that can only see the top half of the door frame.