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Comment by kentonv

5 days ago

The cat room fans are standard bathroom fans. At present we just leave them on all the time -- you can see the switches taped down in the photos. I suppose it might be a good idea to rig up a sensor...

Might be able to use a flipper zero as the sensor, if the cats are chipped. Then you'll have data to catch any unusual usage, like a urinary blockage, before it becomes a serious problem! At that point you're a smart switch and Home Assistant script away from fan control.

  • I would recommend to use an TVOC sensor that detects smell very easily and then automatically switch on a fan. Could be a fun project.

    Just need: - TVOC sensor like the SGP41

    - ESP32 microcontroller

    - Electric Relay

    • I’m highly unimpressed by my couple of SGP41 sensors, but they would probably work for this application.

    • Interesting idea. Do TVOC respond with enough signal to low level aromatics verses all the particles from cooking or pollution?

  • Garply had a blockage once and he did a remarkably good job of communicating the problem to us directly!

    • As a fellow cat person, I feel pretty confident interpreting what’s being implied here. :-)

      Beautiful home and contents, btw! It seems expensive but more than a few folks would have spent the same money on “nicer marble” or something.

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Constant fans are sucking outside air into your house. Could be part of your Heat/AC efficiency problem mentioned in your post. A timer to run every 10th minute would be a simple improvement.

  • A lot of newer building codes require fans to be constantly running anyway due to the other part of the building codes requiring high r-value insulation.

A sensor would be easy enough, there are simple non-smart sensor fan timer that will activate a fan for a programable time.