Instructables

Step 9: Arduino Extension and a Bathroom Vent Version

Some cats can be extremely finicky about changes or slight noise in the cat-box, and may start crapping all over the place as a result.  If this ends up being the case, you might consider tweaking this design to put the fan on the window-end of the system.   If you want a further challenge, try rigging up two PIR sensors with an Arduino and a relay switch for the fan like I did for my Mom.  The fan shuts off whenever the cat comes near the litter box, and stays off for 30 seconds after the last detected motion.  Problem solved! Lot's of fun.

If you prefer to have the litter box in a bathroom, you can build a homemade hose coupling that fits over the bathroom exhaust fan / vent.  Because 4" duct is a bit unsightly snaking up to the ceiling, it's probably worth using a design with smaller diameter hose, like 2.5" sump pump hose.  Smaller cans, like those used for tomato paste, could provide the way here...
 
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Would you mind making a DIY for your Arduino system? I'm not very familiar with them and would love to learn how to make PIR system for my litter box. Great DIY by the way.
Quester553 years ago
As Humans, We tend to forget how Sensitive an Animal like a Cat or Dog can be to Sounds We don't Hear or Vibrations We don't Feel.
Consider how you'd feel if you started Hearing the Whirl of a fan or feel your Hair move in a wind where none existed before, Each time you used the Potty, Now Amplify that a hundred times, That's what your Cat is going through. You might try Switching the Fan from the Box to the Window, To Quiet things down a bit, As well as making a Diffuser at the Box-End to tone-down the Suction under the Hose outlet.