I've been toying with a variant of this project for my Honeywell home air filters. I have one in all my "big" rooms, and I like to keep them running at a low speed most of the day.
But I also have time-of-day energy pricing, and it would be nice to automatically turn off (or at least slow) my air filters during the 5pm-8pm window. This project inspires me to at least look into the feasibility of adding that functionality myself.
Depending on your air filter you might be able to just use a smart plug, I went down a similar route this summer before realizing that mine would remember their power state and settings when powered off.
So now I just have them plugged into a few smart plugs with automations in homeassistant
I would need a device with a physical switch rather than a touch control. Sadly many devices, mine included, have "power was cycled = device is off" logic.
It's been working so well I was actually surprised one night when the dehumidifier in the bedroom turned itself on from the automation (which I have set to do after dark if humidity is higher then 70%).
It had been within tolerance for ages and I just hadn't had to even think about it.
You should, it is very DIYable! I did it and reverse engineered it myself a while back. You dont need to make a custom circuit board if you are fine with losing the touch controls
But I also have time-of-day energy pricing, and it would be nice to automatically turn off (or at least slow) my air filters during the 5pm-8pm window. This project inspires me to at least look into the feasibility of adding that functionality myself.