Because I live in the American South and because we recently had our water plumbing explode, the humidity in our house tends to be sky high. Like 60% or higher high. To counter this I picked up a large dehumidifier from Amazon which has largely worked well controlling the humidity until recently.

Recently though I noticed that the humidifier kept turning off and on. Dehumidifier was set to 35 but the household thermostat was reading 55% humidity. As a check, I set the dehumidifier to run continuously. It stayed running and the humidity in the house started dropping and is down to the 30’s in the room where the device is located and down to 46 at the thermostat. My conclusion was that the humidity sensor on the device had failed.

I could go the hard route. Take apart the dehumidifier, try to find the problem and do a board level repair. Go the expensive route and replace a generally functioning dehumidifier. Or I could take cheap, simple, and admitedly jerry-rigged option. Home Assistant.

My first idea was to use Node-Red to kitbash a hygrostat together with some basic safeties, but as I was putting the devices and sensors into helpers I found that Home Assistant has a new (to me anyways) helper called a Generic Hygostat that can connect a humidity sensor like this one by Third Reality to a smart outlet or plug and control that outlet based on a humidity level you set. It can be set to control either a humidifier or dehumidifier. Once you’ve created the helper you can add the helper to your dashboard and it gives you thermostat like control over your de/humidifier. Pretty slick.