Turn smart outlet on/off based on Dew Point?

I would like to turn a smart outlet connected to my ST hub on or off based on the dew point temperature in my crawl space. I basically want to keep the crawl space below a certain dew point temp to keep water moisture in the air from condensing on the ductwork.

How can I do this? Thanks!

Normally people are looking at dew point in a gas or for precision equipment, in which case you need to know the atmospheric pressure.

But for your purposes, you can just use a pretty easy approximation based on temperature and humidity:

If you are interested in a simpler calculation that gives an approximation of dew point temperature if you know the observed temperature and relative humidity, the following formula was proposed in a 2005 article by Mark G. Lawrence in the Bulletin of the American Meteorological Society:
Td = T - ((100 - RH)/5.)


So you can use any ST-compatible sensor that gives you temperature and humidity, put it on the floor of the attic and use Webcore to calculate a value you can then trigger off of. :sunglasses:

Thanks! You are correct! An approximation would be perfect in my case. This simple formula would work great.

The problem is I have no idea how to write the webcore program.

I was going to hang the temp/humidity sensor with a string from the joist in the crawl space and have the dehumidifier turn on at a DP of 65F or higher and run for a minimum of 1 hour (to keep it from having it’s power cycle on and off too frequently).

Anybody want to help with the webcore part? Any advice or sample programs would be greatly appreciated!

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