Your Humidity Sensor Experiences?

erco

I've been planning to install automatic switches on two bathroom exhaust fans so they turn on when people take showers. My plan is to duplicate a thermistor circuit that has worked perfectly for years in my living room, which turns on several ceiling fans when my natural gas floor furnace kicks on. In that app, I installed a thermistor on the exhaust duct, which gets hot from gas combustion. The thermistor is connected to a simple LM339 comparator so that it closes the fan relay any time the exhaust duct gets above ~110 degrees. I can install similar thermistors on the bathtub hot water supply line so that any time the pipe is above ~110 degrees (hot water flowing) the exhaust fan comes on. A pot adjustment allows fine tuning, which keeps the fan running for a while after the shower water flow stops and the pipe cools down.

But I just saw Parallax' DoD today, which is the humidity sensor. A variable capacitance sensor which I have never tried. Could also probably work in this app. Anyone have any experience or recommendations with this particular sensor?

http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/ProductID/554/List/0/Default.aspx?SortField=ProductName,ProductName

Phil Pilgrim (PhiPi)

Not to denigrate Parallax's offerings or one's do-it-yourself inclinations, but I've had a Honeywell humidistat (now discontinued) installed inline with my bathroom fan for years, and it "just works"^TM. There are less expensive ones available now that will probably work just as well.

-Phil

LoopyByteloose

I'd say the particular humidity sensor you ask about is quite robust. I have the other, I believe it is a Sensitron temperature and humidity sensor and it seems good, but I fear it may not be as durable due to the different kind of humidity sensor it provides.