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[on:]

I am new to Arduino, so I hope somebody can help me.  I want to control a ventilation fan for my basement.  There are lots of similar threads about humidistats, but my control needs to be a little more complicated.  I want the fan to switch on if the basement relative humidity (RH) is greater than 60% but only if the external RH is at least 10% less than the basement RH.  The fan is about 30 feet from the external wall, so one of the sensor wires will be about the same length.

My questions are:

1. What type of sensor should I use (1-wire or otherwise);
2. How should I compare the RHs - with an op amp voltage comparator circuit, or should I use two inputs of the Arduino board.

Thanks, Juliet

[Reply #1 on:]

I don't know anything about the sensors, but computers (and microcontrollers) are really good at math!    So, I'd do the comparison (and the 60% threshold) in software.

[Reply #2 on:]

Take a look at the "DHT11" (or 22) sensors.