Patent ID: 7345491

Claim:
A moisture sensing circuit for a clothes dryer in which clothes tumble during drying, the circuit comprising: a pair of spaced apart electrode sensors for sensing the electrical resistance of the clothes when the clothes contact the electrode sensors; a first low pass filter having two low pass filter inputs each connected with one of the electrode sensors and one first low pass filter output; a voltage follower amplifier with high input resistance and low output resistance, the voltage follower amplifier having a first input coupled to the one low pass filter output, and the voltage follower amplifier having a first output that provides a voltage signal representative of voltage drop across the electrode sensors when clothes contact the sensors; and, an active filter having a second input coupled with the first output of the voltage follower amplifier, the active filter further comprising a second output and the active filter suppressing noise related to operating line frequency of the clothes dryer to provide at the second output a filtered voltage signal representative of voltage drop across the electrode sensors with the operating line frequency noise suppressed.