Clothes dryer moisture sensing circuit
First Claim
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1. 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.
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Abstract
A moisture sensing circuit for a clothes dryer in which clothes tumble during drying has a pair of spaced apart electrode sensors for sensing the electrical resistance of the clothes when the clothes contact the electrodes. The circuit has an active filter for suppressing noise related to the operating line frequency of the clothes dryer to provide a filtered voltage signal representative of voltage drop across the electrode sensors with the line frequency noise suppressed.
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Citations
6 Claims
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1. A moisture sensing circuit for a clothes dryer in which clothes tumble during drying, the circuit comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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