Detector circuit with automatic sensitivity control and post detection filtering for touch control circuitry

Claim 2

A touch control switch circuit for detecting a touch input applied to the circuit, comprising: a touch receptor operable by electrical contact with a human body for producing an oscillating signal which increases in amplitude in response to a touch input applied to said receptor; detecting means responsive to the oscillating signal for producing an output to indicate the increase in the amplitude of the oscillating signal; a feedback path including a low pass filter responsive to the output of said detecting means for controlling the sensitivity of said detecting means to the oscillating signal; and means responsive to the output of said detecting means for eliminating undesired frequency components from the output of said detecting means to produce a signal indicating the occurrence of the touch input.

Claim 3

The touch control switch circuit of claim 1, wherein: said detecting means comprises a detector circuit and a variable gain amplifier having an input responsive to the oscillating signal and an output coupled to said detector circuit; and said feedback path is coupled to said amplifier to control the gain of said amplifier to decrease the sensitivity of said detecting means to the oscillating signal upon the occurrence of a protracted increase in its amplitude.

Claim 4

The touch control switch circuit of claim 1, wherein: said detecting means comprises a trigger circuit having a variable threshold; and said feedback path is coupled to said trigger circuit to control the threshold of said trigger circuit to decrease the sensitivity of said trigger circuit to the oscillating signal upon the occurrence of a protracted increase in its amplitude.

Claim 5

A touch control switch circuit operable by an increase in a hum pickup signal resulting from a touch input, cOmprising: a touch receptor for producing a hum pickup signal of ambient magnitude in the absence of the touch input and an oscillating signal of increased amplitude upon the occurrence of the touch input; a detector having an input responsive to the hum pickup signal from said touch receptor and an output for producing an output signal to indicate the occurrence of an increase in the amplitude of the hum pickup signal; a feedback path including a low pass filter responsive to the output of said detector and a variable shunt coupled to the input of said detector and controlled by said low pass filter for diverting a portion of the hum pickup signal from the input of said detector to decrease the sensitivity of the detector upon the occurrence of a protracted increase in the hum pickup signal; and filtering means responsive to the output of said detector for eliminating undesired frequency components from the output signal of said detector to produce a signal indicating the occurrence of the touch input.

Claim 6

A touch control switch circuit operable by an increase in a hum pickup signal resulting from a touch input, cOmprising: a touch receptor for producing a hum pickup signal of ambient magnitude in the absence of the touch input and an oscillating signal of increased amplitude upon the occurrence of the touch input; a detector having an input responsive to the hum pickup signal from said touch receptor and an output for producing an output signal to indicate the occurrence of an increase in the amplitude of the hum pickup signal; a feedback path including a low pass filter responsive to the output of said detector and a variable shunt coupled to the input of said detector and controlled by said low pass filter for diverting a portion of the hum pickup signal from the input of said detector to decrease the sensitivity of the detector upon the occurrence of a protracted increase in the hum pickup signal; and filtering means responsive to the output of said detector for eliminating undesired frequency components from the output signal of said detector to produce a signal indicating the occurrence of the touch input.

Claim 7

The circuit of claim 4, wherein said detector includes: an amplifier circuit responsive to the hum pickup signal from said touch receptor; and a diode coupled to the output of said amplifier for detecting the hum pickup signal and producing an output signal corresponding to the detected envelope of the hum pickup signal.

Claim 8

The circuit of claim 5, wherein said filtering means comprises a band pass filter coupled to the output of said diode.

Claim 9

The circuit of claim 4, wherein said variable shunt comprises: a variable impedance element coupled to the input of said detector and controlled by the output of said low pass filter for diverting a portion of the hum pickup signal from the input of said detector determined by the output signal produced by said detector.

Claim 10

The circuit of claim 7, wherein said variable impedance element comprises: a field transistor having its gate electrode coupled to the output of said low pass filter, its drain electrode coupled to the input of said detector, and its source electrode coupled to ground.

Claim 11

A touch control switch circuit operating in response to an increase in a hum pickup signal resulting from a touch input, comprising: a touch receptor for producing a hum pickup signal of ambient magnitude in the absence of the touch input and a hum pickup signal of increased magnitude upon the occurrence of the touch input; a variable threshold trigger circuit having an input responsive to the hum pickup signal from said touch receptor and an output for producing a series of output pulses in response to the touch input; a feedback path including a low pass filter responsive to the output of said trigger circuit; a voltage divider coupled to the input of said trigger circuit, said voltage divider including a variable impedance element operative in response to the output of said low pass filter to increase the threshold of said trigger circuit upon the occurrence of a protracted increase in the hum pickup signal; and filtering means responsive to the output of said trigger circuit for producing an output signal to indicate the occurrence of a touch input of a predetermined duration.

Claim 12

A touch control switch circuit operating in response to an increase in a hum pickup signal resulting from a touch input, comprising: a touch receptor for producing a hum pickup signal of ambient magnitude in the absence of the touch input and a hum pickup signal of increased magnitude upon the occurrence of the touch input; a variable threshold trigger circuit having an input responsive to the hum pickup signal from said touch receptor and an output for producing a series of output pulses in response to the touch input; a feedback path including a low pass filter responsive to the output of said trigger circuit; a voltage divider coupled to the input of said trigger circuit, said voltage divider including a variable impedance element operative in response to the output of said low pass filter to increase the threshold of said trigger circuit upon the occurrence of a protracted increase in the hum pickup signal; and filtering means responsive to the output of said trigger circuit for producing an output signal to indicate the occurrence of a touch input of a predetermined duration.

Claim 13

The circuit of claim 9, wherein said variable impedance element comprises: a field effect transistor having its gate electrode coupled to the output of said low pass filter, its drain electrode coupled to the input of said trigger circuit, and its source electrode coupled to ground.

Claim 14

The circuit of claim 9, wherein: said trigger circuit comprises a monostable multivibrator; and said filtering means comprises a digital filter including a binary counter responsive to the output pulses produced by said monostable multivibrator for producing a pulse output upon the occurrence of a predetermined number of pulses from said monostable multivibrator.

Claim 15

The circuit of claim 9, wherein: said trigger comprises a Schmitt trigger; and said filtering meaNs comprises a band pass filter coupled to the output of said Schmitt trigger.