US 5,510,783 A · Adaptive keypad

Abstract

An adaptive keypad which has one or more keys includes, for each key, a pressure transducer positioned below a semi-rigid faceplate where the pressure transducer has a resistance which decreases as the pressure compressing the transducer increases. The transducer is connected in series with a capacitor to define an RC circuit for each key. Each RC circuit has a charge time proportional to the pressure applied to the key. A time capture circuit initially and thereafter intermittently, obtains the charge time for each RC circuit for each key and computes a conductance value from that time. The initial conductance value is stored in a memory. A comparing circuit intermittently compares the initial conductance value with each subsequent conductance value generated for a key. If the comparison value generated is greater than a predefined amount, a signal is generated indicating that a key has been depressed. If the comparison value is greater than a predefined amount over a selected period of time indicating a key is permanently depressed, the initial conductance stored in the memory for that key will be modified to a new value against which subsequent comparisons will be made to determine if a key is depressed.

Claims18

Dependent claims

An adaptive key pad apparatus having at least one key, comprising:

a pressure transducer apparatus for each key defining a pressure responsive sensor, each sensor generating a parameter which varies in response to an amount of pressure applied to the sensor;
a measurement device coupled for obtaining an initial measure of the parameter for each sensor and thereafter intermittently obtaining a subsequent measure of the parameter for each sensor;
a memory for storing the initial parameter for each sensor;
a comparing device coupled to the measurement device and to the memory for generating a comparison value for each sensor in response to a comparison of each subsequent parameter measure of that sensor with the initial parameter measure of that sensor and generating an depressed key indication when the comparison value for that sensor meets a first predefined criteria;
and
an adaptive device coupled to the memory and to the measurement device for modifying the initial parameter stored in the memory for each sensor when the subsequent parameter measure for that sensor satisfies a second predefined criteria.

3 more elements

Dependencies are inferred from the claim text.

Adaptive keypad

Life of this patent

Adaptive keypad

Life of this patent

Abstract

Claims18