Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1992-07-13
1996-04-23
Peng, John K.
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 26, 338 47, H03K 1796
Patent
active
055107834
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.
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Findlater Stewart M.
Hickman Kenneth T.
Interlink Electronics, Inc.
Peng John K.
Wu Daniel J.
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