Adaptive keypad
US5510783A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 13, 1992 |
| Grant date | Apr 23, 1996 |
| Priority date | — |
| Expiry date | Jul 13, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01H2239/038
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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 determ…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.