Current sensing of capacitive keyboard arrays
US4405918A · kind A · utility
33Cited by
4References
17Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Mar 3, 1980 |
| Grant date | Sep 20, 1983 |
| Priority date | — |
| Expiry date | Mar 3, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K2017/9615
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Current sensing circuits especially adapted for use with either capacitive touch plate or mechanical switch keys. The circuits include a transistor whose base is connected to a constant voltage source and whose emitter-collector circuit is connected between the touch plate or switch keys and an input to a comparator. A second transistor and a capacitor are interconnected with the first transistor to provide transient surge protection. The circuits distinguish between differing values of current and activate the comparator which produces a signal indicative of the existing condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.