Capacitive sensing, solid state touch button system
US5036321A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 1989 |
| Grant date | Jul 30, 1991 |
| Priority date | — |
| Expiry date | Aug 31, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K11/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A solid state touch or control button assembly (10), with no moving button parts and operated by capacitive sensing by monitoring the phase shift of a signal applied to the face of the button, including in a first embodiment (FIGS. 2A & 2B) a auto balancing button and in a second embodiment (FIGS. 3A & 3B) a constant pressure button. If skin or other material comes into contact with the touch surface, the capacitance is changed and sensed, causing the electrical or electronic function controlled by the touch button to be activated (or deactivated, depending on the design, or otherwise altered). LEDs then are activated, providing visual feedback to the button pusher through a light ring (2A) surrounding the button surface (1). False activation of the button by residual impedance and external influences, such as temperature change, cleaner residue build-up and other deposits, are avoided by compensating for them by slowly auto balancing to all such phase shifts, with the rate of auto balance being set to be faster than the rate of change of the steady state phase shift; and, additionally, false activations by noise transients, including those due to EMI, FRI and other environmental f…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.