Variable sensitivity motion detector
US4636774A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 8, 1983 |
| Grant date | Jan 13, 1987 |
| Priority date | — |
| Expiry date | Nov 8, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/181
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
The motion detector of the present invention, together with associated AC switching circuitry form a lighting control system which turns on room lights when the room is occupied, and extinguishes the lights when unoccupied. The detector sensitivity or threshold is adjusted in response to the previously detected conditions, providing reliable indication of both entry and continued presence in the controlled area, and producing few false alarms. The present embodiment of the invention has two threshold levels of detection, the higher level being used to detect initial entry into the room. After entry is detected, the motion detector lowers the threshold to detect the weaker signals usually occurring for continued presence in the area of the detector. When the occupant leaves the area, the motion detector threshold or sensitivity returns to the original value after a timeout period.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.