Occupancy sensor
US4661720A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 9, 1986 |
| Grant date | Apr 28, 1987 |
| Priority date | — |
| Expiry date | Jun 9, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S15/523
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An improved apparatus for switching off power to an electric load in the absence of the detection of movement from the doppler shift of a transmission signal. An oscillator generates an ultrasonic transmission frequency which is transmitted via a transmission plate coupled to the oscillator. A plurality of receivers detect reflections of the ultrasonic sound signal and supply the detected signal to a bandpass filter which passes the transmission frequency. A low-pass demodulator will detect any doppler signal which modulates the transmission signal and will supply it to an amplifier for amplification. The amplified signal is then provided to a narrow band filter which will pass only a narrow band of doppler-shift signals which correspond to the frequencies of human movement. The signal is then supplied to a switching means which, when activated, will discharge a first node. The first node is charged via a resistor and a capacitor coupled to a voltage source. A comparator is coupled to the first node and is also coupled to a voltage reference. The comparator will produce an output signal when the first node has a higher voltage than the voltage reference, thereby enabling a control …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.