Proximity switch for lights - detects movement using Doppler effect and takes time of day and background illumination into account

摘要

The proximity switch consists of a combination of a conventional timing circuit and a circuit for measuring background illumination. An ultrasonic signal (or similar) is transmitted and reflected from objects in the vicinity of the switch. A comparator compares the transmitted (S) with the reflected (E) received signal and initiates the timing circuit, which in turn initiates the drive circuit that controls the light. A circuit to suppress certain kinds of movement is located between the comparator (U) and the timing circuit (T). A circuit that disables the proximity switch at certain times and/or at certain background levels of illumination is located between the timing circuit and the drive circuit.