Photoelectric control circuit for lighting

Lighting lights include street lights, corridor lights and courtyard lights and other public place lighting, its control switch is often usedOptoelectronic sensitive devicesRealize automatic control. After the lighting is automatically controlled by photoelectricity, it is decided whether to turn on the light according to the natural light situation in order to save electricity. This is shown in Figure 3-17It is the simplest automatic control circuit of lighting lamp with photosensitive device as photoelectric sensitive device. The circuit consists of 3 parts: Part 1 is the causeRectifier diodesVD and filter capacitor C constitute a half-wave rectifier filter circuit, which provides DC power for the photoelectric control circuit; Part 2 is by the current limiting resistors R,CdSPhotoresistorsandRelaysCircuits for metering and control of windings; Part 3 is an execution circuit consisting of the normally closed contacts of a relay, which controls the switching of the lamp.

CdS is photosensitive when natural light is dim and lights need to be litresistanceThe resistance value is very high, the winding current of relay K becomes very small, can not maintain work and close, normally closed contact makes the lamp light; When the natural light is enhanced to a certain illuminance Ev, the resistance of the photoresistor is reduced to a certain value, the current flowing through the relay makes the relay K operate, and the normally closed contact is disconnected to extinguish the lamp. Let the illuminance of the lamp be Ev, the DC resistance of the relay winding be Rk, and the minimum current of the relay to close is Imin,PhotoresistorsThe photoconductivity sensitivity is Sg, the dark conductance g0-0, obviously, this simplest photoelectric control circuit has many shortcomings and needs to be improved. In practical applications, other circuits are often added, such as corridor lighting, often equipped with voice-activated switches or microwavesProximity switch, so that the lamp is lit when there is an activity; The street lighting controller should add measures to prevent lightning radiation or artificial light sources (such as flashlights, etc.) from interfering with the control circuit.