Human body sensing multifunctional controller made with infrared sensor

After the switch SA1 is switched, the device can automatically control the lighting in corridors and public toilets in public places, so that the lighting is turned off during the day, and the lights are turned on when people come and off when people leave at night, so as to achieve energy saving; it can be used for automatic control of electric fans, exhaust fans, etc.

1. Working Principle The circuit of this device is shown in the attached figure. It is mainly composed of infrared sensor BH, amplifier, comparator, photosensitive element, conversion switch and control circuit. Infrared sensor BH can detect weak infrared rays emitted by human movement at a long distance. When BH detects the infrared signal emitted by human movement, it is converted into a low-frequency electrical signal, which is output from pin ② of BH to IC2A for amplification, and then output from pin ① of IC2A and coupled to IC2B through C1O for further amplification.

IC2C and IC2D form a voltage comparator. When the voltage amplitude of the signal output from pin 7 of IC2B is between UA and UB (i.e., less than UA and greater than UB), pin 8 of IC2C outputs a high level, and then is isolated from each other through VD6 and VD7 (positive or gate). A control signal UK is output through R16 and R17 and added to pin 5 of IC3B. IC3A~IC3C form a voltage comparator. RG is a photoresistor. When the switch SA1-2 is turned to the ① end, the light is automatically controlled. During the day, due to the light irradiation, RG is in a low resistance state. The voltage of pin 2 of IC3A is higher than that of pin 3, and pin 1 of IC3A is low level. At this time, VD8 is forward biased and UK is clamped at a low potential. At this time, regardless of whether BH receives the infrared signal from the human body, since UK is clamped at a low level, pins 7 and 8 of IC3B and IC3C are both low level, VT1 is cut off, and the light is off. When it is dark or the ambient brightness is reduced. RG is in high impedance state, and the voltage of IC3A's pin ② is lower than that of its pin ③. Then IC3A's pin ① is high level, VD8 is reverse biased and cut off, isolating UK.

After receiving the infrared signal from the moving human body, BH outputs UK and compares it with the reference voltage of IC3B pin ⑤ and pin ⑥. When UK, i.e. the voltage of pin ⑤, is greater than the voltage of pin ⑥, IC3BC pin ⑦ outputs a high level. Similarly, IC3C⑧ also outputs a high level, VT1 is saturated and turned on, J is electrically attracted, and the normally open contact of J is closed, turning on the lighting. When SA1-2 is turned to the ② end, R19 is connected to the circuit. Due to the high resistance value, its working principle is the same as when there is no light.

In the figure, the lighting time and the working time of the controller are determined by RP3, C15 and R27.

2. Production and Adjustment Fresnel lens is required during production. For infrared sensors, the detection radius is less than 2 meters without lens, and the detection distance will increase to more than ten meters after adding lens. When installing, the lens should be fixed 1 to 5 cm in front of BH.

When debugging, first adjust RP2. Block the hole of the RG photoresistor, adjust RP2 to make the first pin of IC3A high level, then make RG receive light, at this time the first pin of IC3A should be low level, then adjust RP1 to make the light on when the human body is about 5 to 7 meters away from the lens. Adjust RP3 to adjust the working time.