Human body sensing multi-function controller based on infrared sensor

The device is switched by the switch SA1. It can automatically control the lighting of corridors and public toilets in public places, so that it can be extinguished during the day. When people come to light at night, people turn off the lights to save energy. It can be used for automatic control of fans and exhaust fans.

First, the working principle

The circuit of this device is shown as in Fig. 1. It mainly consists of infrared sensor BH, amplifier, comparator, light sensor and switch and control circuit. The infrared sensor BH can detect the weak infrared rays emitted by the human body at a long distance. When the BH detects the infrared signal emitted by the human body. After being converted into a low-frequency electrical signal, it is output from the 2 pin of BH to IC2A for amplification, and then the signal of 1 pin of IC2A is coupled to IC2B by C1O to further amplify the signal.

IC2C and IC2D form a voltage comparator. When IC7B's 7-pin output signal voltage amplitude is between UA and UB (ie, less than UA, greater than UB), IC2C8 pin outputs a high level, and then is isolated from each other (positive OR gate) via VD6 and VD7. A control signal UK is output via R16 and R17, and is added to IC5B's 5 pin. IC3A~IC3C form a voltage comparator, RG is a photoresistor. When switch SA1-2 is set to 1 terminal, it is the state of automatic light control during the day. Since the light RG is in a low resistance state, the IC3A2 pin voltage is higher than the 3-pin voltage, and the IC3A1 pin is at a low level, and the VD8 is positively turned on. UK is clamped to a low potential. At this time. Regardless of whether the BH receives the infrared signal of the human body, since the UK is clamped at a low level, the pins 7 and 8 of IC3B and IC3C are at a low level, and VT1 is turned off, and the light is not lit. When the day is dark or the ambient brightness is lowered. RG is in a high-impedance state. At this time, the IC3A2 pin voltage is lower than the 3-pin voltage. Then IC1's 1 pin is high level, VD8 is reverse biased off, and is isolated from UK.

The BH receives the infrared signal from the mobile body and outputs the UK and compares it with the IC3B5 pin and the 6-pin reference voltage. When the UK 5-pin voltage is greater than the 6-pin voltage, the IC3BC7 pin outputs a high level. Similarly, IC3C8 also outputs a high level, VT1 is saturated, J is electrically connected, J normally open contact is closed, and the illumination is turned on. When SA1-2 is dialed to the 2nd end, R19 is connected to the circuit. Because of the high resistance, its working principle is the same as that of no light illumination.

In the figure, the length of time the lamp is on and the time it is operated by the controller is determined by RP3, C15, and R27.

Second, production and adjustment

A Feiner lens is required for production. For infrared sensors. Without a lens, the detection radius is less than 2 meters, and the detection distance will increase to more than ten meters when equipped with a lens. The lens should be fixed 1 to 5 cm in front of the BH during installation.

When debugging, first adjust RP2. Block the hole of RG photoresistor, adjust RP2 to make IC3A1 pin high level, then let RG receive light, then IC3A pin 1 should be low level, then adjust RP1 to make human body lens The light can be illuminated from 5 to 7 meters. Adjust RP3 to adjust the length of working time.

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