利用可见光监视的门卫,Using visible light to monitor guard

    这是利用可见光作监视的门卫威廉希尔官方网站 。发射器改用白色发光二极管，接收可见光束的传感器件也改用光敏电阻(LDR)，控制威廉希尔官方网站 采用uA741运算放大器作电压比较器。预置电位器VR1提供基准电压至uA741(IC1)的同相输入端③，而光敏电阻LDR1和电阻R1则连接至IC1的反相输入端②。

    LED1和LDR1分设在大门进口的两侧，这样，在大门关上时，从LED1射出的可见光束可落到LDR1上面。

    在有LED光束射至LDR1时。LDR1的电阻相比R1变小，因此IC1的输出脚⑥变低电位，这时LED2开始闪烁而蜂鸣器PZ1则停止呜叫，这表示大门是关着的。

    当有人打开大门进入或走出时，从LED1照射到LDR1的光线被阻断，LDR1的电阻变得极高。结果IC1的输出脚⑥变高电位，这时LED2停止闪烁而蜂鸣器PZ1则发出鸣叫，这表示大门已经被人打开。

 

google translate:

 

Using visible light to monitor guard
    This is the use of visible light for monitoring the guard circuit. Using white light-emitting diode transmitter, the receiver can use photosensitive resistor (LDR), control circuit uA741 op amp for voltage comparator. Preset potentiometer VR1 to provide reference voltage to uA741 (IC1) of the same phase input ③, and photosensitive resistance LDR1 and resistance R1 is connected to the inverting input of IC1 ②.
    LED1 and LDR1 situated at the entrance on both sides of door, so that when in close the door, the receiver can receive the signal.
    when  LDR1 receive the signal. the resistance of LDR1 become smalle, so the output of IC1 (⑥ )goes low potential , then LED2 will start flashing and the buzzer PZ1  stop, which means that the door is closed.
    When someone opens the door to enter or get out when the light from LED1 to LDR1 is blocked, LDR1 resistance becomes extremely high. Results  IC1's output pin⑥ becomes higher potential, then LED2 will stop flashing  which means that the door has been opened.