The working principle of the photoresistor is based on the internal photoelectric effect, that is, the electrode leads are installed at both ends of the semiconductor photosensitive material, and the photoresistor is formed by encapsulating it in a shell with a transparent window. In order to increase the sensitivity, the two electrodes are usually made into a comb shape.

1. The photoresistor module has high sensitivity to the environment and the light source, and is mostly used to detect the brightness and light intensity of the surrounding environment.

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　　 2. When the module has no light source or the light intensity has not reached the critical point, the DO port will output a high level. When the light intensity exceeds the critical point, the module D0 outputs a low level.

　　3. The digital output D0 of the small board can be directly connected to the single-chip microcomputer.

　　4. The analog output AO of the small board can be connected to the AD module, and through AD conversion, more accurate ambient light intensity values can be obtained.