Comparatively this circuit employees some different type of light sensor, and also a different type of transistor. It has a similar three-stage system diagram as shown below:
The Input is made to the light-dependent resistor (LDR). This is constructed from a semiconductor material such as cadmium sulphide. The resistance of this substance varies according the amount of light that falling on it. The typical range of resistance of an LDR is about 100 Ω when it is in bright light to about 1 MΩ in darkness.
