Working of Photo Conductive cell

Photo Conductive cell 

Photo conductive switch is a that transducer which conductivity is directly proportional to solar radiation.  or it convert solar radiation into conductivity .
In these various type material are used
1. Ge
2. Si
3. Cd
Photo conductive material is convert in form of photo conductive switch by help  of ceramic base. For safety purpose a glass window is also covered above it.
Photo cell is combined form of conductive switch and electric source.

Application of photo conductive cell

It is used in automatic street light. which  is being  OFF in morning and ON in during night period.  According to diagram when photo conductive got sufficient sun light then its conductivity being increase during this period. and it work like a close switch. For this reason relay is being charged and his NC contact is being open. light will close .
In night period will not got sun light so conductivity will less so contact will also open. RElay being discharged  and NC contact is closed so light being ON.