LDR stops switching street light after 4 hours of operation—what could be wrong?

I am facing issue in the LDR switching. It is used for street light to turn on & off automatically. but it works untill street light gets warm after 4 hours. so it will stop switching.

Hi,
As I understand LDRs, they are just resistors dependent on light. It is mostly used for measuring light levels. In this case, the LDR stops working because the street light gets warm after 4 hours? Isn't that normal for street lights?

What transistor did you use for this?

In most cases, I have seen LDR used in street lights. The switching happens when there is no light present or below the threshold of the resistor. Light dependent resistor has high resistance value in darkness as light illumination on the resistor increases resistance value decreases.

Thank you for reply,


Yes, as street light gets on for continuously, the Fixture gets heated, & this thermal effects the LDR circuit. & as i have used relay for switching it wont switch after 4 hours.

I have used BC817 transistor.

kindly suggest any changes in circuit.