Here are some DIY LDR switch circuits available on our website and the web. LDR switches are used to switch a relay or other device when light are present or absent. LDRs or Light Dependent Resistors ...

This circuit ... also avoids relay clicking. Diode D1 removes back e.m.f when T1 switches off. Note: LDR should be placed away from the Lamp light but it should get day light. Use 6 Volt PCB relay.