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 musical light alarm circuit is very simple, uses only 7 components, a LDR and a 3.6 V battery or 3 x 1.2 volts rechargeable batteries. The well-known UM66 is used as the sound generator and will ...