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 are very useful especially in light/dark sensor circuits.
Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.
This is a light switch or light activated relay circuit. The relay on when LDR uncoverd and relay off when LDR covered. Adjust VR1 for light sensitive.
LED will turn on at the same time with relay.