To make light operated switch, you need to know these circuits:
– You need to keep LDR in dark case so that the relay remains active all the time(Pole connects to NO).
– When you put light on LDR, the relay switches off and Pole connects to NC; this operation toggles 555 timer and switches on the LED D1.
-When you put light again on LDR, LED D1 switches off.
Fig. Light operated switch (Click on the schematic to enlarge it)
You can use this circuit to make remote operated switch.
Fig. Remote operated switch (Click on the schematic to enlarge it)