Made a simple light sensor to control a surveillance camera to work at day light only. Power source is a small 60 W solar cell system:
The light sensor controls the power to the USB socket that provides power to the surveillance camera. The schematic for the light sensor switch with pot.meter to adjust the LDR threshold levels:
The LDR 5K Light Dependent Resistor and the 50K pot.meter sets the trig and threshold levels for the bright/dark relation for the SE555N comparator inputs. The BC639 transistor is able to sink 1 A to enable the 12 V USB socket.