Light sensor

The light sensor senses the solar output and keeps the connected load turned off until a certain brightness of the light which can be controlled using a pot. When the brightness goes down the required value then the load is turned on automatically. The circuit uses a LDR [Light dependent resistor] and a transistor 2N3904 to detect the light and give output from the relay.

List of components:

1. Resistor: 470ohm / 1watt
2. Capacitors : 0.68uF and 47uF
3. Diodes: 1N4007
4. Zener diode: 15V, 1/2W
5. Transistor: 2N3904
6. Pot :10k , pcb mountable
7. Relay: any 5V single pole relay
8. Green connectors : 2nos [ 1for input and the other for output]
9. LDR [ light dependent resistor]

The pcb layout

Light Sensor by

The PCB operates on very simple basis, the transistor turns the relay on and off. The LDR when exposed to light actuates the relay which in turn opens the light circuit, when there is no light to LDR then the relay is deactivated which turns on the light.

The same PCB can be used for some other applications such as automatic door bell, unmanned railway crossings and many more. Make sure to connect the line and neutral in proper fashion as shown in the image above.

Note: Make an alternate wiring for the light such that in case of necessity we get to turn on the light even on day time and if possible to turn it off too.