• A Light dependent resistor(LDR)
• A NPN transistor- BC547
• A Resistor- 100 K Ohm
• A Resistor-470 Ohm
• Light emitting diode(LED)
• Connecting wires- Use single-core plastic-coated wire
• 9V DC Battery
• What is a Light Dependent?
• LDR is a semiconductor device. When light fall on LDR, LDR acts high resistance and
when dark fall on LDR, acts low resistance.
7. LED LIGHT:
• What is the LED light?
• A light-emitting diode (LED) is a semiconductor device. LED have two junction. One
p-junction and another n-junction. P-type connect with positive side of battery and N-
type connect with negative side of battery.
8. NPN TRANSISTOR:
• NPN transistor is a semiconductor device. NPN transistor have three junction. Two n-
type semiconductor and one p-type semiconductor. NPN transistor have three
terminal. Base, collector and emitter.
10. WORKING PROCESS:
• LDR have two side. One side connect with transistor base terminal and another
side connect with transistor emitter terminal.
• R2 100k resistor connect one side connect base terminal and another side
connect with R1 470Ohm resistor.
• R1 resistor have tow side. One side connect with R2 and battery positive
side. And another side connect with positive side of LED.
• A D1 LED diode one side connect with R2 resistor and another side connect
with transistor collector terminal.
• Transistor base terminal connect with LDR and R2 resistor. Collector
connect with LED negative side. And emitter terminal connect with LDR and
battery negative side.
• Battery positive side connect with R1 resistor. And negative side connect with
transistor emitter terminal.
• Road Light Control.
• Lamp post.
• Home Security Light Control.
• CC Camera (Night Mode).
• Mobile Phone Tower Signal Light.
• When electricity is gone light is on and when electricity is come light is
off at home.
• This circuit save time.
• It save Power.
• It help to Smart Life.
• Low maintenance.
• Automatic control.