AUTOMATIC STREET LIGHT

Requirements

• LDR Light Dependent Resistor
• Take 2 transistors. (NPN transistor- BC547 or  BC548)
• Resistor- 1K, 330Ohm-2
• Light emitting diode (LED) - Any color
• Connecting wires- Use single-core plastic-coated wire of 0.6mm diameter (the standard size)-You can use wire that is used for Computer Networking.
• Power supply-6V or 9V

Procedure

• Insert first transistor Q1-BC548 (NPN) on breadboard (or general PCB) as shown in the circuit diagram 1.
• Connect another transistor Q2- BC548 (NPN) on breadboard as in step 1.
• Connect  wires across emitter pin of both transistors and –ve terminal of battery (lowest/ bottom row of breadboard.)
• Connect  a wire across Collector pin of transistor Q1 and Base pin of transistor Q2.
• Connect a resistor 1K across positive terminal of battery (topmost row of breadboard) and Collector pin of transistor Q1.
• Connect  Light Dependent Resistor (LDR) across positive terminal of battery (topmost row of breadboard) and base terminal of transistor Q1.
• insert a resistor- 330 Ohm across base pin of transistor Q1 and negative terminal of battery (lowest bottom row of breadboard).
• Connect a resistor 330R across positive terminal of battery (topmost row of breadboard) and anode terminal of LED (Light emitting diode) & Connect the cathode terminal of LED to Collector pin of transistor Q2.

The simple circuit is ready for testing now. Connect 6V battery terminals to the circuit as show in figand see the output. As you block light falling on Light dependent resistor (LDR), the LED glows.

LED GLOWS EVEN IN LESS DARKNESS. Use torch light or Lighter if the LED glows in less darkness. in addition, you can try to adjust the sensitivity of this circuit by using a variable resistor in place of R1-300Ohm. Try this circuit with other resistances as well, (e.g, 1KΩ, 10KΩ and 100KΩ, etc)

 

Circuit Diagram 1.Automatic Street Light Control System.(Sensor using LDR & Transistor BC 547.) Very Simple.  We have tried this one in this tutorial bu you can also try the second one

Circuit Diagram 2 .Automatic Street Light Control System.(Sensor using LDR & Transistor BC 547/ BC548.) Very Simple.