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Battery-Powered Light-Activated LED Circuit with BC547 Transistor

Image of Battery-Powered Light-Activated LED Circuit with BC547 Transistor

Circuit Documentation

Summary

This circuit is a light-dependent LED driver. It uses a Light Dependent Resistor (LDR) to sense ambient light levels and a BC547 transistor to control the LED. When the ambient light level drops below a certain threshold, the LED will turn on. The circuit is powered by a 9V battery.

Component List

  1. BC547 Transistor

    • Description: NPN Bipolar Junction Transistor
    • Pins: Collector, Base, Emitter
  2. 9V Battery

    • Description: Power source
    • Pins: Positive (+), Negative (-)
  3. Resistor (470 Ohms)

    • Description: Limits current to the LED
    • Pins: Pin 1, Pin 2
    • Properties: Resistance: 470 Ohms
  4. Resistor (100k Ohms)

    • Description: Forms a voltage divider with the LDR
    • Pins: Pin 1, Pin 2
    • Properties: Resistance: 100k Ohms
  5. Photocell (LDR)

    • Description: Light-dependent resistor
    • Pins: Pin 0, Pin 1
  6. LED (Red)

    • Description: Light Emitting Diode
    • Pins: Anode, Cathode

Wiring Details

BC547 Transistor

  • Collector: Connected to the anode of the LED.
  • Base: Connected to Pin 2 of the 100k Ohm resistor and Pin 1 of the LDR.
  • Emitter: Connected to Pin 0 of the LDR and the negative terminal of the 9V battery.

9V Battery

  • Positive (+): Connected to Pin 1 of the 470 Ohm resistor and Pin 1 of the 100k Ohm resistor.
  • Negative (-): Connected to Pin 0 of the LDR and the emitter of the BC547 transistor.

Resistor (470 Ohms)

  • Pin 1: Connected to the positive terminal of the 9V battery.
  • Pin 2: Connected to the cathode of the LED.

Resistor (100k Ohms)

  • Pin 1: Connected to the positive terminal of the 9V battery.
  • Pin 2: Connected to the base of the BC547 transistor and Pin 1 of the LDR.

Photocell (LDR)

  • Pin 0: Connected to the emitter of the BC547 transistor and the negative terminal of the 9V battery.
  • Pin 1: Connected to Pin 2 of the 100k Ohm resistor and the base of the BC547 transistor.

LED (Red)

  • Anode: Connected to the collector of the BC547 transistor.
  • Cathode: Connected to Pin 2 of the 470 Ohm resistor.

Code

No microcontroller code is used in this circuit.