Automatic Street Light System Without Microcontrollers

This automatic street light system operates without microcontrollers, relying on basic electronic components like transistors, resistors, light-dependent resistors (LDRs), and LEDs.

Key Components & Their Roles

1. Light-Dependent Resistor (LDR) – Detects ambient light levels and triggers the circuit when it gets dark.
2. NPN Transistors – Act as electronic switches, controlling the LED based on LDR readings.
3. Resistors – Limit current flow to protect components.
4. LED – Represents the street light, turning on when darkness is detected.
5. 9V Battery – Powers the circuit.

Working Principle

• The LDR detects ambient light levels.
• When light levels drop (e.g., at night), the LDR’s resistance increases, causing a voltage drop that activates the first transistor.
• The first transistor then triggers the second transistor, allowing current to flow through the LED, turning it on.
• When daylight returns, the LDR’s resistance decreases, turning off the transistors and the LED.

Wiring Connections

Component	Connection
LDR	Connected to transistor base
Resistor	Limits current to transistor
Transistor Collector	Connected to LED
Transistor Emitter	Connected to ground
9V Battery	Powers the circuit

Advantages of This System

✅ No Microcontroller Required – Simple and cost-effective.
✅ Instant Response – Detects darkness and activates the light immediately.
✅ Low Power Consumption – Operates efficiently with minimal energy.
✅ Easy to Build – Uses basic electronic components.