IoT Case Study: Smart City Streetlights Control & Monitoring

1. Introduction & Problem Statement (In Simple Words)

In traditional city street lighting (like older setups in Indore, Bhopal, or Jabalpur), streetlights are turned ON and OFF manually by municipal staff or using simple timers.

This causes three major problems:

1. Huge Wastage of Electricity: Streetlights stay turned ON at 100% full brightness all night long (for 10 to 12 hours), even from 1:00 AM to 5:00 AM when the roads are completely empty!
2. High Municipal Bills: Streetlights alone consume up to 40% of a city municipal corporation’s entire electricity budget.
3. No Automatic Fault Alerts: When a light bulb burns out, the municipal corporation only finds out days later when citizens complain or patrol vans spot it in the dark.

An IoT-Based Smart Streetlight System solves all these problems by automatically adjusting light brightness based on natural sunlight, detecting moving cars, and sending instant alerts when a bulb burns out!

2. System Architecture & Hardware Components

The system connects every streetlight pole in the city to a central cloud dashboard:

Detailed Hardware Breakdown:

1. LDR (Light Dependent Resistor): Senses daylight. Turns the streetlight system completely OFF during daytime and activates it at sunset.
2. PIR / Radar Motion Sensor: Detects approaching vehicles, motorbikes, and pedestrians from 30 to 50 meters away.
3. ACS712 Current Sensor: Measures electric current flowing through the LED bulb to check if the bulb is working or burnt out.
4. ESP32 Microcontroller: The brain on each pole. It reads the sensors, controls LED brightness using PWM, and sends Wi-Fi/cellular updates to the cloud.
5. PWM LED Dimmer: Adjusts light brightness smoothly between 0% (OFF), 30% (DIM), and 100% (FULL BRIGHTNESS).
6. Central City Dashboard: A web dashboard in the municipal control room showing a live map of all light poles across the city.

3. Step-by-Step Operating Logic & Modes

[ Read LDR Sensor (Sunlight Level) ]
            │
            ▼
   Is it Daytime (Sunlight detected) ?
      ├── YES ──▶ [ Turn Light completely OFF (0% Power) ]
      │
      └── NO (Nighttime)
            │
            ▼
   Is a Car or Person Approaching (PIR = HIGH) ?
      ├── YES ──▶ [ Surge Brightness to 100% Full Power ]
      └── NO  ──▶ [ Dim Light to 30% Energy-Saving Mode ]
            │
            ▼
   [ Measure Electric Current via ACS712 Sensor ]
   Is Light ON, but Current is 0 Amps ?
      ├── YES ──▶ [ Publish Urgent Fault Alert via MQTT to City Control Room! ]
      └── NO  ──▶ [ Report Normal Operation ]

The 4 Operational Modes:

• Mode 1: Daytime Standby (0% Power): During sunny daylight, the streetlight remains completely OFF.
• Mode 2: Quiet Night Conservation (30% Power): During late-night hours when no cars or pedestrians are around, the streetlight stays at a gentle 30% brightness. This saves up to 70% electricity while keeping the street safely lit.
• Mode 3: Vehicle Approach (100% Power): The instant a car or bicycle approaches, the motion sensor detects it and immediately surges the light to 100% full brightness! It can also signal ahead to the next streetlight to brighten in advance.
• Mode 4: Automatic Fault Detection: If the system turns a light ON but the current sensor reads 0 Amperes, it means the bulb has fused or a wire was cut! The ESP32 immediately publishes an MQTT alert to the control room:

  {
    "pole_id": "ST-INDORE-MG-42",
    "status": "LAMP_FAILURE",
    "timestamp": "2026-10-23 11:30 PM",
    "location": {"lat": 22.7196, "lng": 75.8577}
  }

  The municipal office dispatches an electrician straight to the exact pole without waiting for citizen complaints!

4. Key Benefits for Smart Cities

💡 DAVV Exam Preparation Tips

5-Mark Question: “Explain the role of LDR and PIR sensors in smart streetlight systems.”

• LDR (Light Dependent Resistor): Measures daylight. Automatically turns the light system OFF in the morning and ON at sunset.
• PIR (Passive Infrared Sensor): Detects moving vehicles and pedestrians. Automatically switches the light from 30% dim mode to 100% bright mode.

5-Mark Question: “How does an IoT smart streetlight system detect bulb failures automatically?”

• Uses an ACS712 current sensor connected in line with the bulb.
• When the microcontroller turns the relay ON, it checks if electric current is flowing.
• If the current is 0 Amps, the bulb has burnt out. The microcontroller instantly publishes an MQTT alert with the pole’s GPS location to the city control room.

10-Mark Question: “Present a comprehensive IoT case study on ‘Smart City Streetlights Control and Monitoring’. Detail the problem statement, hardware architecture, communication protocols, step-by-step operating mechanism, and societal benefits.”

• State the problems of traditional streetlights (high electricity waste, 40% city power budget, manual inspection).
• Draw the complete architecture diagram (Sensors ➔ ESP32 ➔ Dimmer & LED ➔ MQTT ➔ Cloud Dashboard).
• Detail all hardware parts (LDR, PIR, ACS712, ESP32, Relay/PWM).
• Explain the 4 operating modes (Daytime, Quiet Night 30%, Vehicle Detection 100%, Fault Alert).
• Include the JSON MQTT fault message example.
• Summarize key benefits (50% to 70% energy savings, instant repair dispatch, longer bulb life).