🚨 Emergency LED Mesh Network System

A self-organizing, fault-tolerant WiFi mesh network for coordinated emergency LED signaling using ESP32-C3 microcontrollers.

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📋 Overview

This system creates an autonomous mesh network where multiple ESP32-C3 devices discover each other, self-organize, and execute synchronized LED sequences. Perfect for emergency signaling, visual status indicators, or distributed lighting displays.

Example showcase of 4 ESP32-C3

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✨ Key Highlights

• 🔄 Zero-configuration deployment - Flash and forget
• 🏆 Automatic leader election - Self-organizing with master failover
• 📡 UDP-based broadcasting - Lightweight mesh communication
• 🔌 Hot-plug support - Devices can join/leave dynamically
• ⚡ Power-efficient - Runs at 80MHz for extended battery life
• 🎯 Scalable - Supports unlimited devices (tested with 4)

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🛠️ Hardware Requirements

Component	Specification	Notes
MCU	ESP32-C3	Any variant with WiFi
MCU External LED	GPIO 5	Main signaling
MCU Internal LED	GPIO 8	May variates
Power	Battery	2x 3.7V 18650 Battery
Additional	MOSFET	IRLZ44N
Additional	Converter	Step down converter to 3.3V
Additional	Resistors	5Ω 5W / 1kΩ / 100kΩ
Additional	2x LED	RED LED 3W (Forw. Voltage 2-2.2V) (Forw. current 700mA)

📐 Wiring Diagram

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🎯 Features

Network Capabilities

• ✅ Self-organizing mesh - Devices automatically discover peers via WiFi scanning
• ✅ Dynamic master election - Lowest MAC address becomes coordinator
• ✅ Fault tolerance - System recovers from device failures automatically
• ✅ Real-time discovery - New devices join sequence within 1 second
• ✅ Dual-mode operation - Each device acts as both AP and Station

LED Control

• ✅ Synchronized sequencing - All devices maintain perfect timing
• ✅ Cascading blink pattern - Sequential activation across network
• ✅ Configurable timing - Adjustable blink duration and intervals
• ✅ Visual feedback - Both external and internal LED support

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⚙️ Configuration

Network Settings

SSID:               ERMG_MESH
Password:           emergency123
UDP Port:           4210
Discovery Interval: 1000ms
CPU Frequency:      80MHz

Timing Parameters

Blink Duration:     200ms
All-Off Duration:   2000ms
WiFi Scan Timeout:  5000ms

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📊 LED Sequence Behavior

The system creates a cascading wave pattern where LEDs illuminate sequentially:

STEP │ ESP1 │ ESP2 │ ESP3 │ ESP4   │ ...  │ Description
─────┼──────┼──────┼──────┼────────┼──────┼─────────────────
  1  │  🔴  │  ⚫  │  ⚫  │  ⚫  │ ...  │ First device ON
  2  │  ⚫  │  🔴  │  ⚫  │  ⚫  │ ...  │ Second device ON
  3  │  ⚫  │  ⚫  │  🔴  │  ⚫  │ ...  │ Third device ON
  4  │  ⚫  │  ⚫  │  ⚫  │  🔴  │ ...  │ Fourth device ON
  n  │  ⚫  │  ⚫  │  ⚫  │  ⚫  │ ...  │ Nth device ON
 n+1 │  ⚫  │  ⚫  │  ⚫  │  ⚫  │ ...  │ All OFF (pause)
  1  │  🔴  │  ⚫  │  ⚫  │  ⚫  │ ...  │ Cycle restarts

Note: Internal LED has inverted logic (HIGH = ON)
Note: Sequence dynamically adjusts as devices join/leave

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🚀 Getting Started

1️⃣ Installation

• Install Arduino IDE with ESP32 board support
• Add correct ESP32 board manager
• Clone this repo

2️⃣ Upload

• Open ERMG_LED.ino in Arduino IDE
• Select: Tools → Board → ESP32C3 Dev Module [or your variant]
• Select: Tools → Port → [your COM Port]

3️⃣ Deploy

• Flash code to multiple ESP32-C3 devices
• Power them on simultaneously or sequentially
• Devices auto-discover and organize within ~2 seconds
• Watch the synchronized LED sequence begin!

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🔧 How It Works

Network Architecture

┌─────────────┐     ┌─────────────┐     ┌─────────────┐
│   Device A  │────▶│   Device B  │────▶│   Device C  │
│  (Master)   │◀────│  (Slave)    │◀────│  (Slave)    │
└─────────────┘     └─────────────┘     └─────────────┘
       │                   │                   │
       └───────────────────┴───────────────────┘
              UDP Broadcast Network

Communication Protocol

Message Type	Format	Purpose
ANNOUNCE:	ANNOUNCE:[MAC]	Device presence announcement
DEVICES:	DEVICES:[MAC1],[MAC2],...	Master broadcasts device list
BLINK:	BLINK:[STEP]	Master triggers sequence step

State Machine

[Power On] → [Scan WiFi] → [Found SSID?]
                                 │
                    ┌────────────┴────────────┐
                   YES                       NO
                    │                         │
              [Connect] → [Slave]      [Create AP] → [Master]
                    │                         │
                    └────────[Join Mesh]──────┘
                                 │
                         [Sync & Sequence]

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🎨 Customization

Change Network Credentials

#define MESH_SSID "YOUR_SSID"
#define MESH_PASSWORD "YOUR_PASSWORD"

Adjust LED Pins

#define LED_EXTERNAL 5  // Change to your pin
#define LED_INTERNAL 8  // Change to your pin (if your ESP32 has an internal pin)

Modify Timing

#define BLINK_DURATION 200      // 200ms ON time
#define ALL_OFF_DURATION 2000   // 2s pause between cycles

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🧪 Testing

Single Device Test

• Flash one device → Currently constant ON

Multi-Device Test

• Flash 2+ devices → Should see cascading pattern
• Power off master → New master elected automatically
• Add new device → Joins sequence

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🐛 Troubleshooting

Issue	Possible Cause	Solution
Desynchronized	Network congestion	Reduce discovery interval
LED always ON	Inverted logic	Swap HIGH/LOW in code

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📚 Technical Specifications

• Protocol: UDP broadcast
• WiFi Mode: AP + STA (dual mode)
• Discovery: Active scanning + periodic announcements
• Coordination: Master-slave with automatic failover
• Timing Precision: ±100ms synchronization
• Network Capacity: 4 ESP's tested

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🎓 Use Cases

• 🚨 Emergency evacuation signaling
• 🏗️ Construction site safety indicators

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Roadmap

• Add patterns?

📄 License

This project is open-source. Feel free to modify and use for any purpose.

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Made with ❤️ for emergency preparedness and distributed systems