📮 Low-Power Mailbox Notifier System

A robust, long-range mailbox notification system using ESP8266 microcontrollers and HC-12 433MHz long-range radio modules. Designed for maximum battery life with intelligent power management and seamless Home Assistant integration.

✨ Key Features

📬 Transmitter (Battery-Powered)

🔋 Ultra-Low Power: Multi-month battery life using deep sleep optimization
📏 Mail Detection: HC-SR04P ultrasonic sensor for precise distance measurement
🏠 Hall Sensor Support: Optional mailbox door detection (KY-024)
🔄 Reliable Delivery: ACK confirmation with retry logic (up to 5 attempts)
⚡ Battery Monitoring: Real-time voltage monitoring with low-voltage cutoff
🔋 Flexible Power: Supports 18650 Li-ion or 2x AA NiMH configurations

🏠 Receiver (Always-On Gateway)

⏰ Time Synchronization: NTP sync with automatic DST handling
📱 Visual Display: 16×2 I2C LCD showing status and timestamps
💡 Smart LED: Breathing effect for new notifications
📊 Home Assistant: Native ESPHome integration with MQTT support
🏃 Presence Detection: Optional RCWL-0516 for automatic light control
🔄 Manual Control: Touch button for notification management

🎯 Choose Your Integration Option

This project offers two firmware approaches to suit different needs:

Option	Description	Best For
🔧 Standalone Arduino	Traditional Arduino IDE programming with direct HC-12 communication	Users who prefer direct control without Home Assistant dependencies
🏠 ESPHome Integration	Native Home Assistant sensors with YAML configuration	Smart home enthusiasts wanting automation and dashboard integration

📋 Feature Comparison

Feature	Standalone Arduino	ESPHome Integration
Programming	Arduino IDE (.ino files)	ESPHome YAML configuration
Home Assistant	Not integrated	Native sensors and entities
LCD Display	✅ Supported	✅ Supported
MQTT Publishing	✅ Optional	✅ Built-in
OTA Updates	❌ Manual only	✅ Automatic
Configuration	Code modification	YAML files and web interface
Learning Curve	Medium (Arduino)	Easy (YAML)
Dependency	Arduino IDE	ESPHome + Home Assistant

📦 Required Components

Category	Component	Qty	Notes
Microcontrollers	WeMos D1 Mini (ESP8266)	2	Main control units
Radio Communication	HC-12 433MHz Modules	2	Long-range wireless link
Sensing	HC-SR04P Ultrasonic Sensor	1	Mail detection
Sensing (Optional)	KY-024 Hall Effect Sensor	1	Door detection
Display	16×2 I2C LCD (0x27/0x3F)	1	Status and time display
Power (Transmitter)	18650 Li-ion or 2× AA NiMH	1/2	Battery supply
Power (Receiver)	5V USB Power Adapter	1	Permanent gateway power

⚡ Power Management Components

Battery Type	DC-DC Converter	Voltage Divider	Efficiency
18650 Li-ion	TPS63070 (7µA IQ)	390kΩ + 100kΩ	95%+
2× AA NiMH	TPS63020 (50µA IQ)	220kΩ + 100kΩ	90%+

🛠️ Hardware Setup

📬 Transmitter Wiring

graph LR
    A[ESP8266 D1 Mini] --> B[HC-SR04P]
    A --> C[HC-12]
    A --> D[KY-024 Hall]
    A --> E[Battery Monitor]
    A --> F[Status LED]
    A --> G[Test Button]
    
    B --> H[Trig:D1, Echo:D2]
    C --> I[RX:D5, TX:D6]
    D --> J[Signal:D3]
    E --> K[A0 via Divider]
    F --> L[D8]
    G --> M[D7]

Component	ESP8266 Pin	GPIO	Function
HC-12 RX	D5	GPIO14	Serial RX
HC-12 TX	D6	GPIO12	Serial TX
HC-SR04P Trig	D1	GPIO5	Ultrasonic trigger
HC-SR04P Echo	D2	GPIO4	Ultrasonic echo
Hall Sensor	D3	GPIO0	Door detection
Status LED	D8	GPIO15	Activity indicator
Test Button	D7	GPIO13	Manual trigger
Battery Monitor	A0	ADC	Voltage sensing

🏠 Receiver Wiring

graph LR
    A[ESP8266 D1 Mini] --> B[16×2 LCD]
    A --> C[HC-12]
    A --> D[TTP223 Touch]
    A --> E[Breathing LED]
    A --> F[RCWL-0516]
    
    B --> G[SDA:D2, SCL:D1]
    C --> H[RX:D5, TX:D6]
    D --> I[D8]
    E --> J[D7]
    F --> K[D3]

Component	ESP8266 Pin	GPIO	Function
LCD SDA	D2	GPIO4	I2C data
LCD SCL	D1	GPIO5	I2C clock
HC-12 RX	D5	GPIO14	Serial RX
HC-12 TX	D6	GPIO12	Serial TX
Touch Button	D8	GPIO15	Reset control
Breathing LED	D7	GPIO13	PWM indicator
Presence Sensor	D3	GPIO0	Motion detection

💻 Software Configuration

📋 Firmware Options

Choose one of the two firmware approaches based on your needs:

🔧 Option 1: Standalone Arduino (No Home Assistant)

For users who prefer traditional Arduino programming without smart home integration.

Files needed:

Low-Power-Mailbox-Notifier_Transmitter.ino (transmitter)
Low-Power-Mailbox-Notifier_Receiver_Gateway.ino (receiver)

Setup Steps:

Install Arduino IDE with ESP8266 board support
Open the .ino files in Arduino IDE
Configure battery type and WiFi credentials in receiver code
Upload to respective ESP8266 modules

Features:

Direct LCD display control
Serial monitor debugging
Manual configuration via code
No external dependencies

🏠 Option 2: ESPHome Integration (Home Assistant)

For users wanting smart home automation and dashboard integration.

1️⃣ ESPHome Setup

Prerequisites:

ESPHome installed: pip install esphome
Home Assistant with ESPHome integration

Installation Steps:

Copy mailbox_receiver.yaml to your ESPHome configuration directory

Update secrets in your secrets.yaml:

wifi_ssid: "Your_WiFi_SSID"
wifi_password: "Your_WiFi_Password"
mqtt_broker: "192.168.1.100"
mqtt_username: "mqtt_user"
mqtt_password: "mqtt_password"

Compile and flash:
```
esphome run mailbox_receiver.yaml
```

2️⃣ Transmitter Configuration

Battery Type Selection (in Transmitter.ino):

// Choose ONE:
#define BATTERY_TYPE_18650  // For 3.0V-4.2V Li-ion
// #define BATTERY_TYPE_NIMH // For 2.0V-2.8V NiMH

DC-DC Converter Setup:

TPS63070: Connect PS pin to GND, EN pin to V_BAT
TPS63020: Same configuration for NiMH operation

Voltage Divider Wiring:

Battery (+) → 390kΩ (Li-ion) or 220kΩ (NiMH) → ESP8266 A0
                                 ↓
                             100kΩ → GND

🏡 ESPHome Integration Features (ESPHome Option Only)

This section applies only to the ESPHome integration option. Standalone Arduino users can skip this section.

📊 Available Home Assistant Sensors

Sensor	Entity ID	Description
Status	`sensor.mailbox_status`	Current mailbox state
Battery	`sensor.mailbox_battery_level`	Transmitter battery %
Time	`sensor.mailbox_last_reception_time`	Last reception timestamp
WiFi	`sensor.mailbox_receiver_wifi_signal`	Gateway signal strength
Presence	`binary_sensor.mailbox_presence_detected`	Motion detection

🎛️ Available Controls

Control	Entity ID	Function
Reset Button	`button.mailbox_reset_notification`	Clear notification
LED Control	`switch.mailbox_indicator_led`	Manual LED control
LCD Backlight	`switch.mailbox_lcd_backlight`	Display backlight

📱 MQTT Topics (Alternative Integration)

# Subscribe to these topics in Home Assistant
home/mailbox/message     # Status messages
home/mailbox/battery     # Battery percentage
home/mailbox/reception_time  # Timestamp

🔋 Power Optimization Details

🎯 Deep Sleep Strategy

Wake Interval: 1 second (timer-based)
Deep Sleep Duration: 1 second (continuous cycle)
Active Time: <50ms per wake cycle
Average Current: <10µA during sleep

⚡ Power Consumption Breakdown

Component	Sleep Current	Active Current	Duty Cycle
ESP8266	5µA	80mA	0.005%
HC-12	3µA	100mA	0.1%
TPS63070	7µA	40mA	100%
Sensors	0µA	20mA	0.01%
Total	15µA	~100mA	<1%

🔋 Battery Life Estimation

Battery Type	Capacity	Daily Consumption	Expected Life
18650	2500mAh	0.36mAh	~2.5 years
2× AA NiMH	2000mAh	0.36mAh	~2 years

📡 Communication Protocol

🔄 Message Format

typedef struct {
    char message[20];      // Status message
    int battery_percent;   // Battery level (0-100)
} MailboxData;

📋 Message Types

Message	Description	Trigger
`"Mail available"`	Mail detected	Distance change
`"Mail picked up"`	Mail retrieved	Hall sensor
`"Test successful"`	Manual test	Test button
`"Charge battery"`	Low voltage	Voltage < threshold

🤝 ACK Protocol

Transmission: Transmitter sends message
ACK Wait: Listen for 200ms for 'K' response
Retry Logic: Up to 5 attempts if no ACK
Success: Reset retry count on ACK receipt

🛡️ Troubleshooting

🔧 Common Issues

Issue	Cause	Solution
No ACK received	HC-12 channel mismatch	Verify same channel/baud rate
High battery drain	Hall sensor LED not removed	Desolder power LED on KY-024
Poor range	Antenna orientation	Position antennas vertically
LCD showing errors	WiFi connection	Check WiFi credentials
Intermittent operation	Power supply noise	Add 100µF capacitor near ESP8266

📊 Signal Quality Testing

// Monitor HC-12 signal strength
void testSignalQuality() {
    Serial.println("Testing HC-12 range...");
    for(int i = 1; i <= 10; i++) {
        delay(1000);
        Serial.printf("Signal test %d/10\n", i);
        // Transmission test code here
    }
}

📚 Documentation & Resources

📖 Additional Guides

🎯 Advanced Configuration

🤝 Contributing

We welcome contributions! Please see our Contributing Guidelines for details.

📝 Development Setup

# Clone the repository
git clone https://github.com/Legolas-2025/Low-Power-Mailbox-Notifier.git
cd Low-Power-Mailbox-Notifier

# Install dependencies
pip install esphome platformio

# Build for development
esphome run mailbox_receiver.yaml --device auto

📁 Project Files Summary

🔧 Standalone Arduino Approach

File	Purpose	Status
`Low-Power-Mailbox-Notifier_Transmitter.ino`	Battery-powered transmitter	✅ Complete
`Low-Power-Mailbox-Notifier_Receiver_Gateway.ino`	Always-on receiver with LCD	✅ Complete

🏠 ESPHome Integration Approach

File	Purpose	Status
`mailbox_receiver.yaml`	ESPHome configuration for receiver	✅ Complete
`secrets_template.yaml`	Configuration template	✅ Complete
`Low-Power-Mailbox-Notifier_Transmitter.ino`	Transmitter (same for both approaches)	✅ Complete

📚 Documentation

File	Purpose	Status
`README.md`	Project overview and quick start	✅ Complete
`HARDWARE_SETUP.md`	Assembly and wiring guide	✅ Complete
`HOME_ASSISTANT_INTEGRATION.md`	HA integration guide	✅ Complete
`FIRMWARE_COMPARISON.md`	Approach comparison guide	✅ Complete
`TROUBLESHOOTING.md`	Problem resolution guide	✅ Complete
`CHANGELOG.md`	Version history	✅ Complete

📜 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

ESP8266 Community for excellent documentation
ESPHome Team for the powerful integration framework
Texas Instruments for ultra-low power DC-DC converters
Home Assistant community for MQTT integration examples

🏠 Home Assistant Integration • 📱 Mobile App • 🔧 Troubleshooting • 💬 Discussions

⭐ If this project helped you, please give it a star!

Name		Name	Last commit message	Last commit date
Latest commit History 6 Commits
CHANGELOG.md		CHANGELOG.md
FIRMWARE_COMPARISON.md		FIRMWARE_COMPARISON.md
HARDWARE_SETUP.md		HARDWARE_SETUP.md
HOME_ASSISTANT_INTEGRATION.md		HOME_ASSISTANT_INTEGRATION.md
LICENSE		LICENSE
Low-Power-Mailbox-Notifier_Receiver_Gateway.ino		Low-Power-Mailbox-Notifier_Receiver_Gateway.ino
Low-Power-Mailbox-Notifier_Transmitter.ino		Low-Power-Mailbox-Notifier_Transmitter.ino
PROJECT_SUMMARY.md		PROJECT_SUMMARY.md
README.md		README.md
TROUBLESHOOTING.md		TROUBLESHOOTING.md
header.png		header.png
mailbox_receiver.yaml		mailbox_receiver.yaml
secrets_template.yaml		secrets_template.yaml
voltage-divider.jpg		voltage-divider.jpg

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Legolas-2025/Low-Power-Mailbox-Notifier-System

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