LoRaWAN Mailbox Notifier: ESP32 and Ultra-Low Power

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Background

The mailbox sits far from the house, and I wanted to know when the mail arrives. The solution was an ESP32-based device using a PIR sensor for motion detection and LoRaWAN for message delivery.

Architecture

The system consists of:

1. Field device — ESP32 + PIR sensor inside the mailbox
2. Gateway — LoRaWAN gateway
3. Server — ChirpStack → InfluxDB → Grafana → email alert

Power consumption

The ESP32’s ULP coprocessor monitors the PIR sensor while the main CPU sleeps:

// ULP wakes main CPU when PIR triggers
ulp_set_wakeup_period(0, 100000); // 100ms polling interval

Deep sleep current draw is approximately 10 µA, enabling months of operation on a small battery.

Next steps

• Solar panel charging
• Temperature and humidity measurement on the same device
• OTA updates over LoRaWAN