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How To Add LTR390 UV Light Sensor To Your Meshtastic Node

Add the LTR390UV sensor to your ESP32 Meshtastic node to monitor UV index in real time. Get accurate sunlight, health, and environmental UV data over LoRa with simple wiring and low-cost hardware for safer outdoor activities.

How To Add LTR390 UV Light Sensor To Your Meshtastic Node

Integrate an LTR390UV ultraviolet light sensor into your ESP32-based LoRa Meshtastic Node for UV index monitoring, sun safety tracking, and environmental UV measurements.

Hardware

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What is the LTR390 UV Sensor?

The LTR390UV is a compact digital sensor that measures ultraviolet (UV) light and ambient brightness. It’s commonly used in weather stations, wearables, and IoT projects to monitor sun exposure and calculate UV index values, helping people stay safe outdoors.

Key Features:

  • Measures UV light for UV index monitoring
  • Detects ambient light (brightness)
  • I²C communication for easy integration with microcontrollers
  • Low power consumption, ideal for battery-powered devices like Meshtastic
  • Works with 3.3V systems like ESP32 and nRF52840
  • Small, lightweight form factor
  • Built-in temperature compensation for stable readings

Assembly

The hardware is all ready and set now to the wiring. For this, we will follow the following Schematics.

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Please keep in mind we are assuming here you already soldered the headers on the board so it will be a matter of connecting pins to the right place.

LTR390 UV Sensor - Heltec V3 Lora ESP32

LTR390 UV Sensor - Heltec V3 Lora ESP32

Wiring Connections:

  • VIN -> 3.3V
  • SCL -> PIN 42
  • SDA -> PIN 41
  • GND -> GND
  • INT -> Optional GPIO (for interrupt operation)
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For boards other, use the I²C SDA/SCL pins as defined in the board documentation.
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Critical Sensor Placement: The sensor MUST have direct exposure to sky/sunlight for accurate UV readings. UV light cannot penetrate most plastics or glass. Mount externally or use UV-transparent materials.

Meshtastic Settings

  1. Open Meshtastic App
  2. Go to Settings → Telemetry (Sensor)
  3. Toggle Enable Environment Metrics
  4. Press Save

In conclusion, the LTR390UV adds a nice health and safety monitoring to your Meshtastic Node by tracking ultraviolet radiation levels. Whether you're building a weather station, creating a sun safety device for outdoor activities, or monitoring UV for agricultural or scientific purposes, the LTR390UV provides good and affordable UV sensing. Remember that proper sensor placement is critical - UV light cannot penetrate most enclosure materials, so external mounting or UV-transparent windows are essential for accurate readings. With UV-related skin damage affecting millions globally, having real-time UV data from your mesh network can help protect users from overexposure.

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