Field Sensor Deployment Guide

Site Selection

Place sensors where you need data - not where it is convenient to access. Ideal sites are often inconvenient: a peak for a weather station, a stream bank for water level, a crop row for soil temperature. Choose the site first, then engineer the power and connectivity to support it.

Weatherproofing Sensors

Temperature and humidity sensors require a radiation shield (white louvered housing) for accurate readings. In direct sunlight a bare sensor's error can exceed 10 °C, sometimes much more, depending on wind and the sensor (see weather-station siting references). Heat trapped inside a sealed enclosure will do the same. Rules:

• Never seal a BME280 or BME680 inside a closed waterproof enclosure - humidity will read 100 % and temperature will reflect enclosure heat, not ambient air.
• Mount the sensor in a louvered radiation shield. A hobby plastic louvered shield runs roughly $10-25 (price varies; check a current product listing), while a full traditional Stevenson screen is considerably more expensive.
• If you cannot use a radiation shield, at minimum shade the sensor from direct sun and allow free airflow.

Enclosure Strategy

Keep electronics and sensors in separate compartments:

• Main board, battery, and solar charge controller in an IP67 sealed enclosure (ABS or polycarbonate, UV-rated).
• Run sensor wiring through a cable gland or a small hole sealed with self-amalgamating tape.
• BME280 / BME680: mount in the radiation shield outside the enclosure and run I2C wiring inside. Keep I2C cable runs short - under ~50 cm is a useful rule of thumb, ultimately governed by the 400 pF total bus-capacitance limit in the I2C specification (NXP UM10204). For longer runs use an active I2C bus extender/repeater rather than a simple buffer.
• For insect protection, cover any ventilation holes with fine stainless mesh - spiders love warm enclosures.

Power Sizing

Sensor node consumption is low with the right hardware and firmware. The figures below are an idealized best case (they exclude regulator quiescent draw and wake/active current); real nodes often run somewhat higher:

• Battery-only: 3 000 mAh LiPo → ~600 days as a theoretical maximum. Derate for LiPo self-discharge and regulator quiescent draw - real runtime will be shorter.
• Solar-maintained: a 1 W (6 V) panel can keep a 3 000 mAh pack topped up at sites that reliably get ~4+ peak-sun-hours, but this does not hold in every climate - high-latitude winters and shaded/canopy sites can fall short for extended periods. Size conservatively for worst-case winter insolation rather than assuming indefinite operation. Also ensure the battery is not charged below 0 °C: use a charge controller with a low-temperature charge cutoff (charging any lithium cell, including LiFePO4, below freezing causes plating and permanent damage).
• For critical sensors in low-light environments (north-facing, dense canopy), upsize to 2 - 3 W and add a 5 000 - 6 000 mAh pack. Tie panel/battery sizing to your actual load budget and local peak-sun-hours (e.g. via PVWatts/ NREL insolation data) rather than fixed numbers.

Connectivity Range

Sensor nodes use the same LoRa mesh relay infrastructure as every other node. A sensor 20 km from the nearest internet gateway can deliver data with low latency when the relay path is healthy, but mesh delivery is best-effort: expect dropped readings and gaps whenever any hop fails (see Data Gaps below). Do not rely on near-real-time delivery for time-critical or safety-of-life monitoring. When planning a sensor deployment, map out the relay chain first:

1. Identify the target sensor location.
2. Verify line-of-sight or near-LOS to at least one repeater.
3. Trace that repeater's path to a node with internet/MQTT uplink.
4. Add intermediate repeaters if any hop is marginal.

Data Gaps and Local Storage

If the mesh path to a gateway is down, sensor readings are lost - sensor nodes have no local storage. Mitigation options:

• Store-and-Forward (Meshtastic): the Store & Forward module requires a dedicated ESP32 node with PSRAM acting as a S&F server on a private channel, and it primarily re-serves text-message history on request. It is not a transparent telemetry buffer that automatically backfills sensor data across gateway outages. For sensor-data gap recovery, prefer local SD logging (below).
• MeshCore room servers: a Room Server is a store-and-forward BBS that holds room chat history for clients on request - it is not a sensor-telemetry buffer that flushes accumulated readings across a gateway outage. See MeshCore docs; do not rely on it to recover lost telemetry.
• Local SD card logging: for critical sensors add an SD card module and log locally in CSV format. This is the recommended way to recover from gateway outages. A recovery script can push historical data to InfluxDB when connectivity is restored.

Maintenance Planning

Remote sensor nodes require infrequent but non-zero maintenance:

• BME280 radiation shield accumulates dust, pollen, and spider webs over time - clean annually or after wildfire smoke events.
• Fit an in-line fuse (or PTC/polyfuse) on the battery positive lead of every field node. Outdoor wiring is exposed to corrosion, abrasion, and water, and an unfused lithium pack can start a fire on a short. Inspect the fuse and connections during the annual maintenance visit.
• INA219 shunt connections can corrode in marine environments - inspect annually and apply dielectric grease.
• Battery capacity degrades over 2 - 4 years - plan for a pack swap.
• Label every enclosure with the node name, deployment date, battery install date, and a contact name/number. Future you (or a search and rescue volunteer) will be grateful.
• Design for access: if a node is on a 3-hour hike, make the enclosure tool-free to open (quarter-turn latches rather than screws).