Industrial Lorawan Temperature Logger

An energy-harvesting industrial temperature logger featuring LoRaWAN connectivity and a 2-year battery life target for sheltered indoor environments.

Executive Summary

This reference design defines the system architecture, critical component candidates, risk register, and validation path for Industrial Lorawan Temperature Logger. It is a system-level design deliverable; verify critical claims with manufacturer evidence and prototype testing before production release.

Design Overview

Requirements Coverage

System Architecture

Power Topology: Solar Panel feeds TI BQ25570 MPPT harvester, charging a rechargeable LiFePO4 cell. BQ25570 outputs a stable regulated 3.3V rail powering the STM32WLE5JC MCU/SoC and TMP117 temperature sensor.

Module List

Power Tree and Signal Interfaces

Design Schemes

Solar Energy Harvesting with LiFePO4 & STM32WL ★

Utilizes TI BQ25570 MPPT harvester, LiFePO4 battery for sub-zero charging safety, and STM32WLE5JC wireless SoC.

Trade-offs: Offers long-term maintenance-free operation down to -20°C, but requires precise MPPT tuning and careful solar panel sizing for indoor/sheltered environments.

Key IC selection

Main processing and wireless communication

• Need: Ultra-low power ARM Cortex-M4 core with integrated sub-GHz LoRa transceiver supporting sub-GHz bands for telemetry
• Class: Wireless Microcontroller SoC
• Shortlist: STMicroelectronics STM32WLE series, Silicon Labs EFR32XG series
• Pick: Select based on integrated Sub-GHz radio performance, sleep current consumption, and flash/RAM sizing for LoRaWAN stack.

Energy harvesting power management IC

• Need: Nano-power boost charger with maximum power point tracking (MPPT) for photovoltaic input and low-voltage battery regulation
• Class: Solar/Thermal Energy Harvesting PMIC
• Shortlist: Texas Instruments BQ25570, Analog Devices LTC3105
• Pick: Select based on quiescent current, programmable MPPT sample-and-hold interval, and output voltage regulation thresholds for LiFePO4.

High-accuracy ambient temperature measurement

• Need: High precision digital temperature sensor with I2C interface, low operating current, and calibrated accuracy across -20°C to +70°C
• Class: Digital Temperature Sensor IC
• Shortlist: Texas Instruments TMP117, Maxim Integrated MAX31875
• Pick: Select based on high-accuracy industrial grade calibration specs, conversion current, and small package size.

Risk register

Bring-up and Validation Plan

1. Power-off inspection and rail resistance checks
2. Current-limited first power-up; verify every rail before enabling loads
3. Validate interfaces and timing one subsystem at a time
4. Run thermal, fault-injection, EMC pre-scan, and endurance tests for the target environment

Key Components

5/6 modules matched to real parts. See the BOM tab for the full component table.

Monocrystalline Solar Panel (Indoor/Outdoor rated) (KXOB25-04X3F)

The candidate's MPN (KXOB25-04X3F) and manufacturer (IXYS) exactly match the requested primary MPN and preferred manufac

Texas Instruments BQ25570 (BQ25570RGRT)

The candidate BQ25570RGRT matches the primary MPN BQ25570 with a valid ordering suffix for reel/tape packaging, is manuf

Rechargeable LiFePO4 Cell (3.2V) (LIFEPO4)

The candidate matches the requested LiFePO4 battery chemistry for the energy storage module, although the manufacturer (

STMicroelectronics STM32WLE5JC (STM32WLE5JCI6)

Candidate 3 (STM32WLE5JCI6TR) is the exact match for the primary MPN STM32WLE5JC with standard tape and reel packaging s

Sub-GHz Chip Antenna / PCB Trace Antenna (Sub-GHz Chip Antenna / PCB Trace Antenna)

Web recommendation: Sub-GHz Chip Antenna / PCB Trace Antenna (not in ES)

Build Summary

• Difficulty: Intermediate
• Estimated time: 4-8 hours
• Tools required: Soldering iron, Multimeter, Computer

See the Build tab for the full step-by-step assembly guide.

Evidence and Limitations

• Confirm part parameters, certifications, and compatibility against current manufacturer documents.
• Treat industry compliance without test or certificate evidence as a compliance gap, not an approval.
• See Reference Images for visual artifacts and Build Guide for detailed assembly and bring-up steps.