LoRa End Node & Remote Monitoring System

A LoRa remote solar powered monitoring system designed to be as flexible as possible and connect to a variety of sensors/sensor modules

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The LoRa remote monitor consists of three custom PCBs, a IP67 enclosure, and a 6V or 12V solar panel.

Software is developed using Arduino IDE, STM32 Arduino core library, Arduino LMIC library, and libraries for sensors.

* LoRa End Node PCB
STM32L15X MPU with RFM95 LoRa Module (915Mhz).

* Sensor I/O Interface PCB
3 - 12 posistion screw terminals to I2C, UART, ADC/DAC, GPIO.
24LC32 EEPROM for configuration information, EUI etc.

* MPPT Solar Power Module PCB
6V or 12V Solar panel to 3.7/7.4V LiPo battery.

* IP67 Enclosure and Monitor

LoRa Transceiver


   -Input Voltage:

         5.2 - 10 VDC
         Reverse polarity input protection (R2)

            256K Flash Memory
            32K SRAM

         RTC Support - 32Khz Crystal

         RS-232 3.3V TTL Debug Port

         ST-LINK SWDIO Programming header

         Transceiver : HopeRF RFM95W US 915Mhz FCC certified

  - I/O
         ADCs:  ADC6,ADC7,ADC8,ADC9
         DACs:  DACOUT1, DACOUT2

  - Power Rails
         5V   Digital
         3.3V Digital
         3.3V Analog
         Load Current:  500mA Max

LoRa I/O Board


  - 3x 1x12 screw terminal blocks to connect to sensor modules via:

         LTC4311 I2C bus accelerator for extended lengths on the I2C-2.

         24LC32 EEPROM - static storage for LoRaWan EUI, board ID/type etc.

MPPT Solar Power Module (R2)


    Panels Supported : 6V to 12V
    Charge Rate      : 2A Max
    Battery          : 3.7V LiPO
    Output Voltage   : 6.0V No Load
                       5.6V Load
    Voltage and Current monitoring of solar panel input, LiPO battery and Output

  • LRMS MPPT Solar Power Module - Test and Characterization

    jstuart09/25/2022 at 03:34 0 comments

    R1  used with a INA3221 voltage and current monitor as a prototype model for revision 2. 

    Prototype for revision 2:

    Weather conditions:

    2022/09/22 : Sunny with occasional high thin clouds

    2022/09/23 : Early morning thin overcast followed Sun with intermittent cloud coverage

    Solar Panel Configuration:

    Orientation: South

    Latitude: 48°4’41”N

    Panel Angle: 50 degrees

    Panel Width: 221mm

    Panel Length :257mm

    MPPT Solar Power Module:

    Battery : 2500mAh 3.7V LiPO 1S cell

    MPPT Charge Current : 200 mA

    Charge Control Termination: C/10

    MPPT LiPO Cell maximum charge level : 4.15V

    Boost Converter Efficiency :

    3.3 Vin 6.0 Vout I_Load 10mA 80 percent

    3.3 Vin 6.0 Vout I_Load 200mA 85 percent

    4.2Vin 6.0 Vout I_Load 200mA 80> percent

    4.2Vin 6.0 Vout I_Load 200mA 90> percent

    Load Current : 20mA

    V_Batt Load Voltage : 5.832V

    Solar Panel : Voltaic Systems P109 6Volt 9 Watt

    Panel Ratings



    Open-Circuit Voltage





    Voltage at Max Power





    Short-Circuit Current





    Current at Max Power





    Maximum Power





    2022-09-23 07:20:50 : Battery level 3.872 V

    2022-09-23 10:10:24 : 4.144 V

  • LRMS Analog IO Board - R1

    jstuart09/12/2022 at 23:36 0 comments

    The LRMS analog I/O board is intended for analog sensors or custom sensor designs that do not have digital interfaces. In addition to the analog I/O the  board also supports I2C and TTL UART connections.

    A high speed amplifier with a sample and hold peak detector with a DC boost converter has been included for photo detectors such as a silicon photo-multiplier.

    Board Connectors:

    J1 & J2 : Two Configurable nano power operational amplifiers, can be configured as Differential, Single ended Non-Inverting/Inverting. Each amplifier output  is buffered with a unity gain amplifier to the ADC channels.

    (6Kz unity gain, 350nA per channel)

    J3 : One high speed non-inverting operational amplifier with sample and hold peak detector.

    (250Mhz unity gain, 100Mhz GBW)

    J8: DC boost converter up to 32 volts DC.

    J6 & J7 : I2C bus interface connectors

    J5 : RS-232 TTL UART Connector

  • LRMS Monitoring Station R1 - Operating Status 8/19/2022

    jstuart08/19/2022 at 22:11 0 comments

    Revision 1 of the LRMS monitoring station has been continuously operating outdoors for 8 months beginning January 2022. The sensors for the station are the usual temperature and humidity sensors found on many projects but I added a UV sensor to make the R1 station more unique and test the hardware and software.

    Here are a couple of screen shots showing the data collected from LRMS R1

    The sensors used are a DS18B20 temperature probe, Si7021 temperature and humidity sensor, and a LTR390 UV sensor in a PVC T pipe fitting.

    UV & Humidity Sensor Module

    The UV sensor has a 20mm x 20mm fused silica window epoxied in front of the LTR390 sensor (right side of photo)
    to protect from weather and for maximum transmission of UV to sensor.

    The Si7021 located inside of PVC L fitting.

    The DS18B20 is a water proof module and is shielded from direct solar exposure with a PVC pipe section.

    March 15 2022 14:50PST

    August 05 2022 14:19 PDT

  • LRMS Revision 2 PCBs - Initial Route Complete

    jstuart08/17/2022 at 23:00 0 comments

    Initial PCB routing is competed and I am working cleaning up traces and adding text to silkscreen for headers etc.

    All three boards pass design rules checks.

    LRMS  LoRa Transceiver R2

    LRMS LoRa Gas Sensor R2

    MPPT Solar Power Module R2

  • LRMS Revision 2 PCBs - 3D models

    jstuart08/11/2022 at 23:19 0 comments

    I have been working on revision 2 of the LRMS boards. Component placement is completed and I will be routing 
    Transceiver and gas sensor boards.

    • All  board dimensions have been updated to 90mm x 70mm (LxW). This supports inexpensive 70mmx90mm prototyping boards.
    • Connectors have been changed to 2x10 row connectors and aligned on 2.54mm spacing from board edges.
    • Added a new board - LRMS Environmental Gas Sensor. This a design based on my original Rev 1  test board.

    LRMS LoRa Transceiver R2

    Revision 2 :

    • uSD card connector for data logging

    • JST connector for connection to LRMS MPPT Solar Power Module

    • Reverse power  polarity protection

    LRMS Environmental Gas Sensor

    • Spec Sensors Electrochemical gas sensor array
    • 3.0V Lithium Cell or 3.0V LDO regulator
    •  Ultra low power op-amps for
    • I2C bus connector
    • UART connector

    LRMS MPPT Solar Power Module

    • J7 & J8 JST connectors changed to 5 pins. J7 is for I2C bus interface and J8 is for INA3221 status.

  • Update to LoRa_RMS on GitHub

    jstuart08/03/2022 at 19:06 0 comments

    LoRa_RMS on Github has been updated to include initial release of code and installation instructions.  See Software directory for details. LoRa_RMS is the directory for the system.

  • Design files now on Github

    jstuart08/02/2022 at 22:43 0 comments

    The design files for the LoRa Remote Monitoring system are now on GitHub.

    I am in the process of working on revision 2 of the PCB board set and documentation.

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