Over the last 15 years, a remote unheated off-grid cabin has been monitored using a variety of hardware and software solutions. The problems of limited sun and cold temperatures at the Alaska location have been solved using both custom and commercially available equipment. For anyone wanting to duplicate this project, using A/I to get software solutions is very helpful. Very few A/I answers work completely without modifications. An example is the word “slave” as used in Modbus has been replaced due to social pressure.

A custom solution using a low power linux computer with a cellular module was developed by Serenity Lake Communications. This custom solution had the advantage of very low data consumption and very low power usage. For hourly monitoring of 50 data points, data consumption averaged 1/2 megabyte per month. A special mode using a sleep mode of the low power linux computer used 6 watts for a few seconds, 2.4 watts for 2 minutes each hour with near 0 watts for 58 minutes for an average consumption of 1/10th watt.

For extended industrial temperature ratings (-40°C to +85°C), the line of equipment from Morningstar Corporation is an excellent solution. Morningstar Corporation provides guidance for cellular or satellite connected monitoring of their equipment. The actual implementation of monitoring is left to the end user. Serenity Lake Communications has developed solutions for monitoring the Morningstar Corporation equipment as well as weather stations, cameras, heating systems and limited security systems.

Since our test location is in South Central Alaska, the extended industrial temperature ratings are sufficient. The following list describes various ratings:

• Full Military: −55 °C to 125 °C
• Automotive: −25 °C to 125 °C
• AEC-Q100 Level 2: −40 °C to 105 °C
• Extended Industrial: −40 °C to 85 °C
• Industrial: −20 °C to 85 °C

In Alaska, the low temperature range required for some locations go below the industrial ratings and some type of heat is required for power source. The test location is in an off-grid neighborhood. The full-time residents all use solar supplemented with lithium batteries and generators in a heated building. Testing in more extreme low temperature environments was not conducted.

Rechargeable Lithium batteries are not suitable for use in unheated locations. Lead-Acid batteries have limited power available at low temperatures; however, with proper management, they can be used down to temperatures below -40°C. In multiple year testing at temperatures down to -40°C, extended periods of low sunlight and low temperatures required reduction of loads to near zero. Each December with the exception of the very warm 2024-2025 winter, near the winter solstice, the system went into a low power shutdown mode until enough solar power to recharge batteries was available.

Ongoing research is focused on extremely low power and low data usage applications. Testing was conducted using several cellular modules using many protocols and services. The UDP transmission protocol was selected for minimum data usage. Data usage cost is in the $1.00 per year range using a specialized IoT data provider (1NCE.COM).

Our test location is in the Matanuska-Susitna Valley of Alaska where temperatures go slightly below -40°degrees C most winters. Commercial products from Victron Energy were also tested and functioned without failure.

Components Required To Monitor Morningstar Devices using Cellular Communications (reference Morningstar Corporation Product Connectivity Manual)

• Cellular Connection
  1. embedded module (NimbeLink, Quectel, Sierra Wireless, Telit), or
  2. USB modem (Huawei) and router (GL.iNet), or
  3. cellular modem-router (Sierra Wireless)
• Computer
  1. local with Modbus program and direct connection to cellular, or
  2. EMC-1 and VPN connection to cellular, or
  3. remote computer using MSView or other Modbus software and VPN connection to cellular
  4. Most Cellular and satellite internet connections require VPN to connect
  5. The MorningStar Ready Edge requires connection to internet for the SolarConnect web site (VPN not required for cellular or satellite connection)
• Connection to Morningstar device using
  1. USB (UMC-1), or
  2. RS-232 Serial (MSC), or
  3. EIA-485 Serial to RS-232 Serial (multiple devices) (RSC-1 and MSC), or
  4. Ethernet (TriStar MPPT charge controller), or
  5. EMC-1
  6. Ready Edge

Alternatives other than Morningstar devices tested:

The GlobalLink 520 monitoring device coupled with a Victron charge controller and Victron Smart Shunt battery monitor was a good solution for an unheated, low power installation in locations where temperatures seldom go below the rated temperature of -20°C (-4°F). In our test, the internal unit temperatures were high enough to continue working down to the extreme low of -40°C (-40°F) outside temperature. In addition to the solar power and battery monitoring, the unit was used to provide temperature from a RuuviTag and the single relay was used to supply power to a LTE Solar PTZ security camera with Lithium Polymer batteries. This arrangement allowed the security camera to function at temperatures below 0° C(+32°F) and prolonged darkness.

EXTENDED RESEARCH: Communications using cellular modules for monitoring of any data. The available cellular modules support many communication protocols including http, https, ssl, ftp, mqtt, sms, udp, coap, lwm2m and smtp (email). Actual availability of protocols varies with particular module. Power consumption can be extremely small when not actually transmitting data down to the picoAmp level. Cellular standards such as LTE-M, NB-IoT and LTE Cat 1 bis allow lower power consumption and lower hardware cost and are appropriate for low data usage applications.

Research has transitioned into sending monitoring data using many different protocols, devices and transmission standards to evaluate effectiveness. Hardware solutions have included small microprocessors and newer cellular modules that do not require a separate microprocessor.

SPECIAL CONSIDERATIONS: The most robust lower cost solutions are provided by companies located in China. The leading company, Quectel, is on the United States DOD 1260H restricted device list. As such, research is limited to applications that do not involve areas sensitive to United States national security.

Cold Weather Operation

This section describes research supporting a specific project located at an unattended remote Alaska location powered by solar panels and batteries. Temperatures in this location go below -40 and solar power limited in winter due to latitude and weather. Location is south of Arctic Circle and some sun is potentially available on all days.

Davis Weather Station

The console on the new Davis Weather station has a limitation of +14 F for operation and +5 F for storage. The Davis Weather Sensor Suite will operate down to -40; however, the console unit must be in a warm location. To operate without a warm location, the console must be replaced with an alternate method of obtaining weather data from the outdoor sensor suite and transmitting that data to Wunderground or other services.

Solution 1: use the older model console 6312 with the data logger. That console is not certified for low temperatures; however, my console successfully operated in temperatures down to -27 C (-15 F) for two winters. Outside temperatures were down to -33 C (-26 F) with the unheated log cabin keeping console and inside temperatures slightly warmer. In my test location, temperatures down to -40 only occur in rare years like 2025-2026 winter.

Solution 2: use a Software Defined Radio (SDR) to directly receive the data down to the -40 C limit of the Davis Sensor Suite. The weewx support community has developed a program called “rtldavis” to provide this capability. The Raspberry Pi can be replaced with any linux computer to run the software. The product RTL-SDR (Realtek Semiconductor RTL8232U based) is the device that plugs in to the USB port of a computer to provide data reception. The NESDR Smart device was used for testing. The RTL-SDR does consume up to 2.5 watts of power (measured at 2.1 watts) and will be noticeably warm (measured test device at 35 F warmer than ambient). Placing RTL-SDR device inside equipment cabinet may help keep other components warm. Total power consumption of this solution will be about 50% higher than solution 1. In extreme cold temperatures with intermittent power supply, a period of device temperature stabilization required. The Davis Sensor Suite does not measure barometric pressure as that measurement is in the console. A separate sensor like the BME280 or an onboard pressure sensor on the linux computer is an option. Tested a BME280 with both a Raspberry Pi and EmbeddedTS linux computer with weewx software. The BME280 can supply barometric pressure, temperature (set to inside temperature) and humidity (set to inside humidity) which are normally provided by the Davis console. Startup time for receiving data is several minutes. ( 6 – 8 minutes observed and posting will be delayed until next schedule report. For an actual installation, an SDR dongle with temperature compensation like the NESDR Smart V 5 or RTL-SDR blog V4 is recommended for low temperature operation.

Computer

The Raspberry Pi uses an SD card for memory and may be corrupted by frequent power shutdowns.

Testing in cold weather is done using specialized linux computers certified down to -40 and having a graceful power loss shutdown provision using super capacitors and memory chips that are resistant to corruption. https://www.embeddedts.com/products/TS-7553-V2

Additional Options

Operating a computer during the winter offers many options that can completely change the concept of winter operation. The computer has a very small clock that keeps reasonably accurate time, when power becomes available to the computer, relays can be controlled that will selectively activate high load items such as the Starlink Mini or the Camera. Operating the high load items only when needed, would allow operation of the system up to 24 hours 7 days per week with the exception of winter solstice and extended cloudy weather.

The computer can also have a VPN feature (Raspberry Pi uses the rpi-connect app for this capability) which allows remote control of the computer or other devices. That feature would only be available when internet connectivity is available (such as Starlink). VPN feature would allow commands to be sent to computer through the Starlink connection.

Practical application scenario: When power comes on, the computer only will start up and activate Starlink only. Starlink takes a considerable amount of time to provide internet connectivity (10 – 15 minutes observed – longer if snow melting required), after internet connectivity is established, camera is turned on and camera transmits pictures to cloud. Camera is then turned off and Starlink is turned off. Computer goes to extreme low power mode for a period of time. If power is lost prior to entering low power mode, computer has a backup power source to gracefully shut down. If the designated sleep time expires with power still on, the computer starts the cycle over.

Iridium or GlobalStar

Both Iridium and GlobalStar offer low data, low power communications useful for IoT applications. Most common implementations are Asset Trackers, Data reporters and security systems. Personal communicators like Garmin InReach or GlobalStar Spot use this technology. Apple iPhones use GlobalStar. For long term operation without recharging batteries, a very low power standby state is used with a one transmission daily system able to operate 10 years on a few AA batteries.

Iridium Add-On (monthly fee + Iridium Modem and antenna): Computer can send and receive short control commands and reports using Iridium Short Burst Data (SBD) without needing Starlink. Not suitable for images. Practical application – Send commands to computer such as activate Starlink on demand without relying on set clock timings in computer. Transmit weather data to Wunderground.com using satellite instead of relying on Starlink.

Relative cost of Iridium connection – Current pricing for small size customers varies depending on usage and contract. Hourly weather reports would cost approximately $40 per month with a contract.

Globalstar: Higher development cost with similar monthly cost for a weather station application. Apple uses Globalstar for their satellite connectivity and satellite availability in Alaska is limited. Would be suitable for non time-sensitive reporting as 15 – 30 minute delays may be experienced. Globalstar coverage between 60 N and 70 N may experience problems. Utqiagvik, Alaska (formerly known as Barrow) is outside primary coverage area for commercial IoT. Antenna design slightly more susceptible to snow degradation.

Future Potential: Starlink has an IoT solution available using T-Mobile and other companies outside United States. Currently that service is only available in Southwest Alaska below 57N (Aleutian Islands, Sand Point, Kodiak) with a satellite orbit limit of 53N. That service may be available in additional locations in the future.

Test Program

Over the years, cellular connections have been used to control the computer and attached devices. The low power GlobalLink 520 monitor uses a method of communicating once every 15 minutes to report data and check for any desired changes such as activating or deactivating relays. The ts7553v2 single board linux computer can be programmed using similar logic to reduce power consumption.

The following tests have been conducted to test some options in a power limited, cold weather environment.

Test 1: Using a Sierra Wireless MP70 cellular modem and router with four ethernet ports and wi-fi, Starlink connectivity with VPN capability tested. P2P connections with various devices tested. Direct connection over VPN to Starlink using iOS or Android mobile device tested. The MP70 has a standby mode that can be controlled by time or voltage.

TS7553v2 linux computer is also capable of a VPN connection when connected to internet.

• The Starlink devices use a connection referred to as CGNAT (Carrier Grade Network Address Translation). Remote devices connected to Starlink cannot be directly contacted using the IP address of the Starlink. Options are available to connect devices without needing the direct IP connection. Most common solutions are P2P (Peer to Peer), VPN (Virtual Private Network) and Reverse ARP (Address Resolution Protocol). Most Starlink settings can be accessed remotely using Starlink mobile App. Modifying sleep mode on Starlink is not available remotely.
• Testing conducted using Starlink Mini in Standby (Low data rate 500 kpbs – up or down) on the roaming plan and on standard rate (45 – 280 Mbps download, 10 – 25 Mbps upload) roaming plan. Primary application is remote cameras so upload speed is limiting factor. Following observations based on low data rate plan.
• The only Starlink setting that requires mobile device direct connection is modifying sleep mode.
• MP70 as router connected in Bypass mode — mobile device connected to MP70 wifi can modify sleep mode settings. Starlink detects VPN connection and does not allow sleep mode modification remotely.
• Using VPN connection resulted in data throughput that was not sufficient to stream video. IP camera web page accessible; but slow. When MP70 connected to Starlink router (not using bypass mode), VPN connection using double NAT (network address translation) resulted in extremely slow connection.
• IP camera and Raspberry Pi have PTP (peer to peer) connectivity and those connections had reasonable performance. Video streaming worked at a low data rate 256 kbps connection. The Raspberry Pi rpi-connect app allowed connection to screen mirroring. With screen mirroring connection, the Raspberry Pi web browser can be used to access other devices on MP70 local area network. Depending on quality of Starlink connection, these connections had quality issues like missing frames of video or slow response to interaction with Raspberry Pi. Access to Starlink statistics page (192.168.100.1) only available when not using bypass mode. Earlier tests with Starlink subscription at full speed were very good. Starlink mini does not have enough upload bandwidth for reliable 4K video at full speed ( Observed upload limit 8 Mbps – advertised 10 – 25 Mbps) ( 4K spec is 20 Mbps – 80 Mbps).
• Reverse-ARP connection used by the Victron Energy Cerbo monitor tested successfully.
• SUMMARY: VPN connection has high burden on data usage and should only be used when necessary to remotely connect directly to other devices. Setup would be complex and high speed data plan on Starlink required for video. Applications that might require direct connection include video streaming to remote NAS (Network Attached Storage) device.

Test 2: Linux computer will be used to command and control up to 4 relays using a relay driver. Relays will be used to switch higher load devices on or off to conserve battery. This system has been tested successfuly using cellular connection.

• Several control systems and relay types tested here. More details later.
• Control systems
  • Internal relay on computer
    • Relay on normal off condition when computer off or in standby
    • Relay can support load up to 5 amps. Relay used to turn RS-485 power on. Not sufficient capacity to power Camera and Starlink Mini with snow melting active. Relay can be used to drive a single higher power mechanical relay.
  • Morningstar Corporation RD-1 Relay Driver controlled using Modbus commands
    • Solid State Relays – perfect for use with relay driver. Relay driver use a sink on low side.
    • Mechanical Relays – The relays I have for test are not suitable for use with the relay driver as they require activation on high side – exception: a single relay can be controlled by sinking the common low side.
  • Modbus command methods
    • Serial port on linux computer – tested using pyModbus[Serial]
    • USB to Serial adapter – tested using pyModbus[Serial]
    • RS [EIA] -485 connection – tested using pyModbus[Serial]
    • Ethernet to GridConnect device – tested using pyModbusTCP
      • RS-232
      • RS-485
• Voltage and Current usage of various solutions (test conducted at 12 volts)
  • Relay driver uses 7 mA
  • Activation of a single SSR (Solid State Relay) relay uses ~60 mA
  • Voltage drop over SSR with 1/2 amp load about 0.03 volts
  • USB and RS485 connection each use about 60 mA at 12 volts
    • USB connection power can be controlled on TS7553v2
    • RS485 bus power controlled by on board relay
  • Mechanical Relay control current 0.9 mA (relay driver not used)
  • Mechanical Relay activation current ~80 mA
  • Mechanical Relay voltage drop – n/a

Test 3: Low power sleep mode of linux computer tested.

• TS7553V2 linux arm based single board computer tested using the SiLabs super capacitor and sleep mode.
• Sleep mode does a shutdown of computer and all processes are stopped except the sleep monitor program. Power to computer is provided by Super capacitors with the Super capacitors being recharged with short pulses of power every few seconds. In the event power is lost to computer, Super capacitors will power an orderly shutdown and continue to provide power for a period of time. 20 minutes of monitor power observed without external power. Computer will restart after a designated timer expires as long as external power is applied. With power failure computer will restart on power restoration after Super capacitors are fully discharged. If power is restored prior to full capacitor discharge, computer will wait for expiration of designated time. Average power consumption 200 mW.
• Test program consisted of setting computer up for a once hourly wakeup and enough operating time to perform designated tasks.
  • Task 1 – Check for internet connectivity (few seconds)
  • Task 2 – Check for messages (if internet available) (few seconds)
  • Task 3 – Connect to weather station ( ~4 minutes 6312 console, ~8 minutes RTL-SDR)
  • Task 4 – Transmit data from weather station (if internet available, otherwise data is stored) (several seconds)
  • Additional Tasks in Test 2 above and Test 4 below

Test 4: Command and control using Iridium 9602/9603 SBD (short burst data) tested. Compressed data transmission of weather data tested. Commands included includes control of relays to activate and deactivate high load items such as Starlink and heated camera. Primary test is activation of Starlink, transition to Starlink internet connection and deactivation using Starlink and return to Iridium monitoring.

• Messages to Iridium modem connected to computer are sent using HTTP POST
• Messages from computer using Iridium modem are relayed via any or all of several methods including email, HTTP POST, HTTP_JSON and other methods. A publicly available server is used to receive and send messages including interpreting the messages for command, control and data purposes. The local computer formats messages for transmission and interprets received messages for action.
• Data transmission: Many different contract plans have minimum billable data of about 9 – 10 bytes per transmission. For minimum cost, data sent from computer is compressed.
  • A standard 9-byte telemetry layout looks like this:
    • Byte 1–2 (16 bits): Ambient Temperature & Relative Humidity
    • Byte 3–4 (16 bits): Barometric Pressure
    • Byte 5–6 (16 bits): Wind Speed & Wind Direction
    • Byte 7–8 (16 bits): Rainfall Accumulation / Solar Radiation
    • Byte 9 (8 bits): Battery Status & System Flags
    • Byte 10 (8 bits) (Iridium only) – Additional Data
• Commands include turning Starlink Mini on or off, turning Camera on or off, changing standby time period, shutting down computer to standby status. Computer will monitor system voltage and will disconnect high load items without external command. Computer will go to standby mode based on predetermined active time or voltage. Relay control tests are detailed in Test 2 above.
• Web or mobile device interface can be developed to facilitate user interaction.
• Real-time access not considered due to power and Iridium connectivity limitations.
• Cost for testing based on a pre-paid monthly service is about $40 for one month service with 100 messages. Contract allows 720 10 byte messages for about $40 per month. Different prices are available for different usage scenarios.

Components on hand for testing:

• Sierra Wireless MP70 & MP70A cellular modem routers with ethernet and wifi
• Raspberry Pi 4b & 5
• TS7553V2 linux computer with SiLabs Supercapacitors
• TS7100 linux computer with SiLabs Supercapacitors
• Rockblock 9602 Iridium modem with USB connectivity
• NeSDR RTL-SDR
• BME680 environmental sensor (I2C)
• INA226 Analog to Digital converter measuring voltage and amperage (I2C)
• Ruuvi Bluetooth BLE environmental sensor
• Davis Vantage Pro 2 Weather Station with 6312 console
• Morningstar Relay Driver
• Grid Connect Ethernet to RS232 modbus
• Grid Connect Ethernet to RS485 modbus
• Morningstar EIA-485 adapters
• Solid State Relays
• Mechanical Relays
• PoE injectors (12 volt DC to 48 volt 30 watt, 115 volt to 48 volt 30 watt, 48 volt 100 watt)
• Amcrest/Reolink PoE camera
• Starlink Mini
• Various Starlink power options. — USB-C (20 volt) (5 – 10 meter maximum), 12 volt to 30 volt converter (15 meter maximum) and 12 volt to 48 volt for Starlink PoE power (70 meter [225 feet] maximum)
• Starlink Ethernet connections
• Victron and Morningstar Corporation Charge controllers and monitoring systems

Typical scenario based on previous experience using cellular connections:

• Power will be independently disconnected when battery level below a pre-determined value. In past tests, that shutdown occurred near the winter solstice when low temperatures and/or extended cloudy weather occurred. In one instance, heavy snowfall blocked solar panels requiring manual clearing.
• For minimum power scenario, computer will enter low power sleep state after any desired actions are completed.
• At end of sleep state, computer will boot up and activate desired programs. Power requirements: Up to 12 watts for a short period.
  • 6 watts for about 60 seconds to charge Supercapacitors
  • 1.35 watts operational
  • 1 watt for RTL-SDR based weather station
  • 1 watt for RS-485 bus
  • 0.2 watts average, 2.5 watts peak for Iridium 9602 modem
• For Iridium communications, several minutes required to be able to transmit and receive data. Power requirement 0.2 watts average; 7 watts peak during transmit – few seconds – the Rockblock unit uses super capacitors to provide peak transmit power so power supplied by computer is limited to USB port power supply (2.5 watts).
• For transmission of video, a minimum of approximately 20 minutes required to allow Starlink to provide useable connectivity. If snow melting required, that time can be longer. Power requirement up to 90 watts including heated camera. When Starlink has connectivity, additional items such as MP70 modem router can be used for VPN connectivity.
• High power usage limited with relays disconnecting Camera and Starlink based on desired action or battery voltage above the system shutdown voltage. Voltage on battery based system will rise after high load items are disconnected.
• When not needed, computer will return to low power state for a designated time. (No communications). In cellular based systems, connection time is short and computer can be in low power state for a high percentage of time. For satellite based system, a longer time period for connectivity required.

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