The Arctic Malaise Trap experiment involves the deployment of low cost, extremely low power ESP8266 WiFi microcontrollers. However, the ESP8266 microcontroller itself does not have a real time clock. And rather than installing a real-time clock on each ESP8266 microcontroller, it instead makes more sense to take advantage of it's WiFi capabilities. The ESP8266 will connect to a wireless network, check the current date and time via NTP and at the designated time trigger the malaise trap deployment or sample deposition into the permafrost.
Since the ESP8266 cannot accurately keep the correct date/time, the ESP8266 will instead need to connect to a WiFi network being served by a Raspberry Pi. The Raspberry Pi will have multiple redundant methods of either checking the current time via GPS, or keeping the date and time via a real-time clock battery.
The first method is via a GPS device connected to the Raspberry Pi, a secondary real-time clock is included on the GPS breakout board via a CR1220 coin cell battery. The third is via a separate real time clock on a power management board which also includes CR2023 coin cell battery.
The first Raspberry Pi with integraded WiFi and bluetooth was the Raspberry Pi 3. As a result, that is the model that is most likely to be used.
Additionally, the later Raspberry Pi versions do offer greater performance but at the cost of greater power consumption. Additionally, an alternative involves the use of the Raspberry Pi Zero W or Raspberry Pi Zero 2 W.
Rather than relying on an operating system installed on a microSD card, the use of TinyCore Linux will need to be used. TinyCore Linux allows the microSD card to only be used to boot the operating system and never perform writes. Since most microSD cards and failures of Raspberry Pi occur during power failures during write operations to it's microSD card, this effectively means that the Raspberry Pi can be made to be extremely reliable in the field. It does however mean that you need to utilize a USB drive for any writeable data, logs, and to execute any WiringPi or other associated code.
The Adafruit Ultimate GPS breakout board is a low cost GPS receiver that can accurately provide GPS coordinates, and the current correct UTC date/time. The Adafruit Ultimate GPS Breakout board also includes an external uFL antenna connector.
The Adafruit Ultimate GPS Breakout board also includes a coin cell battery to serve as a power source for the maintenance of a real-time clock.
The Witty Pi is an add-on board for the Raspberry Pi that adds a realtime clock and OS integrated power management. It can define your Raspberry Pi’s ON/OFF sequence, and significantly reduce energy usage by allowing the Raspberry Pi to be turned off gracefully and started up again at specific dates/times and intervals.
The Witty Pi 4 also includes a DC to DC converter to accept incoming power between 6 Volts DC and 30 Volts DC. This means that the Witty Pi 4 and the Raspberry Pi can run off both solar and battery power.
To determine differenes in operational power requirements, the use of a Raspberry Pi Zero W and/or Raspberry Pi Zero 2 W will be deployed concurrently to the Raspberry Pi.
The Witty Pi 4L3V7 is a power mangement and real-time clock for the Raspberry Pi Zero.