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Node Hardware

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Bryan Runck edited this page Nov 10, 2019 · 3 revisions

Node Hardware

Overview:

The node hardware can generally be separated into 3 sections:

  • Sensors
  • Processor
  • Telemetry/Data storage

You can think of these components like those of a computer.

A sensor is like a keyboard, or camera, something which allows the computer to connect with the outside world, and convert images, touch, etc, into electrical signals it can understand.

The processor is just a very small version of the CPU of your computer, the "thinking" portion of the system. This portion asks the sensors for their information, then decides what to do with it based on how we have programmed it.

This leads us to the last step, which is telemetry and data storage. Information in a computer is nice, but if I want to show it to someone else, I need to do something extra. I can either print it out or store it on a flash drive and take it to them (this is data storage). Or I can plug my computer into a modem (Internet) and send it to them over this channel. The methods vary, but the principal remains the same.

Modules:

For our purposes these are some of the systems we will use for the categories outlined in the overview.

Sensors:

Soil Moisture Sensor

  • Use: Measuring the relative moisture content of soil. Not able to give a percentage of moisture due to ambiguity of soil type, etc, but very useful for determining relative moisture content (very dry, somewhat dry, moist, wet, etc)
  • Output: Analog voltage
  • Wiki

Temperature Sensor (DS18B20)

  • Use: Measuring temperature in moist/harsh environments, able to place several together and measure temperature at multiple points at the same time to measure the change spatially
  • Output: Digital, Addressable (OneWire)
  • Product Info

Processor:

Atmega 32u41

  • Highly capable, low power microcontroller capable of interfacing with many sensors and data storage
  • Interfaces:
    • UART
    • I2C
    • SPI
    • Analog Voltage
    • Digital IO

Telemetry:

LoRa Radio1

  • Low power, highly versatile point to point or node radio transmitter
  • Able to talk to other LoRa transceivers (both sender and receiver), message sorting must be handled in the firmware to only respond to desired messages
  • Interfaces to processor via SPI

1In our case, both of these units are combined into a single board for convenience, made by BSFrance:

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