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I am building a prototype with temperature and humidity sensors for rural areas and I am trying to determine which is the best way to gather data, since Internet may not be available (no WiFi).

I am thinking about radio frequencies, Bluetooth or maybe a GSM module to send data through SMS. It has to be also cheap. 500 metres of range should be enough.

I am wondering if I could get some recommendations from this community.

Warm Regards, Carlos

  • 1
    How far would you like to transfer the data? – Dániel Kis Apr 22 '17 at 19:13
  • Hi Dániel, I am planning to install the sensors in livestock farms and they could vary on size. I guess, I could make a batch of info and make it send the info when ever someone is close by with a device. I guess 500 mts would enough – carlosgmeyer Apr 23 '17 at 19:03
  • You may find it is more cost effective / less hassle / quicker to buy a ruggedised 2G/3G USB modem and transmit the data directly to the cloud. Unless you are doing real time streaming, a small amount of data on a regular basis will be fine over 2G. I've used Teltonika devices a few years ago at farms to do this; others are probably available now. – Aitch Apr 28 '17 at 13:57
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Adafruit.com sells the Adafruit RFM95W LoRa Radio Transceiver Breakout - 868 or 915 MHz for $20. They can easily go 2 Km line of sight using simple wire antennas, or up to 20Km with directional antennas and settings tweakings

  • Packet radio with ready-to-go Arduino libraries
  • Uses the license-free ISM band: "European ISM" @ 868MHz or "American ISM" @ 915MHz
  • Use a simple wire antenna or spot for uFL or SMA radio connector SX1276 LoRa® based module with SPI interface
  • +5 to +20 dBm up to 100 mW Power Output Capability (power output selectable in software) ~100mA peak during +20dBm transmit, ~30mA during active radio listening.
  • Range of approx. 2Km, depending on obstructions, frequency, antenna and power output

All radios are sold individually and can only talk to radios of the same part number. E.g. RFM69 900 MHz can only talk to RFM69 900 MHz, LoRa 433 MHz can only talk to LoRa 433, etc.

Each radio comes with some header, a 3.3V voltage regulator and levelshifter that can handle 3-5V DC power and logic so you can use it with 3V or 5V devices. Some soldering is required to attach the header. You will need to cut and solder on a small piece of wire (any solid or stranded core is fine) in order to create your antenna. Optionally you can pick up a uFL or SMA edge-mount connector and attach an external duck.

Disclaimer: I do not work for Adafruit or the manufacturer. I have not used this product myself.

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Google for "APRS-Telemetry-Toolkit". APRS was designed for the Amateur Radio network, but you can implement this over a cheap pair of unlicensed handi-talkies. You can leverage the direwolf telemetry source code to suit your needs.

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