DC Power Meter LoRaWAN Connector Node

LoRaWAN node to send data from the GC90/GC91 DC power meters via TTN. Based on an Arduino Pro Mini and the RFM95 LoRa module.

Hardware

• Arduino Pro Mini 3.3V 8Mhz
• RFM95/96 LoRaWAN module
• uFL socket or edge mount SMA socket
• 2 BSS138 MOSFETs (Q1/Q2) and 2x 10k resistors (R3/R4, 0805) for the level shifter
• USB A socket
• 2 resistors (R1/R2, 0805) to form a voltage divider for measuring the input voltage (optional, values depending on voltage range)
• Groove connector (optional)

Payload decoder

If you use the TTN network, you can use the following payload decoder:

function Decoder(bytes, port) {
  // Decode an uplink message from a buffer
  // (array) of bytes to an object of fields.
  var decoded = {};
  decoded.voltage = (bytes[2] << 8 | bytes[1]) / 100;
  decoded.current = (bytes[4] << 8 | bytes[3]) / 1000;
  decoded.usage = (bytes[8] << 24 | bytes[7] << 16 | bytes[6] << 8 | bytes[5]) / 1000;
  decoded.cum_usage = (bytes[12] << 24 | bytes[11] << 16 | bytes[10] << 8 | bytes[9]) / 1000;

  return decoded;
}

License

• Hardware is based off a design by Doug Larue with additions by me, Severin Schols. It's licensed under Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0)
• Software (firmware and the payload decoder) are licensed under MIT License