EmonTx Shield






The emonTx Shield is an open hardware arduino compatible shield for electricity monitoring that can be connected to any standard Arduino UNO, Leonardo or Duemilanove.


  • Apparent Power, Real Power*, Power Factor* and AC RMS voltage readings*
  • 4 x CT Current Sensor input
  • AC 9V RMS voltage sensor input
  • 433/868Mhz RFM12B (HopeRF) wireless transceiver to transmit/receive data to other OpenEnergyMonitor and JeeNode modules
  • On-board DS18B20 digital temperature sensor (not included as standard)
  • Status LED
  • Compatible with Arduino Duemilanove, Uno and Leonardo
  • Compatible with OpenEnergyMonitor modules (emonGLCD, emonBase - NanodeRF etc.)

* with 9V AC adapter

Build Guide

emonTx Shield Technical Documentation Wiki Page (including build guide)

Open Hardware

The emontx shield is open hardware with the designs released under the Creative Commons Attribution-ShareAlike 3.0 Unported License. The schematics and board files can be viewed and downloaded from the openenergymonitor github hardware repository here:

Firmware examples

EmonTx Shield Arduino example code can be found on github here:

Application examples


Further reading

  • For more information on AC Power theory, AC Power sensor circuit design and firmware design see the electricity monitoring section of building blocks for a wealth of information. There is also good information there on calibration and accuracy.