EmonTx Arduino Shield

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emonTx Arduino Shield

An open-hardware wireless energy monitoring Arduino compatible (Duemilanove,Uno and Leonardo) shield.

emonTx Shield BackemonTx Shield Front

See non-invasive section of building blocks for theory behind CT energy monitoring.


  • 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
  • Status LED
  • Compatible with Duemilanove,Uno and Leonardo
  • Compatible with OpenEnergyMonitor modules (emonGLCD, emonBase - NannodeRF etc.)

* with 9V AC adapter

Design Files & Part List

  • 10 x 470K (yellow, violet, yellow, gold)
  • 5 x 10uF
  • 4 x 33R 1% (orange, orange, black, gold, brown)
  • 4 x 10K 1% (brown, black, black, red, brown)
  • 4 x 4K7 (yellow, violet, red, yellow, gold)
  • 4 x 3.5mm jack (Rapid: 20-0157)
  • 1 x 0.1uF (100nF)
  • 1 x 470R (yellow, violet, brown, gold)
  • 1 x 100K 1% (brown, black, black yellow, brown)
  • 1 x 2.1mm DC barrel
  • 1 x RFM12B 868/433Mhz (HopeRf)
  • 1 x 82mm/165mm Ant
  • 1 x 3mm LED
  • 1 x DS18B20 temperature sensor (optional - not included as standard)
  • 1 x 6 pin ISP header (female)
  • 2 x 6 pin header*
  • 2 x 8 pin header*

* or 1 x 28 pin header

See OpenEnergyMonitor Shop for recommended CT and recommended plug-in AC-AC adapter See building blocks for more information on CT's and AC-AC adapters.

The emonTx Shield schematic and board design in Eagle CAD format can be viewed and downloaded from the emonTx Shield SolderPad Git Repo

Build Guide

Port Map

Function Arduino Port
9V AC sample ADC0
CT 1-4 ADC 1-4
DS18B20 Temperature Dig4
LED Dig9
RFM12B SS Dig10 (recommended) / Dig5
RFM12B INT Dig3 Leonardo / Dig2 Uno

Example Arduino Sketches

See emonTx Shield Folder in emonTx Firmware examples GitHub Repo

Follow instructions on the GitHub readme for required Arduino libraries