6. Add Energy Sensing Node(s)

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Additional energy monitoring node(s)

Additional energy monitoring nodes can be added if additional AC circuits require monitoring or the location of the circuits is inconvenient to access power outlet and network connectivity. There are two options emonTx or IoTaWatt:


The emonTx is an low power RF remote sensor node. Data is transmitted to an emonPi or an emonBase via a low power 433MHz radio.


Key Features

  • 4 x single-phase current sense (CT) channels
  • 1 x AC VRMS Channel
  • Supports multiple temperature sensors
  • Supports Optical Pulse Sensor
  • Can be powered single AC-AC adaptor (DC PSU not required)
  • Battery power option
  • RF Range is approximately similar to home WiFi (real world range depends on many factors e.g. thick stone walls)
  • Up to 2x emonTx can be connected to a single emonPi (up to 30x is possible with manual RF node ID setting)
  • Approximate three-phase possible with firmware update
  • Wall-mount option

Note: it is possible to use emonTx ‘standalone’ (without emonPi / emonBase) with the addition of an ESP8266 WiFi module running EmonESP to post directly to Emoncms. See Using emonTx with the ESP8266 WiFi module

Setup emonTxView in Shop →


IotaWatttm is an open-hardware 14 channel WiFi connected electric power monitor. It’s based on the ESP8266 IoT platform using MCP3208 12 bit ADCs to sample voltage and current.


IoTaWatt can post directly to Emoncms.org (emonPi / emonBase not required). However IoTaWatt can post to a local Emoncms server e.g. emonPi

Key Features

  • 14 x single-phase current sense (CT) channels
  • 1 x AC VRMS Channel
  • Compatible with multiple types of CT sensors and AC-AC voltage sensor adaptor
  • Local SD card logging
  • WiFi connected to post to Emoncms
  • Sample rate: 35-40 channels per second
  • Voltage (VRMS), Power (W) and Energy (kWh) logged to local SD card - every 5s
  • On-board Real-time-clock (RTC) with battery backup
  • Web-config interface
  • Secure encrypted data connection to emoncms.org
  • Secure automatic OTA firmware updates
  • 5V Micro USB power supply required
  • Wall-mount option

View in Shop → Setup IoTaWatt

Next step: Add Temperature Node(s) »