emonTx arduino shield question

Hello, I’m planning to purchase the emonTx V3, but I’m not sure if purchasing the whole product or if it’s the same if I purchase only the arduino shield with the 4 current clips.

That is, could I get the same if I already have an arduino uno and only I buy the arduino shield plus the current clips that the complete emonTx V3 product?


The emonTx Shield is an add-on that has the RFM69CW radio and its interface, and the interface between the ‘real-world’ inputs - the a.c. adapter and current transformers. It does not have any sort of processor, therefore it needs an Arduino.

The emonTx V3.4 is a fully self-contained unit.

The Shield has 4 current inputs that are all the same (100 A using the ‘shop’ current transformer), the emonTx has 3 inputs like that and one high sensitivity one rated at 18.33 A.

Except for calibration of the inputs, the same sketches run on both.

Thank you for your answer Robert.
So, asuming that I have an arduino and a raspberry Pi, what thinks should I buy from openenergymonitor?

  • The arduino shield.
  • 4 current clips
  • The RFM12B module for the raspberry Pi

It’s all?

That will give you the ability to measure 4 currents (remember that all OEM products are designed for a single phase supply). If you want power from that, you can only have apparent power based of what you say your voltage is. If you want to measure the voltage to have a more accurate value, you must add an a.c. adapter.
If you have a 3-phase supply and want to measure real power in all 3 phases, then you will need to reprogram your Arduino with the 3-phase sketch, downloaded from GitHub.

You will need this radio module: http://shop.openenergymonitor.com/rfm69pi-433mhz-raspberry-pi-base-station-receiver-board/