One power AC-AC 9v for several emonTX

i would like to know if it is possible to use only one power AC-AC 9v with two emontx or emon tx arduino
thank you

Welcome to the OEM forum.

What does this mean? An emonTx is a self-contained unit, but it uses the same processor as an Arduino Uno. Do you really an EmonTx Shield when you write “emon tx arduino”?
An emonTx Shield is not the same as an emonTx. See

The emonTx uses the a.c. adapter to do two things: it measures the line voltage to use in the calculations, and it draws power from it at the same time. It is possible to power two emonTx’s by the same a.c. adapter, but the power drawn by the emonTx distorts the waveform that is used to measure the voltage, therefore if you have two using the same a.c. adapter, you cannot rely on the measurements being accurate.

But the emonTx Shield does not draw power from the a.c. adapter, neither does the emonTx when it is powered by the 5 V USB power input and the link on the circuit board is removed, and in that case you only measure the voltage using the a.c. adapter, and you can connect any number of emonTx’s or emonTx Shields.

thank you for your answerr
I have wrote a misteak , sorry, I was talking about a “emonTX arduino shield”

sorry i am not English and it seems that i don’t understand all the things about difference between emonTX and emonTX aruino shield: i was thinking that both two do the same

  • I don’t understand what “drawind power” mean ? why can it be usefull ?
    ok both two use the ac adapter to mesure the voltage

and so if i use emon tx arduino shield, i can use only one ac adaptater.
thank you for your answer

Yes, they DO the same thing, but they are very different - for example: the processor works at a different voltage.

Correct. The Arduino takes the power from the 5 V d.c. or 8 - 12 V d.c.

The two Arduinos should have their GND terminals connected together, they can share the same 5 V or 8 - 12 V d.c. power supply.