Newby - Please be Gentle!

Hi All

Firstly what a great resource, I'm really looking forward to building some great monitoring stuff and then being able to control my home properly on the back of it !

For my first project I thought that id aim high and build a device for monitoring my heatpump including 4 CT coils 6 temperature sensors and a pulsed output flow sensor (nothing like coming in with a bang)

I'm basing this on the emontx shield with no RF (i have ethernet connection by my heatpump!)

So I've constructed the kit supplied through the project shop and you can see my work in the attachment (I haven't soldered for around 6 years so i don't think its too bad!)

I have a couple of questions though - 

1. In the attached photo you will see that there are 3 No.  4k7 resistors not supplied, i am assuming that this is due to there not being an RF module on board?

2. I intend using this shield with an Arduino with integrated ethernet - where does that leave me in relation to the solder tab connection on the left hand side of the board - ie does the Ardunio with integrated ethernet use digital pin 10?

I hope that someone can assist and i look forward being able to update you as this progresses 


Griff Thomas

Robert Wall's picture

Re: Newby - Please be Gentle!

If you download the emonTx shield circuit diagram (link on this page:, it all becomes clear. The 4k7 resistors are part of the potential divided to reduce the 5 V Arduino outputs to 3.3 V for the RFM12B, so are not needed.

Also on the circuit diagram is a note that either Digital 10 or Digital 5 can be used as the SEL line for the RFM12B. If you had an RFM12B, would need to use Digital 5 as the note says the Ethernet shield uses Digital 10.

(BTW, when you upload an attachment, you need to tick "List" for it to show on the post.) 

GTEC's picture

Re: Newby - Please be Gentle!

Hi There

Thank you for that, the mist is starting to clear now :)

I did see the note about using either 5 or 10 and from you explanation following my post, my understanding is that as there is no RFM12B on board then i can leave this connection "floating" ?

Thank you so much for taking the time to answer

PS - my post does have "list" ticked, can you not see the image under my posting?


Robert Wall's picture

Re: Newby - Please be Gentle!

Yes, that pad is an input to the RFM12B. You'll be connecting the Ethernet shield to the Arduino via the headers and using the signal that way, so it needs to be floating.

And I ticked the box for you!

GTEC's picture

Re: Newby - Please be Gentle!

Hi There - Apologies, i just checked my post and saw that "list" was ticked so thought it was me, ill make sure next time!

The Ardunio that I am planning to use has Ethernet connection "onboard" so no additional shield and no connection through headers (, but I'm assuming that one of the channels will still be needed for the connection - FYI the board hasn't arrived yet :(

Ill know more when it lands I guess


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