Suggestions for improving the guide for installing a new emonTX 3.4

Hi folks,

I have an existing emonbase + emonTX installation monitoring Solar PV and house usage and had a Powervault 3 battery installed a week ago. I bought a new emonTX 3.4 and DS18B20 temp sensor from the shop, but have had a few challenges and wanted to share, and see if the documentation can be improved, or whether I was just being a numpty!

  1. I started by testing the emonTX in the house, just to check it was working. I used a USB/UART cable and connected to the UART socket and used Arduino IDE and the Serial Monitor. At first I got nothing as the IDE needed configuring so I turned to the guide and looked at the emonTX page but nothing of this detailed nature, so I searched and then found the wiki page for the emonTX. It would have been helpful if there was a link to this wiki page within the guide.

  2. However this didn’t give me the settings for Ardino IDE, so after more searching I found the Arduino IDE section in the learning section. It would have been helpful if this was linked to from the emonTX wiki page.

  3. I was now getting garbage on the Serial monitor in Arduino IDE, which reminded me that the serial baud must match the device. After trial and error I found the correct answer was 115200. It would have been hepful if this was mentioned in the Learn document above.

  4. I could now see the output in the serial monitor, and that it was running the sketch, and transmitted some initial data but then stopped. I didn’t have a CT connected, but I did have a DS18B20 temp sensor and was expecting to see data every 10 seconds. After more digging and entering the “l” command to list values I saw:

Temperature Sensors found = 0 of 1

Temperature measurement is NOT enabled.

I suspected and later confirmed that this was becuase I was using the USB UART cable to power the emonTX, and presumably there was not enough power to run the unit and the temp sensor? Maybe worth a mention in the emonTX wiki page? After plugging in the AC adaptor, the sketch would then run and send data to the emonbase.

  1. Looking at the inputs in my local emoncms installation, all of the fields were showing the same value 24185 (or maybe 28145) apart from the RSSI. Eventually I spotted that I needed a new emonhub decoder as described here which I added to my emonhub.conf and hey presto, I had correctly formatted data in the input. Hurrah! Maybe this should be mentioned in the guide somehwre? My local emoncms is running emoncms low-write 10.1.5 on Raspberry Pi 3.


  1. The wiki has a section called “Arduino Firmware Info” which states " All emonTx V3s sold pre-assembled with a radio module are shipped with Discrete Sampling firmware" but other documents say they are now shipped with Continuous monitoring" so I believe this needs an update.

  2. The guide says " If more than one emonTx is to be used with the same base-station set the node ID using the on-board DIP switches" and then there is an asterisk with comments relating to more than 2 emonTX. Should these comments refer to more than one, or more than two emonTX? And how about mentioning the option to select NodeID 16 when ordering from the shop, which is what I had done, and so I was puzzled that I might also need to change the dip switch?

  3. There is a bit of a typo in this section as it says “This can be done This can be done via serial node ID config”

  4. I was also caught out by the lack of red LED flashing every 10 seconds that made me think the system was not finding the AC waveform as stated in the guides, but I then spotted that @glyn.hudson has raised this as an issue so hopefully it will get fixed soon, as it did cause me to doubt the documentation, or suspect my unit was faulty!

Sorry for the long post, but I hope this can help others to avoid some of the issues I encountered.



I don’t believe that to be true. I think it’s much more likely that the temperature sensor was not detected at power-up (or when the emonTx reset). Was it plugged in after you powered the emonTx?

There is a real possibility that too many temperature sensors will cause the emonTx to fail when powered from the a.c. adapter only, but I’ve never been unable to read the temperature sensor or sensors when powering an emonTx via the shop programmer.

Thank you for the excellent feedback, we’ll get to work on updating the documentation. We’re sorry you had a frustrating time getting everything to work.


Excellent news!

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