emonTx V3 - No AC detection LED or sampling flash on power up

I have received a new emonTx V3 including 9V AC-AC transformer, 2 CT sensors, and emonBase unit (shop order ID #21786).

I have followed the instructions here: setup emonTx

When I power up the emonTx from the 9V transformer, the red LED lights for about 5 seconds, and then does not light again.

In the instructions it says:

  1. Indicator LED
  • Illuminates solid for a 10 seconds on first power up
  • Flash multiple times to indicate an AC-AC waveform has been detected (if powering via AC-AC adapter)
  • Flash once every 10s to indicate sampling and RF transmission interval

In the emonBase log I can see occasional RFM2Pi messages from Node 15 so I guess the emonTx is working. (I also see many “RFM2Pi Discarding RX frame ‘unreliable content’?” messages in the log, I live in a block of flats and I guess there are other RF devices nearby transmitting and that this is normal).

However the emonTx seems to not have detected the AC as the LED is not flashing after the initial 5 seconds illumination after power up, and it is not flashing every 10 seconds, and the emonBase has not automatically detected any inputs.

Can anyone offer some advice?



Hello @EdwardB sorry for the confusion, we need to update that documentation, the new firmware (continuous sampling) does not flash the LED in the same way, but it sounds like the data is coming through ok on Node 15. If the power values look ok it will be using the voltage adapter

Hi @TrystanLea,

Thanks for the explanation. It would be great if you can update that documentation, it made me think it wasn’t working. Is there a way for me to check that the AC waveform is detected now that the firmware doesn’t flash the LED?

I cannot say if the power values look OK because the inputs from emonTx have not been detected by emonBase when I click Setup > Inputs.

The documentation here setup suggests that the emonBase unit should detect the inputs automatically. Is this documentation still correct? (I am seeing occasional RFM2Pi messages from Node 15 in the emonBase log).

Do you see the node 15 inputs in the emoncms input list?

The AC adapter is a requirement for this firmware to work. It stops at the start if it cant detect the AC waveform. Do you have CT’s plugged in?

To clarify, if there is no a.c. adapter connected, and no other source of power, the emonTx cannot operate at all. If there is an alternative power supply (5 V d.c. via the USB socket, or the FTDI connector, the sketch will run but, with no a.c. voltage being measured, the power and energy reported will be zero - unless you have changed the default sketch to report current, when that will be reported correctly.

That might not be the case. If your copy of emonhub.conf predates the release of your sketch, then you need to manually add the required information to allow it to decode the incoming data. This is:

  nodename = EmonTxV3CM_15
    names = MSG, Vrms, P1, P2, P3, P4, E1, E2, E3, E4, T1, T2, T3, pulse
    datacodes = L,h,h,h,h,h,L,L,L,L,h,h,h,L
    scales = 1,0.01,1,1,1,1,1,1,1,1,0.01,0.01,0.01,1
    units = n,V,W,W,W,W,Wh,Wh,Wh,Wh,C,C,C,p
    whitening = 1

Copy and paste it into emonhub.conf, in number order of nodeID - that’s the [[15]] bit - is a good idea.

Thanks @Robert.Wall,

The node section you mentioned was in fact already present in the emonBase config.

When I looked at the Emonbase config I saw that Emonbase was sending messages to https://emoncms.org, so I created an account on emoncms, generated an API key, added the API key to my emonbase config, and voila, I was able then to see my Inputs on Emoncms.

To get the local emonBase unit to recognize the inputs from the EmonTx V3 unit, I found the solution in here:

EmonHub configuration

I needed to generate the API key for the local emonBase then add this section in the emonBase config:

        Type = EmonHubEmoncmsHTTPInterfacer
            pubchannels = ToRFM12,
            subchannels = ToEmonCMS,
            url =
            apikey = (my-api-key)
            senddata = 1
            sendstatus = 1

Now I have the inputs I can now create the feeds on the local emonBase unit.

In here [2. Log Locally - Guide | OpenEnergyMonitor] (2. Log Locally - Guide | OpenEnergyMonitor) it says

“You should now see an updating input list of connected nodes (e.g emonPi, emonTx, emonTH) and they keys (e.g. power1, power2 etc.) together with the last received value.”

This did not happen until I added the localhost interface, and the Troubleshooting section did not mention this either.

Based on the setup guide I expected the emonBase would recognize the emonTx inputs automatically, but I guess this only applies to the emonPi self-contained unit, not to emonBase receiving from emonTx.

The setup guide could be clearer, it was not easy for a novice like me to figure this out.

Does your emonTx send the data by radio (RFM 433MHz), or do you have the ESP8266 WiFi addon module?

Just to be clear, this is the emonhub config.

The ‘EmonBase’ is the combination of the RFM card and the RPi it is attatched to.

Emonhub is a software subsystem that runs on the Pi and converts the data from the serial input of the RFM card and sends it on via any number of protocols and to different systems (including the local Emoncms & emoncms.org).

Just helps us if you understand a little of the setup :slight_smile:.

I now have my multigraph working on emoncms.org, I can see the fridge coming on about every 50 mins! Hot water and heating are off and show approx 1-2W each, and the 25W baseline is probably the router, TV switched off, and other small things.

It’s great!


@Robert.Wall : My emonTx sends by RFM 433MHz. I have it working locally now, but only after I added the local interface to…

@borpin : what I should have said, the emonhub config.

It’s pretty confusing!

In that case, I don’t know why it didn’t show up initially. But then, I’m not an emonCMS expert.

I agree. A lot of the documentation here makes assumptions. @gwil please note for your “To Do” list. :face_with_hand_over_mouth:

I’d certainly agree with that!

Odd as by default (on an EmonSD setup), the inputs should be routed from emonhub via MQTT to the local EmonCMS. Is the Mosquitto and emoncms_mqtt services showing green in the Admin page?