OpenEnergyMonitor Community

Emon TX V3 capabilities

Before I start - apologies because I am new to this and I know I have asked related questions before.
But a few months on I am revisiting this project so in a way I am starting from scratch.

My aim is to collect energy details from both our grid supply and our PV environment. Because I was trying to stagger the costs I first purchased an emon TX v3 along with PSU and power clamps.

So my core question is this. If I install this device and attach the CTs to the relevant feeds can I only use the emon to feed information to OpenEnergyMonitor Raspberry PI based services? I do have a raspberry PI in the house which runs homeassistant (including database services such as influx DB) so in an ideal world I would love to be able to pump data into into a database reservered for that purpose.

If that is not possible could I run the required OpenEnergyMonitor collection component on a VM on a platform such as hyperv?

Thank you in advance for your patience

I should have added that any collection devices would be connected to the same internal network as the emonTX so at a network layer connectivity isn’t a problem.

Do you mean Current Transformers?

Does your emonTx have an ESP8266 either internally or externally, functioning as a Wi-Fi adapter, or do you want to use the built-in ISM band radio to get the data to wherever? If the first (or you add an ESP8266), then you can send the data by Wi-Fi onto your LAN, then to anywhere - or emoncms running on your own server (which could be another RPi). If you want to take the second option, then you probably want an emonBase, which could of course sit on your LAN to send the data onwards (as well as keeping its own database).

My colleague @borpin always recommends one RPi per task, so a RPi with the RFM69Pi transceiver would be the way he recommends, rather than running emonCMS in parallel with other tasks on the same RPi. Obviously a higher-powered server would be more capable of running several tasks at the same time.

Thank you for your comprehensive reply

Yes, I mean current transformers (Sorry - wrong terminology)

As for your question about the ESP8266 - how would I verify this? The unit, as purchased, was supplied with a screw-on antenna but that probably doesn’t help much. The product description (as per invoice) is an emonttxv3 emergy monitor transmitter in case (pre-assembled). Is the next step to open it up and have a look at the PCB?

Am I irght in thinking the RJ45 socket is not for lan connectivity?

Ta again

You won’t have an ESP8266 inside (if it had, you would have bought this) - though there is probably a header to accept it. You can open it up and look to verify. If there’s no header, the ESP8266 connects to the programmer port, but take care and look very carefully at the photos in the User Guide (link on that Shop page), because one pin needs cutting off, and another bent across.

Correct, it is not. It is for the pulse and temperature sensor inputs only.

So here is a photo of the inside of the unit. Since my last post I have done some more reading and it looks like the RJ45 is for temperature sensors (if I understand correctly)

I’m still not sure if I need to add an 8266 - there is a uart connection on the back of th3 unit that I would normally associate with a programming function…

More reseatxh is obviously needed on my part !

JP3 is where the header goes to accept an ESP8266. You don’t have either header or ESP8266. In its absence, you need to connect the ESP8266 as I mentioned to the programmer port (next to the RJ45), as per those photos.
Note: The (huge - comparatively) extra current needed for WiFi means you also need a 5 V USB adapter to power it. You don’t need the 5 V power (only the a.c. adapter) if you use the internal radio (right behind the antenna socket) and a RFM69Pi on an RPi instead of WiFi.

That makes perfect sense - thank you.

Strictly, I’d recommend a PiZeroW connected directly (wired) to the EmonTX rather than the ESP module and this wouldn’t need the RFM module (unless it was collecting data from another EmonTX).

@BerkshireBugsy Search for ‘PiZero’ and you will find plenty of help (starter for 10)

Many thanks everyone. I like the idea of the Zero - I would prefer a wired connection for obvious reasons.

Sadly work is getting in the way today but - once I understand more about th3 solution - I may just head over to amazon to order the bits :slight_smile:

Thanks again

So having done some reading this morning it would seem that if I want to go down the PiZero route I need the following:

  1. PiZero 2 (I believe that is the current version)
    2)MicroSD card
  2. Software for the above (this I’m currently confused about because as far as I understand the role of the Pizero is to accept the data from the EmonTX and transmit it on to another local device (or in my case cloud)
  3. PSU for the Zero Pi (Note to self - check if the EmonTX stiff needs a 5v supply)
  4. Bits of wire
  5. case for ZeroPI

Have I missed anything?

The PiZero devices didn’t exist when I got into emon, my emonTX V2 is still going strong handling my power reporting as well as Solar Diversion.
So instead I used an OpenWRT device that basically is the same as a PiZero but without needing an SD card. All it does is just reads the emonTX’s serial port and pushes that data directly to emonCMS via its HTTP csv input. I have updated that to also push that csv string to MQTT too.

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If you’re only using the serial port, and not drawing any power from the emonTx (i.e. whatever you connect to it is powered from somewhere else), then the a.c. adapter can supply enough power to the emonTx. The trouble starts when you connect something that needs more than a few milliamps, because the extra current spoils the shape of the wave you’re measuring, and makes the readings wrong.

Thank you so much for your reply. Is the openwrt device still available ? Thank you

OpenWRT was never a device as such. It was a linux operating system that you could run on several embedded hardware platforms. I ran it on a cheap TL link router. The advantage is that the TL link device had a serial port input, a WiFi adapter and a LAN port. So everything I needed to simply build a bridge between a serial port and the LAN. You don’t need to do any of that now. There are several off the shelf serial to LAN devices available.
Or just use an ESP (or similar), if you are happy with WiFi.

Found this, which will do the job just fine. You can power the TP link and the emonTX from the same 5V PSU.

I have also used devices that provide a cheap Serial to Ethernet bridge.
And while they work fine, they are closed firmware and that means that you need some scripting on the emoncms server to read the data from the LAN device it creates and push that into emonCMS or similar.


£6.46 10%OFF | FS100P USR-TCP232-T2 Tiny Serial Ethernet Converter Module Serial UART TTL to Ethernet TCPIP Module Support DHCP and DNS

That is really interesting. Care to start a new thread and explain how you did that?

Looks much the same as these devices which I have used with great success for an IOT AP.

In theory, if the EmonCMS server is running emonhub, that should be straightforward.

@TrystanLea @glyn.hudson might be something to explore.

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I was just looking at that and trying to figure out just how @bruce_miranda used it - it looks like a wireless access point to me - Ethernet ↔ WiFi, which I think isn’t how we use the PiZeroW, or the plain RPi or ESP8266/

Effectively, OpenWRT is a mini Linux OS so you can run a script on it to read the Serial Port and do what ever else you want.

Very clever idea as often you could make use of the AP in that remote location as well.