AVR-DB: emonTx V4, new hardware in progress

The decision not to offer the ability to mount a PiZ inside now seems odd therefore.

And again. The Pi decision seems odder.

I think the strategy is a little confused.

My understanding was that the PiZ has a limit on how many can be sold per customer (e.g Raspberry Pi Zero 2 W — Cool Components) and also availability is not great: https://rpilocator.com, all out of stock at the moment, though it does look like many have had stock in the last few months. We will contact RaspberryPi to clarify, as we were able to get a limited Pi4 stock directly.

Yes, but the cost difference is astronomical. How about the Pico? Not looked at that in detail. A Pi4 is overkill for emoncms.

Glyn has contacted RaspberryPi to ask, if it’s an option for us to use and we can get stock we will definitely consider it. We did ideally want to continue with Pi3’s given their lower cost but were not able to get stock of those, hence the Pi4’s. It’s hopefully a short term issue until availability improves and a wider set of options open up again.

Pi’s are an issue, I managed to get a ZeroW last year from CPC, ordered another in March and here we are in August still waiting… website says expected May 2023!

I am having quote for new CU and hope to add more granular circuit monitoring in future so the V4 looks great but the dedicated £50 psu seems a bit limiting? Can V4 not be fed from usb and the old £10 ac-ac brick?

Not really - because the emonVs is a universal power supply and a precision voltage monitor- far more accurate than the Ideal 9 V a.c. or equivalent.

For cost reduction, what about putting a ZMPT101B, primary MOV, fuse, primary resistors and secondary resistor plus any EMI bits into a 13A plug top enclosure, for single phase use?

If a plug top enclosure with a brass earth pin and a means of connecting to it could be sourced, then this would also provide the ground for the emonTX4.

Most 5V USB adapters are universal voltage, and one could be used to power the emonTX4. Many homes will have a redundant USB adaptor and perhaps would just need a USB-A to USB-C cable, otherwise a Raspberry Pi4 adapter (£8.10) could be used.

This solution would require two 13A sockets to supply the emonTX4, but this could be achieved from a single socket using a 13A 2 or 3 way adapter.

We have thought to provide this as an option, as long as people are aware it’s less accurate and are happy thats fine. I guess one of the challenges is that it might be with calibration, especially phase calibration. I know we haven’t discussed this between us yet, especially with your work on the new firmware, so it probably needs some more thought and consideration.

Thanks @rupert yes we have also been thinking along similar lines. Another similar option is a smaller single phase voltage sensor only without PSU unit with a cable and mains plug - giving more flexibility in terms of grounding and EU/US variants.

As it stands, the emonVs is designed to be capable of operating on any voltage below 254 V rms, including the N.American 120 V, the UK industrial 110 V and the Asian 100 V. In fact, when I checked the sample @TrystanLea sent me, it and the emonTx V4 together worked down to some ridiculous voltage - I can’t remember the actual voltage but I think it was below 40 V. This of course removes the complication of needing to adjust the calibration to suit the local mains voltage - particularly appealing to N.American & continental European users.

One major design influence was the ability to require just a single socket. This has been on the ‘wish list’ since the emonTx V2 and was the reason for developing the internal power supply for the emonTx V3, so removing the need for a 5 V d.c. adapter and socket as well as the 9 V a.c. adapter and socket.

Which of course means it can only be used in the UK and those places where a “Type G” socket is available.

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The smaller single phase voltage sensor (without PSU) with a cable and mains plug is a good idea.

The OpenEnergyMonitor shop sells versions of the current AC-AC voltage sensor with UK, Euro and US plugs, presumably reflecting demand.

The simplest solution for a ZMPT plug top module would be to find one case with options for the required range of plugs, at a suitable price. Then the same PCB could be used in all versions. This may not be possible and may require a small number of different PCBs. A contract manufacturer could perhaps do it all!

In countries where a plug top ZMPT module is not available, then the emonVS, or the smaller single phase voltage sensor (without PSU) can be used.

A brief look on the web shows that evatron supply their FE4 plug top enclosure with either UK or Euro plugs. The web site doesn’t mention a US plug, but it may be worth enquiring.

OKW supply a plug top case with UK, German, French, Euro, Swiss or US plug options.

As plug top supplies are used widely across the world, there will be other manufacturers out there … the problem is finding the right one!

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I have an EmonPI, it is connected via an Ethernet cable

I’d like to install an EmonTX V4 next to it. I have a few questions!

  1. Presumably with the EmonPi I already have, I don’t need an EmonBase?

  2. Can I have a direct cable connect between the EmonPi and EmonTX V4? Is that USB?

  3. Will I need 3 mains sockets (EmonPi 5V adapter, EmonPi AC adapter and EmonVs)?
    Or could I power the EmonPi from the USB 5V on the EmonTX?

  4. For 3 phase monitoring, will I need anything else in addition to EmonPi, EmonTX V4, EmonVs and sufficient CTs?

  5. I see you hope to have stock in September. Are you accepting orders yet? :grinning:



Thanks for the input @Robert.Wall @rupert will get back to you on the above soon.

Thanks @PeteBee

Yes that is correct.

Yes and yes USB.

You can power the EmonPi from the EmonVs, which would reduce the requirement to 2 mains sockets. One for the emonVs and another for the AC adapter for the EmonPi. You can hard wire the emonVs to your consumer unit but if you already have the AC sockets there for the AC adapter that’s probably less of an advantage.

No I dont think so, assuming you are intending to use EmonTx v4 and EmonVs for your 3 phase measurement. We are however not there yet with the 3 phase firmware, the intention is to release initially with the single phase firmware and then once complete bring out the 3 phase firmware. I cant give you a specific date on that yet.

Thanks! we will have the units available for pre-order soon in the shop and a clarification on the availability date. I will update here once they are available for pre-order.

Thanks for the clear and concise answers. I’ll keep a look out for the pre-order availability - I’ll be happy to buy one initially and update the firmware for the proper 3 phase monitoring later.

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Any chance of using the Pi Pico W to transfer the data back from the emontx and the pi
Small power usage, cheap and available?

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I want to say I love this project. And I especially love that it is completely open source! Very soon I will be assembling my own emontx v4 from scratch. This will be the first time I have taken on a project like this that isn’t my own design and I can’t wait!

I have one question regarding pulse inputs. Will it be possible to attach a second pulse sensor to the digital input? The hardware should support it the question is will it be supported in firmware? The reason I ask is my meter has 2 pulse outputs I believe for 2 different tariffs.

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An interesting idea, is there any reason why this would be better than an ESP32 approach? Are there any good Pi Pico software projects that you would recommend that handle reading from serial and sending data on to a remote server? I guess it might be possible to use it with the EmonTx4 as is if it can link via a usb c to micro cable?

Thanks @brandon3055, so far I’ve only tested with a single pulse input, as you say it should be possible to extend to more once implemented in firmware.

Glad to say the RFM69 packet loss issue has now been sorted, luckily just a register change in the firmware.

Mmm, I think I did suggest it earlier :laughing:

Not used it but looks like there is a MicroPython option.

Advantages - are they UK produced? Something you like.

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