AVR-DB: emonTx V4, new hardware in progress

The one has the same size conductors as the cable we’re using. I’ve double-checked and the current cable has 1mm^2 conductors.

Unfortunately that’s one is out stock and more expensive than our current cable

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It’s got 1mm^2 conductors which is not that large. I think it’s the fact there are three conductors which makes it seem larger than most lamp flex cables

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Fair enough but you did say 1.5mm² originally :slight_smile:

I would advise reading this piece with a degree of caution. Even though it is written with good intentions, there’s one glaring mistake throughout: what is referred to as the “input impedance” in most cases isn’t that at all, it’s the combination of the output impedance of the voltage source (the “source impedance”) and the input impedance of the ADC in series. And again in most cases, the former will be dominant because the manufacturer of the ADC will strive to make the true input resistance along the charging path to the sample-and-hold capacitor as low as possible, while making the impedance of any shunt paths for bias or protection as high an impedance as possible.

The demarkation point between the source impedance and the input impedance is usually the ADC input pin.

Sorry, about that I just double-checked, and they are 1mm^2. It would be nice if we could use 0.5mm^2, I looked into getting cables custom-made, but they were more expensive than using off-the-shelf moulded plugs. For the next batch I’m looking into purchasing them custom-made in bulk which should reduce the cost and allow us to use slightly thinner flex.

The best option for a tidy installation is to choose the emonVS without any plug and hardwire to an FCU, there’s not getting away from the fact UK plugs are bulky! I

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If it comes back in stock, this might be a good one too https://cpc.farnell.com/pro-elec/pel01285/uk-plug-to-open-end-0-75mm-white/dp/PL16107?st=pel01285

Or PEL01284

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Just curious: why does the emonVS use an earth connection as a voltage reference? What does it provide that the line and neutral alone cannot?

2 posts were split to a new topic: New emonTX4 - data loss

It doesn’t appear to. The earth connects to the ground plane under the ZMPT101B transformers and the 5 V output, hence to the emonTx V4 and GND and the c.t. input sockets sleeve connection.

So it should be providing some earthed screening to the low-level signals.

The voltage input is tapped off Line(s) and Neutral.

We made the change to include the earthed screening before a later change to the way the bias is applied on the input circuitry (with one side of the CT and Voltage sensor now being tied to emonTx4 GND), adding the earth made a noticeable difference previously but actually retesting here today, I cant notice a difference with or without the earth connected. So it may be something we can revisit now that the other changes have mitigated the original observed noise. I will have to do some more indepth testing, we had to move quite quickly and not change too many things through the design process for the emonTx4 so it may be that this earth connection is something to revisit again.

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Postman finally turned up with my EmonTX4 yesterday (it shipped last Friday, ironically an IP camera I was waiting for shipped from Hong Kong Monday and arrived first - Royal Mail living up to its reputation!).

First impression was it was a large cable in a box with some other stuff :rofl: as others have commented the cable is huge, mine was 2m not 1m - I assume the moulded plug is for regs?

I would consider looking at IEC leads, they are cheap and plentiful and you can just chop the IEC and wire it in? I need to change the lead somehow as this one is massive and I have no where to hide it in the WC where the builder helpfully installed our CU. I’ll have to look at adding a fused plate maybe and wiring it into that directly to neaten it all up - low WAF as shipped (Wife Acceptance Factor).

I will update my EmonPi first, I am on 11.0.9, reading the release notes can’t see much change to 11.2.3 but might as well be current.

My EmonTX are all CM FW now, can the EmonPi run continuous monitoring by default, or is it still for experimenting only? At the moment my solar is on the EmonPi so any increase in accuracy is welcome.

-5c here in the south of England this morning, but the sun is out and the skies are clear so off the grid at least!

In case it helps anyone, it looks like EmonTX4 is Node17, its confusing as I already had an EmonTX4 which seems to be my 2nd EmonTX3 with Node ID 16.

I clearly need to do more reading as I am not sure if you can rename nodes already in use? As long as the feeds are not touched it seems you can delete and add nodes and inputs freely?

Is there any news on the 6 CT Expansion Board yet ?
Also will it fit into the existing case ?

Hello @Tank, the firmware to support 12 CT sensors is almost ready, going through testing at the moment. I cant say exactly when it will be available in the shop yet. The Expansion board itself does fit in the existing case, it just needs a different fascia. Are you interested to add this to an emonTx4 that you have already or is this a new system?

Thanks @TrystanLea , It’s to add to my existing Tx4.
That’s good to hear that it will fit in the existing case as well…