AVR-DB: emonTx V4, new hardware in progress

Thanks @borpin! Yes pretty happy with how this is shaping up.

Unfortunately I made an oversight in not routing the 5V rail to the uart connector on the current version of the EmonTx v4, I had thought it would not be needed. The onboard 3.3V supply does not provide enough power for the Pi Zero and so yes it does require the external supply - though that can be supplied from the single emonVs voltage sensor and power supply (which has two outputs). The next version of the EmonTx4 will have the 5V rail routed through to the uart pin allowing the Pi Zero to be powered without the additional cable.

The Pi Zero adapter does have the option to power the EmonTx4 if voltage sensing without the integrated power supply is used.

No not on the first batch at least but I can see your point and it’s probably something that we should think more about on later versions.

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Rats! Is there any where a jumper wire could be easily connected from? Powering internally is one of the key benefits.

No easy jumpers unfortunately but our first batch is not that large and I’d expect that we will be on the next batch by the time pi zero’s become available anyway.

The pi Pico and esp can be powered internally via 3.3v so those are fine.


It would probably be a bit too much of a bodge to sell boards with this but you could theoretically easily run a DIY bodge wire on the back of the board from the 5V pin on the RJ11 to the UART connector.
The only possible concern would be the extra current flow through the analog ground section throwing off the readings. But that would probably be negligible.
Just a thought.

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Yes, that’s a good idea, it would also be possible with care to solder a link from the 5v input to the voltage regulator, but it’s perhaps a bit fidly given that its quite a small SMT part.

I’m behind the curve here, but I noticed today there is a Pi Zero 2!

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Raspberry Pis are amazing but currently they are sold out everywhere owing to massive demand. I have a Zero 2 W and it is a very welcome upgrade over the original one.

The Raspberry Pi Pico W is worth considering instead though. It’s cheaper, there’s greater supply, excellent documentation and an increasing amount of information and examples available on the web.

Just in case you did not see it, Trystan has been working on that too.

We (The OEM Shop) have good stock of Raspberry Pi 4’s ready for the short to medium term, so that is what we will be shipping. But thanks to Trystan’s hard work, there are options available for the user and the future.

I had to check twice but I assume that “The OEM Shop” is https://shop.openenergymonitor.com/. I assume that you mean that you have a stock of Pi 4s ready to go when designs are finalised. Because, at the moment, Pi devices appears to be out-of-stock.

Yes, correct. The emonPi units are out of stock because we can’t get hold of Atmega328 microchips to manufacture any more of the electricity monitoring boards that sit on the Pi.

That is the reason we are moving to a platform based on the newer chip as detailed in this thread.

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I have a question regarding the CT expansion board.
I noticed from the PCB picture you posted on May 10th that you changed up the sensing circuit a bit. From what I could tell you were using something like this.

Which while using the exact same components does seem like it could be better than what’s used in the tx4 main board as it is functionally the same but removes any possible bias that could be applied by the 0.512v divider.
I’m just curious why you didn’t end up using this in the design you posted on github.
Was there an issue with it? Or was it just unnecessary?

Hello @brandon3055 the main reason for the change to the new design is that providing a low impedance path to ground by grounding one side of the CT really helps with noise at low power levels.
I have since updated the design for the expander board as well to match.

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Ahh, I had it backwards. The schematic I posted is actually the old design.
That makes more sense. And yea I didn’t consider noise.

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Hi there, just wondering if you have an updated ETA for the new hardware? Thanks!

Production is starting next week! We should have the boards ready in the shop in a couple of weeks :smiley:


The long wait has been mostly the PCB production and component sourcing which happens first. Our contract manufacturer now has everything in place to do the SMT assembly starting next week!


Super awesome! Looking forward to it! Moving from Flukso to emon! YAY!


A post was split to a new topic: How to get stated with a new system

Any updates team? :smiley:

We should be getting assembled units next week :smiley:

Expect them to be in the shop in 1-2 weeeks