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.
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.
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.
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.