If we were a boiler manufacturer you’d get a trip to somewhere exotic to undo all the carbon savings 
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I’ve adjusted the text here to be less hyperbolic. I’ve tested up to 6 DS18B20 temperature sensors at any one time. There’s a useful discussion here about others more general experience of the number of DS18B20 temperature sensors that can be connected to a RaspberryPi digital input that may be useful. The OpenEnergyMonitor documentation also covers some of the intricacies around cable lengths etc when using DS18B20 temperature sensors here Temperature Sensing Using DS18B20 Digital Sensors — OpenEnergyMonitor 0.0.1 documentation
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Looks really great.
Couple of suggestions for shop page;
- Add the cost of the option in brackets (e.g. different emonVs)
- change the CT selectors to dropdowns (so more compact - when you have the option of 12…). Alternatively, a choice of number of each type of CT like the temperature sensors (would need user to configure then of course) which then could have a price next to it.
One other note - at the bottom of the emonPi2 page, the Wi-Fi version of the TX4 is listed. This isn’t listed on the Electricity Monitoring - Shop | OpenEnergyMonitor page 
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If I am ordering for the US, and I want EMONVS, what plug do I select, the “no plug, single phase emonVS” option?
You do want “No plug”, and you’ll need to wire it to a suitable plug, or you can of course (and probably better and more reliable) make a permanent connection, but I understand you’ll need a registered electrician for this. Do you want to monitor the voltage on both legs of your split-phase supply? If so, contact ‘The Shop’ and ask, because you’ll want a special ‘two-input’ version, alternatively the 3-phase version with only two inputs used.
See also emonTx V4, emonVS in North America
Just a (unfortunately rather late!) thought - could something like a Panel Mount Extension Cable (50cm) – USB micro-B to A (e.g. Pimoroni CAB0902) be fitted between the RaspberryPi Zero 2W USB port and the Raspberry Pi 4 connector knock-out panel?
Would this allow the Zero 2W emonPi 2 to be used to update the firmware on other emon units? …
Also to allow a wired connection between say an emonTx4 and the emonPi 2? …
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@TrystanLea this looks like a very nice addition to the line up. My EmonPi is currently run of an EmonVS usb connection and uses the traditional block for the voltage source. The EmonVS rj11 runs an EmonTx4. Would the emon Pi2 (Pi4) be able to piggyback off the EmonVS voltage connection to get a voltage, or would it try and draw power too?
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This is a good idea, but probably a mico to micro would be better although quite a lot of cable to ‘lose’ (Panel Mount Extension USB Cable - Micro-USB Male to Female | The Pi Hut).
Personally, I’d notch the end panel and just put an OTG cable through that, plus a short HDMI cable too (that would be useful for the usual Pi as well 
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I chose a USB-A female connector to go on the knock-out panel to give external access, because:
a) It would be the same USB connector as that used on the emonPi2 Pi 4B version and the original emonPi.
b) If you want a direct cable connection to an emonTx4, you would need a USB-A male to USB-C male cable, which are fairly common.
c) If you want to update/serial connect to an emonTx3, or update an emonTH, you would need a USB to serial TTL adapter. My USB to serial TTL adapters all have USB-micro female connectors on them. I have plenty of USB-A male to USB-micro male cables (from old phones), but no USB-micro male to USB-micro male cables.
d) Most (all?) of my separate USB to USB cables (apart from Pi Zero USB adapter cables!), have a USB-A male connector on one end. I’m not sure about the availability of a USB micro male to USB-C male cable, or a USB micro male to USB-micro male cable.
For a diy modification, then the connector used would obviously be a personal choice! 
Always assuming that I haven’t missed something in the basic idea of connecting to the Pi Zero 2W USB connector!
A hole large enough to put the connector through or/and with a gland?
We wont be able to make changes on the current design for this batch of course but open to ideas for iterations down the line. One consideration is that the cost difference between the Pi4 and the Zero, £30 doesn’t give a whole lot of room here, once you start adding bits like this, customising to fit nicely in the case and assembly it will start erode that cost difference a bit… A simple cut out panel big enough to pass the cables through for direct connection to the Pi Zero is probably the least cost option
It would be nice I agree a USB-A connector on the back plate, something to look into for sure for future variants.
Hello Andy, while not so easy out of the box I will definitely try to find a good solution for you here as the answer is technically yes. Are you replacing the original emonPi? and I assume this is all in close proximity , emonVs, emonTx4 and emonPi /2 replacement?
@TrystanLea Thanks for considering this! Yes, I’d replace the current EmonPi in order to upgrade the CT capabilities and would move the temperature monitoring from EmonTx4 to the EmonPi2. Everything is within 500mm of each other, and connected via usb for data. Currently the EmonPi also gathers data from 5 emonTH units.
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No, literally a notch in the faceplate down far enough and wide enough to accommodate the cable going through.
I’d not clicked through and found the Micro to A
Yes, Pimoroni does seem to have a good selection of USB panel mount cables
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Adapting an existing emonVs used with an EmonTx4 (RJ11 cable) to power and provide a voltage signal to the emonPi2:
It is relatively simple to adapt an existing emonVs to power an emonPi2 as well as an existing emonTx4.
For those happy to do this DIY we can supply the RJ45 cable pre-prepared, there are three connections to make. GND, 5V and the 1-phase voltage signal. Confusingly the DC ground is the brown and brown-white pair. 5V the blue and blue-white pair. These are pairs to carry more current. The orange-white single cable is the 1-phase voltage signal. Soldered in here to a spare hole next to R9 (furthest away from the RJ11 socket).
The RJ45 cables we provide have multi-strand cores and so are a bit stronger especially when soldered as in the 1-phase voltage signal here. Care does still need to be taken of course when putting the case back together.
Make sure to disconnect mains power before opening the emonVs case, given that this board handles mains voltages when powered!
For those uncomfortable with making this modification, we are happy to offer an adaptation service if you would like to send the emonVs back to us or if you are happy to wait we are considering an adapter cable to go from an RJ11 splitter to both an RJ45 cable and an RJ11 for the emonTx4.
Interested in any pointers in terms of demand for what would work best for people.
So would you need to power the emonPi2 via USB-C if using this method to get the mains voltage reference? (All the emonVs units shipped alongside the emonTx4 had a USB-C cable available.)
The USB-C cable is not needed to power the emonPi2 and can be removed if not used by anything else. The RJ45 cable can carry enough current to power the emonPi2 as well as provide the voltage signal.
Interested to know the design decision around using different connections on the 2 devices. Why not use an RJ11 on both?