I’m only now just catching up - that’s a very full and informative reply, @Mike_Henderson - thanks! I’ll need a little while to digest all that detail.
In the meantime, may I pose the question that was in my mind before seeing your reply. Perhaps it is already answered by your Device 12…
In my case, the EmonTx is in location (A) by the distribution board and is monitoring mains voltage and current, and also counting pulses on the meter. (I’ve little interest in temperature down there.)
At location (B) are the new boiler (I’d like to monitor the flow temp and both returns, CH and HW), so 3 sensors;
At location (C) are the HW cylinder (two coils), pump and HW and CH valves (5 sensors?)
So far, I have no EmonTHs at all, and my RFM69Pi-equipped RPi3 is in the room next door to the EmonTx. Once this initial learning/setup phase has died down, I expect to want an EmonTH in each of 4, perhaps 5 rooms. Any or all of those could, early on and temporarily, have a couple of external sensors attached to the flow and return of one radiator or another.
Evohome is all very clever and all, but it’s a bit of a black box (and some of that box is in the cloud). Hence my interest in monitoring things that I can understand, to create a view of how heat is being moved around (and lost), as a basis for judging whether the evohome is doing what seem to be sensible things.
I’m very new to Emoncms, and extremely new to evohome [but am just about at the point of looking back on a few decades spent thinking about and measuring heat transfers as my day job - I had colleagues who did/do the hard work of making and setting up the kit, which involves parts with masses in the range 1 to 1000 g, powers measured in uW, and we were aiming for sub 1% accuracy in measurements of temperature changes of around 1mK. I am/was more focused on making sense of it all.]
That is/was a setup that’s many orders of magnitude different from my new “homework”, but I’ve been delighted at how directly ways of thinking learned before, seem to transfer to the (control of) heating in domestic buildings.
But I have exactly zero experience of the 1-wire system for linking sensors, and so have basic questions like:
Can I have one EmonTH sitting in the airing cupboard, and as many as 5 external sensors patched into it via an RJ45 to terminal block breakout? (Even if the RJ45 sockets would actually be unused, the terminal block could be a convenient way to connect those 5 sensors in a star, with the 6th connection being to the EmonTH. Would the sensors all still work with passive power, or does the EmonTH effectively provide the power directly, to them all, in such a configuration? Perhaps the batteries wouldn’t last so long, but this would only be a temporary setup, so that’s not a problem. [The question arose because I really need sensors with 2m leads and so am looking at the (non-encapsulated) ones from sheepwalk, who ask bluntly: passive or not? But in typing this out, I realise that might just be a matter of how an RJ45 is wired - and I’m thinking of using a terminal block, i.e. bare wires, so the question is moot. If I’m thinking straight.]
Your device 12 makes me wonder if the EmonTx needs to be where it is but, on reflection, I suppose it does because, although an EmonTH could count pulses from the meter, only an EmonTx could monitor the mains supply. (If I understand things correctly.)
With apologies for a somewhat disorganised and working-things-out-as-I-type response, but I wanted to get things down in black and white while it’s all fresh in the mind.
Cheers, and thanks in anticipation for any thoughts you might care to share