Monitoring power and temperature across various rooms

Hi all,

I’ll be doing some improvements in a flat and moving there soon and so decided that it is a good time to start monitoring power consumption and such.

I’ve planned on using emoncms before at another location but I’m still a bit overwhelmed with all the possibilities of emoncms [such as monitoring power, temperature, humidity, water and gas consumption and temperatures of the heating systems]. Given this, my idea is to start with the basics (power+temp) and progress from there.

The question is: What is the best solution to monitor power consumption and temperature in several rooms (and humidity for some)? My idea is:

  • Power: emonPi or emonTx + emonBase (any major difference apart from price? emonPi seems bigger, might be harder to fit in limited space).

  • Temperature: Here lies my problem:
    a) emonTH is interesting (temp+humidity) but would have to buy one for each room (+ one for outside temp?).
    b) there are also the DS18B20 sensors which can be connected to RJ45 (up to 6 to one emonTx?) but would need to pass cables in order to connect them all.

I’m planning on buying an emonPI and a few emonTHs (2 or 3) to start. Am I doing the wrong choice and should take advantage of the improvements and pass some cables and DS18B20 sensors?

Thanks a lot and sorry for the long post.

… but have at least an outline plan of where you intend to end up, so that you don’t spend money and effort on something that isn’t capable of meeting your final requirements. This is just a gentle warning because as you’ve realised, there’s a lot to take in and it’s very easy to get overwhelmed, and you don’t want to lose sight of the big picture.

Can you install pipes between strategic places that you can thread with cables as your needs evolve?

The emonPi is in fact a Raspberry Pi emonBase but with a cut-down (i.e. only 2 current channels) version of an emonTx inside the box, and with a small LCD display added. So if you want only 1 or 2 current (which translates to power and energy) measurements at or very near to the place where your base station will be, then an emonPi might be better.

Not necessarily an RJ45. It is arguably better to wire the temperature sensors ‘daisy-chain’ fashion, and the emonTx uses a screw terminal block OR RJ45 connector. You should probably read the ‘Resources’ > Building Blocks page on temperature sensing to understand how to use the DS18B20 sensors.

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Thanks @Robert.Wall, excellent overview.

@panda user guide is a good place to start:

Thanks both for your replies.

I’ve read the guides and other resources around here but still a bit undecided in some points.

@Robert.Wall I think I have an idea of what I would like to achieve. Based on other guides, I would like to: primarily, monitor power consumption. Then, also measure temperature (and sometimes humidity) in different rooms and possible outside; possibly measure water and gas consumption.

Since I don’t have previous experience, I thought it would be better to start with small goals (of the big plan): adding power measurement and eventually a few temperatures, instead of trying to plan it all for long and never get it done. :stuck_out_tongue:

I will be doing some (smallish) rebuildings soon and so it may be possibly to install some pipes inside some walls. That was the main reason to post the topic here. I don’t want to complete the improvements and later discover that I should have passed some cable when I had the chance. Any place where I can read some guidelines on this? My experience is nil but still AFAIK, if I pass a bigger pipe around some more important rooms / points, later I can easily(?) pass an RJ45 (or other cable I find useful) and connect some DS18B20 in daisy-chain. Right?
Question: In that setup, there is also the limitation of 6 DS18B20 max per emonTx?

As for the emonPi vs emonTx+Base previous question. I see that with emonPi I’m more limited in terms of CT clips (2 vs 4). Still, is it that useful to have 4CTs? It seems that to start, I would be fine with one connected to neutral or live. Plus would still have one if I wanted a more detailed monitor of some subset of electronics (and since the flat isn’t that big). Do they both support OTA updates for lazy people?

Cheers and thank you again :slight_smile:

Exactly - but I meant have the big plan in outline, not necessarily in full detail - but in enough detail not to have to backtrack.

The pipe wants to be big enough for cables and connectors to pass through easily, even when there are a few cables in place. Only you know the layout of your place and where you’re likely to want things cabled. I don’t know of any guides that might help.

That’s only a limitation of the default software. The actual limit is something of an unknown, depending very much on how the wiring is arranged physically.

No, you need a programmer and physical access to plug in for the emonTx, and physical access initially for the emonPi to set up the Wi-Fi.

Thanks @Robert.Wall!

Just one more question. Wasn’t considering connectors. What pipe diameter / size is big enough? Something that allows to pass there e few extra (2 or 3?) rj45 (or other) cables? Is is easy to pass an extra cable trough the pipe in the future if needed? Not sure yet if it will be possible, but my idea would be to set up some pipes between the major divisions and have a small box (derivation box? not sure if that’s the proper english name) where I could access them.

I cannot say what size you require - only you know that! But you will not be happy if it is too small. You can (and probably should) seal one end of the pipe when you have fed the cables through, to prevent insects and fire spreading from room to room.

Usually, the cable will be rigid enough to push through, unless the pipe is very long. In that case, you can either run a loop of cord through the pipe, then when you want to pull a new cable in, you tie the cable onto the join in the cord and pull it through (this needs two people - one pulling the cable and the cord through, and one feeding the cable and pulling the other side of the loop of cord back), or you can buy a set of screwed rods designed for the job:

You can use a small junction box, or a small piece of floor that you can lift up if the pipes are under a floor.