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Multiple EmonTH and EmonPi

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Hello All,

A project was started at my company and I am working to finish it. I do not know all of the details of their initial plan.

I have 2 EmonPi devices and 8 EmonTH devices. I believe that their initial plan was to set it up so that 4 EmonTH devices each would communicate with 1 EmonPi. I have tried having the batteries in 4 EmonTH and power supplied to 1 EmonPi, confirming they display in EmonCMS, disconnecting power and removing the batteries and then doing this for the other set. But it seems that when all 8 EmonTH and both EmonPi are active, the EmonTH aren’t dedicated to the EmonPi they were originally synced up with.

  1. In EmonCMS they show up as EmonTH5, EmonTH6, EmonTH7, and EmonTH8. Is there a way to rename them? I don’t know why it would start at 5 and not 1.

  2. Is it possible to set up 4 EmonTH to communicate with one EmonPi and the other 4 with the other EmonPi? I thought this might be possible since the EmonPi have their own IP address. But to me it doesn’t seem the EmonTH are dedicated to the EmonPi they are set up with.

I would like to do this without going in and changing the node ID if possible. But if that is the route we end up going, if the company were to expand past 30 EmonTH throughout the facility, how could we use more than one EmonPi for such an application?

These temperature sensors are not close enough to hard wire into the EmonPi themselves.

Thank you!

I think the original plan was formulated on a fundamental misunderstanding. Unless the two sets of equipment - each one emonPi and 4 emonTHs - use different radio frequency bands, then there can be no ‘pairing’ or ‘synced’ behaviour. From what you write, all 10 items work on the same frequency band, that is most likely the 433 MHz band (but it could be 868 MHz - you can tell from the length of the antenna, or look at the radio module). Therefore, you are correct when you write “EmonTH aren’t dedicated to the EmonPi they were originally synced up with”.

The thing that identifies each emonTH to emonHub is the NodeID. You can edit a file via emonCMS - emonhub.conf (accessible via the web browser) - and put whatever name you want to that NodeID.

The IP address of the emonPi is on the WiFi/Ethernet side of the emonPi, it has absolutely nothing to do with the 433 MHz / 868 MHz radio network that the emonPi shares with the emonTHs.
But you need not handle the data from nodes that you don’t want to. Just because the data is received does not mean it must be processed and stored.

You have no choice but to change the NodeIDs. Each item on the network must have its own ID, therefore you must change one of the emonPis and four of the emonTHs. We have allocated NodeIDs in emonhub.conf, but there is no need for you to keep those IDs - you may choose in the range 1 - 30, but I recommend you keep Node 5 for one emonPi and Nodes 19 - 26 for your emonTHs.

  1. You could use the other radio band - this would involve removing the RFM69CW radio module from a set of emonPi + emonTHs and replace it with a module that works on the other band. This would give you another 29 emonTHs.
  2. You could change the “Network Group” for a set of emonPi + emonTHs from our default of 210. However, this is only a software ‘filter’ and all the nodes still use the same radio band, so as the number of transmitters increases, you increase the risk of one transmitter jamming another if the transmissions overlap.
  3. You might be able to choose the locations so that one set is physically screened from the other set.
  4. You could modify the JeeLib library to cater for more NodeIDs. This would make your entire installation special to you, and not something anyone here would be able to offer very much support for. It would also give you problems when you update your emonPi software. You would need to modify all 8 emonTHs and your emonPis.
  5. You could change to a different library for the RFM radio modules, possibly LowPowerLabs. Again, you would need to modify all 8 emonTHs and your emonPis, and again, it is something that would give you problems when you update your emonPi software. As far as I’m aware, it’s not been tested for compatibility, so we would not be able to offer very much support, and still, congestion of the radio band is a concern.
  1. You could ask the shop to supply half the emonTH’s with a 868 rfm module fitted (maybe for a small fee, but they have previously said this is possible) and use a 868 JeeLink plugged in to a emonpi USB port. emonhub will then be able to manage both networks on one device (range permitting) or you can use the 2nd emonPi and split the network into 2 zones.

@pb66
Kindi wrote “I have…” so I think the emonTHs are already on site. Removing the radio module is tricky without the proper work station and experience, so not a preferred route to follow. If it’s being done in the firm’s time, it could actually be cheaper to buy new than to convert.

I’m not suggesting he removes the 8 he has, but if he wants to avoid congestion beyond 30 nodes working 2 frequencies will help. I know the modules are hard to remove, that’s why I suggested asking the shop to do them. @glyn.hudson has previously said they are a breeze to swap with the hot air rework station and also that 868 devices can be supplied to special order.

Plugging a JeeLink into an existing emonPi saves converting that to 868, or indeed it can be plugged in to the same “433” emonpi so one emonpi can work both frequencies.

Just stumbled across this from March this year.