Multiple CT sensor monitoring using emonTx V3

Hi i want to monitor values from around 32 CT sensors.I was planning to use the emonTx V3. But this has a capability to fit 4 sensors at a time. is there any other model which i can use to increase the number of CTs which can be monitored at a time ?

Or i will have to use multiple emonTx V3 modules, will a single emonBase(raspberry pie) suffice to acquire data from multiple emonTx V3 modules?

Will there be any cross talk associated with using multiple emonTx V3 modules in the same room/hall with a single or multiple bases??

and what is the range(distance) across which the emonTx V3 will transmit data?

goodfidelity's picture

Re: Multiple CT sensor monitoring using emonTx V3

Hello Skg!

I cant really answer your question in a way that is simple or fast. But this is one alternative:

http://boredomprojects.net/index.php/projects/home-energy-monitor

He fits quite alot of them. And the Due has many inputs. Maybe you can just expand this idea to anything you like.

Best regards

//J

Robert Wall's picture

Re: Multiple CT sensor monitoring using emonTx V3

This is a question that is asked fairly frequently, so if you search here you'll find answers.

Basically you can have multiple emonTx's or you can build a custom front-end for an Arduino that has that many analogue inputs.

If you have multiple emonTx's, they will all use the same radio channel so there's a possibility that you will miss some readings if two try to transmit at the same time and block each other. I think 8 is somewhere close to the point where that's a real possibility. I don't understand what you mean by crosstalk, the messages are digital and they either get through or they don't. Each emonTx must have its own ID of course so that you know where each reading came from.

The range depends on many things, principally obstructions in the path (the construction of the building) and the proximity of interfering transmissions. Operation over a distance in excess of 300 m has been claimed (https://github.com/LowPowerLab/RFM69) - but note we use JeeLib, not the LowPowerLab library.

skg's picture

Re: Multiple CT sensor monitoring using emonTx V3

Hey thanks for the link, it has good information !!

skg's picture

Re: Multiple CT sensor monitoring using emonTx V3

Hi thanks for the information. Yes i wont be able to use more than 2 EmonTx V3 at the same time. as they use the same frequency i might miss out on readings.

Robert Wall's picture

Re: Multiple CT sensor monitoring using emonTx V3

Many others have used more than 2 transmitters, there is supposed to be a mechanism in the JeeLib library to prevent collisions, but it depends on both transmitters being able to hear each other, and I'm not certain that it's been rigorously tested. You can of course reduce the probability of a collision by keeping the length of the data packet short and the time between transmissions long.

Failing that, you would probably need to invent a master-slave protocol whereby each sensor node waits until the master (the Hub) requests a reply, then only the one that's been asked responds.

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