EmonTx and EmonBase relationship

Hardware emonTx
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Hello,

I am looking to use multiple EmonTx’s and storing the data locally.
The EmonTx has a wifi adapter but this means having 2 power supplies per EmonTx.
It would be better to have the EmonTx’s communicate with an EmonBase so it’s only 1 extra plug.

For my questions:

  1. Is it possible to have many EmonTx’s communicate with a single EmonBase?
  2. If it is possible then how many Tx’s can a EmonBase reliably handle?

Thanks.

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Welcome, Niall, to OEM.

Not necessarily. The emonTx, provided that you don’t have too many extra sensors over and above the 4 c.t’s, can normally run off the a.c. adapter alone.

I don’t understand what you mean by that. By design, emonTx’s do communicate with the emonBase or emonPi.

Yes it is.

That depends on your definition of reliability. All units use the same radio channel. The RF library we use, JeeLib, has a mechanism whereby a node wanting to transmit will wait until the channel is clear - but that depends on it being able to hear all other transmissions. If that’s not the case, it’s quite possible that two nodes will transmit simultaneously, and each will jam the other. It appears that an acceptable number is somewhere around 4 - 6.

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Do you mean the inbuilt RFM wireless or the ESP8266 card?

If you need more than 3 CTs in one place, then the IOTAWatt might suit your needs better. There is a dedicated forum for questions about that product.

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It would be better to have the EmonTx’s communicate with an EmonBase so it’s only 1 extra plug.

If I was using an EmonTx with a WiFi adapter I assumed an extra plug would be required for each EmonTx, meaning 2 plugs per EmonTx, as opposed to 1 extra plug for the base station. However I do see that you said it could run off the AC adapter alone if it used the wifi module, something to consider for sure.

Thanks for your help.

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Do you mean the inbuilt RFM wireless or the ESP8266 card?

Wifi adapter

Ah! The IOTAWatt might be what I need. Do you know of other similar devices? Just to compare prices and features.

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Your original post said “Wireless” when what you actually meant to say was WiFi. I do believe the EmonTx does require 5V DC power if you use an ESP8266 WiFi adapter.

The EmonTx comes with a built-in Wireless radio that is not WiFi, thus the importance to be accurate in your questions to get accurate answers :slight_smile:

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I do believe the EmonTx does require 5V DC power if you use an ESP8266 WiFi adapter.

Indeed it does. The ESP8266 WifFi module draws ~140 mA when transmitting.
The maximum output from the emonTx power supply is spec’d at 60 mA.

Ref: EmonTx V3.4 - OpenEnergyMonitor Wiki

  • Important note regarding powering with AC: powering via AC is recommended only for standard emonTx operation without auxiliary sensors (apart from a maximum of 4 DS18B20 temperature sensors) or equipment (e.g. relay modules) connected. Correct operation via the AC supply is critically dependent upon using the correct AC-AC adapter. If you are using the recommended AC-AC adapter and the current draw exceeds 10 mA and the mains supply is below the minimum allowable, then circuit operation will be impaired, adversely affecting the accuracy of the emonTx. To avoid damage to the emonTx V3 circuits, the current drawn from the AC circuit should never exceed 60mA - see the technical wiki for more info. If more than 10 mA of current is required, it is recommended to remove jumper 2 (JP2) and power the emonTx via the 5V mini-USB connector. When JP2 is removed, the AC-AC adapter (if connected) will be used only to provide an AC voltage sample, i.e. it will not power the emonTx*
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thumbsup

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I edited my main post accordingly. Thanks.

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What, though, do you mean by EmonBase?

EmonBase usually means a Pi with an RFM board so you do not need the WiFi adapter (as the TX has the RFM comms by default) unless the range between the TX and Base is too great.