emonTx and emonBase Radio Link

I am planning to monitor two Grid and one Solar supplies. Both Grid supplies are off he same phase (General Domestics and Night Storage Heating) From reading the blogs I recon that I need a eanonTx and a base unit. Both units will be located beside each other and I was planning to hard wire the data connection. My question is, How do I switch off the radio link? Thanks.

Welcome, Philip, to the OEM forum.

From what you write, an emonTx and a Raspberry Pi (not the full emonBase, which is essentially an emonPi with the radio receiver) is all you need.

If there’s nothing to receive the data, you don’t need to disable the emonTx’s transmitter, but if you do, it can be turned off in software after you’ve established the serial connection and have emonCMS running on your RPi.

Details of the serial connection to your Raspberry Pi are here:
Best pictures: EmonTX to Rpi - Direct Serial Connection - #38 by borpin
Wiring diagram: 4 CT emonBase using emonTx and Pi Zero W - #17 by pb66

Serial Wired connection to PiZeroW: Avoiding wireless connections - EmonTX serial RPiZero solution - #119 by haffle or PDF Doc: https://community.openenergymonitor.org/uploads/short-url/b5MaNnyfwWswBldi6CHAprrX4JY.pdf

Shield Signal Raspberry Pi
Name Pin Pin Name
5 V 3 Power 2 5 V
“Tx” 4 ←data 8 Tx
“Rx” 5 data→ 10 Rx
RST 6 Reset 7 GPIO 4

Note: The Shield V2.4 and emonTx V3.4 send on the “Rx” pin and receive on the “Tx” pin. The emonTx V3.2 and heatpump board are labelled correctly.
The pin numbers (counting GND = 1) will always be correct.

For one-way data, with no programming from the Pi, only GND, 5 V & Data→ are required.

EmonTx V3.4 - Wiki | OpenEnergyMonitor (includes link to ESP changes for emonHub at emonhub/conf/interfacer_examples/directserial-serialtx3e at emon-pi · openenergymonitor/emonhub · GitHub)
Ordinary EmonHub plain serial interfacer: emonhub/conf/interfacer_examples/directserial at emon-pi · openenergymonitor/emonhub · GitHub

Serial Interfacer for direct connection:
The NodeID is by default 0. If you want to change this you need to add the nodeoffset option such that

     Type = EmonHubTx3eInterfacer
           com_port= /dev/ttyAMA0
           com_baud = 115200
           pubchannels = ToEmonCMS,

           nodeoffset = 1

Note the comma at the end of the pubchannels line and the blank line. As the data comes in as name:value pairs, there is no need for a node definition to decode the data, so for the nodeoffset, choose an unused number (0-4) or if you want to use a NodeID for which there already is a node definition, delete that node definition.

Note also a very big problem that continues to confuse everyone: Tx and Rx are swapped on the emonTx pcb, so as I’ve written so many times here, the emonTx is sending data on the pin labelled “Rx”, and it’s looking for data coming in on the pin labelled “Tx”. That’s contrary to convention (unless the emonTx is a modem!) This applies to all except the EmonTx V3.2 and the Heatpump board

I’ve no doubt all this will confuse you, so don’t hesitate to come back with questions.

Hi Robert,
Thanks for your quick reply. I understand from what you said that I use a Raspberry Pi as the link between my Lan and the emonTx. I have a bit of reading to do as I have never used a Pi before.

If you download emonCMS as an SD Card image, and write it to a card, plug it into a RPi, it’s all there bar the connections and setting up emonCMS.

Thanks Robert will give it a try

Hi Robert,
From reading the links you sent it looks like the emonTx voltage supply is powering both the emonTx and Raspberry Pi. Can it do this or do both need there own supplies?

No, it’s the other way round. The a.c. to the emonTx (in this case) is not a power supply, it’s only measuring the voltage. Everything runs off the RPi’s power. So you need two adapters: d.c. for power, a.c. for measurement.

This might clarify: EmonTx V3.4 - Wiki | OpenEnergyMonitor

Hi Robert,
Thanks for the reply.

Answering the question just deleted: Does the emonTx require both adapters?

It does if you add the ESP8266, otherwise no.

It all comes down to current draw: The a.c. adapter is quite capable of supplying the necessary power, but its source impedance means that the internal voltage drop makes an unacceptable dent in the wave it’s trying to measure, so the current drawn is deliberately limited, and there isn’t enough to supply anything other than the emonTx itself, plus a limited number of DS18B20 temperature sensors.

Thanks Robert for the info.