EmonTx setup problems

Hi All,

I have a Pi base station that listens and uploads data to Emoncms from an EmonTH which works really well on frequency 433Mhz. I also have a Tx v3 which I had hoped I could measure power usage. Unfortunately, I can't see the output in my inputs tab on Emoncms or on the emonGLCD.

On powering up with an AC-AC Power Supply Adapter, the onboard led on the TX stays on for 5 seconds and then flashes for 5 seconds then flashes once every 10 seconds.

I've checked the broadcast frequency on the Tx is set in the firmware to 433Mhz, the node is set to 10 and the network group at the default 210.

I've used the Arduino serial monitor to see what happens on power up and it finds and reports the external temperature from the wired DS18B20 sensor. It also detects the RFµ328.

Can anyone suggest what to look at next.

Thank you in anticipation.








glyn.hudson's picture

Re: EmonTx setup problems

Hi Mark,

Mmm it sounds from the serial output and LED behavior that the emonTx is working fine. Can you see the power values being printed out? At least one CT 3.5mm jack must be connected for the emonTx V3 to work, any 3.5mm jack plugged in will trick it if you dont have a CT to hand. Make sure you hit the reset button one a 3.5mm jack has been inserted. 

earlscroft's picture

Re: EmonTx setup problems

Hi Glyn,

I've managed to get the GLCD to show the power. The GLCD was too far away. I have to bring  it within 2 metres of the Tx and then it fires into action. I'm assuming the range should be more than that. Could there be some interference or a wiring problem.

If it helps, here's the output, with power, from the serial monitor.

emonTx V3 Discrete Sampling
CT 1 Calibration: 90.90
CT 2 Calibration: 90.90
CT 3 Calibration: 90.90
CT 4 Calibration: 16.60
RMS Voltage on AC-AC Adapter input is: ~3V
AC-AC adapter NOT detected - Apparent Power measurements enabled
Assuming VRMS to be 230V
Assuming powering from batteries / 5V USB - power saving mode enabled
CT 1 detected
Detected 1 DS18B20..using this for temperature reading
RFM12B Initiated:
Node: 10 Freq: 433Mhz Network: 210
temperature: 8.10
temperature: 8.10



vikasha's picture

Re: EmonTx setup problems

hai  i have sum problems in emontx v2. i program in this kit um error come there that is

"avrdude: stk500_getsync(): not in sync: resp=0x00 " 

please help me.........

glyn.hudson's picture

Re: EmonTx setup problems

All looks good from the serial output. Is the emonGLCD also 433mhz? Rang should definitely be greater than that. What are you using antenna wise? Is the antenna 165mm long? 


What about the rfm12pi? Are you know receiving data on the Pi? 

@vikasha this is a different issue. Sounds like problem with Arduino ide or USB to uart cable. Have you selected uno under board type before uploading? Best start a fresh thread then then hijack this one 

earlscroft's picture

Re: EmonTx setup problems


Yes, all devices have 433 hardware.

Ref: Antenna length

I hadn't considered antenna length. I'm not at home with the kit, but I know that one of the units (Pi, GLCD emonth and tx) has a shorter antenna length than the others. I found these details

433 1/4 wave = 164.7mm
433 1/2 wave = 329.4mm
433 full wave = 692.7mm

868 1/4 wave = 82.2mm
868 1/2 wave = 164.3mm
868 full wave = 345.5mm

I'm pretty sure one of the devices has an 82mm antenna. I'll check and if necessary extend. Should there be a significant improvement if I extend all devices to 692.7mm. Forgive me if this a dumb question.


Bill Thomson's picture

Re: EmonTx setup problems

Hi Earl,

You'll want to make both of your antennas 1/4 wave. (although Robin, aka calypso_rae, reports he has better luck with 1/2 wave antennsas) but definitely not full wave. Try got get your measurements as close as possible since even a small error of say 3 or 4 millimeters can affect antenna performance quite a bit.


Bill Thomson


MartinR's picture

Re: EmonTx setup problems

It sounds like the RFM12B on your emonTx V3 might be an 868MHz device. These will still work if programmed for 434MHz but the range is very short. You can check by looking at the capacitor arrowed at the bottom of this photo. If it's missing then you have an 868MHz part...


TrystanLea's picture

Re: EmonTx setup problems

Another photo to help identification here: http://openenergymonitor.org/emon/buildingblocks/rfm12b-wireless

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