Emontx v3.2 problems with vrms readings from AC-AC supply

Hardware
1

Hello,

I am trying to get my one of my old emontx v3 (v3.2, Oct 2013, as written on the pcb) going to do some appliance monitoring. I’m having issues reading the Vrms from my AC-AC adapter. Things I have ruled out;

  • The AC-AC adapter is fine. It reads 11.1V. Also, I have another adapter which is functioning perfectly when connected to my other emonTX v3.

  • Sketch is fine. I am using the same sketch on my other emontx v3, and it is reporting sensible values to emoncms (but note I have changed the node number)

Serial monitor output pasted below. Initially there is a large reading (430V), followed by lots of low readings which vary between 5 and 30V.

Has anyone come across this issue before? So far I am thinking there is an issue with the emontx, what would you suggest I do to fault-find?

Thanks!

Chris

emonTx V3.2 Discrete Sampling V2.00
OpenEnergyMonitor.org
POST…wait 10s
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: ~430V
AC-AC adapter detected - Real Power measurements enabled
assuming powering from AC-AC adapter (jumper closed)
Vcal: 268.97
Phase Shift: 1.70
NO CT’s detected
No temperature sensor
RFM12B Initiated:
Node: 8 Freq: 868Mhz Network: 210
CT1 CT2 CT3 CT4 VRMS/BATT PULSE
6443 0 0 0 13803 0
0 0 0 0 145 0
0 0 0 0 25 0
0 0 0 0 7 0
0 0 0 0 3 0
0 0 0 0 20 0
0 0 0 0 3 0
0 0 0 0 10 0
0 0 0 0 5 0
0 0 0 0 18 0
0 0 0 0 5 0
0 0 0 0 15 0
0 0 0 0 6 0
0 0 0 0 18 0
0 0 0 0 1 0
0 0 0 0 21 0
0 0 0 0 5 0
0 0 0 0 11 0

2

It looks as if you could be right there! We have two people having trouble at the moment with c.t’s, but I haven’t come across this before. I don’t think those readings are 5-10 V, looking at what I think is your sketch, they are 5-10 centivolts (i.e. V × 100 - as sent to emoncms). So they are noise. The initial large reading is the filter settling. But, it should not need to settle - the quiescent value is pre-loaded. So I think there’s a problem with the input circuitry.

Do you have a multimeter? If so, can you check the d.c. voltage on the junction of R11 & R12 (the end of either nearest the RFμ) It should be close to 1.65 V.
Also/instead, you could load Robin’s diagnostic sketch https://openenergymonitor.org/forum-archive/sites/default/files/RawSamplesTool_4ss_2.ino_.zip and run that, change the input pin numbers to suit:
byte voltageSensorPin = 0;
byte currentSensorPin = 1;

That will show the a.c. wave as seen by the ADC, and it should be a nice sine wave centred down the middle. I suspect it won’t be.

For reference, here’s what I get under similar circumstances. Note the filter on the current input 1 settling because the input is grounded, but the filter was initialised to the nominal half-rail working point (so it takes time to get down from 1.65 V / 512 counts to zero).

CT1 CT2 CT3 CT4 VRMS/BATT PULSE 256 0 0 0 24014 0 55 0 0 0 24009 0 40 0 0 0 23998 0 0 0 0 0 24003 0 6 0 0 0 24023 0 0 0 0 0 24000 0 1 0 0 0 23936 0 0 0 0 0 23943 0