I have an odd failure to get any readings from a particular branch circuit. I’m using an EmonTX5 w/12 ports on US power (split phase, 120V, 60Hz).
Using a 20 Amp CT from the OEM shop on the target line gives me a static value in EmonCMS (and also seen directly in the packets) of -1. If I move the CT to another circuit, keeping the lead plugged into the same socket (CT 8 on the EmonTX), I get valid readings. Similarly, if I put another CT plugged into another socket on this same branch circuit, I also get valid readings.
This circuit is where my network/compute equipment is located, almost all of which is behind a UPS (if that matters). I’ve put a large resistive load (a space heater) on this circuit and still get the -1 readings, only getting valid readings using a different CT.
I’ve confirmed the calibration values are correct and that the reference voltage is getting applied correctly.
Since this CT works on different circuits, I can’t chalk this up to a bad CT. I’m at a loss of what else can be going on here. Anyone have thoughts on what may be going on here and how to diagnose this further?
That’s weird. It something either very, very complicated or something very, very silly. I suggest you look for the very silly first - like a broken wire which is making contact in one position and not in another.
There’s nothing particularly significant about the -1 – it’s just pickup with a massive phase shift. By “reference voltage” you mean what - the emonVs measuring the voltages on the two legs of your supply?
What you haven’t said is what happens if you plug another c.t. moved onto the same wire/branch circuit into c.t channel 8? I’d expect this to be correct (or proportional if it’s not the same rating - say a 100 A should read a fifth of what you expect, and that would be a good enough test).
I’ve just taken a CT giving me good readings (plugged into another port) on another branch and moved it over to the target branch. When plugged into its original port, readings of the target branch using the known good CT are fine. When plugged into port 8 on the EmonTX, no readings occur.
This sure seems to be something around that EmonTX port in particular. Any thoughts on looking at that port? It may be time for me to punt this over to the shop.
What about Channels 2, 5 & 11? Do they give readings above the noise level (say > 10 W)?
Why I ask is it appears The Shop has been sending the 3-phase sketch to split-phase N.American customers - and the sketch links the input channels 1 - 12 to the phases 1,2,3,1,2,3,1,2,3,1,2,3, and if you nave no voltage input on Phase 2, you’ll get nothing on those 4 input channels. Did they include a source (,ino) file for your sketch? - you could look at that if they did.
You need to look at line 254 #if NUM_V_CHANNELS == 3 onwards (there is NO 2 × V-channels option) and change the second number in each function call to 1, 2, 1, 2 etc in sequence to allocate odd numbered breakers to Phase 1 (or Leg A) and even numbered to Phase 2 (or Leg B). (And look a bit further down for what to do with your 240 V loads.)
I understand a version with this voltage to channel allocation is now available for the EmonTx5, emonPi2 and EmonTx4, available via the firmware upload tool in emonCMS (presumably you must update your emonCMS first).
Yes. I have valid readings on 2, 5, & 11. You helped me identify the 3-phase firmware issue in another thread. I have recompiled my firmware as single phase, applying the same reference voltage to all CTs.
Ack. Sorry. I must have gotten confused with all the various configurations I’ve been trying. Checking the feed that this port this is logging to in EmonCMS, I’m pretty sure this port has never seen a valid reading. There’s a couple of 2W spikes that I want to verify. It may be a day before I can take this apart and take another look, but I’ll do that as soon as I can and report back!
This is the first time a UPS has been mentioned. @davidski What do you mean by this - is it the only connection (apart from instrumentation or alarms) between the breaker in your load centre and the UPS (so it’s 120 V or 240 V 60 Hz a.c., or something else?
Thanks @davidski this sounds like a dry solder joint somewhere, thinking about it the most likely place would be on the connector between the expansion board and the base board… could you take it out of the case and take a picture of the expansion board connector? top and bottom…?
EDIT: Looks like using Chrome allows my images to upload correctly
Attached are photos of the expansion board and the connector mate on the main board. Nothing jump out at me, though my soldering skills are pretty basic.
Good catch! I carefully used a fingernail and a small flathead to clean out the spaces between the blobs. Unfortunately, no change. CT8 still gives me no readings. Here’s a close up of the connector after my clean up work.
To add on to this, I’ve now realized that not only is CT8 affected, but so is CT7. CT9-CT12 look to be working as expected.
Known working loads, when plugged into CT7, give no readings. Taking the CT that is plugged into CT7 and putting it on another port, gives good readings.
A bit of testing across the various resistors on the expansion board show no obvious differences in connectivity in the good v. bad ports. I’d appreciate any tips on specific bits to look at to diagnose further.
The 2nd, 5th, 8th and 9th joints on the bottom of the green PCB (1st picture)
look suspect to me. Especially, the 2nd one. It may just be the way the light is bouncing off of it, and the camera angle, but they sure look like hitting them with an iron and some
solder wouldn’t be a bad idea.
I don’t claim any expertise in this h/w, but it looks like CT7 and CT8 are the two right-most solder blobs in your zoomed in photo above. Things look a bit beat up around there - it might be worth buzzing them through to their corresponding processor pins to make sure the tracks aren’t damaged - you can just follow the tracks to see which pins.
@davidski
With the expander board unplugged, can you temporarily connect the socket for CT7 & CT8 (separately) to the equivalent point on any one of CT1 - CT6 inputs, which is the cathode of the protection diode (next to the label, the non-grounded end) – whichever is convenient, and report what CT7 (8) displays. It should read the same, as a percentage of the CT rating, as the ‘host’ channel reads. If it does, the main board is OK and it’s the expansion board. Be careful - this is the processor input pin.
This is in essence equivalent to @dBC 's suggestion, but will, if it reads a sensible value, also prove the software (even though the non-zero readings seem to indicate this is not the problem).
@TrystanLea Is there any chance of a set of Kicad (preferably) or Eagle files for the emonTx5/emonPi2 board? I can’t find them in Docs.
I have recompiled my firmware as single phase, applying the same reference voltage to all CTs.
CT9-CT12 look to be working as expected.