EmonPi2 for cohousing project: feeds not working

A few years ago I was investigating the use of EmonPi monitoring systems for a cohousing project that I’m part of: EmonPi for Cohousing project? - #12 by Robinlovelace

Now we’re actually looking to do it!

We have an EmonPi and I’m trying to test it. Unfortunately all the Feeds in the left hand EmonCMS panel seem to be off.

I suspect we’re missing something obvious but having had an EmonPi working on a previous house, and having read posts like this emonPi Inputs not working (I think we’re hitting a similar issue) we’re stumped.

Any pointers of things to test very welcome. Can provide details and screenshots below, it’s up and running and this is what I see:

Or an emonPi2? If it is an emonPi2, is it exactly how it came from the shop, because if it is, you should be seeing inputs from itself. I’d suggest contacting ‘The Shop’ in this case.

If you’ve changed something, then the first step is to say so and say what you changed. Look in the emonHub log. This is the place where data enters from the “emonTx4” pcb in the emonPi2. If valid data is not there, it won’t show on the Inputs page.

I can see you bought an emonPi2 in one order and later bought some more CT’s in another. Did you configure the CT’s yourself using the serial config tool? Did you stop and then restart emonHub?

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Do you have the emonPi2 powered by an emonVS voltage sensor? The voltage sensor and at least one CT sensor is required for power readings

Thanks for all the responses and ideas. To answer the questions:

  • Yes we’re using EmonPi2

Did you configure the CT’s yourself using the serial config tool

  • No but having a look at the settings now as per screenshot below

Did you stop and then restart emonHub?


Do you have the emonPi2 powered by an emonVS voltage sensor?

No, just the current is what we’re trying to monitor for now.

How can we check to see if the CT feed is working? A 20 A CT sensor is plugged into the CT 1 hole. Will aim to share photos below…

Bit of explanation regarding the second photo: that is my neighbour’s represenation of a ring main in miniature. We want to check to see that it can monitor this set-up. Plan if this test works is to get an EmonPi2 (this one) working in our distribution board.

We want to measure total current in the ring to find out which rings (e.g. laundry room vs communal kitchen) are using.

Minor update from this morning: we have tried a few more times with reference to the documentation.

This is what we now see:

The bit from the relevant documentation on CT Calibration Selection that seems to not be working is this:

After a couple of seconds the emonPi2 will print out its current configuration which will populate the interface (if it does not do this type l and click Send to reload the calibration details from the emonPi2 measurement board).

Before that that stage we “Select[ed] serial port /dev/ttyAMA0 and click[ed] Connect [the button in the top right actually says Start not Connect]”.

Nothing happens. In the console below it just says:

service-runner trigger sent for '/var/www/emoncms/scripts/serialmonitor/start.sh 9600 /dev/ttyAMA0'

We’ve tried all three board rates.

Unless you’ve got the “current-only” sketch loaded into the “emon” front end of your emonPi2, you won’t get sensible values. I only looked at one of the other sketches, the one I guess is likely to be the default factory-installed one, and this requires the voltage to calculate power - as you’d expect. If this is what you have, at best you’ll only get zero or very small values for power. emonLibDB, which I think is used by all the other sketches, was never designed to run without at least one voltage input on Voltage Channel 1. If it does run, it’s only by virtue of pick-up on the input.

There maybe other issues I’m not seeing, but going by your photo it looks like you haven’t got a emonVs voltage sensor connected, which is required as per Glyn’s post above. Once all connected, follow instructions, not forgetting to select emonLibDB in Firmware version and enter 101.30 in the voltage calibration box and save changes, or type ‘s’ and press send. When you navigate away and back to Serial Config, type ‘l’ and press send to load your previous configuration.

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So seems like we need to get a voltage sensor: AC-AC voltage sensor (UK Plug) - Shop | OpenEnergyMonitor

Seeing as they’re currently out of stock, any suggestions of where we can get one?

And just to check: what we’re seeing is expected?

I would have expected to at least see some numbers. Cc @Gwil and @glyn.hudson happy to have a follow-up call to ensure we get this set up. Additional message from Bill who’s helping with this who has the same question but in different words:

How feasible is it to use emonPi2 to monitor power consumption in various single phase circuits on different phases in a three phase distribution board? Which version and accessories would I need?

Er… No. Or you need an adapter as well. The emonPi2 voltage input is on an RJ45 socket, on the right in the photo below, and the voltage is about 1 V rms (i.e. roughly the same as the c.t’s). A design was proposed - a barrel socket to RJ45 plug, with a resistive voltage divider to reduce the voltage to the same as the emonVs. I’m not certain one has ever been put on sale.

You will need a 3-phase emonVs to provide the three voltage references for each of the phases, and you will of course need the appropriate sketch: EmonPi2_DB_6CT_3phase from Github if it’s not pre-loaded and available via the ‘Update’ option.

You need an emonVS voltage sensor power supply, it will power the emonpi2 and provide an accurate voltage sample.

Sorry for the confusion.

Many thanks for all the replies. Will liaise with others and get back here, likely after installing the emonVS power supply as Glyn suggests. Such a great community, I’m impressed with the speed and quality of supportive feedback.

Follow-up question for everyone and particularly to @glyn.hudson

After we’ve got the voltage monitor will kit do a 3-phase distribution board? Issue we foresee is that the voltage is likely to be measured across just one of the phases.

I did but was thinking about monitoring one phase at a time. The 3-phase emonVs is needed if we want to monitor use of all 3 phases simultaneously, right?

Grateful for all this info and feedback, keep it coming.

For three-phase monitoring, you’ll need a three-phase emonVS and your emonPi needs to running three-phase firmware:

The three-phase emonVS needs to be wired in directly via a low rated three-phase MCB to be able to read the voltage from each phase.