Logging domestic power consumption?

[T i m]

Hi all,

Using the app to look at my mates solar battery performance (inverter output) ... and the likes of Gridwatch (TNP has done something right with that ) I thought it might be interesting to look at out usage here, mainly for the S&G's but also as sort as a trail blazer for my mate to be able to extend the data logging on his PV / battery system to be able to log both, with remote (Internet) viewing as the cherry on the cake.

I did have a system (possibly a basic Owl system) that was given to me by a mate that allowed me to see a live display of the current energy used but it didn't have an output to a PC or if it did, I couldn't get it working with anything.

So, I wondered if anyone could recommend something that could monitor two sources (for him), have the PC / Internet access remote from the sensors and / or just stream serial data or store and hold for weekly viewing etc.

Would something like the OWL +USB CM160 or OWL Intuition-E be a good starting point, or (in the spirit of d-i-y) build my own with an Arduino or some such?

Cheers, T i m

[Caecilius]

If it's an Owl, then it doesn't really measure power; only current. Its input comes from a current transformer that clips over one of the tails.

You can use this to estimate power if you make assumptions about voltage and power factor. But these are not constant, so it will only ever be an estimate.

I don't think the Owl type units have any way to output to a PC either.

That arduino project seems to do a decent job, as it measures both voltage and current.

But if you're measuring near the meter (and generally you will be if you're putting a current transformer on the tails), then I'd consider sensing the light from the flashing LED on the meter. Most modern meters have these, and the meter is doing all the voltage/current/power factor conversion for you.

[T i m]

Understood.

Ok. Well, I think I'd be interested in seeing trends (compared with a complete power cut situation) rather than absolutes as such so that could be ok.

I think this one does:

Ok, I'll give it (and others) a closer look.

Ok ...

Yes, ours does ... so I'm guessing you are suggesting each flash indicates an accurate unit of measurement, like 1 or .1 kWh or some such?

So an opto-sensor, RTC and SD card module?

Cheers, T i m

[Bob Eager]

arduino-energy-monitor

Here's a really simple, basic one from years ago:

[newshound]

If I may slightly hijack the thread, I have a slightly different power monitoring requirement. I suspect the DIY arduino project mentioned elsewhere would do the job (and it is on my job list to get an Arduino and/or Raspberry Pi to play with) but right now I'd prefer an off the shelf solution (if not too expensive).

I am reorganising my office / computer room. Currently, I have spreaders arranged so that I can switch off the printers, monitors, and switch at a single point, while leaving the wifi extender, desktop base units and laptop powered so that I can leave them on, off, or asleep from the keyboard as required.

But I am wondering whether to leave one of more of the printers "live" as well, so that I can print from elsewhere without powering them all up. (I have a Laserjet mono, a Lexmark colour laser, and a Brother inkjet all-in-one). So I was thinking about getting one of the plug-in monitors, provided it is sufficiently sensitive to measure the consumption of things like switches and printers when they have shut themselves down into standby.

Any suggestions? TIA.

[T i m]

Thanks for that Bob. ;-)

I'm happy with the electronics side and with some help from a coding mate of mine I'm sure I can make it work with an Arduino, it's just the 'typically 800 times per kilowatt hour' thing.

The only disadvantage with using the flashing light is if there is a very light load then the flash interval may be quite slow so the data acquisition period might have to be quite long?

Maybe a mix of the flashing light and a current clamp.

Cheers, T i m

[T i m]

Whilst I'm not particularly good with the coding there is so much out there for the Arduino's (and other similar devices) that I can usually get something going, if only to test the basic sub-modules.

I have only really used Pi's as micro Linux PC's, not interfaced them with anything.

That is my only though, being that my 'To do' list is now longer than the time left I have on that earth. ;-(

Ok.

I currently do that with my main colour laser and may be doing the similar with the Dymo LabelWriter on a Pi.

It did on my Ricoh Colour Laser with it reading about what the spec said it should on standby (around 3W) and my OpenMediaVault fileserver running on a Pi3 draws about 3.3W with the hard drive spun down.

Also, if we are talking about indoors and in the winter, all of this 'standby' energy is only going into the house as heat. Not so good in the summer of course. ;-(

Not all plug in energy monitors may be equal of course and their accuracy may depend on the power factor and other variables.

Cheers, T i m

[Dave Liquorice]

But a PDG estimate. The *limits* on voltage are -5% +10% on nominal

230V so 216 to 253 V. Our supply varies by 10 V from lowest to highest so 2% on average. I doubt power factor is significant for domestic loads, most homes have workshops full of BFO motors all running.

It's a while since I compared my logged consumption(*) with the bills last time I did bills and logged were within a few percent of each other.

(*) Current Cost unit, current transformer only. Unit has a TTL level "RS232" serial data ouput that carries historical and current information in XML. Linx based server does the logging via USB and a Current Cost serial to USB adapter.

[dennis]

The problem with that is that the current clamp may not be very good at low currents.

My meter does 1000 flashes/kW hour so about 300-400 flashes an hr background use.

[Theo]

I've been using oen of these:

which has a module that plugs into a Raspberry Pi. There's some Python software that talks to any number of adaptors and logs voltage/frequency/power to a CSV file. It only logs in whole watts at a 10 second granularity, but that's mostly good enough.

That particular module has a switch which makes it more expensive. They also have a cheaper monitor-only module, and a swishy gateway with mobile app if writing Python isn't your cup of tea.

(Also to note, the Pi adaptor is an RFM69 433MHz module on an adaptor board

- there wasn't stock when I bought, so I just got the module from ebay for $2 and made my own adaptor and antenna)

If you need to monitor lots of sockets, I'm also using an mPower PRO (EU):

- that has ethernet and wifi.

That allows switching and monitoring 6 sockets at once, either with a web app or via a shell script (you can SSH in). It gives instantaneous measurements - I think the idea is you use their controller for graphing, but SSH allows you to extract the data. There are some downsides:

1. There isn't a UK version, so you have to use Schuko plugs. Schuko kettle leads do the trick for lots of equipment.

1. There's a default username and password for all devices. You really should change this asap.

2. The thing runs Linux on a wifi-router chip. Ubiquiti have basically given up on mPower, so the firmware is quite outdated and won't be updated (it's on kernel 2.6.32 still). The drivers for the power monitor chip are a binary-only kernel module, so it's not possible to build a later kernel. Ubiquiti are GPL hostile and haven't responded to my request for the GPL sources for the device they shipped.

Basically it's already obsolete. But might be OK if you can lock it down. (ie don't put it anywhere near the internet)

Theo

[Theo]

It's a bit of a pricey way to do it, but the Energenie kit I mentioned in my other post will get both.

This:

is the house current monitor

This:

will give you voltage and frequency from a socket (and power consumption of that socket), and a module to plug into a raspberry pi.

All the kit is connected by 443MHz radio, so no wires.

The software to do it is pretty simple - download their Python code, tell it you have the two devices. Then it'll log from both. eg to a CSV file.

You just need to do V*I in your spreadsheet (or whatever) and you're done.

Theo

[T i m]

Understood.

Since last posting I see mine is marked similarly (and have read where one flash can = 1 or 1.25 Wh) so knowing that makes it more calculable.

I have since also found several Arduino based projects (using the flashing light method) so it looks like an option.

Cheers, T i m

[T i m]

'Needs must'.

It 'isn't hard' with a bit of training / self reading / practice I'm guessing ... none of the things I'm particularly interested in doing for something I've not had need for so far and would be entry 1024 on my ToDo list if I did? ;-(

I have *used* spreadsheets when moving address books from one phone to another in the olden days but not used any of the match / script functions (because I'm not into maths nor a script kiddy).

Cheers, T i m

[Chris J Dixon]

Plus USB data cable.

Chris

[T i m]

Thanks for that Chris, I've forwarded the links to my cous.

Do you actually have experience of such yourself OOI and if so, any additional thoughts / comments / suggestions please?

Cheers, T i m

[dennis]

£80+ for what? Its easy to go around with a mk1 eyeball and see which appliances/lights use power and which could make savings.

If you have solar then you probably would have had an inverter fitted with monitoring already built in (eg sunny boy via bluetooth).

The traffic lights aren't much use unless you intend to switch stuff off every time a cloud passes. Anyway most people fit solar to get the revenue not to save energy whatever they claim.

I have a power monitor that came free with the meter, its turned off until I want a meter reading to post on the web as I switched supplier and the new one can't read it. It never really affected our usage.

[Chris J Dixon]

I have had this unit for about 3 years now, and it enables me to keep an eye on my PV system and usage. I like being able to glance at the display and also look at the real time graph on my PC.

Although I do download the data onto the PC, I don't often look at it analytically - my official meter readings give me what I need for my spreadsheets.

Getting a good signal for the remote display can be tricky, and I don't have thick walls or a long distance to cope with.

The accuracy is generally acceptable, though it sometimes seems to imagine PV generation at night, or spells of zero usage.

Chris

[Richard]

I have Domoticz running on a Raspberry PI 3.

It receives data via 433 MHz from on OWL CM119. The consumption data is logged and can be viewed via a web browser. Graphs are provided for daily, monthly and yearly use. Domoticz can do much more and no coding is required.

Domoticz needs a 433 MHz receiver. For example

Richard

[T i m]

Interesting, Ta.

I think that's what I've got here (well, the transmitter part, the receiver is here *somewhere*). However, I didn't think there was any PC interface on the receiver or are you saying the Pi replaces the Owl receiver / display bit?

That sounds like the sort of result I'm looking for.

Even better. ;-)

Sorry, I'm not sure what hardware (if there is hardware) this is talking about? I need to see the bigger picture to 'get' how all the bits interrelate?

I know I will need at least an AC pickup transformer and a RF transmitter to send that date to a receiver of some sort. The data would then be decoded from the RF and either display real time, and / or logged and / or outputted via a dataport / LAN / BT Smartphone etc?

Cheers, T i m

[T i m]

OK.

I've learned to appreciate the saying 'You can manage what you can measure' and things like instant MPG readouts and the like.

I think it could be one of those things that would only be really interesting if it showed up something unexpected or was good enough to confirm (or deny) the suppliers own readings. I also think it would be of more interest to someone like you (or my cousin) with both the grid and solar PV to monitor.

Understood.

Noted.

;-)

Thanks for the feedback Chris.

Cheers, T i m