Does anyone know of an energy monitor for the electricity that I could use without having to sign up for a smart meter ?
I see lots of "smart plugs", but want to monitor the whole house. not one socket.
From memory the difference in voltage and current phasing is a function off loading, so in theory it's a possibility.
They do exist. Using clamp on current and a voltage probe for the volts
Typically a current clamp and then a plug-in device to get the voltage. You can get various depending on whether you have power near your meter or whether it needs to send the current reading to another box.
I would normally recommend looking at:
You can also find various options on ebay, as offered by eg British Gas before the smart meter rollout. The 'Owl' range was popular, and they can be picked up fairly cheap. Typically they're just sending data to a home display - some have a USB stick option for PC access, although I'm not sure what the software side of that looks like.
Theo
I have an 'Owl' that I got some years ago from SSE. It does not have a voltage probe, nor any output option, but it gives a readout of current amps. It has been ignored for months, years even.
If you are happy to cobble something together, then it is a fairly straight forward build... by coincidence I was experimenting for a very basic device that gives a "whole house" instant display of total voltage, current, pF, power etc. (kind of like a DIY smart meter live readout)[1]
Kit required: one Arduino dev board, a LCD display (preferably with i2c interface module on it), a current transformer, a 9V AC/AC power adaptor (old modem power adaptors are often good), and a USB power supply for the microcontroller, plus a few passive components to scale and offset the waveforms you read from the the AC PSU and the CT, so they can be safely fed into the Arduino ADCs 0-5V range. (prolly £20 all in from AliExpress)
The CT will let you read a real time current waveform. The AC/AC adaptor will let you read a proxy for the mains voltage. The rest is just some number crunching (the EmonLib library already has all you need).
In fact, looking that the library example code gives an idea of the complexity:
// EmonLibrary examples openenergymonitor.org, Licence GNU GPL V3
#include "EmonLib.h" // Include Emon Library EnergyMonitor emon1; // Create an instance
void setup() { Serial.begin(9600);
emon1.voltage(2, 234.26, 1.7); // Voltage: input pin, calibration, phase_shift emon1.current(1, 111.1); // Current: input pin, calibration. }
void loop() { emon1.calcVI(20,2000); // Calculate all. No.of half wavelengths (crossings), time-out emon1.serialprint(); // Print out all variables (realpower, apparent power, Vrms, Irms, power factor)
float realPower = emon1.realPower; //extract Real Power into variable float apparentPower = emon1.apparentPower; //extract Apparent Power into variable float powerFActor = emon1.powerFactor; //extract Power Factor into Variable float supplyVoltage = emon1.Vrms; //extract Vrms into Variable float Irms = emon1.Irms; //extract Irms into Variable }
So all you would need to add would be a bit at the end to format those variable into output strings, and update a 16x2 line LCD or similar... (again, load appropriate LCD library - so about 5 lines of code to initialise it, clear the screen, position the cursor, and output the formatted text).
[1] At some point when I can find the right shape of tuit, I was thinking of doing a multi channel version that could log data to a database for more in depth analysis on a circuit by circuit basis.
You can certainly get units which go ‘in line’ with your supply, some fit in the consumer unit, which measure and display consumption.
When my middle daughter bought her house, the previous owner had a ‘spur’ for the shed / garden office. It had a dedicated consumer unit with one fitted. They had it all removed - the shed was a bit dilapidated etc.
I expect you can get ‘ smart ‘ ones now with Wi-Fi / Bluetooth etc.
I had one about ten years ago that transmitted from a current clamp to a plug in display in the living room, they were being given away by one of the big power companies.
There was an Owl II with USB capability. But the ancient basic Owl is good enough to show you where the vampire power usage is going. Their website still exists but the products apparently do not.
Other brands are available Energenie being the current brand du jour.
I have one of these, an Eon meter, and it is basically misleading:
1) Switched everything off in the house (took a while as I forgot things like alarm system and security light). 2) The Eon meter read 13 watts in use, but the rotating disc in the real meter didn't move in 15 minutes. 3) Unclipped the cable current clamp, meter read zero, put it back - 13 watts4) Switched the security light back on - it didn't light as it was daylight. The meter now read 0 watts!
5) Switched it off - back to 13 watts. Back on again = 0 watts.6) The gutter press states microwaves cost a fortune when in standby. So switched the Panasonic on, display illuminated - Eon meter now reads 18 watts. But the disc in the real meter didn't move in 10 minutes.
7) Opened the microwave door, light came on and Eon reading increased by 16 watts. The disc is now rotating slowly as expected.Hmm!
GrahamC
The current clamp is presumably sized for 100A maximum load. 13W is 54mA, which is 1800x less than the maximum current. I'm not surprised that accuracy suffers at that end of the scale. I wouldn't be using a 100A clamp meter to chase loads that small - it isn't really sized for that.
Also, if it doesn't have a voltage input (eg an AC transformer) it's only reading current and you probably have some devices with a non-unity power factor. It can't tell that the current is out of phase with the voltage and so it records as consumption, even though the reactive device returns the power back again in the other half of the mains cycle.
Theo
About 5W sounds reasonable for a microwave with a timer display illuminated. Many consumer items have standby power <0.5W now.
Some older TVs and set top boxes tend to be power hogs.
I suspect what it actually tells us is that your ancient spinning disk meter has bearing stiction and doesn't move at all for loads under 15W!
Mmm. Wattless current?
13 watts on 230v is 50mA
It was measuring something then
Sounds like some sort of mains filter issue
Since electricity is now about the same price as oil per actual Kwh, I am not bothered about electricity heating the house.
So did I, used it until I did have a Smart Meter fitted.
It was pretty good I thought (for a 'giveaway' device). I'm sure not super accurate, but gave good enough 'ball park' figures
It could well be reactive power.
I think you may have unrealistic expectations...
Most of the clip on "whole house" monitors will be using a current transformer with a range of 0 to 100A. The CT will generate (say) up to
50mA of current into a burden resistor. You then use the voltage drop across that to feed a ADC so you can read a value.However before you can feed the ADC, that voltage will need to be biased up so that the waveform never crosses zero on the negative part of the wave, and scaled to fit into the typical 3.3V or 5V range acceptable to the ADC. So to allow a bit of headroom you will probably scale the waveform to be around 4V peak to peak (on an ADC with a 5V range). If you are feeding a 10 bit ADC (fairly typical of many off the shelf microcontrollers), you have 1024 possible values, of which you are using
4/5s of them due to the scaling. That is around 820 possible discrete readings, to cover a reading range of 100A. Hence you have only ~8 possible readings per amp - a resolution of 125mA. That is 30W at 240V. Even if you use a discrete 12 bit ADC you are still looking at a minimum resolvable load of around 7W.Then you need to consider that ADCs will typically get some jitter in the least significant bits - that can vary with temperature and the local electrical noise. You can assume that the bias and scaling elements are not 100% accurate and stable either - especially as the bias will typically be derived from the units own PSU.
So errors of only 10s of watts on a metering range that covers 24kW seems "pretty good".
So probably a movement of 1 least significant bit on the digitized current reading. To look at small loads like that with any accuracy, you will need to meeter with a much tighter range to get enough resolution.
(Imagine if you were using a DMM set to the 10A range while looking of low mA changes in the readings).
For entertainment, I built one:
Its nice but note it does not account for the power factor. Most modern devices use switched mode PSUs and present a highly reactive load to mains. This means this will over-read for many loads, especially for devices in standby, LED lamps etc.
Dave
When you say does not account for the power factor, could you clarify what you mean?
After all it does calculate the pf, display it on screen, and show you both the VA and real power loads on the display...
Indeed...
One question - of purely academic interest to me as I've no ambitions to build one. If (please read a BIG if) I u/s correctly "emon.calcVI( 20,
2000 )" means the readings are an average over 0.2 seconds, updated every 2 seconds. Left me wondering about what - if any - differences there are in practice* from that compared with - say - averaging over 2 seconds. *I wouldn't count as "in practice" for this purpose edge cases such as lights that flash every 2 seconds :)
you are right I mis-read the article. And current transformers are cheap enough to build a multi-sense version....
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