At the risk of being seen to do something non-cool but practical...

[Ken]

Does anyone have experience with modern electicity meters?

Silicon Chip magazine has a circuit-ideas article on reading, sending, & displaying, the one pulse per watthour LED on electricity meters.
(I didn't know there was one!)
It uses a Picaxe to send over 433MHz, and display on 7-segment digits.

My current electricity meter has the old turning disk.
The one in my new house is modern.

I have a gadget that measures the currents in three phases and sends to a console inside.
But it is not too accurate (doesn't measure voltage or current phase), and doesn't connect to a PC too well.

I feel a project coming on.

Ken.

[Steve Roehrs]

Hi Ken

 

My meter collates data for every half-hour interval over the day and sends it to Origin nightly via GPRS.  It also uses Zigbee to talk to an in-home display that shows the instantaneous power being drawn, as well as current days graph and historical graphs, and weather reports.  Unfortunately the display doesn't handle my solar export, and apparently the zigbee protocol is completely locked up (i.e. encrypted) and the metering people (Metropolis) aren't about to hand out the keys so I can read it.

 

So, the only hacking has been writing a script to download the usage (import/export) from their website every morning, throw it in a database, merge it with the solar generation data that my inverter sends out, and draw pretty graphs.  If I had something that could read the kWh pulse LED as well that'd be great, so I could display instantaneous power draw.  Count me in as interested :)

 

Steve

Ken.

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[Scott B]

Has anyone done anything with image recognition?

 

If you want instantanious data then CT's and a voltage tap is the only real way to do it, but it is a bit involved to get accurate (taking in to account RMS and power factor etc).

 

You can buy commercial power meters that do it all for you, and have a modbus interface so that you can talk to it - but you won't get much change out of $1000 for one of these.

 

If I had the time and knowledge, I was thinking of just pointing a cheap webcam at the power meter, and trying to use some kind of image recognition to simply read the numbers on the meter as it scrolls through them non stop all day/ every day... that way you are 100% accurate to your ETSA meter, however generally you will only be able to get import/export/offpeak kWh - unless you rig up a servo to push the button every now and again, then you could also get instant volts, amps kW etc.

 

On Thursday, June 28, 2012 1:32:37 PM UTC+9:30, Steve wrote:

Hi Ken

 

My meter collates data for every half-hour interval over the day and sends it to Origin nightly via GPRS.  It also uses Zigbee to talk to an in-home display that shows the instantaneous power being drawn, as well as current days graph and historical graphs, and weather reports.  Unfortunately the display doesn't handle my solar export, and apparently the zigbee protocol is completely locked up (i.e. encrypted) and the metering people (Metropolis) aren't about to hand out the keys so I can read it.

 

So, the only hacking has been writing a script to download the usage (import/export) from their website every morning, throw it in a database, merge it with the solar generation data that my inverter sends out, and draw pretty graphs.  If I had something that could read the kWh pulse LED as well that'd be great, so I could display instantaneous power draw.  Count me in as interested :)

 

Steve

On Thu, Jun 28, 2012 at 1:23 PM, Ken <k...@waggies.net> wrote:

Does anyone have experience with modern electicity meters?

Silicon Chip magazine has a circuit-ideas article on reading, sending, & displaying, the one pulse per watthour LED on electricity meters.
(I didn't know there was one!)
It uses a Picaxe to send over 433MHz, and display on 7-segment digits.

My current electricity meter has the old turning disk.
The one in my new house is modern.

I have a gadget that measures the currents in three phases and sends to a console inside.
But it is not too accurate (doesn't measure voltage or current phase), and doesn't connect to a PC too well.

I feel a project coming on.

Ken.

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[pault]

For anybody with the old style spinning wheel meters, there is a
sensor made by
Black and Decker USA that senses the black stripe on an old style
meter wheel as it spins

http://the-gadgeteer.com/assets/black-and-decker-power-monitor-9.jpg
http://the-gadgeteer.com/2008/11/21/black_decker_power_monitor_review/

My guess is that its just an infrared diode and receiver, that senses
the different intensity
of reflection between black and white, the infrared is possibly pulsed
at
about 38khz so that ambient light effects can be filtered out in the
same way
as tv remoted controls work.

Should be buildable but attaching it to Australian meters might be a
bit harder
than attaching to those round American ones.

--paul (the lurker)

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[Damien P]

On Thursday, June 28, 2012 4:07:12 PM UTC+9:30, pault wrote:

For anybody with the old style spinning wheel meters,

I'd thought of pointing a laser at the wheel, and measuring the reflection with a phototransistor.  The laser would probably only need to be on 5% of the time.  The light should be fairly dull inside the power box.  Like you said though attaching it would be a bit difficult.

[Christopher Yeoh]

and won't freak out the meter reader at all :-)

Chris

[Ken]

Well I've moved into my new house and had a peek at the electricity meter.
It has a one-pulse-per-kwhr LED, and another one whose purpose I'm not too sure of.

But when I think on it more, while it would be nice to graph the exact usage over time, the LED isn't going to update too often under light load/usage.

So I'd still like a power reading that updates frequently.
The unit I have does it every 6 seconds, but isn't hugely accurate, and doesn't interface usefully to a computer.  (Only gives a history, in a proprietary format.)

I think the electronics and maths etc are too much hassle to do from scratch (for a lazy person like me).
-Needs to measure 3 phases of current, power factor, voltage, calculate instantaneous power on each, then send to a remote point.

So if anyone is aware of any gear that can be bought for this purpose (at hobby type prices), I'd like to hear from you.
Failing a bought unit, I'd need a fairly fast micro to measure all those values, compare phase and calculate, 3 times over.

Ken.

[Scott B]

are you sure its one pulse per kWh? not 1 pulse per Wh?

[Ken]

Sorry, yes Scott.
So at 100W load, the updates would be every 36 seconds.  (Please check my maths.)
It is probable that most of the time I'll be using enough juice to get reasonably short update periods.
I'll give it a go to find out.

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[Scott B]

yep 100W load would be 36 seconds between flashes.

so if you counted flashes per (say) 5 minute period, you would have about a 12W accuracy - which should be plenty accurate enough to know whats going on.

Generally a house will run at 50 - 100W background (a couple TV's etc on standby, a PVR, a modem, perhaps a second wireless router, clock radio's etc), if a fridge kicks in it that will be another 100 - 150W, and as soon as a TV goes on, heaters cooking appliances etc it sky-rockets from there.

Do you have solar panels? I haven't checked mine yet, but i suspect the same LED flashed for import and export, so this could make things a little more complex.

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[Paul Schulz]

You might also get an interesting story to tell.. (for those that missed it)
http://www.rowetel.com/blog/?p=2381

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[Ken]

Good one Paul. :)
I've been able to do similar (but not party busting) with just the weatherstation.
On a hot day when I am at work, if there is a dip in the house temperature, I know the airconditioner has been turned on.
Since I don't have any kids at home now, I don't expect to be catching anyone out.

My weatherstation has got a bit tired -plastic deteriorating, an anemometer cup busted etc.  So I've just today ordered another one off eBay.
Once it arrives, I get my server back on the air, and get ADSL, I'll be able to read it over the net.
And I'll probably be setting a up a webcam again.

If anyone else is interested, less than $100 buys a reasonable (cheap Chinese) wireless weatherstation which measures indoor & outdoor temperature, atmospheric pressure, wind speed, rainfall, with a console for viewing inside, and a USB cable for connecting to a PC, where open-source software can read it (or you can use the crappy supplied Windows S/W).

Ken.

[Damien P]

On Thursday, June 28, 2012 1:23:54 PM UTC+9:30, Ken wrote:

Silicon Chip magazine has a circuit-ideas article on reading, sending, & displaying, the one pulse per watthour LED on electricity meters.

Here's a gadget to monitor your energy use. It looks like you clamp a sensor around one of the cables leading into the power box.

http://www.catchoftheday.com.au/smallfish_info.php?event_id=1521

[Ken]

I have an efergy unit, which connects to a PC, and takes three sensors for 3-phase.
It works OK, sort of.

Caveats with that unit from catchoftheday:
Doesn't connect to a PC, can't log or make readings available on the net.
May only take one sensor input, so probably only works on one phase.  (Doesn't say.)

Caveats with the unit I have (with 3 sensors):
Connects to a PC via USB, but program is Windows only, protocol is unknown, can only put history onto the PC, not current values.
Doesn't measure voltage or phase, so readings are somewhat approximate.
Can't do 3 phases and J-tariff, its either/or.

Caveats with all those gadgets:
Can give you a shock when you see how much juice you are using.

I'd look elsewhere if you want accuracy or net-connectedness.

Ken.

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