Reading led pulses on Energy meter

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pengoomeister

New Member
Hi,

I am about to build an led pulse reader for my energy meter, I think I know how to build the circuit. But, can someone lead me in the right direction regarding the PICAXE code?
 
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dennis

Member
If you do a search for "Timing Pulses over a wide range" you will find some posts starting on 25/10 2009 that go into this. Count command is not suitable if yoiu have a UK style meter that flashes only every 1Wh
 
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eclectic

Moderator
First, have a look at this thread for a working system:
http://www.picaxeforum.co.uk/showthread.php?t=13694

Then looking at this thread,

http://www.picaxeforum.co.uk/showthread.php?t=11589&highlight=electric*+meter+LED

you could use “Interrupt” , using say circuit 2 here

http://www.fairchildsemi.com/an/AN/AN-3005.pdf


Simple example
Code: 
#picaxe 08M
symbol counter = w0
setint %00000010 , %00000010
;interrupts if pin1 is high

main:
goto main

interrupt:
if pin1 = 1 then interrupt
; waits until pin1 is low

counter = counter +1
sertxd (#counter,cr,lf)

setint %00000010 , %00000010

return

e
 
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papaof2

Senior Member
Would the proper interpretation of the "1000 imp/kWh" label be: 1000 impulses per kilowatt hour? If so, that's 1 pulse per watt hour - which could be quite fast when an appliance is in use...

John
 
slimplynth

slimplynth

Senior Member
I'm not at home so can't try it (please don't burgle me :D) but is there likely to be an issue with a 433 Tx sending to the PC i.e. noise from the meter/the ring circuits etc?
 
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manuka

Senior Member
All manner of such clever non invasive "winking LED" meter readings have been done in recent years. Google! Aside from PICAXE LDR & "count" etc, approaches using cheap USB video cameras feeding PCs running suitable motion detecting software may appeal. Some can even read analog. dials.It's quite legal, & unlike "Current Cost" plug in/clamp style apparent power (VA) sensors, the true power consumption (Watts) indeed will be shown.

Keep in mind however that diverse TOD (Time Of Day) billing rates & service charges may greatly influence the eventual $$$ charge. No doubt my NZ domestic rate is typical -3 different pricing periods, plus a FIXED daily "service charge" & then eventual GST taxes levied. That's right - a tax on a tax, but a prompt payment discount may apply. Estimated readings also arise when the likes of our dog keeps the meter reader away - "GOOD BOY"! The bill gets so confusing that raw PIC programming looks a breeze in comparison. During closed up home periods, holidays or over the summer etc, these tedious $$($) extra charges may be higher (sometimes by an order of magnitude) than the actual $($) energy cost!

But back on topic -stray light is often a hassle for indirect LED reading. Here in NZ my home's NILSEN EMS 2100 smart outdoor utility meter (c/w compulsory cabinet reading window) is bathed in direct sunlight at times, & this fools even a significantly masked sensor.

In my experiences boring aspects like the project power supply & wires trailing to your PC eventually tend to limit the appeal of such a project. SWMBO ("She Who Must Be Obeyed") can find these an eyesore & threaten to turn off your beer fridge etc in protest. Although scope for wireless links (433 MHz/ZigBee?) may arise (& utility companies increasingly fit these for drive by/walk by billing anyway), a grunty battery pack will be needed to handle "always on" DIY readings. Heavy loads mean rapidly flashing LED rates, so even simple PICAXE sleeps are not feasible.

FWIW: I've a mate cursed with a poorly sited high/dark/cobweb covered switchboard,who just mounted a small cheap USB PC camera (& illuminating LED) for more convenient views of the dials from his PC. Such a PC cam approach has appeal for snail mail postboxes - or even rooftop views over the neighbourhood etc! Stan.
 
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dennis

Member
I think you need to decide exactly what you want to do as the approach needed may differ. My main interest is as near an immediate real time display of actual power used as possible. To my mind this is the most fun. I can wander round the house with the receiver and look at the power change when various stuff is unplugged. If you just want an hourly average things are much simpler as you can just count meter flashes every hour.

It looks like your meter has flashes every Wh like mine.
My suggestion is to estimate your minimum and maximum power consumption and what that means to the interval between flashes. For instance at 10 kW there is only 0,36 secs between flashes whereas at 50W you 71 seconds !

If you live on the upper floors of one of those big concrete apartment blocks and the meters are grouped in the basement then I think a radio link is going to be demanding and as Stan mentioned you need to find a way to power it.

On the other hand if you live out in the country in a typical wooden house with the meter in the garage near a convenient mains outlet then I think the task is pretty simple.

I use a small LDR from Rapid electronics and that picks up the meter flash without problems even if the lights are on (see the manuals for the interface circuit and change the resistor if required to avoid false triggering by external light. A rubber patch (old bicycle inner tube) is simply taped to the meter. For me this was a good starting point and I counted flashes over a couple of days and compared these to the meter reading to check that none were missed.

There seems to be no interference issues with the 433MHz AM unit (Maplins cheapest a couple of years ago) and transmissions go through a brick cavity wall and another interior foamed concrete block wall without problems. I think I have been lucky because when I first tested these units a couple of years ago the range was only about 1m line of sight !

Once you can reliably detect flashes the easiest (though not accurate at high power rates) is just to feed the data into a spreadsheet and use the PC clock to determine the time interval. (a free download is the Parallax DAQ). I think this is a good start and then add the wireless link and then add further complexity depending on what your needs are.

I live in the UK but am in Karlstad all this week !
 
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Andrew Cowan

Senior Member
I think that the hard part will be mounting the phototransistor/LDR, and blocking ambient light. Let us know how you get on!

A
 
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nbw

Senior Member
@Stan - a tax on a tax? Our government would never do that to us, would they? Oh wait, there's GST on the tax on petrol. Or do they call it a 'levy' to make us feel better?!?!? ;-)
 
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ciseco

Senior Member
Hi,

Mounting wise (I use a Vishay part its 53 pence link below) I drill out a piece of perpex to mount it in (push fit if you are tidy) and stick the whole thing to the front using "sticky dots" you can get from tescos as they are translucent-ish

This TCRT device, I use a pot to vary the LED emitter so I can read analog gas/water meters too (works really well, tried 8 different devices this was the cheapest that still worked well). Doing an electricity flash LED jobbie, just dont use the IR LED. Because it's IR it works better in changing light conditions if you fancy trying the analog meters.

Somewhere I have the circuit and picaxe code, neither will be pretty, I might be able to dig them out. Nothing complex for LED though, just input high/low. It's doing the analog "rolling numbers" ones needs code to realise rising/falling edges etc.

http://uk.farnell.com/vishay-siliconix/tcrt5000/sensor-optical-transistor-o-p/dp/1470066&crosssellid=1470066&crosssell=true&in_merch=true&

http://www.popartuk.com/general/accessories/sticky-dots-sd1-accessory.asp



Miles
________
starcraft replays
 
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