I know the thread's about sub meter monitoring - but how would one go about monitoring entire usage? My thought was to physically connect some sort of photodiode arrangement to the front of the led flashing in my meter, and then count pulses from that. Or am I missing something obvious?
Jon,
You certianly could do just what you have described and someone has written a web page on how to do this with 1-Wire:
http://www.btinternet.com/%7Ejon00/electmon.shtml
In the sub-metering as described with 1-DIN units Cortex can also show a cumulative collection for total house usage as well as individual readings per ring-main.
Paul
Sub-Meter Electricity Monitoring
AH also had a thread on this maybe a year ago ... inconclusive, though, IIRC ...
presumably pulse-counting doesn't tie Cortex up - or does it ??
Nope, don't believe it does from what I remember with chats with Vivian and Karam. The ODI and other digital interfaces can count locally and then package the information together in a network package for sending to Cortex.
Paul
Slightly off-topic but .....
Hmmm, I was looking at that thinking that looked like a fairly neat & accurate way to find out how much power our house uses over time - it's small and only has one ring main and two lighting curcuits so monitoring things individually might be overkill.Originally Posted by Paul_B
And then I went off at a complete tangent. The downstairs of our house is all open plan so there are no doors for Cortex to monitor to tell if people are moving from room to room so you have to rely on the PIRs triggering, but looking at the kit this project is based on (the Velleman IR Light Barrier http://www.velleman.be/be/en/product/view/?id=342937), I started wondering if you could use that to create a "virtual doorway". When the beam is broken you tell Cortex a door between the rooms has been opened same as you do with a reed swtch for a physical door. Could do the same thing with the stairs as they open directly onto the living room and at the moment you can't tell if someone is going from the living room upstairs until they trigger one of the upstairs PIRs. If you placed one on the lower steps you could tell someone was going upstairs almost immediately.
What's people's opinion - do you think it would work ?
Jamie
Sorry for hijacking the thread somewhat but thanks for that! I think a trip to Maplins at the weekend is on the cards.
Jamie - would it not be much simpler to use a pressure mat?
http://www.connectstores.com/P.E.D/sp_2086-20.html
Cheers
It'd probably work on the stairs but the downstairs is all hard flooring so nowhere to hide the mats :-( Hence the thought about a beam to create a virtual doorway.
Jamie
I think a single photo-transistor tied straight across the digital input terminals via a screened cable might be able to do the job simplty and cheaply but I haven't got one on hand to try and am too lazy to try and guess irradiance level from the meter LED, but you need to get enough light to get ~ 0.6mA through transistor to detect an ON LED. Obviously it also has to get dark enough when LED is off. Go for an NPN one which has a an optical rather than IR spectral response (though usually the response will spread to optical ranges with less sensitivity). To reduce effects of ambient lighting and improve contrast shroud the viewing window with an externally dark tube so transistor can just see what's infront of it. Even better if tube goes all the way to meter LED.
Karam
IDRATEK LTD
Light barrier
A light barrier or retroflective sensor such as the Sharp (GP2D12?) may well help in this situation. Certainly Cortex v23 has an object representation for such a sensor (for connection to a digital input object). I think the results will depend on the detection patterns for such sensors but also what you want to achieve: We are aware of the need to consider open plan spaces but it also comes down to what type of automation might be required in such spaces even if you could zone the presence accurately. For example would you want lighting to behave as if each zone were a different room? Also how to deal with light level spillover, and so on. So its partly about sensing (and positioning of such) and partly about desired behaviours.
Karam
IDRATEK LTD
Pulse counting
Just so that you get this from the horse's mouth :-) :
Some (but not all) modules with digital inputs have a pulse count feature. As others have suggested, this means the module counts pulses within a certain time frame and only then sends the data to Cortex. This avoids the network being hogged by a packet every pulse - though let me tell you that one of our Polish installations actually tied the output of an anemometer to a non pulse count digital input and still happily ran their network alongside several pulses a second on a windy day (NOT RECOMMENDED). The counting time frame is a settable parameter and the value chosen gives a balance between network hogging and rate of information update. For electricity metering it is typically set to 1 minute. And whilst on this subject, when you choose a meter make sure you look carefully at the resolution (how many pulses per Whr) since it obviously determines the resolution with which Cortex can estimate consumption rate (as opposed to consumption).
Modules which presently have Pulse count feature on digital inputs are: QRI, QRH, ODI, DIO (newer variants of latter two). If in doubt ask before assuming :-)
Karam
IDRATEK LTD
Posting Permissions
Reply With Quote