Door Bell usage detection / AirFlow usage detection/cutting


  • Hero Member

    Hello,

    I have two (example) devices I would like to monitor, one is activated by some likely pulse of 24V, the other running 240V for a period of time.

    For both I would like to monitor if they are being used, one is a pulse, the other can be a longer use, and maybe cut the use.

    What I am thinking so far is maybe:

    • have a current sensor carrier in the first case, and have it transform to an impulse maybe using the time debouncing of my water sensor.

    • have in serial for the second a current sensor carrier and a relay for the second on the input (240V) both on the same arduino.

    The current sensor carrier I have seen is the ACS709 ( low-resistance (~1.1 mĪ©) current path and electrical isolation up to 2.1 kV RMS).

    What do you think of it ?


  • Hero Member

    I like the way you're thinking! I have a similar problem where I too want to monitor a wired doorbell. The transformer says AC 12V 1A (but I've only measured 8V at the chime (trms problem with my multimeter?), amps when triggered unknown since I can't measure AC amps). Got tangled up with rectifiers and optocouplers but this type of current sensor you mention looks a lot easier.

    On a similar note, since the transformer seems perfectly capable of running the doorbell button lightbulb 24/7 for the past fifteen years or so (what a waste of energy right?), I figured I might steal some power to run an Arduino sensor or two while I'm at it (one in the hallway by the chime, one outdoors by the button). For that purpose and because I'm lazy and finding it hard to source electronic components for actually building something myself, I got a couple of these converters from Ebay.

    Edit: Ordered a couple of acs712 modules from Ebay for the doorbell. They were cheaper and easier to find. Seems like a solid idea. Haven't seen this item in the store yet? Could be pretty useful, too bad that it is obviously sensitive to magnetic fields. And that all these modules seem to have a bloody LED on board šŸ™‚

    Edit2: Dang. ACS712 only runs on 5V (?) as opposed to the ACS709 you mention which seems fine with 3.3V-5V. Oh well, since I'll power this Arduino from the doorbell transformer itself I might just as well get a 5V Pro Mini. Or use the RAW pin, feed the sensor directly and then a level shifter for the sensor control signal. I don't really know.


  • Hero Member

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  • Hero Member

    @bjornhallberg Hello,

    I've seen today the rboard which is more expensive but more concise.

    For the energy monitoring chip, you would need the emonlib to get some correct reading, and even do a calibration.

    With this you could do some sort of Wall Plug as in z-wave... What do you think ?

    Emmanuel


  • Hero Member

    @epierre Sure, that would nice be if it could be done. I've looked at the (fibaro?) wall plug you mentioned. It seems like quite the feat of engineering. Even fibaro couldn't do it apparently as their plugs got a sales ban šŸ˜‰ I noticed how the openenergymonitor shields and boards all seem to use non-invasive clamp meters. Far from the convenience of the wall plug (and not as non-invasive in practise). And how does all of this factor in with true rms and all that. Are the fibaro wall plugs able to correctly measure / calculate trms? How DO they measure current? Through induction / hall effect as well? So many questions šŸ™‚ This could be something that the MySensors staff could look into building as an official module, just like the battery board currently being prototyped, only running off mains AC power instead. Add some RGB led strips and it would be almost as nice as the fibaro.

    For now I'll be happy to just sense the doorbell. And perhaps use one as a sort of power outage detector (like a security measure to see if someone has short-circuited the power grid or pulled a fuse).


  • Hero Member

    @bjornhallberg For the Wall Plug, there has been only sweden to react, noone else... a real issue ? @Hek has kept all his šŸ˜‰

    The ACS709 does not seems to be available on boards... so a step-up may be needed ?

    I'll try to see if I can sketch something interresting this way, reporting energy may be a plus feature that could be quite easy to add...


  • Hero Member

    @epierre The fibaro wall plug scare was probably a bit unnecessary.

    I couldn't find the ACS709 on Ebay or AliExpress at least. I ordered a couple of logic level converters to move signals between 3.3V and 5V without damaging the Arduino. Don't know if this is the smartest way to do it though. And the ACS712 has to connect to an analog input only. Hmmmm. What are the implications ... it might not matter, I will not run it on batteries anyway, and it'll have to coexist with a motion sensor on the same arduino.


  • Hero Member

    @bjornhallberg have you come through it yet ? I'm searching for it now and it is hard to find how to make it correctly


  • Hero Member

    @epierre I'm afraid I haven't gotten around to it yet. Partly because I have my CCTV that automatically feeds me images of whoever has the misfortune of stepping on the porch and triggering the motion detection so I haven't been in any great hurry exactly. I have all the components around here somewhere though.

    Don't know if the ACS712 + logic level conversion is still the easiest approach or if we're over-complicating things here.


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