Current Sensing?

  • Hardware Contributor

    I would like to just float these questions around here and see what peoples views on this topic are:

    Current sensing, do you guys like the implementation of this in the IoT and Home Automation sector?

    Do you prefer the idea of individual nodes monitoring their current usage or do you prefer a master current measurement using something like a clamp style hall-effect sensor around the main input to the house or even a flashing LED monitor on the electric meter to your house?

    Please include as much opinion as you would like, or just your answers. Would like to hear of past experience with any of these styles of current sensing options if you have any, any issues such as inaccuracy of one compared to the other if any.

  • Admin

    I use a combination of things:

    • A total house consumption using blink sensor.
    • A few claps on the big (variable) consumers, like water heater, heat pump etc.
    • Calculated/fixed consumption on small consumers like (none dimmable) lights.

  • Hardware Contributor

    @hek - Do you find a need to use one type over another or is just what is installed on the module that dictated this? Do you have any reason to think one is more accurate than the other at all?

  • Admin

    It was installed pre-mysensors, so I used the (z-wave) modules available back then.

  • There is a company that is identifying power loads with a little wifi box and some ct clamps on the incoming mains. I saw a demo on an american tv show called this old house(no irony there, right). They were at least able to identify big loads ovens and clothes washers. It appeared to be cloud based, so i'm out, but the concept is intriguing.

  • Hardware Contributor

    @wallyllama - I'm very interested to see how accurate these clamp style or the LED FLashing readers actually are. If they are, i don't see the need for general current monitoring on nodes (unless you need for safety implications such as auto turn off etc etc)

  • @Samuel235 here is a link to the video. It was impressive. Im not going to advertise for the company, but you can find them withnsome simple searches.

  • Hardware Contributor

    This is a very interesting watch if ever you're concerned about the resolution of the readings from the clamp style method. There is nothing saying its accurate but it is obviously grabbing data in high resolution. I have a smart meter here at home and i think i would be able to check the power usage there while using a node with clamps on the input to the house and compare them. If they are pretty similar i think it may be safe to say its accurate enough for our application with a resolution that is pretty impressive. I will post my findings here over the next few weeks and compare my findings to the smart meter. I may even make a flashing LED node too to see what that is like compared.

    Do we know if the flashing LED on electric meters are different for each country or are they a standard protocol of flashing sequences/timings?

    Aside from being used for safety implications, do you see any other advantages of using current sensing on the modules themselves apposed to an overall reading of the house?

  • Mod

    Flashing led on meter is defined on the meter so you need to adjust code accordingly.
    Measuring overall power usage or for individual loads, it's up to you and the amount of details you want to have. If you want to measure individual loads, there is sonoff pow that is quite cheap.

  • Hardware Contributor

    @gohan - Ahh okay, I'm yet to do research into the flashing light LED method, so thanks for pointing that out.

    I'm not after pre-built modules that do current sensing, i'm simply questioning what the personal opinions of our community are, as I have modules that I make that currently do current sensing on-board, but contemplating removing the current sensor and just monitoring the main input to the house 🙂

  • Mod

    If you monitor overall power usage and also ofr some specific appliances you could choose to set rules to cut power to let's say dishwasher or washing machine if overall power usage is exceeding a certain limit in order to prevent the main switch to cut power to the whole house (I am planning to do that later this year)

  • Hero Member

    @Samuel235 My main energy monitoring for AC is individual [p0] ( . These are pretty neat as they display the consumption as well as send a pulse for each Watt hour (precise and low cost). You can calculate actual power and consumption from the pulses.
    On my project list is an intelligent solution which looks at the specific dissipation pattern of typical household items. Something like is doing.

  • Hardware Contributor

    @gohan - This would be the safety measure that I referred to as 'safety concerns'. This is the only real reason i can see this becoming useful on a per node basis, because lets face it, it takes all over 1 minute to calculate how much power a 50 watt bulb is using.

    @AWI - I love your meter project dude, nice work! That product is what @wallyllama mentioned earlier but without promoting their name. TBH, I wanted to keep it to a mysensors device rather than using WIFI to link to my controller. Either way, they're just using CT clamps to monitor the current coming into the house on the input electric feed, grabbing data in the box and sending it via WiFi to the network. I've just ordered a CT clamp meter and when it arrives i propose to make a module that monitors the input line for the house. If that exceeds 100A (which i have a feeling it is) I will purchase more and then attempt to monitor the lines that are coming out of the breakout board, which could possibly be the better idea anyway. Can then have different readings for the lines in the house, downstairs and upstairs lights on two channels, sockets on another, cooker and extension and exterior buildings on other lines.

    I feel yet another module build coming!

  • Mod

    I have seen the Sonoff pow sending out data very quickly if speed is what you are looking for. If you are concerned about safety, just use a fuse.
    Could you please clarify if you are interested in reading power (W or watts per hour) or current (A)?

  • Admin

    Would be great if someone could design a mysensors open hardware board for reading the power meter blinks. One that could be mounted on the meter directly.

  • Hardware Contributor

    @hek - Are you requesting such? 😉

    I wonder how different meters are across the countries we're located in....

  • Mod

    the problem is that they are not the same from country to country

  • Admin

    When googling images of residential power meters they don't look that different to each other. The biggest difference is if they're squarish or round.

    It might be hard to mount the full sensor with batteries on all types without hiding the digital display. So maybe the "eye" must be on a optionally brake away child board.

  • Hardware Contributor

    I will take a look at this once i have my AC double relay with switches sorted. Talking of such, would someone like to take a look at my code to see if i have written any issues in there?

    Don't rely on me getting this made quickly though, too many projects on the go at the moment, but it sure is on the list to do!

    I will start doing some research into the different types of boxes. It maybe a case of just making different enclosure designs to be 3D Printed for this module. Maybe a daught-board config like you're suggesting too @hek.

  • Hardware Contributor

    i've already thought about designing some power monitoring stuff, but i saw there are already nice opensource hw at emon, and didn't want to reinvent the wheel..
    for instance :
    the arduino shield is pretty cheap imho, can be mysensorized as it's rfm69 compatible, or not so hard for nrf as it's a shield
    there's also an optical meter connect it to your favorite node, sensebenber or others homemade, you should be almost done 😉

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