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Thread: Measuring current and/or wattage with Arduino

  1. #11
    Anodized. Again. Konrad's Avatar
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    Default Re: Measuring current and/or wattage with Arduino

    Inductors ... ick. I found a decent linky here.
    My mind says Technic, but my body says Duplo.

  2. #12
    Resident 100HP water-cannon operator SXRguyinMA's Avatar
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    Default Re: Measuring current and/or wattage with Arduino

    cool I'll check that out. thanks!

  3. #13
    Will YOU be ready when the zombies rise? x88x's Avatar
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    Default Re: Measuring current and/or wattage with Arduino

    If you're still looking for a shunt, I've been looking around out of curiosity, and weirdly, I can't seem to find many. All of the ones on Mouser top out around 140A and are pretty expensive. I found these that are priced quite nicely and you can get from 20A ($6.50) up to 500A ($16.50). I've never heard of the store though, and I didn't see any reviews of them in a quick search. Really though, like I mentioned, it's just a chunk of metal with a very low, known resistance, so a bundle of 12ga wire or some grounding braid should do the job just as well (come to think of it, maybe that's why I can't find many ). In fact, one of the ones I found for sale on eBay was just that..some copper grounding braid with metal hookup clamps on either end.
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  4. #14
    Resident 100HP water-cannon operator SXRguyinMA's Avatar
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    Default Re: Measuring current and/or wattage with Arduino

    well I was looking through konrad's link and it looks like my best bet is to go with a classic positive supply rail current sense setup. the only problem I'm running into is finding 0.2Ohm precision resistors, and finding the LT1637CN8 in quantities less than 2500 lol

    this link, first page top right is the setup
    http://www.linear.com/ad/02-high_side.pdf

  5. #15
    Anodized. Again. Konrad's Avatar
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    Default Re: Measuring current and/or wattage with Arduino

    200mOhm resistors ... that seems a bit odd. Can you rework the circuit for a more common resistor value?

    You can try this if extreme precision isn't absolutely required.

    An alternative would be SMT resistors, like this one, or a 5% RMCF0805JTR200, or a 1% CSR1206FKR200. They'd have very low wattage capacities, though.

    Another alternative is to build a network from precision resistors to gain your final 200mOhm value ... again, precision may not be great if the combined tolerances are all factored in. You might be able to hand-match specific pieces, although you'd want to measure their values across the entire expected temperature operating range to assure best precision.

    You might gain best accuracy for such a low-voltage application by using a Wheatstone bridge (or similar balanced bridge) circuit.
    My mind says Technic, but my body says Duplo.

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