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  1. #1
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    Cool DIY ammeter - dead cool

    Well that was a productive couple of hours. Been thinking now and again with this idea for a while and finally stuck it in a case and wrote a little code to make it work, little baby steps but successful so far.

    So what we got is >>


    The bigger board at the bottom is an ESP8266 - like a arduino with wifi, very cool board and capable of doing lots - it has wifi built in. Then the little board bottom right is an INA219. Another great little board, it can measure up to 32V and up to 3.2A *REALLY* accurately. So they say anyway, I have nothing anywhere near accurate enough onboard to check. The battery isn't connected yet but it will allow the unit to run without being plugged in.
    So 12v goes in then out again and into something (which uses less than 3.2A) The the ESP measures the current and voltage and sends it over wifi. The laptop reads this and a great program called node-red will display it. Or save it to a file, or loads of other options. So this is what a Nasa AIS engine draws....>>



    The next stop down the road could be even better - it *should* be possible to connect this to the battery monitor shunt. Says google. Hard to guess the accuracy but apparently down to a few hundred mA. Which would be great, I've a Raspberry Pi recording loads all day every day already so having amps in/out would be nice to keep an eye on the batteries. Then, even better if it works - it might be possible to do a constant current load test - Without turning anything off!! Maybe. Have an external load controlled by the ESP with a few mosfets so the actual load coming out of the batteries stays constant -fridge goes on, external load goes a bit less. Unlikely to go all the way down to complete discharge at anchor but on a living on the hook cruising boat it would just great to do a partial load test once a month and graph ontop of other months to see it the batteries are happy or close to death. With temperature logged as well of course!


    Phew......
    Last edited by GHA; 06-06-18 at 21:21.

  2. #2
    Join Date
    May 2001
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    Default Re: DIY ammeter - dead cool

    Isn't this rather sad? Is this what boating has become?

  3. #3
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    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by pvb View Post
    Isn't this rather sad? Is this what boating has become?
    What do you do at home? Don't you have any hobbies? Rather sad. Maybe why you're always so negative....


    Forum: Practical Boat Owner's Reader to Reader

    Share practical, hands-on information.
    All positive posters welcome, I'll stick the code up if anyone is interested

  4. #4
    Join Date
    May 2005
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    up on the moors.
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    33,154

    Default Re: DIY ammeter - dead cool

    Nice work GHA. Good to read how practical boat owning is pushing forward the boundaries. If it makes quality of life a lot better on board - and safer, too ! - then that's even better.


    EDIT Overlapped PRV's contribution. I can only assume that he uses hemp ropes, and a large stone with a hole in it for an anchor. Sad, innit.

    EDIT 2


    Looking at the sampling rate for the program... the display is rate 1sec, but is the input more frequent ? I am wondering if it could track surge uses of e.g. engine starter/anchor winch, and see how near the fuse capacity the system is demanding.
    Last edited by sarabande; 06-06-18 at 21:30.
    I think, therefore I am. I am, therefore I sail.

  5. #5
    Join Date
    Oct 2017
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    solent
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    Default Re: DIY ammeter - dead cool

    I love the way there is a marriage between high and low tech in yachting. All this Arduino stuff has so far pretty much passed me by, but it is interesting to see what others do with it. One day I will have a go myself. Beats jamming components into a breadboard and relying on dodgy old 555 timer chips for everything!

  6. #6
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    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by GHA View Post
    What do you do at home? Don't you have any hobbies? Rather sad. Maybe why you're always so negative....
    I have loads of hobbies, and sailing is one of them. Lots of sailors survive quite happily without even a basic ammeter, let alone a wifi-enabled recording jobbie. This is supposed to be a Practical Boat Owner's forum, not nerds unlimited.

  7. #7
    Join Date
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    Default Re: DIY ammeter - dead cool

    OK, PVB, electronics may not be your bag, but for some people knowing discharge rates to a 1/10A may be part of the fun of sailing. I know a distinguished and gallant forumite who would really really love to be able to track air pressure to 0.1mb, and air temp and rel humidity to a similar precision.

    It would be hard to get a more practical demonstration of Solent's "marriage between high and low tech in yachting" than GHA ammeter.

    What's the cut-off point for tech gear on your boat ? Do you have DSCVHF, an echo sounder, any LEDs ? I am not suggesting we all go out and add foils to the hull, or change our solid long-life terylene sails for one-season laminates, but there has to be acceptance of progress, or you end up being a less competent, riskier, unsafer sailor.
    I think, therefore I am. I am, therefore I sail.

  8. #8
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    solent
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    Default Re: DIY ammeter - dead cool

    I do have one criticism, that project box is way too big, don't you know small is beautiful these days. Has to be on our little tub anyway! As for boats and hi tech, we had a lovely sail marred this evening by the departure of the Princess of the Sea, I kid you not, it left Southampton docks with a TV screen on top of the thing, about as big as two semi detached houses, visible from a long way away, and playing La Macarena through a very loud music system while the Dj implored all on board to clap their hands. Then the ships horn erupted not with a log sonorous moan, but a full tune worthy of an ice cream van... The days of the White Star line are truly gone. Maybe you could invent a noise cancelling cockpit device for us?
    Last edited by solent clown; 06-06-18 at 21:49.

  9. #9
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    May 2001
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    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by sarabande View Post
    What's the cut-off point for tech gear on your boat ? Do you have DSCVHF, an echo sounder, any LEDs ?
    Yes, I have DSC VHF, full instrumentation, AIS receive, plotter, radar, 2 handhelds, autopilot (interfaced to wind), 3 battery banks (one for the thruster) and LED lighting (both inside and nav lights). But I don't have an ammeter!

  10. #10
    Join Date
    Aug 2004
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    682

    Default Re: DIY ammeter - dead cool

    Well i think this is rather cool!

    I would be interested in the code (github?)

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