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  1. #1
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,197

    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.

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