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  1. #31
    Join Date
    Mar 2005
    Location
    Essex
    Posts
    528

    Default Re: DIY ammeter - dead cool

    Thanks for sharing this. I too love tinkering with things electronic although keep my sailing fairly basic. Your elegant solution for a perceived need may well adapt well to someone else's need. Thanks
    David Morgan

  2. #32
    Join Date
    Jul 2003
    Location
    West Australia
    Posts
    11,518

    Default Re: DIY ammeter - dead cool

    Haven't actually read all of this thread, however it occurred to me that reading the title some members may be hoping for a simple amp meter. What may be very simple and useful is to use a digital multimeter on 200mv scale to measure volt drop from the big terminal on the alternator to the other end of that same wire. If the wire is long and not so heavy when the alternator is charging you will get a volt drop that is measurable. It might be convenient to bring a wire out from the 2 points to a place where you can touch the meter probes on. The volts measured will not give you actual amps but will give a voltage commensurate with alternator output amps. If you file this number away when you reckon the system is working fine especially if you keep a log of the number under various circumstances. ie battery low and also when well charged you could build up a sort of calibration in relation to correct operation of alternator. Of course if you can fit an amp meter or have access to a clamp amp meter you could calibrate your millivolt drop into actual amps. Just a thought for a very simple amp meter that does not require disturbing wiring.
    Note if you measure voltage from alternator to battery terminal this will be via isolation switch possibly diodes or VSR so while it may detect a fault condition will not be reliably indicating amps due to variable resistance in switch etc. Just check over the wire itself hoping the terminals are good.
    olewill

  3. #33
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,197

    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by GHA View Post


    The next stop down the road could be even better - it *should* be possible to connect this to the battery monitor shunt. Says google.
    And finally got round to crawling under the chart table to hook it up. Works! Yippee! Major leap forward in keeping an eye on battery health. The current INO219 current sensor is just attached across the battery monitor shunt with croc clips, it's a bit noisy at the moment but with some proper crimped short twisted cables that should hopefully get a lot better. Data goes as signalk straight into the Pi where a signalk app saves it into a database then easy to view after that.

    This a few hours discharge than back on with the charger.


  4. #34
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,197

    Default Re: DIY ammeter - dead cool

    And this is what a 3 hour equalizing cycle looks like (fridge still running)


  5. #35
    Join Date
    Feb 2009
    Location
    Greece (Aegean)
    Posts
    2,642

    Default Re: DIY ammeter - dead cool

    These things can grow. My Scheiber multi-display stopped working and I was tempted to build a replacement because the unit had several features I didn't like. I decided Arduino was the way to go and not too difficult to learn wrt code and circuit design.

    The project grew a little .

    1) Proved impossible to find a reasonably priced serial graphic transflective display with the correct dimensions. No room to fit a larger display and only render to visible part either. I finally settled on a parallel display, problem solved

    2) Available IO pins in short supply because the parallel display was using almost all of them. I considered using something with more IO pins or building a board to convert serial to parallel. The Ardiuno was so cheap that it was simpler and cheaper to use a second Arduino. One board handles the inputs from buttons and sensors whilst the second one runs the display side. The display Arduino acts as a slave and is controlled by a serial link from the other Arduino.

    3) I wasn't happy with the fragility of the original Scheiber unit as it didn't like 15V and I think a spike killed it. I designed an IO board to handle all sensor inputs up to 100V and also the odd spike (hopefully). It also included transistor switches to power backlight, fuels sensor circuit etc. on and off. The board uses 2 four channel ADS1115 ADCs.

    I copied look of each page on Scheiber unit and also used the original control buttons. It all seems to work, looks like the original (though display not quite as good as the original). One big advantage is that I could calibrate tanks to give meaningful readings. Original only gave a VERY general indication of fuel and water levels. New unit actually gives meaningful readings.
    Domestic: Volts & Amps
    Engine & Bowthruster: Volts
    Water level forward and aft
    Fuel level in litres
    Plus more features if I feel the need to extend it (e.g. display readings from other kit).

    Interesting little project for my first look at an Arduino and I'll certainly consider using these to fix a few other items I've been meaning to replace (e.g. Boat alarm with SMS alert, doubles as anchor alarm).

    Perhaps something a bit simpler might have been better, but as I said "these things grow".

    Last edited by Mistroma; 29-08-18 at 08:33.

  6. #36
    Join Date
    Mar 2006
    Location
    Surrey
    Posts
    8,489

    Default Re: DIY ammeter - dead cool

    Perhaps you could modify the circuits a bit to help poor old RichardS find the missing watts in his Smart Meter problem as mentioned in The Lounge!
    Gosport NCI - Call us on Ch 65 for a radio check if passing.

  7. #37
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,197

    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by Mistroma View Post

    Interesting little project for my first look at an Arduino and I'll certainly consider using these to fix a few other items I've been meaning to replace (e.g. Boat alarm with SMS alert, doubles as anchor alarm).
    Oh that's lovely!!

    Played with esp8266's yet?
    You should be able to just use the same arduino code but they can do so much more! With built in wifi you can create you own web page on board, send data to the web if you have access, lots of fun

  8. #38
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,184

    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by GHA View Post
    Well that was a productive couple of hours.
    So what we got is >>

    That's an ammeter ?

    This is an ammeter!


  9. #39
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,197

    Default Re: DIY ammeter - dead cool

    Quote Originally Posted by VicS View Post
    That's an ammeter ?

    This is an ammeter!



    Was that way back when we were all battery murderers giving them half hour engine when the lights got dim?

  10. #40
    Join Date
    Jun 2015
    Posts
    1,022

    Default Re: DIY ammeter - dead cool

    Amp meter still hanging around !1-P1010551.JPG

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