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Thread: The ACME computer/rebreather controller

  1. #21
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: The ACME computer/rebreather controller

    Hi Chris,
    Great. Thanks for the details.

    If I understand, you needed to add a preamplifier to increase the cell voltages to allow faster noise free measurments by your AD converter. I suppose you designed the input stage with a fixed amplification factor and control the calibration with software?

    How fast responding is your readout of cell ppo2 / mv? Is it essentially "real time" like a digital voltmeter?

    Are you going to give it a HUD device with warning lights, etc?

    Thanks,
    Mark

  2. #22
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    If I understand, you needed to add a preamplifier to increase the cell voltages to allow faster noise free measurments by your AD converter. I suppose you designed the input stage with a fixed amplification factor and control the calibration with software?
    Yes, I put together a preamp. It's actually more than just speed at stake. When I modeled putting the electronics in situ in the rebreather it appears it will be necessary on the low end of the cell output range to get a reading at all as the signal is on the threshold of what the ADC will take. The pre-amp is set up for variable amplification as it incorporates a rheostat. The way I have the software set up it doesn't care about the amplification but I have to respect that the ADC maxes out at 3.3V and I have taken that into consideration. I do have to make adjustments in the software if I want the option to read true mV's but that's not an issue.

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    How fast responding is your readout of cell ppo2 / mv? Is it essentially "real time" like a digital voltmeter?
    It's better than a digital volt meter in the sense that the ADC is capable of 384 ksps. The actual capability of the system is probably far away from this for a variety of reasons, but it's plenty fast. The speed with which I see the cell ppO2 readings is dependent on how I prioritize the other things that the software program does. Right now I have everything in a continuous loop of: update cell readings, update depth, time, and NDL, update ceiling, stop time and TTS, update current gf, gas mix and temp. The last three groupings of three items get 2.5 seconds each on one line of the display, and ppO2 is constantly shown on the other line. I have it set this way for debugging. I have in mind to intersperse updating of cell readings between the three other "screens" updates so I'll have that every few seconds. Anyway, right now there aren't any real limitations from my perspective, only choices.

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    Are you going to give it a HUD device with warning lights, etc?
    I just don't like HUDs. I like to see numbers.

    Chris


    .
    Last edited by cys; 29th August 2012 at 05:40.

  3. #23
    Moderator jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski has a reputation beyond repute jradomski's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by cys  View Original Post
    I guess you know my comment about the Netduino was only in response to the specific question that, if one were going to use a Netduino, whether it is a good idea to start with the Netduino Mini or regular Netduino, and my answer is that the documentation isn't as good for the Mini so the regular Netduino has advantages as a starting point. However, there are sooo many things to do other than optimizing code that I don't really see why anyone doing something like this for themselves would want to be resource constrained when it isn't really necessary. Also, what off the shelf implementations are you referring to for embedded applications?

    I'm talking about coverting any of the buhlman code out there... it generally requires little work to get going on any platform, but they are mostly all brute force and lots of unnecessary work is constantly being done...
    Joe Radomski
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  4. #24
    RBW Member Apeturbo is an unknown quantity at this point Apeturbo's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by cys  View Original Post
    It compares the cell readings to each other to see if they agree within a set +/- threshold.
    Do you use a constant +/- threshold or a linear one?
    for example:
    1) constant threshold: +/- 0.05: if average of sensors is 1.00 the threshold is 0.95/1.05; but if the average is 0.30, the treshold is 0.25/0.35

    2) linear threshold: +/- 5%: if average of sensor is 1.00, the threshold is 0.95/1.05 and if the average is 0.30, threshold is 0.286/0.315

    In my controller i use the second type of system, i've found very efficient.

    Daniele

  5. #25
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Apeturbo  View Original Post
    Do you use a constant +/- threshold or a linear one?
    for example:
    1) constant threshold: +/- 0.05: if average of sensors is 1.00 the threshold is 0.95/1.05; but if the average is 0.30, the treshold is 0.25/0.35

    2) linear threshold: +/- 5%: if average of sensor is 1.00, the threshold is 0.95/1.05 and if the average is 0.30, threshold is 0.286/0.315

    In my controller i use the second type of system, i've found very efficient.

    Daniele
    I use the second type of system that you noted, +/- a percentage.

    Chris

  6. #26
    RBW Member Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P's Avatar
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    Which oled did you use?

    Quote Originally Posted by cys  View Original Post
    For the housing, I responded to a for sale ad here on RBW from lof. Kevin at Juergensen Marine would be the main source, though. I get my OLED's from Newhaven.



    Best,

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  7. #27
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Igor P  View Original Post
    Which oled did you use?
    The NHD-0216KZW-AG5.

  8. #28
    RBW Member Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by cys  View Original Post
    In January of this year I decided to start a computer/rebreather controller project.

    Chris
    Nice job!!

  9. #29
    RBW Member Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T is just really nice Andy T's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by jradomski  View Original Post
    I'm talking about coverting any of the buhlman code out there... it generally requires little work to get going on any platform, but they are mostly all brute force and lots of unnecessary work is constantly being done...
    I have to agree with Joe, ZHL16 does not require much computing power to run. I've had it running on a PIC without any trouble.

  10. #30
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Andy T  View Original Post
    I have to agree with Joe, ZHL16 does not require much computing power to run. I've had it running on a PIC without any trouble.

    I agree too. I chose to work with the Netduino Mini because I liked the development environment, I liked the size, and I liked the price -- $29.95.

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