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Thread: The ACME computer/rebreather controller

  1. #11
    RBW Member priestlay is an unknown quantity at this point priestlay's Avatar
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    Awesome guys i wish i had the knowledge to do something like this and replace the huge handsets on my inspo classic.

  2. #12
    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 pegcjs  View Original Post
    Hi Daniele
    I've tried doing this using pinguino pic32 micro but the code is very memory hungry - I got a full deco calculation up and running (16 tissue compartments) but had no space left for any of the display drivers and sensor readout.
    You're right, but before changing platform i have to learn .net....
    with Atmega328, with 30kb for the code, the program runs ok for Nitrox deco, but was very very slow with NDL calculation, expecially after 10 minutes of deco, so my idea to try with pic32.

    Where i could find some sketch or manual or anything else to learn .net? And do you think i could learn and debug everything directly with a a Netduino Mini? it's better for install into a small house...

  3. #13
    Dive different. cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Apeturbo  View Original Post
    By the way, where have you find the piezo button i have seen in the photo?
    Piezo buttons came with the empty handset. Digikey has piezo buttons but not sure of the sizes they offer.

    Chris

  4. #14
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Apeturbo  View Original Post
    And do you think i could learn and debug everything directly with a a Netduino Mini? it's better for install into a small house...
    If I were to start over again I would still begin with the Netduino and then move over to the Netduino Mini. As products get used by fewer and fewer people there is less and less documentation. The Netduino pretty much works as expected.

    Chris

  5. #15
    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,
    Be sure to use a soft potting material. Hard materials like epoxy or resin will cause the solder joints to "work" with hot and cold cycles. The solder connections will break sooner or later and become intermittent. Solder is very soft and weak compared to the circuit board and components.
    Mark

    I'm thinking of just embedding all my electronics in polyester resin - including the battery....[/QUOTE]

  6. #16
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by cys  View Original Post
    If I were to start over again I would still begin with the Netduino and then move over to the Netduino Mini. As products get used by fewer and fewer people there is less and less documentation. The Netduino pretty much works as expected.

    Chris

    There is at least 1 current commercial computer out there running off a pic... a few commercial products I know of use ARM and TI mcus..

    if your code is highly optimized, you don't need a fast chip.. if you use off the shelf implementations and don't optimize it you better have a mcu with some speed..

    my last computer design, I was running a ti cpu at 4mhz and a 100m dive with a 1hr bottom time only took a few seconds to compute the TTS..
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  7. #17
    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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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by trimix1965  View Original Post
    Hi Igor how is you build going, you got some pic's to send to me?
    Tony
    PM sent

  8. #18
    Dive different. cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by jradomski  View Original Post
    There is at least 1 current commercial computer out there running off a pic... a few commercial products I know of use ARM and TI mcus..

    if your code is highly optimized, you don't need a fast chip.. if you use off the shelf implementations and don't optimize it you better have a mcu with some speed..

    my last computer design, I was running a ti cpu at 4mhz and a 100m dive with a 1hr bottom time only took a few seconds to compute the TTS..
    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?

  9. #19
    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,
    I'm interested to know some details about your program.

    Does it sample the cells and perform a "voting logic" operation?

    How does it work?

    How long / short is the sample period of each cell? Is each sample integrated over a period of time or an instantaneous reading?

    How does the system deal with an "unstable" cell?

    How do you perform calibration?


    Your unit looks great! Thanks for the very interesting information.

    Mark Thompson

  10. #20
    Dive different. cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys has much to be proud of cys's Avatar
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    Re: The ACME computer/rebreather controller

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    Hi Chris,
    I'm interested to know some details about your program.

    Does it sample the cells and perform a "voting logic" operation?

    How does it work?

    How long / short is the sample period of each cell? Is each sample integrated over a period of time or an instantaneous reading?

    How does the system deal with an "unstable" cell?

    How do you perform calibration?


    Your unit looks great! Thanks for the very interesting information.

    Mark Thompson

    Hi Mark,

    The part that you are asking about is the stuff that remains to be tested in the water. I've done what I could with it on land, though.

    Does it sample the cells and perform a "voting logic" operation?

    Yes.

    How does it work?

    It compares the cell readings to each other to see if they agree within a set +/- threshold. If they all agree within the threshold they are all averaged together. If only two agree, only those are averaged. If none agree then there is no averaging. I'm leaving out any warning/alarm conditions that the last two categories would lead to. On top of this goes all strengths and weaknesses of voting logic. If two cells agree one needs to get an outside opinion on whether the two that agree are correct or the outlier is correct. Beyond this, there is the specific approach to this in the code, but for the time being I'm keeping that close. It's nothing special. I just started typing one evening and a few hours later there was a workable voting logic scheme.

    How long / short is the sample period of each cell? Is each sample integrated over a period of time or an instantaneous reading?

    What I have found is that when I have been on the edge of what the Netduino's ADC can read, deep sampling of the sensor values has been necessary to get stable readings. To avoid this problem when actually using the system as opposed to just testing it on a bench top, I have just recently built an opamp board for the sensor outputs. My approach has been to go as far as possible within the limitations of what I have at hand with the smallest fixes possible to get things at least operational.


    How does the system deal with an "unstable" cell?

    It votes it out. The thing is that right now I'm including myself as part of the system, given that I'm the only end user I have in mind. Still I have put some alarm conditions into the handset already even though they should be obvious enough by looking at the handset alone, just because it seemed like a fun thing to do. One could track what cells do over time and then use that as a basis for judging the sanity of a given cell, but I like less code, not more.

    How do you perform calibration?

    I have calibration as a sub-menu item. I also have the calibration sub-menu set up to be inactive at depth. The calibration is done by flushing the rig with oxygen and then selecting calibration in the menu. Code wise one determines a factor that makes each sensor give a ppO2 = 1.00 based on the cell mV reading in pure O2. I also have a sub-menu that displays sensor readings as mV values.

    Chris



    .
    Last edited by cys; 29th August 2012 at 02:04.

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