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Thread: Analog electronic 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: Analog electronic controller.

    [QUOTE=moribund;368090]Keep in mind that there are newer versions of many devices that are lower power and more efficient than the originals.

    Hi,
    Yes. I will be using the best components that I can find! I'm not primarily looking at low power consumption. Also in a wet, salt enviornment, low power circuits are more troublesome. Low power circuits involve small currents and high impedance. A tiny leakage current due to moisture can upset the circuit.
    The same leakage current will not even be noticed in a normal circuit.
    Regards,
    Mark Thompson

  2. #22
    RBW Member anarchista is an unknown quantity at this point anarchista's Avatar
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    Re: Analog electronic controller.

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    The interval of the solonoid opening is proportional to the amount of O2 needed at the sample time. That is the only time that the cell output is considered. The 6 second interval allows the O2 level to stabalize before the next measurement sample.
    Short-term consumption of oxygen metabolism that 4l/min. The circuit consumes 0.4 l stirred 6s which can change the ppO2 0.02 bar.
    The proposal is too frequent sampling. In the proposed system.

    Check how often accidents due to failure of the electrical valve.

    rc greet

  3. #23
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: Analog electronic controller.

    Quote Originally Posted by anarchista  View Original Post
    Short-term consumption of oxygen metabolism that 4l/min. The circuit consumes 0.4 l stirred 6s which can change the ppO2 0.02 bar.
    The proposal is too frequent sampling. In the proposed system.

    Check how often accidents due to failure of the electrical valve.

    rc greet
    Hi,
    Do you think the "hold off" period should be longer? How much? It is true that the O2 content will not change much in only 6 seconds. I think the Inspiration designers were trying for very close specifications of ppO2. Maybe at the expense of solonoid usage.
    Regards,
    Mark Thompson

  4. #24
    RBW Member anarchista is an unknown quantity at this point anarchista's Avatar
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    Re: Analog electronic controller.

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    Hi,
    Do you think the "hold off" period should be longer? How much? It is true that the O2 content will not change much in only 6 seconds. I think the Inspiration designers were trying for very close specifications of ppO2. Maybe at the expense of solonoid usage.
    Decision is made by you.
    Consider what else you can do digitally, what is more difficult analog.

    I have the new solution does not reported in Patent Office, cease to speak.

    greet rc

  5. #25
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: Analog electronic controller.

    Hi All,
    I am designing my wrist mounted indicator to go with my analog controller. It will contain a 20 point LED dot graph meter based on two LM-3914 ICs. This makes a nice bright meter which your eye does not have to focus on to get the essential information. The scale will be 0.10 ppO2 per segment. Full scale will be 2.00 I have it scaled so that full scale is 2.00 VDC.

    The row of LEDs will be different colors to reinforce the significance of the reading. Of course the numbers representing danger will be red. The numbers representing caution will be yellow. Green for OK. For example 1.40 might be yellow, 1.50 through 2.00 will be red.

    An extra led will be located next to the 1.30 and 0.70 LEDs to indicate the active set point. So at a glance you can judge whether the ppO2 is holding at the setpoint (and whether the setpoint is correct). When the setpoint and measurement LEDs are lighted side-by-side, all is well.

    This meter contains its own voltage reference independent of the other references in the controller. It serves as a verification of the correct operation of the system. It will not be used during system calibration.

    To improve the resolution of the 20 point system, a "dither" signal will be used. This blurs the reading so that instead of jumping point to point, it will smoothly move from one LED to the next. This doubles the effective resolution of the meter.

    I have a rough breadboard set up now. It works really cool!
    Regards,
    Mark Thompson

  6. #26
    RBW Member jknights is on a distinguished road jknights is on a distinguished road jknights's Avatar
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    Re: Analog electronic controller.

    Do you intend to publish the circuit diagram ?
    I'd be interested to see it and also a picture of the finished item.

  7. #27
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: Analog electronic controller.

    Hi All,
    I'm back at work on my electronic controller. I hope to have it ready to test in the water soon. The prototype unit is physically crude but the electronics is carefully worked out. When I finish testing, I will rebuild it using surface-mount components to reduce the size.

    The wrist mounted unit will connect via a hose ( full of wires ) to a housing installed under the scrubber. The battery will be in that housing also. Another hose will enter the lid and connect to the cells and solonoid. No electronics or battery will be inside the lid. I will probably use the original buzzer on it's hose.

    After I'm sure it works OK, I will make the wiring diagrams available. For informational purposes only! This project is for fun only. Not for sale.

    Mark

  8. #28
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: Analog electronic controller.

    Hi Everyone,
    I attached a picture of the wrist mounted monitor display. This unit is handmade and a bit crude but will serve for testing. Also included is a picture of the circuit cards. These two cards contain the circuitry for the controller. The circuit cards will be enclosed in a lexan box which will fit below the scrubber canister. The system works "on the bench" and the next step is to install it in the rebreather.

    Mark Thompson
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  9. #29

    Re: Analog electronic controller.

    That's nice stuff, looks like you've poured a lot of hard work into it.

    I work with microcontrollers and have always envied a good analog designer. Any chance you'd discuss your overall work flow with us?

    -Jon

  10. #30
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Re: Analog electronic controller.

    Hi Everyone,
    I have installed the experimental analog controller in the Inspiration RB. Yes, it is a bit crude! Hardware store technology at it's best. If I like the way it works, I will rebuild it with a nice package including surface mount electronics. The electronic action of this analog circuit closely duplicates the action of the original Inspiration controller so I expect it will work great in the water.

    Mark
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