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Thread: Analog electronic controller.

  1. #1
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Classic Inspiration

    Analog electronic controller.

    Hi Everyone,
    I have started building a controller for eCCR using analog circuitry and no microprocessor or software. I wonder if anyone has built such an item lately?

    You might wonder... why build such a thing? Simple. I have years of expierence with RF and analog circuitry but no experience with programming. You might say I'm on the wrong side of the "digital divide". So analog it will be.

    Any thoughts?

    Regards,
    Mark Thompson

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    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 Everyone,
    I have started building a controller for eCCR using analog circuitry and no microprocessor or software. I wonder if anyone has built such an item lately?
    It is easy. These operational amplifiers with very low offset voltage, are very cheap and 4 in one housing.

    But first you need to choose a dosage of oxygen. It follows from this arrangement.

    Just a question, do you know all the processes that have controlled electronics?

    What type of equalizer ppO2 the ascent thinking about electronic or mechanical?

    rc greet

  3. #3
    RBW Member Bottom Dollar Diver is an unknown quantity at this point Bottom Dollar Diver's Avatar
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    Classic Inspiration

    Re: Analog electronic controller.

    Hi,
    I plan to install this controller in my Classic Inspiration for testing. I will use the existing solonoid valve and all plumbing. The new controller will emulate exactly the action of the original Inspiration controller. For example the solonoid valve opening will be zero to 17 seconds with a 6 second "hold off" period. The "loop gain" of the system will be the same as original. So I expect it to work just like the original as far as stability. I have the original control system and I have done detailed testing of it's action. Using this data, I can tailor my new system to be very similar.

    My object is to make a simple system with wrist mounted display and easy to see bright LED readout. Also it will have warning lights for different conditions, not just a buzzer. My original system is too hard for me to see and read underwater in our dim and murky conditions and therefore not really safe anymore.
    Regards,
    Mark Thompson

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    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
    I plan to install this controller in my Classic Inspiration for testing. I will use the existing solonoid valve and all plumbing. The new controller will emulate exactly the action of the original Inspiration controller. For example the solonoid valve opening will be zero to 17 seconds with a 6 second "hold off" period.
    Interesting is the type of controller you want to use the PID? or what.
    High maximum dosage of oxygen, that is needed so big?
    Probably not.
    Also opening time from zero is a pure waste of energy, 1s minimum can be enough.

    greet rc

  5. #5
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    Re: Analog electronic controller.

    It's already done, the old Mk15 Rev G pods. Absolutely superb controller. There was a guy selling one on Ebay recently, wouldn't be hard to wire one into another unit, just swap the R22D type cells for the high output versions.

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    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,
    Yes, if I ever have a chance to get a MK 15 system that would be interesting. I know its origins date from pre-microprocessor days. Of course I'm also looking for the fun of building it myself. The DIY instinct lives on.

    The solonoid times that I mentioned are taken from the Inspiration manual and I have verified that my unit conforms to these specs. The minimum solonoid opening is shorter than one second and smoothly fades to zero as you reach the setpoint. When you test the system with simulated cell inputs, you can observe very short solonoid bursts. When diving, I don't think you really hear the very short bursts.
    Regards,
    mark Thompson

  7. #7
    RBW Member kopaz is on a distinguished road kopaz is on a distinguished road kopaz's Avatar
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    rEvo II

    Re: Analog electronic controller.

    It would be cool to make 3 circuits in parallel OR-ing the outputs with each set for a different setpoint (e.g. 0.4, 1.0, 1.3)

    then you can disable the higher ones' output to give you selectable setpoints without having to mess with a variable pot for a Vref - they can be "factory fixed"...

    you could also take advantage of the parallel output and make each circuit tuned to a narrower activation cycle (where the lowest setpoint circuit has the longest average on time)

    and finally each circuit can have it's own alarm, but this time OR-ing the outputs in a cascade... so the lower setpoint circuit's alarm is disabled when the higher setpoint circuit is happy... (and you can get intermediate value alarms too... <0.4, 0.4< x <1.0, 1.0< x <1.3, >1.3)

    (I actually started a design for this a number of years ago - with a stoplight HUD)

    this is not a new idea - I am applying the "sub-sumption architecture" of robotics by Brooks.

    ref: Cambrian Intelligence by Rodney A. Brooks, The MIT Press, 1999
    Last edited by kopaz; 24th June 2011 at 05:45.

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    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 minimum solonoid opening is shorter than one second and smoothly fades to zero as you reach the setpoint. When you test the system with simulated cell inputs, you can observe very short solonoid bursts. When diving, I don't think you really hear the very short bursts.
    Exactly cut it short inclusions are unnecessary and consume a solenoid mechanically draw too much energy.

    greet rc

  9. #9
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    Re: Analog electronic controller.

    Quote Originally Posted by Bottom Dollar Diver  View Original Post
    Hi,
    Yes, if I ever have a chance to get a MK 15 system that would be interesting. I know its origins date from pre-microprocessor days. Of course I'm also looking for the fun of building it myself. The DIY instinct lives on.
    You can't really see much on the pod as the whole thing is potted. There's a copy of the manual posted somewhere on here, it has the circuit diagrams in it.

  10. #10
    RBW Member moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund is a glorious beacon of light moribund's Avatar
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    Oxygen Rebreather

    RG/U-FM mCCR

    Re: Analog electronic controller.

    You may want to check out the Electrolung Rebreather, which was one of the first and had a very clever analog display for PPO2. Browse here for a good write-up.

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