Valves control

Discussion in 'The Projects Forum' started by phddas, Jul 26, 2013.

  1. phddas

    Thread Starter New Member

    Jul 25, 2013
    5
    0
    Hello

    I am thinking to build a pressure swing adsorption to generate up to 30L/min oxygen and food grade nitrogen. I think I will be using zeolite X13 as it is much cheaper than A5.


    I will use 4 tanks size 5 Lt. each.
    Each tank goes through 4 stages, 10 seconds each.
    1- Air pressure build up.
    2- Adsorption.
    3- Exhaust of Oxygen.
    4- Regeneration/exhaust of Nitrogen.

    After 40 seconds I should have 20L of gas and after 60 seconds I should have 30L of gas.
    Each tank will be connected to exhaust pipe at the top and inlet pipe at the bottom, the exhaust pipe will have a electrically controlled valve to either open or close, but the inlet pipe will have a 2 way valve to either let 20psi air in “build up stage” or let vacuum in “regeneration/exhaust of nitrogen”.

    Any ideas from experienced members on how to build the circuit, which will control the pressure swing adsorption process, would be much appreciated.

    Points to consider:
    dial control to adjust the 10 second period for fine tuning to achieve max. gas purity.
    there might be other points to consider but I can not think of any thing right now.

    Thanks a lot
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,083
    3,021
    You can take for granted that the electronics for this are relatively trivial compared to the mechanical issues. Once you have your valves chosen, the circuitry can be tailored to drive them. They'll have specific needs for voltage, current and so on.

    You could do the sequencing without a computer, but I think most folks would recommend a micro controller to allow the most flexibility and security, for instance guaranteeing that one valve is closed before another opens. If you want to pursue this, you should let the experts know what your skill level is, what programming language you know and so on. It's tougher for a beginner.
     
  3. phddas

    Thread Starter New Member

    Jul 25, 2013
    5
    0
    Hi
    I could arrange the mechanical part with out much difficulty. I did a lot of C++ 10 years along with Perl and Regex. Now I am running windows OS XP.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,083
    3,021
    The DIY, non-µC approach would be to use a 555 timer as a clock. In this case a 10 second, adjustable clock. I would then use a counter such as 4017 to direct the sequence. (The 4017 can count to ten, and they can be cascaded if you need more.) Each tick of the clock would advance the state of the system. In each state you define the position of all the valves and send them the appropriate signal triggered by the counter. If you need small delays built in, for instance one valve to wait 0.5 seconds for another to finish changing, this could be accomplished by more 555 timers (or other techniques) to delay the on or off of your specific valve.

    The control signals will be used to switch a MOSFET capable of handling the needs of the valve.

    All in all, it doesn't sound so bad even without the µC.
     
  5. phddas

    Thread Starter New Member

    Jul 25, 2013
    5
    0
    Thanks for your help. I will give it some thoughts and study and get back with some drawing for the circuit you suggested.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,979
    3,686

    If you have the mechanicals all set and you are sure the x13 will work with reasonable efficiency, this is a very cool project.

    A residential lawn sprinkler system might be a good starting point to control the valves (their intended function anyhow). If you go this route, it will be more of a hack instead of a build from scratch. I assume your goal is access to the gasses rather than the joy of building it.

    The hack will be to change the oscillator crystal since sprinkler system clocks will run on the minute scale instead of second. A fairly complex controller with multiple zones and multiple cycles costs about $100 or less.

    Good luck and I look forward to seeing your progress.
     
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