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Automatic Control of PRESSURE & TIME of gas flow from H tank cylinders

Discussion in 'Electronic Basics' started by [email protected], Jan 10, 2005.

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  1. Guest

    I have a gas cylinder - H Tank (that can hold oxygen, helium, etc... at
    50 psi pressure) that is used for clinical simulation. It has its own
    valve that can be switched on / off manually.

    1) My requirement is to automate this valve by having a controller to
    control the flow of gas in terms of both PRESUURE and TIME based on the
    user inputs.

    2) Provide a set of knobs / digital input switches each for TIME period
    of gas flow - 2 seconds, 5 seconds, and 10 seconds.
    (If I choose 10 seconds TIME, the valve opens for 10 seconds, sends the
    gas and automatically shuts after 10 seconds)

    3) Provide another set of knobs / digital input switches for the LAG
    period of gas flow - 10 seconds, 15 seconds, 25 seconds.
    (If I choose 15 seconds input, then the valve has to be in the closed
    mode for 15 seconds after which it automatically opens
    for TIME input that I have chosen in step 2)

    4) Provide another set of knobs / digital input switches for the
    PRESSURE of gas flow - 25 psi, 35 psi, 50 seconds.
    (If I chose 25 psi, then the pressure of the gas coming out of the
    cylinder should be 25 psi)

    5) My final extension is to control the same knobs / inputs remotely
    from my computer through a user interface

    (Example, If I chose TIME = 5seconds, LAG = 10 seconds, PRESSURE = 25
    psi, the gas flows out of the cylinder at a pressure of 25 psi for a 5
    seconds period after a periodic 10 seconds break meaning 5sec ON, 10
    sec OFF, 5 sec ON, 10 sec OFF, etc...)

    Is there a readymade product that can handle this and what are the
    specifications*** that I should look for when I buy such a product ?

    How do I approach if I would like to assemble my own system to handle
    my requirement and what would be the design ?

    In order to handle from the computer remotely, I can connect using a
    serial / USB port, is there a free downloadable software
    that can convert the serial / usb signals to handle such requirements
    based on the circuit ?

    I assume that I can have a timer and a pressure sensor to do this that
    again converts to mechanical energy in order to stop /
    open the valve and regulate the pressure. At the same time, I can also
    have some readymade PCBs that understand the serial /

    usb signals that I send from my computer to do the job, but I need a
    very clear cut design with specifications and implementation procedure
    in order to execute this. What are the basic technical specifications
    that I have to look for in this new system ? I am basically looking for
    an economic solution that can be implemented in my lab for experiments.

    Any pointers to this would be of greatest help.
    Thanks in advance!!!
  2. CWatters

    CWatters Guest

    Perhaps they a company like this...
    They have equipment for mixing/controlling gasses...
  3. JeffM

    JeffM Guest

    gas cylinder...can hold oxygen, helium, etc....
    The *clinical* part bothers me.
    Do you mean that you will be using it on humans?
    I suggest hiring a Biomedical Engineer.

    I have a story about a young, eager physician
    doing a pulmonary experiment using a helium mixture
    on a Saturday with no one else around.
    He survived, but it could have gone very badly.

    A little light reading about Pneumatic Solenoid Valves:

    I also suggest
    that you remove the from your user name.
    The Google arcive now mungs all email addresses
    (especially when you post there)
    so that they look like this: .
    (I had to make an effort to un-mung it.)
  4. Bob Masta

    Bob Masta Guest

    I also have a story like that, only my boss wanted to
    use hydrogen and oxygen premixed in a stochiometric mixture.
    (This was for auditory research on Guinea pigs.)
    Luckily for us all, he wasn't able to find a supplier and
    asked me to help. It took some doing, but I finally
    convinced him that this was a REALLY bad idea, even
    if he found some fool to mix it for him. From what
    I was able to find out at the time, there were no valves
    available that could respond fast enough to prevent a flame
    front from travelling back into the tank and turning
    it into a scale model Saturn V rocket.

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
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