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Air pump questions

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  • Air pump questions

    I'm not only a newbie, but not even a model maker, so please forgive the odd questions.
    For some biomedical research I need to produce positive and negative pressures in a small air cavity. I came across the GSV2512N12V 'Air Pump For Subs' and wonder if it might work for me. One question is whether by any chance it can be run backwards by reversing the voltage, to produce either positive or negative pressures in a cavity. If not, perhaps I could hook up two of them, one to push air into the cavity and one to pull it back out? When the pumps are stopped, are they air-tight?
    (The cavity volume would be on the order of 1 mL, but a larger buffer volume can be used. The pressures would be something like +/- 5 kPa. We'd be using a pressure sensor to measure the actual pressure.)
    I also noticed the 400P Gear Pump. It is reversible but it's intended for water, and I haven't found any specs or price for it.
    Thanks for any advice you can give.
    - Robert

  • #2
    Nope, our pumps are not reversible. But, they are positive displacement (piston/diaphragm) types. As you suggest, you can hook two on a switching manifold to get either a partial vacuum or a positive pressure.

    You're best bet is a peristaltic pump -- rip one out of a heart-lung machine when no ones looking. Operate its shaft by hand for precise control of the vacuum-pressure.

    David,
    "... well, that takes care of Jorgenson's theory!"

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    • #3
      I have a few peristaltic pumops which would work for you. They're about 1" cube and need a motor attached to them. $45.00
      Stop messing about - just get a Sub-driver!

      Comment


      • #4
        Kazzer, that sounds more practical than David's suggestion about heart-lung machines. How do I find out more? - Robert

        Comment


        • #5
          ... or, if the gas/liquid volume is not big, a syringe!

          David,
          "... well, that takes care of Jorgenson's theory!"

          Comment


          • #6
            David, in my reply to Kazzer I neglected to thank you for your first response (even if I'm not sure I can use the heart-lung suggestion). I'd thought of peristaltic but hadn't found any inexpensive ones. One thing I didn't mention is that we want this setup to be under computer control. I'd thought of using a syringe, with some sort of linear actuator attached, but it would be pretty klugy. Thanks again. - Robert

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            • #7
              How about using a servo to move the syringe plunger ? You could use a large barrelled syringe like 10-20 ml so that you could have a short stroke.
              Make it simple, make strong, make it work!

              Comment


              • #8
                Specifications for pumps?

                Thanks for all the responses!
                To get started, I've ordered two of the 'Air Pump For Subs' pumps (GSV2512N12V) as well as one of the peristaltic pumps that Kazzer mentioned. While waiting for them to arrive: do both kinds of pumps have regular brushed DC motors? Are any specs available for the peristaltic pumps? Does anyone have any experience controlling the speeds of either of these pumps?
                - Robert

                Comment


                • #9
                  Hi Robert,

                  I can't speak to a certainty on the motor type in the peristalic pump, but the air pumps are definitely BDC. (Chances are the peristalic is too.) You can coarsly adjust the speed of the pump with an inline resistor, but I don't know how repeatable the resulting flow rate will be. The ESC's we use to control our drive motors could also be used to control the speed of the pump, and would probably offer control over a wider range, but you'll also need a means to "set" the speed of the ESC. (A common "servo driver" would do this.)
                  Kevin McLeod - Oscar II driver
                  KMc Designs

                  Comment


                  • #10
                    How about using the pump to pressurize one reservoir while putting a vacuum on another reservoir.
                    Then use the pressure and vacuum through the use of valves and regulators to put the right
                    amount of pressure/vacuum in the test chamber.

                    Scott

                    Comment


                    • #11
                      Scott - That's a good idea, and I have colleagues who have done that. It works well for setting and holding a pressure, which is our first requirement. We even have vacuum and pressurized-air lines in the wall that we could use. Later, though, I hope to be able to generate slow ramps of pressures. - Robert

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                      • #12
                        Kevin - Thanks for the information. We'll keep it in mind. - Robert

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