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How can the frequency be made vaiable — Parallax Forums

How can the frequency be made vaiable

SiriSiri Posts: 220
edited 2009-11-25 07:07 in General Discussion
I have a Solenoid piston driven AC 110V 60Hz air pump.[noparse][[/noparse]EcoPlus Commercial air 1 #728450].These are normally used as aquarium air pumps.
I am trying to use for another application where I would like to be able to vary rate of the pumping action.When connected to AC as it is the pumps frequency is @ 3200/min.
The application I am working on require a variable frequency 30-600/min.

How can I achieve this?

Thanks,

Siri

P.S :

http://www.underwaterwarehouse.com/Medo-Linear-Air-Pumps-Air-Pumps-And-Accessories-sc-38.html

Please check this site for details of mechanism.

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-20 17:35
    The pulse rate you've mentioned is awfully close to 60 Hz to be a coincidence. So I'm guessing it's more like 3600/min. What this means is that you will probably have to create a 110VAC signal at the much lower frequency. Even this could be a problem, though, if the pump design relies on a mechanical resonance. If so, it may be better (and much simpler) just to pulse the 60Hz mains supply on and off using a SSR with a zero-crossing detector.

    What is your overall obejctive here? Reduced flow, or ... ?

    -Phil
  • SiriSiri Posts: 220
    edited 2009-11-21 17:00
    Phil,
    My overall objective is to reduce the rate of the pulses to about 2400/min.

    I will give SSR with zero-crossing detector.

    Thanks,
    Phil
  • SiriSiri Posts: 220
    edited 2009-11-24 18:16
    Phil,

    I found this AC frequency changer for ? AC motors - can this be used to drive the Solenoid air pump.

    i am attaching the specs of the frequency changer.

    The site for the air pump is ----> http://www.underwaterwarehouse.com/Medo-Linear-Air-Pumps-Air-Pumps-And-Accessories-sc-38.html

    The SSR only give me control of time but not the number of strokes.Changing thr stroke frquency is wgat I am after.

    Thanks,

    Siri
    pdf
    pdf
    Adjustable_Frequency_NFX9000_SERIES.pdf
    260K
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-24 18:41
    The variable frequency drive seems like overkill, since it's rated for 5HP, but it could work. But again, it will depend on whether or not the pump was designed to resonate mechanically at 60Hz. If it was, it could run rough (or not at all) at a different frequency. You could ask the pump manufacturer, or else just try it.

    -Phil
  • SiriSiri Posts: 220
    edited 2009-11-24 19:38
    Thanks - Phil

    Siri
  • kwinnkwinn Posts: 8,697
    edited 2009-11-24 21:37
    Most of the small aquarium air pumps are designed so the mechanical masses oscillate at 60Hz. They would not run well at different frequencies, and the circuitry to make them do so is not cheap. Your best bet is to use a triac to turn it on for a few (whole) cycles, then off for a few. By varying the ratio of off to on cycles you should be able to get close to the rate you want.
  • VIRANDVIRAND Posts: 656
    edited 2009-11-25 07:07
    Old (1A2?) PBXs from mid 1900s had a weird transformer that made 30 Hz,
    apparently by resonance and a diode, the waveform was mostly 30Hz with a CRO-visible 60hz bump.
    And there was another way to do it with 3 donut-sized toroids.
    (Rotary phones ring with usually 20 Hz 90 V, but 30 Hz 100 V worked too)

    Analog frequency division is black magic, except by dynamotor.
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