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powerful servo needed

Discussion in 'Hobby Electronics' started by Craig Curtin, Oct 6, 2004.

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  1. Craig Curtin

    Craig Curtin Guest


    Anyone know where i can get a grunty servo at a reasonable price ?? I
    want to use it to automate the turning of swimming pool valves i.e.
    the large plastic handled valves you see on the 40 and 50mm hi
    pressure PVC pipe near pool pumps and the like.

    Jandy have a unit which is purpose built but costs around $200US - no
    idea what a big servo would cost - but more to the point where to get
    one from ???

  2. pcman

    pcman Guest

    wouldnt you be better off replacing the valves with electronic controlled
    solinoids ??
  3. PE

    PE Guest

    Just keep in mind what people say about a drip under pressure.....

    Pump off.... change flow..... check flow HAS changed..... Pump on.........

    Not gained through experience................ yet!

  4. Craig Curtin

    Craig Curtin Guest

    Problem is i am not aware of any at a reasonable price for 40mm
    pressure pipe that do not restrict the flow. The Jandy solution
    appears to be the industry accepted one for automating switching
    betwen spas and pools etc and i was wondering if there was a cheaper
    way of doing it

  5. Check out some of the flow control valves from the bigger agricultural
    equipment suppliers. They use motorised valves for eg boomspray
    control, although I dont know of any as big as 40mm. But maybe you can
    fit one of the motor assemblies on a bigger valve. I still think $200
    or so is a reasonable price for this type of thing - low quantity,
    specialised part, well sealed, etc.


    Adrian Jansen adrianjansen at internode dot on dot net
    Design Engineer J & K Micro Systems
    Microcomputer solutions for industrial control
    Note reply address is invalid, convert address above to machine form.
  6. Bob M

    Bob M Guest

    Greetings from Canada!

    I did a similar thing for my sister/brother-in-law many years back. He
    was a plumber and constructed a solar heater array to heat the
    swimming pool. Basically, we needed a valve that could be controlled
    by a circuit I constructed to determine if the water in the heater was
    warmer than the water in the pool.

    Basically, I cut out an 8 inch circular disc of 3/4 inch fir plywood.
    In the centre of the disc, I cut out the shape of the "T" handle of
    the 2 inch plastic ball valve. A second disc was stacked on top of the
    first, with nothing cut out of it. On the underside of the first disc,
    metal straps were secured to the plywood across the "T" handle to
    permanently attach the plywood to the valve.

    The pool light was powered by a 12 volt battery system, so I chose a
    12 volt car windshield wiper motor to drive the valve (from a 1966
    OLDS). They are very powerful and can easily move the valve. Depending
    on the motor you choose, you need to make an eccentric arm to operate
    the valve. Micro switches were used to stop the motor in the "valve
    open" and "valve closed" position. The motor was powered by a relay.

    Note that the wiper motor draws a significant amount of current. Not
    an issue in our case as the batteries (2 X 6 volt gel cells) could
    supply the intermittent "burst" of current required. The thing worked
    reliably for many years after the mandatory first week of "tinkering"
    to get everything adjusted correctly.

    Hope this helps. If you want more details, send me an email directly
    and I'll do my best. It was about 30 years ago.

    Cheers from Canada!

    Bob M
  7. agamlen

    agamlen Guest

    If by servo you mean a radio controlled type servo rather than a
    servomotor you can get a servo controller from and it will control a cheap windscreen
    wiper motor. The control method is a pulse of 1.5 ms is center, 1ms is
    left and 2ms is right. Pulses every 20ms.
  8. adam_c

    adam_c Guest

    I was gonna suggest a car wiper motor too.

    U could just set limit switches, or, alternatively, Oatley Electronics has
    the servo motor kit that converts wiper motors into huge servos.

    Might wanna give them a go...

  9. Craig Curtin

    Craig Curtin Guest

    Thansk very much for the suggestions guys, looks like some tinkering
    with car wiper motors. I will check out the Oatley Kit

  10. Sounds like you have some things to try now, but just beware of
    one thing. Some of these valves, especially the 6-way ones, have
    a lever handle which must be depressed before being turned. This
    is done to remove the pressure from the seal, which will quickly
    fail if you modify the valve to be turned without needing the
    lever to be depressed.
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