building an external zoom motor for lens

Discussion in 'The Projects Forum' started by regaljohnston, Jan 27, 2013.

  1. regaljohnston

    Thread Starter New Member

    Jan 27, 2013
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    hi,

    this it's my first project, and a good starting point for the pursuing animatronics, which i am very much interested in for video.

    all you really need to know is that i am trying to:

    -make a motor rotate between a range of low speeds, clockwise and anti-clockwise based on the signal from a potentiometer, or some other controller.

    this is to control the zoom ring on my camcorder's lens.

    it needs to:

    -be as quiet as possible (for obvious recording reasons).
    -have a variety of speeds.
    -ease in and out of zoom smoothly/seamlessly.
    -have a control which is operable by my thumb alone (can adapt a potentiometer into a left/right thumb-stick or a seasaw peddle to fit this criteria).

    i am new to all this so please bare with me, i am trying my hardest but would greatly appreciate any advice/guidance.

    this is as far as i have progressed-

    [​IMG]

    -the battery supplies a constant current which is received by the variable resistor (potentiometer).

    -the variable resistor allows a controlled amount of current to pass through it.

    -the current is then passed onto the arduino, which allows me to reverse the polarity of the current (at the flick of a switch?).

    -then the motor receives a controlled level of current at a controlled polarity.

    ---

    so, the potentiometer controls the current (the speed at which the motor will turn) and the arduino H-bridge controls the direction... don't even know if that's how all these parts work, but i'm trying my hardest to learn, so if i am wildly off course then please let me know.

    let me know what your approach would be.

    thanks!

    regal johnston...
     
    Last edited: Jan 27, 2013
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    You may want to take a look at small stepper motors. Small DC Motors run at a very high RPM, unless geared down, which makes a good deal more noise than a stepper does.

    A stepper also gives you precise control of how much to move, rather than guessing how far a DC motor will move after a power/coast/brake cycle.

    How did you plan on linking the motor to the lens?
     
  3. BReeves

    Member

    Nov 24, 2012
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    I've done allot of work with motorized zoom lenses, they use a DC motor and as said are geared down, they also have a built in slip clutch, motor doesn't stall when the lens gets to a stop the slip clutch just starts slipping.

    For a controller you can do it several ways. The simplest is to use two relays, a DPDT to reverse the motor and a SPST to turn on and off the power. By adjusting the relay on time you can do a fair job of setting the lens.

    You should be able to find a schematic for a solid state lens controller with Google. Search for Pelco or Fujinon lens controller. They typically use a push-pull transistor output to control the power and direction of the motor.

    You might be able to couple to the lens with a toothed belt, check micromark for hardware to couple the motor to the lens.


     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    A servo motor is also an option. These are excellent for positioning and used in flaps and rudder for r/c airplanes. All controllers, transmitters and receivers are widely available. Older analog available at very good prices in the secondary market as digital transmitters became available in the past few years (also at good prices).
     
  5. mcgyvr

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    Oct 15, 2009
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  6. regaljohnston

    Thread Starter New Member

    Jan 27, 2013
    2
    0
    thanks for all the input guys, very much appreciated.

    i had planned on linking the motor to the lens via a toothed belt system as suggested above.

    a few people have suggested step motors to me... that seems like the route to take.

    could you suggest a good one for me? or point me in the right direction.

    could/should i use the arduino UNO to do build this?

    somebody in another forum suggested that i use a wii control/ps controller instead of adapting a potentiometer, how do-able is this for a complete noob/layman?

    i figure the best way to move forward is to buy the parts i need and start working on them/figuring them out.

    is that everything i will need? a stepmotor, a wii nunchuk/ps control and an UNO arduino?

    thanks a bunch, very helpful.
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    With microcontrollers, most anything can be done given enough time and coding, limits are speed and memory, but 8 bit micros are very powerful for their size.

    It comes down to how much money you'd like to put into the project, and your skill level.

    Arduino makes more complicated things seem simpler, but the price is higher. It's a decent tradeoff for people just getting started to get an idea of the possible. You'll also want an H-Bridge to drive a motor, or a dual H-bridge for a stepper motor. These are common add-ons for Adruino, as well as the wireless and infrared "shield" for different input methods.
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    You could get an arduino, a couple potentiometers and this and try out all sorts of motor types to see what works best for you.
    http://adafruit.com/products/171
    Thats got a DC motor/a stepper/ and 2 types of servo motors.

    OR strip the motor from an old floppy drive and get a ULN2003A, a couple pots and an arduino.

    or any of the other hundreds of ways..
     
  9. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Cameras use voice coil motors. Not something you could find easily, cheap or even off the shelf.
     
  10. BReeves

    Member

    Nov 24, 2012
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    This is the Zoom motor out of a lens I scraped a while back. It has the gear reduction and slip clutch attached. Normaly the adjustment barrel on the lens has a large gear this engages but it could be done with a toothed belt.

    If you want this I will send it to you for the cost of shipping. I have PayPal and $6.00 would get it to you Priority Mail if you are in the US.

    Sorry for the lousy photo didn't take the time to set the camera on a tripod and just hand held.
     
  11. atferrari

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    Jan 6, 2004
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    Out of curiosity, what type of motor is that?
     
  12. BReeves

    Member

    Nov 24, 2012
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    Just a high quality 6 volt DC motor, some lenses use 12 volt motors but most higher end motorized zoom lenses use the same type of motor and gearing.
     
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