motor + LED help

Discussion in 'The Projects Forum' started by BlightStrider, Sep 5, 2008.

  1. BlightStrider

    Thread Starter New Member

    Sep 5, 2008
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    Hi, I know almost nothing about electronics but I thought that this would be the place to get some advice for a project. Basically I'm modifying an old 8mm projector. I need to replace the bulb with an LED and modify or replace the motor to run the projector at about 2-3 frames per second, which is about 2-3 revolution per second of the motor. The motor is connected to a 2'' wheel which is connected by a belt to another 2'' wheel which spins the shutter and pulldown claw. So there isn't much torque and the motor doesn't need to have a lot of power.

    I was hoping that this was something I could put together pretty easily from some parts from Radio Shack or a place like that. Maybe a hobby motor, something to regulate it with, an LED, and some sort of power source for both. Any help is appreciated.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Welcome to the Forums. :)

    It's been a long time since I've fiddled with 8mm film. Seems to me that the frame rate could be anywhere between 14 to 24 frames per second, inclusive.

    The lamps used in the projectors had to put out a tremendous amount of light in order to project such a tiny image onto a far larger screen, and still have it be visible. Of course, these lamps generated a great deal of heat. If the film got off the track or the pulldown claw malfunctioned, the "stuck" frame of film would quickly overheat, melt, and become charred.

    Running the original lamp at a reduced current, or attempting to use PWM on it would not work, because the color of emitted light would change radically.

    There are a number of super-bright Luxeon-type LEDs out nowadays that produce a good bit of light while generating much less heat. However I'm not terribly optimistic of their ability to produce light intense enough, to project an image bright enough to be able to focus that image on a screen and have it be viewable.

    LEDs of that brightness won't be available at Radio Shack.

    As far as the motor is concerned, I'm not sure what types were used. What is the make and model of your projector?
     
  3. BlightStrider

    Thread Starter New Member

    Sep 5, 2008
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    It is a Bell & Howell 1623 8mm projector. I guess I should be more specific with what I actually need. I need to slow the motor down and replace the light because I'm trying to build a telecine. My plan is to have a still camera set up to take stills of the film frames 1 by 1, so that's why the motor needs to be slowed down or replaced. The film runs at 18 fps so I would need to slow down the motor speed by about 1/9 to get it at 2 fps.

    Since the film will be going through so slow I need to replace the lamp with something that won't generate heat and burn the film, so that's why I thought an LED might do the trick. It doesn't have to be bright enough to project the image, just bright enough so that the camera can pick it up. Either I'll focus the camera on the film itself as it passes through, have the projector focus the image onto the sensor of the camera, or use a condenser lens to produce an image which I can then focus the camera on. Either way the light won't need to travel more than a foot or so.

    Like I said I have very little electrical knowledge, so the simpler the better. Preferably something I could hook up to the motor to control its speed and then some way to power a LED or similar light. Here's a website I got a lot of info from but it's too technical for me to easily figure out but it might give everyone a better idea of what I'm trying to do: http://www.movie2video.com/
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    This is a very interesting project.

    However, I'm afraid that it is also rather advanced. You will need at an absolute minimum a good basic understanding of electronics, as well as being very handy with mechanical things.

    I suggest very kindly that this is not a good candidate for a first-timer's project. The probabilities of success are quite low. However, after you have acquired knowledge and experience in building a number of circuits, this project is certainly do-able.

    Radio Shack sells an "Electronics Learning Lab" for about $70. I highly recommend it. It was designed by Forrest M. Mims III, a widely known and respected Citizen/Scientist, and USAF Veteran. This will be one of the best investments you can make in your introduction to electronics.

    You can only learn so much by reading. You must have "hands-on" time in order to evaluate circuits.

    I thank you most sincerely for referring me to that website. It made me remember that my Grandfather made quite a few 16mm films that have sat in a basement for many years, because we didn't have a projector for them.

    In the meantime, you might look for an 8mm Editor. Editors are manually driven, and the film can be manipulated forwards and backwards by hand cranks, and frames left sitting for any amount of time with little chance of damage. Editors use low-wattage bulbs, so the chance of damaging the film is very small. The illumination method would need no modification, the drive could be automated via stepper motors and a microcontroller; the challenge would be to find a camera that could focus on a screen that small, and capture the image.
     
  5. BlightStrider

    Thread Starter New Member

    Sep 5, 2008
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    0
    I'll like to check out that learning lab. I also just discovered that my projector has a "frame" speed which is about 2fps, so it's practically ready to go. I'd still like to switch out the bulb for something less powerful and more diffuse, but I think I can handle that. I hadn't thought of using a film editor, and for a project with more electrical work that might be easier to use and take apart (and cheaper). Thanks for the advice.
     
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