Automatic Iris motor control

Discussion in 'General Electronics Chat' started by coathangercharlie, Apr 5, 2009.

  1. coathangercharlie

    Thread Starter New Member

    Apr 5, 2009
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    I am looking for a very simple circuit that I can use to control the iris motor in a video lens assembly. The iris is operated by a small 12VDC motor. I would like to use an H-Bridge circuit with a pot on one input and a photocell on the other input so that the motor will rotate one way or the other depending on how much light strikes the photocell. The pot would be used as a sensitivity adjustment. Does anyone know of a good circuit that will do this? I was thinking of using transistors or an IC to do this.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    I think you need to control both the position and the speed of the motor, don't you?

    Is there a position feedback?
     
  3. coathangercharlie

    Thread Starter New Member

    Apr 5, 2009
    2
    0
    I don't think I need to control speed. No there is no position feedback. I built a simple H-Bridge with some transistors and it worked pretty good. I used a CAD protocell mounted in a black brass tube in one input and a pot in the other. When I turned the camera toward a lighter area the iris closed proportional to the light intensity which is what I wanted except that the transistors get hot. I tried power transistors but they were not very sensitive. I think the transistors were all drawing current all the time.
     
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