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focusing head? challenge?

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  • Adam
    would it be possible to use a solar head that would look for sun, and when the light is found, the head would focus a lens (the lens is bigger than the solar
    Message 1 of 3 , Mar 2, 2004
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      would it be possible to use a solar head that would look for sun,
      and when the light is found, the head would focus a lens (the lens
      is bigger than the solar panel) so that more sun would be directed
      to the solar panel? would this be efficient? i'm thinking of a 2
      DOF head, plus the focusing motor, so that's 3 motors that it must
      run, and be completely solar. does anyone wanna try to make a
      circuit that is efficient enough to do this? if so, does anyone
      wanna build the circuit? if so, tell me how it goes.

      Adam
    • GrantM.
      Definitely possible. I did some experiments with a frenel lens a few years ago, I could get about 100mA out of a SC2433 (regular 17mA) the voltage stayed fairy
      Message 2 of 3 , Mar 2, 2004
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        Definitely possible. I did some experiments with a frenel lens a few years
        ago, I could get about 100mA out of a SC2433 (regular 17mA) the voltage
        stayed fairy constant. At least until the solar cell start to smoke...
        You would probably want some sort of passive cooling mechanism.

        As long as the light source you are trying to focus on does not change (the
        sun) and the angle is kept constant (2 dof head) I don't think you would
        need to re focus the lens, that eliminates one motor.

        I have always wanted to build a version of Larry Niven's "sunflower" from
        the Ringworld series. Basically large fields of these carnivorous flowers
        focus light on to an object in the sky (birds), cook it and eat it when it
        hits the ground. I stop to think of the military implication of such a
        device but realize the vulnerability at night or cloudy days.

        GrantM.

        At 12:47 PM 3/2/2004, you wrote:
        >would it be possible to use a solar head that would look for sun,
        >and when the light is found, the head would focus a lens (the lens
        >is bigger than the solar panel) so that more sun would be directed
        >to the solar panel? would this be efficient? i'm thinking of a 2
        >DOF head, plus the focusing motor, so that's 3 motors that it must
        >run, and be completely solar. does anyone wanna try to make a
        >circuit that is efficient enough to do this? if so, does anyone
        >wanna build the circuit? if so, tell me how it goes.
        >
        >Adam
        >
        >
        >
        >
        >
        >Yahoo! Groups Links
        >
        >
        >
        >
      • Bill
        Adam - ... The Sun us sufficienty distant that the rays can be considered to be parallel - so once the lens is focused it will never need to be adjusted
        Message 3 of 3 , Mar 2, 2004
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          Adam -

          --- In beam@yahoogroups.com, "GrantM." <grant@s...> wrote:
          > Definitely possible. I did some experiments with a frenel lens a few years
          > ago, I could get about 100mA out of a SC2433 (regular 17mA) the voltage
          > stayed fairy constant. At least until the solar cell start to smoke...
          > You would probably want some sort of passive cooling mechanism.
          >
          > As long as the light source you are trying to focus on does not change (the
          > sun) and the angle is kept constant (2 dof head) I don't think you would
          > need to re focus the lens, that eliminates one motor.
          >
          The Sun us sufficienty distant that the rays can be considered to be parallel - so once the
          lens is "focused" it will never need to be adjusted again.
          Having said that, I will also say that you want the light to be anything BUT focused! Take
          your thin fresnel lens outside, angle it towards the sun with a piece of wood behind it.
          adjust the distance between lens and wood until the light is focused... now you know why
          you don't want to focus the sunlight! However, if you measure that distance you can then
          grab your pencil and paper and design your optimal system.

          * Measure the long dimension of your lens taking into account that there is a border area
          that is not part of the lens.

          * Draw a vertical line the length of the lens.

          * Half way down that line draw a perpendicular line representing the geometric axis of the
          lens, then mark a spot on the axis using the measurement you made outdoors (the focal
          length of the lens).

          * draw lines from the ends of the vertical line to the mark on the axis. You now have a
          triangle with the lens as its base.

          * The point at which the long dimension of your solarcell (not counting border area) fits
          between the sides of the triangle will give you the optimal distance between lens and
          solarcell, as far as getting all the photons striking the lens to also strike the solar cell.

          (You now know more than most about geometric optics.)

          Go back outside with your lens and place your hand behind it at the distance you just
          obtained. If your hand can handle the heat then it's a good bet your solar cell will, too.

          To learn about designing a simple lens system for forming images do a search on "Thin
          Lens Formula" (which, curiously enough, has nothing to do with the thinness of the lens).

          Be sure to share your results with us.
          - Bill Mason
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