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Best/Easiest/Safe way to boost solar panel current

Discussion in 'General Electronics' started by RC, Mar 3, 2007.

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  1. RC

    RC Guest

    I'm doing a science experiment with my son. We have three 1.5V solar panels
    wired in parallel in order to supply the 1.5V/400mA needed to power a small
    DC fan. This works fine in sunlight or some other really bright light
    source. He needs to do a demo in a classroom and my flashlight doesn't
    supply enough photons to do the job. What's the best way to give the solar
    panel enough help so that it still takes a flashlight to power the motor. A
    (AAA) battery supplies too much current to connect it in parallel with the
    panels. What's the best way to supply just enough current so that I'm still
    under the motor threshold until I shine a flashlight on the panel? I don't
    have an ammeter handy yet, so I can't tell you what sort of current the
    panels are capable of supplying right now with the flashlight.

    Thanks for your help
  2. Karl Uppiano

    Karl Uppiano Guest

    What happens if you connect the solar panels in series? You'll end up with
    4.5 volts (theoretically), but the motor is not likely to be very picky
    about that. Ohms law predicts that the higher voltage should get more
    current going through the system.
  3. Eric Sears

    Eric Sears Guest

    In short - it will be very difficult. Its doubtful whether the
    flashlight produces more than a few milliamps with cells of that size
    - which is hardly enough to even kickstart the motor with some volts
    already on it. You might be able to put something like a 100 ohm pot
    in series with the battery and motor and manage to adjust it; or it
    might need a 1000 ohm pot - I'm just stabbing in the dark (try some
    fixed resistors first to get an idea).

    However, it might be better if you configure all the cells in series,
    and use a white led (eg from a defunct solar garden light), instead of
    the motor. It takes very much less current to show a result!
    Usually about 3 or 4 milliamps will make them glow reasonably

    Eric Sears
  4. RC

    RC Guest

    Thanks. I'll try a battery with a current limiting pot. The motor would
    make a better demo, but I just may have to change the load to something else
    like the light that you suggest.
  5. jasen

    jasen Guest

    a desk lamp may have enough power, if the classroom has a projector that can
    project a white image that'll have plenty of power. if you're expecting sun an shaving mirror may
    be able redirect enough sunlight to run the fan.

    Using a battery is cheating, probably not something you want to teach your

  6. RC

    RC Guest

    Cheating? I'm just trying to demonstrate the photovoltaic effect. No
    photons, the motor doesn't turn...photons, the motor turns. I would explain
    why the battery was needed for indoor use, and I actually think it makes for
    a more interesting problem to work on.
  7. Ronbo

    Ronbo Guest

    Not cheating. In actuality that is the proper way to demo photovoltaic

    Photovoltaic cells are rarely used to drive objects directly but are
    used to charge batteries.

    However if u need to drive a small fan try obtaining and using a small
    micropressor fan. I have seen these at rating well under 100 ma and can
    usally run at low speeds with only a few volts even though they spec at
  8. neon


    Oct 21, 2006
    use the solar panel to charge the battery . if the battery are fuly charged the fan will run at a good speed however it will slow down gradualy lack of power that is when you can introduce any kindof light and it you can vesibly see a fan speed up. that is your demonstation/
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