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Hand crank CD player

Discussion in 'General Electronics Discussion' started by savant, Jan 2, 2014.

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  1. savant


    Jan 2, 2014
    I want to build an electronic music box. I want to drive a portable CD player with a hand-cranked dynamo. My general idea is to use the dynamo from a hand cranked flashlight, connected to super capacitors and then to the CD player through a voltage regulator. The CD player normally takes 2 AA batteries.

    My ideal case is to crank and charge the capacitors, then press a button to start the CD player. The player needs to run for approx. 3 minutes.

    If this run time is too long, it would be OK to crank again during the 3 minutes, as long as the CD plays uninterrupted.

    It would be nice if there was some kind of LED indicator for adequate charge, or a warning that additional charging is necessary.

    I know a little about electronics, but the dynamo-capacitor combination is out of my range. Right now, I'm looking for feedback about whether this is possible or not, and what kind of measurements do I need to take to figure out if this is possible.

    Thanks in advance for any input.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I think you may require more cranking than you think.

    However, that said, there is nothing particularly insurmountable about this problem.

    If I were doing this, I would try to find a CD player with a single 5V rail.

    I would then have a dynamo and capacitor that can be charged up to about 12V.

    And I would have a switchmode regulator to reduce the voltage to 5V.

    Using something like an LM3914, I could have a series of LEDs to show the voltage on the capacitor.

    But the first thing to do is to find the player (an MP3 player would be better as it draws less power) and measure the current required when playing. This will allow you to determine the required sizes of the other components in your circuit (i.e. it allows us to calculate the size capacitor which allows the CD player to operate for a given time. This will help to determine the practicability of this project.

    I feel it is likely to be impractical due to what I assume is a significantly higher power consumption for the CD player as compared to the typical crank torch.

    Another issue is that crank operated torches typically do not need to generate a high voltage (nor do they generate a lot of power), so they may not be able to efficiently charge a capacitor to 12V -- this would be the next thing to try, including timings to see how much cranking would be required
  3. savant


    Jan 2, 2014
    Thanks for your reply. This is exactly the kind of practical insight I was looking for. I will get the CD player and test it for current draw as my first step.
  4. shrtrnd


    Jan 15, 2010
    The Russians, in anticipation of civil defense, came up with a LOT of these hand-cranked
    radio-operating devices that don't require batteries.
    I've seen a lot of them in outddor, survival, type catalogs, that made their way into the
    U.S. market.
    Before reinventing the wheel, I'd look them up on-line, and study what the Ruskies did,
    them decide how you'd like to go about this.
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