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Pedal powered generator

Discussion in 'General Electronics Discussion' started by Gluktar, Aug 3, 2018.

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  1. Gluktar

    Gluktar

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    Jul 10, 2018
    Looking for ideas on how to make a pedal powered charger for the kids to get exercise while they watch a show or play a game.

    I have a big DC motor that I can use to make the power, and I am gonna use some sort of jig to hold the bike in place and turn the motor. But I am looking for thoughts on the power management system.

    My big question is how to provide constant output power from variable input speed/power. Is there a dc to dc device that can do this. Or an inverted that can accept fluctuating inputs?

    I was also thinking that making a true charging system may be challenging but making a small device that flips a shade in front of a projector (essentially turning off the show) would be easier. Then I could just have some variable resistance to adjust for different sized kids. Oh, I was thinking it would still be plugged into the wall and the charging system would be a facade.

    Thoughts?
     
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    A fit human (male?) might generate a few hundred watts but kids are only likely to do a lot less and for a lot shorter time.

    Better idea would be to connect the generator to a simple variable load and bar-graph type display and see if you can encourage them to 'reach the top' of the display (switching to higher loads if they do thereby making their task harder!)

    Might keep them quite for a day or so - then they'll be clamouring for their iPads......... again.
     
    davenn likes this.
  3. Gluktar

    Gluktar

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    Jul 10, 2018
    I like the reach for the top idea. This is also an idea for camping without power so charging the iPads by pedal power...
     
  4. kellys_eye

    kellys_eye

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    Jun 25, 2010
    A simple buck-boost board (module) - they're all over the place on eBay etc - would be able to accept a variable input and give a preset output good enough to charge iPads etc.

    Bridge rectifier and smoothing cap on the input to prevent reverse voltages and add a bit of smoothing will help.
     
  5. WHONOES

    WHONOES

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    What about an old fashioned dynamo that attached to the bike frame and just made contact with the tyre. I can just about remember the last time (getting on for 50 years ago) I rode a bike with one fitted and it certainly made a difference to the amount of effort required which may be enough for the kids.
     
  6. BobK

    BobK

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    We are too easy on the kids today. Charge a phone? That's for a weakling sissy. How about toasting a slice of bread?



    Bob
     
    davenn and darren adcock like this.
  7. WHONOES

    WHONOES

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    May 20, 2017
    I
    I like your style.
     
    davenn likes this.
  8. kellys_eye

    kellys_eye

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    I like toast.....
     
  9. WHONOES

    WHONOES

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    Me too.
     
    davenn likes this.
  10. Gluktar

    Gluktar

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    Jul 10, 2018
    Maybe a party bike full of kids could make some toast.


    I thought I discovered it was called a buck boost board from googling. I like the dynamo idea too. Thanks for the help. Gives me a place to start.
     
  11. dave9

    dave9

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    Mar 5, 2017
    They will hate you for attaching bullsheet to things they would otherwise enjoy.

    If you want them to get more exercise, limit their game time and/or enroll them in sports.

    A charging system is very easy given specifics of the components, but this wild tangent of control is not so simple.

    Hey, you asked for thoughts. Be honest with them about the need for exercise instead of tricking them into thinking they are peddling their way towards a reward. They are humans not gerbils.

    There are many more benefits to physical activity than only exercise, such as coordination, building teamwork skills, getting out of the house, mastering a skill, etc.

    Sorry but I see nothing good about this project. Quite the opposite, this is scary parenting.

    I realize you won't understand the extent to which I mean this. But your children will benefit from the above. An artificial environment where they are exercised instead of real world, real life activities, is a very bad idea, and they only need a finite amount of exercise so this is all completely unnecessary and uncalled for.

    It is no substitute for the normal childhood activities they need, and has no purpose once they have those.
     
    Last edited by a moderator: Aug 5, 2018
  12. Gluktar

    Gluktar

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    Jul 10, 2018
    Wow, this tread took a turn.

    Welcome to electronicsandparentingpoint.com

    I don’t think you quite understand that the goal for this is fun and not control. It’s all how you frame and deliver things. I would expect that if I built this project with my kids and explained it effectively, they would prefer to use a pedal powered generator over the wall plug if given the choice. At least for 5-10 min :)

    But thank you for your thoughts.
     
    davenn likes this.
  13. Bluejets

    Bluejets

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    Wellllll....lovely attitude I don't think.
    Fair go bloke....the Op is building something for his kids and I for one give him 10 out of 10 for that alone.

    I'd be waiting for a call from the moderators on this one for sure if i were you.
     
    davenn likes this.
  14. KJ6EAD

    KJ6EAD

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    I have a 60Wh power bank that can charge from an input voltage between 9 and 24. Unfortunately, the model is discontinued and I don't know if there are any similarly capable units available from reputable manufacturers. If such a thing were available, your kids could just accumulate power for later use.

    One of the overlooked balancing factors of cycling is that by your efforts you get some much needed forced air cooling. Maybe driving a fan would be a good alternative to other devices.
     
    Last edited: Aug 4, 2018
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    You'd be surprised about the endurance of kids. A recent study showed that most kids have the endurance and recovery of adults who are classed as "elite athletes". See here.
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It's also interesting to look at the comparative power output of endurance athletes vs sprint athletes.

    Sprint athletes tend to use an anaerobic process, relying on energy stored in their muscles. This is highly available, and provides a much higher peak power, but results in a buildup of lactic acid which is relatively slow to remove.

    Endurance athletes, on the other hand, use an aerobic process to generate power. This requires less muscle mass (endurance athletes are relatively skinny) but can produce far more power over a longer period.

    See here.

    The sprinter in the video above was able to manage an output power of 700W for a short period, generating 21Wh of energy (that's about 110 seconds).

    On the other hand, the Tour de France rider generates over 1kW of energy over a 5 hour period.

    On one hand this indicates the difference in average power (700W vs 200W), but the endurance is 180 times longer and the total energy is almost 50 times larger. In addition, this rider completed a sprint at the end of his ride!
     
    Last edited: Aug 4, 2018
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