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Self charging keyboard - Is it possible or just funny?

  1. Jan 18, 2016 #1
    Last night I had a drink with my friend and short after he started talking about self charging keyboard. It is a wireless keyboard and it "could" be charged when you are typing ( mechanical to electrical ) or by cleaning it ( whipping off the keyboard with something and then electrons "would" be stored somewhere).

    I think this is fairly funny but that can be good brain teaser... So what do you guys think? I know that this was caused by "few" drinks but still... I would love it if someone could debunk this.
     
  2. jcsd
  3. Jan 18, 2016 #2
    If by self charging you mean wireless charging, then yes it is a possibility. Much like the wireless charging pad Samsung has come up with.
     
  4. Jan 18, 2016 #3

    billy_joule

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    Piezos are possibly the best option:
    https://en.wikipedia.org/wiki/Energy_harvesting#Piezoelectric
    Maybe under each foot, or under every key? my wireless KB states 50mA requirements (max), I'm not sure if that's a reasonable ask from piezos in this application. It may mean uncomfortably hard key action.

    What energy conversion is happening here?
     
  5. Jan 18, 2016 #4
    Maybe a way of taking in and using or storing natural body heat while the user uses the keyboard. Not sure how practical this is, but I'm sure there could be a way. Possibly using the keys or a wrist rest to take in the heat and convert it.
     
  6. Jan 18, 2016 #5

    DaveC426913

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    I think he's thinking of static cling via wiping.
     
  7. Jan 18, 2016 #6

    billy_joule

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    On that scale, Seebeck generators are probably most appropriate:
    https://en.wikipedia.org/wiki/Thermoelectric_generator

    So, yes, it is possible but probably not worth it. These sorts of micro power harvesting methods exist but I think you are applying a solution to a problem that doesn't exist - If you have a computer you clearly have access to power, even if only battery power from your laptop/tablet etc. Building a self powered KB is a waste of time and money (IMO) unless you go all out and power your entire device which would require something like this:
    http://www.cnet.com/news/pedal-power-pedal-your-desk-to-power-your-laptop/
    or a huge array of Seebeck generators and a roaring fire.
     
  8. Jan 18, 2016 #7

    russ_watters

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    It is certainly possible in principle, so what is needed now is to figure out if it would be practical. See if you can find a wireless keyboard with listed battery specs from which you can calculate the power drain. Then try to calculate the power you could generate by typing based on the key stroke distance and force.
     
  9. Jan 20, 2016 #8

    CWatters

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    The AAA batteries in my keyboard lasts quite a few weeks
     
  10. Jan 20, 2016 #9
    I've got a calculator that runs off of light. There's a little strip that absorbs the stuff. It's about 40 years old.
     
  11. Jan 21, 2016 #10

    DaveC426913

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    Yeah but pocket calcs don't have to broadcast signals.
     
  12. Jan 21, 2016 #11

    CWatters

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    I tried to run some numbers but the tricky part for me was estimating how many key presses I average a day.
     
  13. Jan 21, 2016 #12
    You could use a keylogger to keep track. Maybe track over the course of a week or two and then find the average.
     
  14. Jan 21, 2016 #13
    I create around 4000 words per day and 5 letters aprox for one word.
     
  15. Jan 21, 2016 #14

    billy_joule

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    My wireless KB has no power switch. This suggests it only transmits when used, or at least power drain when unused is negligible. So I don't thing key strokes/day is the important metric, the real question is if energy generation of a stroke > energy consumption of a stroke transmission.
     
  16. Jan 21, 2016 #15
    @ billy_joule
    energy generation of a stroke > energy consumption of a stroke transmission - Valid
    The minimum we can get out from all of this is to extend battery life ... still need to calculate how much energy we can get from typing.
     
  17. Jan 22, 2016 #16

    CWatters

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    Unless you store the energy then average figures can be used to estimate feasibility.
     
  18. Jan 24, 2016 #17

    CWatters

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    Seems nobody else wants to do the sums so...

    Lets assume that a pair of 1000mAH (1AH) AAA batteries power a keyboard for 4 weeks and the user types 4000 five letter words a day. So that many keystrokes would have to provide the same energy as the battery.

    The number of keystrokes is 4 * 7 * 4000 * 5 = 560,000
    The energy in the battery is 1.5 * 1* 3600 = 5400J

    So each keystroke must provide 5400/560000 = 0.01J

    Work = force * displacement
    so
    force = work/displacement

    Lets say the useful key travel is 2mm or 0.002m..

    Force = 0.01/0.002 = 5N

    I think that's about an order of magnitude too high?

    According to this..
    https://www.kinesis-ergo.com/wp-content/uploads/2013/06/freestyle_vs_ms4000-800x3381.jpg
    ..typical keyboard forces are around 40-60 grams or 0.5N
     
  19. Jan 24, 2016 #18
    Only 10%? That`s barely 3 more days of usage :)
     
  20. Jan 24, 2016 #19

    russ_watters

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    I did, and got a similar answer (mine was all in terms of energy though), but wasn't going to share it with the OP...
     
  21. Jan 25, 2016 #20

    CWatters

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    ???
     
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