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Solved Strange LCD Activity

Discussion in 'Troubleshooting' started by Toro1966, Aug 27, 2016.

  1. Toro1966

    Toro1966 Active Member

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    Hey guys - this may seem minor - and it is - but it is weird. I have a reprap full graphic LCD. It works perfectly fine. I noticed today that with the power off - AND the printer UNPLUGGED - if I move the bed back and forth, the LCD comes on. Not full graphics, just blue background. Is that normal? I know it's hooked up correctly because it works fine. But weird that moving the bed would generate enough power to bring the back light on - even with no plug....
     
    #1 Toro1966, Aug 27, 2016
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    DC motors* will work as generators if you spin them somehow.





    *most
     
    #2 mark tomlinson, Aug 28, 2016
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  3. danzca6

    danzca6 Well-Known Member

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    Printer unplugged? Are you saying the main power cord in the back or the USB? My LCD will be on with the USB.
     
    #3 danzca6, Aug 28, 2016
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Even with all power removed a DC motor will act as a generator if you manually move it :)
     
    #4 mark tomlinson, Aug 28, 2016
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  5. danzca6

    danzca6 Well-Known Member

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    ok...just spent a minute or so moving my x and y...no magic for me I guess. I had to try it. :)
     
    #5 danzca6, Aug 28, 2016
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    It probably depends on the LCD more than anything else. If it is sensitive to low voltages you might see some weirdness like they described. Just pointing out it IS possible. They could stop it by judicious use of clamping diodes, but I doubt they put that much effort into it.
     
    #6 mark tomlinson, Aug 28, 2016
  7. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Mine does that too. with no power and no USB plugged in, if I say, move the bed forward and backward rapidly it generates enough current on the RAMPS board to light up the LCD screen.
     
    #7 WheresWaldo, Aug 28, 2016
  8. danzca6

    danzca6 Well-Known Member

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    Good point. Maybe it is a Full Graphics LCD thing since I know Waldo is using them. Mine is an XXL.
     
    #8 danzca6, Aug 28, 2016
  9. Toro1966

    Toro1966 Active Member

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    Yep D. That's what it does. At least I know I am not the only one! Thanks Mark!

    Sent from my SAMSUNG-SM-G935A using Tapatalk
     
    #9 Toro1966, Aug 28, 2016
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  10. danzca6

    danzca6 Well-Known Member

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    Well I reckon this thread as solved...hahaha...I learned something new this morning. DC Motor voodoo magic :)
     
    #10 danzca6, Aug 28, 2016
  11. Toro1966

    Toro1966 Active Member

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    Yes sir. Thank you.

    Sent from my SAMSUNG-SM-G935A using Tapatalk
     
    #11 Toro1966, Aug 28, 2016

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