problem with leds in arduino

Discussion in 'Embedded Systems and Microcontrollers' started by Dabu WhiteHacker, Apr 3, 2018.

  1. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
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    0
    when i turn on the 7 volt power supply led 9 and 10 are always on
    whats the reason ?
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
    5,972
    1,129
    hi Dabu,
    The drive transistors for D9/10 are PNP, so if the Arduino pins D8 and D9 are Low 0v, the transistors are On..
    E
     
  3. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    they are not low they are turning off and on every 5 volts :/
     
  4. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    shouldnt it turn off when pin 9 and 10 goes high ?
     
  5. ericgibbs

    Moderator

    Jan 29, 2010
    5,972
    1,129
    hi,
    Thats not what you said., you did say you were pulsing them Hi/Low
    when i turn on the 7 volt power supply led 9 and 10 are always on

    EDIT:
    If pins D8 and D9 a switched to +5V and the PNP Emitters are at 5V the transistors should be Off.

     
  6. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    so what could be the problem of not turning off even when arduino pin goes high ?
     
  7. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    sory i forget the emiiter was not at 5 volt :p
    my mistake
     
  8. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    i connected emitter directly to vcc which was 7 volts :3
     
  9. ericgibbs

    Moderator

    Jan 29, 2010
    5,972
    1,129
    Measure the pins D8 and D9 actually are at +5V, if for example the Arduino output was say only 4V the transistors would still be ON.

    EDIT:
    If the Emitters are at 7V a 5V Base signal will not switch them Off...:rolleyes:
     
    Dabu WhiteHacker likes this.
  10. Dabu WhiteHacker

    Thread Starter Member

    Sep 5, 2017
    43
    0
    bro that is working awesome
    you are best (y) have a nice day :D
     
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