Please help me solve this doubt

Discussion in 'The Projects Forum' started by paldep, Mar 8, 2016.

  1. paldep

    Thread Starter Member

    Mar 3, 2016
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    I built this circuit using a red led ,a tip131 transistor and a battery of 3.7 volt. Nothing happens. But if i Connect a dc motor from a cd player in parallel with the led it works. How is it possible? What the dc motor does to the circuit? C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_images5Y3SBMKJ.jpg
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Leds wired in reverse, also you need a series resistor in each led.
     
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  3. paldep

    Thread Starter Member

    Mar 3, 2016
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    Does dc motor invert polarity?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    No, just goes in the opposite direction....
     
  5. paldep

    Thread Starter Member

    Mar 3, 2016
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    And it would affect the led... Anyways led is wired perfectly. Maybe is it wrong the circuit?
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Put the leds across the battery, both ways round, see which way they work...
     
  7. paldep

    Thread Starter Member

    Mar 3, 2016
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    It's very strange because the led starts blinking only when i Connect the motor in parallel with it
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The image is so small and fuzzy that there is not any detail. Please post one that is larger and more clear. Are there any resistors in the circuit anywhere?

    ak
     
  9. paldep

    Thread Starter Member

    Mar 3, 2016
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    No resistors. I found the image on the net. Sorry :(
     
  10. TheButtonThief

    Active Member

    Feb 26, 2011
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    What's with the headphone connector attached to the base and emitter?

    It's a very odd looking circuit. Where's the current limiting resistor for the LED's? Where's the base current limiting resistor? Where does the headphone connector go?

    Your motor is providing a resistance between the collector and emitter and saturating the base of the transistor, it's in open circuit without the resistance of the motor coils.
     
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  11. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Leds need a series resistor to work properly, otherwise they will burn out, try putting one of them across the battery with a 100 to 470ohm resistor in series.
     
  12. paldep

    Thread Starter Member

    Mar 3, 2016
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    The headphones connector goes into an mp3 ipod . I plug it to the output of an amplifier.
    When there's a peak of 0.7 volt the led start to blink. But without a resistor the led will burn. Thank you guys.
     
  13. TheButtonThief

    Active Member

    Feb 26, 2011
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    So it's like a VI meter?
     
  14. paldep

    Thread Starter Member

    Mar 3, 2016
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    It's bass syncing. Not so sensitive but nice to see
     
  15. TheButtonThief

    Active Member

    Feb 26, 2011
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    I'm sure there are plenty of other circuit examples out their in the googleverse that'll actually work. The one you've posted lacks some fundamental components and I'm not suppressed it doesn't work.
     
  16. paldep

    Thread Starter Member

    Mar 3, 2016
    41
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    Can someone draw me a circuit that use a 5 volt source using a transistor a red led and all the necessary components? Thanks
     
  17. paldep

    Thread Starter Member

    Mar 3, 2016
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    The audio souce is from a Pam8403 max 3w running on 5 volt.
     
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