i have a problem with tip 31 transistor

Discussion in 'General Electronics Chat' started by poliguaco34, Jul 18, 2014.

  1. poliguaco34

    Thread Starter New Member

    Jun 6, 2014
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    0
    iam using a tip 31 power transistor to make a simple fan circuit where iam using on the base 5v adaptor with 800ma full range current
    and connecting on the collector the 12v supply
    and on the base iam adding a resistor of 10k and connecting to the ground and parrallel to it iam adding my motor
    my probleeem is that the transistor output is only 2.45 volt and the fan doesnt want to work
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,392
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    Are you trying to make a switch?

    Typical switch configuration places the device you want to turn ON between power supply and collector.

    You have the device in parallel with emitter resistor. I am not sure why you did it that way.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Try this instead...

    [​IMG]
     
  4. poliguaco34

    Thread Starter New Member

    Jun 6, 2014
    4
    0
    sry but i dont know how to connect as this connection one of my freinds told me about so can you pls tell me the right way to use transistor as switch (or isolator)
     
  5. poliguaco34

    Thread Starter New Member

    Jun 6, 2014
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    0
    ok i will try this and tell you
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    See above in post 3
     
  7. crutschow

    Expert

    Mar 14, 2008
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    Your original circuit is an emitter follower so the maximum output voltage is about 0.7V less than the voltage applied to the base.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If you connect the fan between collector and positive rail you will also need a reverse-biased diode in parallel with the fan, to suppress back-emf voltage spikes when the transistor switches off.
     
  9. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Hola Gopher,

    What program did you use for drawing?
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    "iCircuit" for the iPad. It is a simulation software with generic components and some customization for each. I paid something like 6 or 10 USD for it. I usually use free versions but this one is fairly nice. I used it for discussions and quick examples when I was helping with the tech clubs at my sons' high school.
     
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