Amplifying current using a Darlington Transistor

Discussion in 'The Projects Forum' started by zarabotkalesna, Nov 22, 2015.

  1. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    Hello everyone.

    I want to use a Darlington Transistor to amplify current to drive one CPU fan.
    I am limited with supplying sources of 5V.
    CPU fan voltage, power and current: 12V, 2,16W & 180mA.

    Please see picture below and tell me why I cannot reach 180mA?
    Thanks in advance. :)

    Screenshot_3.png
     
  2. ian field

    Distinguished Member

    Oct 27, 2012
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    Probably because you're only giving a 12V fan 5V.
     
    Roderick Young likes this.
  3. ISB123

    Well-Known Member

    May 21, 2014
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    Because Mr.Ohm said that current is directly proportional to the voltage and is inversely proportional to the resistance.
     
  4. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    I knew that, but what's then the purpose of amplifying?

    Screenshot_5.png
     
  5. ISB123

    Well-Known Member

    May 21, 2014
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    You have two choices:
    1. Increase Voltage
    2. Reduce motor windings
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    [Dumbfounded]...................I'll let someone with more patience explain it to you.
     
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  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'm afraid I'm not that someone, but I suggest a search for 'amplifier' will give you plenty of explanatory material.
     
  8. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    Then Sorry for asking... :))

    I'm pretty new to these concepts, and I'm here to learn, but if you don't want to help me that's not a problem, I'm good with that too.
    But remember, even you, as well, didn't known anything until you learnt it.

    Have a nice day :))
     
  9. ian field

    Distinguished Member

    Oct 27, 2012
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    You'd get a little more enthusiasm if you did at least *SOME* research off your own back.
     
  10. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Option 3, replace said 12V fan for a 5 V one....fixed
     
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  11. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    Thanks :)
     
  12. Sinus23

    Member

    Sep 7, 2013
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  13. ian field

    Distinguished Member

    Oct 27, 2012
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    5V fans are pretty gutless - I've been known to run 12V ones up to 18V when mounted next to a light bulb for chopping up flies etc.
     
  14. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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  15. ScottWang

    Moderator

    Aug 23, 2012
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    The purpose of amplifying is to using a small current or voltage to control the bigger current or higher voltage.

    When you can control the current and voltage then you can adjust the speed of motor and the brightness of led or lamp, when you can control the current and voltage then you can control the load through computer, even through the smart phone to adjust the brightness of led or lamp, remote car speed control, etc...
     
  16. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    Understand, Thanks ;)
     
  17. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Because your base current is such a large percentage of the collector current, your circuit is acting as a saturated switch rather than as a linear amplifier. Also, both collector currents are wrong. The direction of collector current in the left transistor is backwards. Since its current does not go through the right transistor, that transistor's current is wrong. Both collector currents go through the right transistor emitter. If you add reference designators to each component, this stuff is a whole lot easier to talk about.

    The circle with 898 next to it is not a standard schematic diagram symbol, so no one here can say what its electrical characteristics are. It is not clear if 61.5 mA is the limit of the current available from the 5 V source, or the current drawn by the magic circle, because both are labeled the same. If the magic circle has an equivalent resistance of 66.7 ohms, then the circuit is behaving.

    The reason you got such poor responses is because your question does not indicate any understanding of the most basic aspects of DC circuits, and without that there is no language for communication.

    ak
     
  18. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    a
    Thanks for your reply.
    I have a basic understanding of DC circuits, but now I'm trying to learn new concepts, and I know those are banal to you...
    Next time I'll do a better research before I post anything.
    Thanks to all :))
     
  19. ian field

    Distinguished Member

    Oct 27, 2012
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    It would probably do the TS some good to search on audio amplifier clipping and read through the articles - they pretty much cover why an active device on a 5V supply cant put 12V into the load.

    The options are; use a 5V fan as you say - or use a flyback converter to boost the voltage.
     
  20. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
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    I understand, thank you :))
     
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