tranisistor application question

Discussion in 'The Projects Forum' started by magnet18, Jan 22, 2012.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    [​IMG]
    in that circuit, can I replace the two switches with BC547B or BC337 transistors to pull the pin below 1/3VCC to trigger it?
    I feel like I'm going to need to change the resistors...

    Also, could the same transistors be used to switch on a 6V (2AA) DC EL-Wire unit?
    as in, put it in the power line and allow current to flow when switched on?

    or do I need to use something more like a 4066?
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Yes you can replace the switches with transistors.

    For the DC EL-wire unit you need to know its current consumption in order to choose the right transistor.
     
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  3. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Thankyou!
    And I can't imagine that the EL wire would draw more than 800mA, so I'm assuming that I will be fine :)
     
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The saturation voltage performance of BC337 is not brilliant at 0.5A, so it may get hot. http://www.fairchildsemi.com/ds/BC/BC337.pdf

    The BC547 is only rated for 100mA maximum. http://www.fairchildsemi.com/ds/BC/BC547.pdf

    You might do better to look for a device with 1A or more current rating: quite likely it would have a lower saturation voltage at the current you need, as well as being potentially more reliable from being run well within its ratings.
     
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  5. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    The numbers I saw showed the max current for the BC337 to be .8A, I was just saying that it was much less than that, it's probably only in the 10's of milliamps, so I should be OK
    It's only going to run for a couple of minutes at most, so if it starts getting hot I'll switch to some beefier transistors
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Always downgrade transistors to 1/2 their max current rating.

    If you don't, you will be replacing a lot of transistors.
     
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  7. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Thanks wookie, I'll keep that in mind :)
    And I'm glad to see you're well enough to post again :)
     
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