Need trasistor to conduct dc source.

Discussion in 'The Projects Forum' started by Parv Bhavsar, Apr 27, 2016.

  1. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
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    Hello,
    I am using a at89c2051 in my project. In which i have +5V on output pin.
    Right now i am using two 2N2222 in """DARLINGTON PAIR""" but it only gives 399mA.....
    What is there any other npn trasistor that can conduct 12v 2-3.5A with less power dissipation.....??
    Or any other logic level switch ICs....???
    Thank you.... :)
    in advanced
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    632
    Welcome to allaboutcirucits.com.

    Making a Darlington was a good idea but with the 2N2222 and that kind of current you need to be careful about it getting too hot.

    A popular method of switching a lot of current based on CMOS signals is to use a logic level drive MOSFET.

    How much current do you need and what is the load?
     
  3. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
    15
    0
    Hello
    I am using loads like motors and
    led max load rating is 12v 1A
    So I need to supply a 12v with atleast 2.5-3 A at lower power dissiption..
     
  4. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
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    I have tried one MOSFET IRF520 but I wasn't able to figure out on which side should I connect +12v source.
    I am using two +12v sources in parallel.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
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    Would you please post the circuit you are using now? Maybe one of use can come up with a suggestion of how to use that MOSFET in your circuit.
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    The circuit as below, you can using the IRF520 to do the test, If the mosfet feel any heat then don't forget to add the heatsink.
    89C205_12V1A_Motor-LedDriver_Parv Bhavsar_ScottWang.gif
     
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  7. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
    15
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    Thank you
    Problem I have here is bit more complicated
    I have attached a image in which I am using two +12v dc sources and one of them I will be controlling through MOSFET.


    20160429_145525_800x600.jpg
     
  8. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
    15
    0
    Thank you
    Problem I have here is bit more complicated
    I hav attached a image in which I am using two +12v dc sources and one of them I will be controlling through MOSFET.

    [​IMG]
     
  9. DickCappels

    Moderator

    Aug 21, 2008
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    It appears that you want to use a MOSFET to tie two +12V supplies together, and your intent is not clear.

    What is it that you wish to accomplish?
     
  10. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
    15
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    I want to control one fluctuating dc source which will triggered when generation is 12v and load is connected.
    Both condition is checked by controller and it gives +5V output from that I want to drive MOSFET
     
  11. ScottWang

    Moderator

    Aug 23, 2012
    4,850
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    The below circuit is according to your hand drawing, but I still can't get the whole picture for what you trying to do.

    89C205_12V1A_Motor-LedDriver_PFet_Parv Bhavsar_ScottWang.gif
     
  12. hp1729

    Well-Known Member

    Nov 23, 2015
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    Do you want to turn on the motor by a manual switch or from the controller? Or do both the switch and the controller have to be enabled before the motor turns on?
     
  13. Parv Bhavsar

    Thread Starter New Member

    Apr 12, 2016
    15
    0
    Yes controller is always enabled as it takes input from hall effect sensor which when ch gives a voltage output when load is connected to primary source.
    In return Controller will give a pupse of +5V
    So I will be using tht output to drive mosfet
     
  14. hp1729

    Well-Known Member

    Nov 23, 2015
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    That doesn't answer the question. By Scott's last design the motor is on all the time and the MOSFET just connects +12 to +12.
    Is the motor supposed to be turned on by the switch?
    So what is the controller for?
    I am missing an idea of the overall plan of operation.
     
  15. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,766
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    Connecting two 12V sources together generally isn't recommended. They will never be identical. The slightly higher voltage source will drive reverse current through the other source. Is that acceptable in your application?
     
  16. crutschow

    Expert

    Mar 14, 2008
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    We are just dancing around here. Your rambling sentences are not clear.
    Your picture shows the right 12V always connected, so the left 12V has no effect, whether the MOSFET is on or off.

    Please tell us exactly what you are trying to do.
    Show the complete circuit.
    List each state of the circuit on a separate line (state table) with what is connected to what for each state.
    Why do you have two supplies?
     
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