Transistor question

Discussion in 'General Electronics Chat' started by GARYN, Sep 5, 2009.

  1. GARYN

    Thread Starter Member

    Sep 4, 2009
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    I am an industrial electrician with basic electronic knowledge, i have just finished building and fitting a control panel for a production line. I used some of the transistor outputs (PNP) on the invertor for alarm indicators, this involved 3 terminals" live in", "switched live out" to load and "0v" which was commonod to the load negative. This makes sense and worked fine, but when i wired the output transistors of the Mitsi PLC in the same panel i only had to connect 2 terminals a "live in "and "live out" to the load, with only one 0v feed direct to the load negative. I wondered how the PLC transistor worked without a 0v connection, i.e where does the base current flow or it it grounded through the load to negative. I am mainly used to relay outputs so any advice would be appreciated......Thanks
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    The control signals to the internal relays of the PLC are connected internally.
     
  3. GARYN

    Thread Starter Member

    Sep 4, 2009
    47
    0
    Thanks but these are Transistor outputs or it it still the same thing?
     
  4. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    435
    What inside is protected, no more diagrams,just input and out put. You may get a member to help more,post all part info and what it is used for.There are members that can give you a good idea of what going on to your satisfaction.Post pictures
    will help.
     
  5. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    It is the same thing. The control signal are inside and you only have access to the part of the transistor which contacts current as to switch on/off relays etc.
     
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