switching a 0v

Discussion in 'General Electronics Chat' started by jonisonvespa, Jan 6, 2013.

  1. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
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    hi
    im trying to switch a 0v into a processor using a 4n25 i think ive finally understood how it works, am i correct in saying when my switch is made s1 i get 0v @ V0, i intend using 1k for both resistors.
    thank you
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    What is Vi? And what is Vcc?
     
  3. tshuck

    Well-Known Member

    Oct 18, 2012
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    Well, you won't get 0V, but you will get a logic 0...
     
  4. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
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    sorry forgot to say
    vi 5v,
    vcc 5v
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    How did you decide on 1k for the resistors? 1k seems a little high for the input resistor and quite low for the output.
     
  6. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
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    ok i will linit the current to led to 25ma using a 200r
    and limit the current into my ic to 10ma using a 500r (max current into the pin 40ma)

    am i still correct in saying i will get a low at v0?
     
    Last edited: Jan 6, 2013
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    As someone who actually looked at the data sheet... go ahead and use 1K/1K, it will work fine like that. Looking at the Vishay data sheet C-E saturation is defined as 0.4V, so you should see less then that as your "0V" output, which is good for a logical zero.
     
  8. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
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    thank you ernie

    my original idea was a bit complex adding a n type mosphet and relay to switch a ov to my pin but i then thought of this, i promise you i did look at the data sheet i have lots in my data sheet folder, im very new to electronics, i kinda of knew a 1k/1k will work but always wanting to reduce my current was my thought of using a 1k

    thank you very much
     
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