opto isolator question

Discussion in 'General Electronics Chat' started by CaliusOptimus, Dec 8, 2009.

  1. CaliusOptimus

    Thread Starter Well-Known Member

    Aug 14, 2005
    59
    0
    ive never used an opto isolator before, and im thinking it will be the best thing to use for a project im working on.

    my local supply has a few of these on the shelf, and im just curious how to use them. pins 1,2,4 and 5 are no-brainers, but i dont know what to do with the base connection.

    say i wanted to use the transistor to control a cmos gate....i would tie the emmiter to gnd, and a 1k resistor between Vdd and the collector. what do i do with the base pin?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You just leave the base open. You will find that a larger pullup will work better, as the 1K value will probably not let the transistor go to 0 volts. See if 47 K doesn't work better.
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
  4. CaliusOptimus

    Thread Starter Well-Known Member

    Aug 14, 2005
    59
    0
    cool! thanks guys, much appreciated.
     
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