optocoupler getting warm

Discussion in 'General Electronics Chat' started by edmundopt, May 31, 2012.

  1. edmundopt

    Thread Starter Member

    May 4, 2011

    I've run into one of my optocoupler getting warm(about 30º Celsius), I will not post a schematic because it fairly simple:

    Optocoupler TLP621 (marked GB)
    input for LED = 5v, about 15mA(330ohm resistor 5%)
    output for photo transistor 12v and about 2mA

    I'e unsoldered the optocoupler, placed into a breadboard, and used 270ohm resistor (because I've run out of 330) resistors on the 5v side, I was surprise because it runs cool.

    What I'am missing here, does the temperature diference is because of saturation of the photo transistor? should I increase the amount of current being transmited into the optocoupler to get it cooler, ou decrease the photo transistor current ?

    regards and keep up this great forum
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    A schematic would be helpful. What is limiting the photo transistor current to 2mA?