Project:Operate a relay with serial port

Discussion in 'The Projects Forum' started by uzair, Dec 31, 2007.

  1. uzair

    Thread Starter Active Member

    Dec 26, 2007
    110
    0
    I want to operate a relay with the data pin of serial port but when the relay is attached to the pin the voltage drops from 11 volts to 2 volts.The relay does not work.How can I manage the voltage drop?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The output of the serial port is a logic level voltage, and is not intended to drive a load like a relay. You would need to construct a circuit that will sense the level shift and drive the relay. An LM311 voltage comparator might be able to do this. It's output will sink 50 ma.
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
  4. uzair

    Thread Starter Active Member

    Dec 26, 2007
    110
    0
    i want to design my own circuit. idont want to use any of the available chips.
    so please provide some logic that i can understand.
    thanks
     
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