Controlling Relays with the Serial Port

Discussion in 'The Projects Forum' started by electronics wiz, Oct 23, 2008.

  1. electronics wiz

    Thread Starter Active Member

    Mar 15, 2007
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    0
    Well, a while back i built a laptop cooler with a simple switch to turn it on, but i wanted to be able to connect it to the serial port to turn it on. So i went to radioshack and bought a 12v relay to be triggered by the serial port
    but the serial port does not have enough current to drive the relay. so i need a way to drive the relay without directly hooking it up to the serial port.

    thanks,
    electronics wiz
     
  2. karthik_dm

    Member

    Oct 16, 2008
    27
    0
    fine...please mention the ratings of the fan you're using for cooling.either you wish to drive the fan using power from the serial port?
     
  3. Externet

    AAC Fanatic!

    Nov 29, 2005
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  4. electronics wiz

    Thread Starter Active Member

    Mar 15, 2007
    54
    0
    i want to control the fans from a 12v wall wart.
    i want to create my own circuit
     
  5. electronics wiz

    Thread Starter Active Member

    Mar 15, 2007
    54
    0
    ok thanks figured it out
     
  6. karthik_dm

    Member

    Oct 16, 2008
    27
    0
    it's waste of time to control a dc motor using serial port...because serial port is a complicated one..we can't easily program using serial port. but instead i suggest to use parallel port for such application, it will work fine..but in laptops it is not present..how ever if you wish trying serial port, use the signal from the TX pin(pin3),gnd pin(5pin).connect a 3.1v zener to Tx pin and a series resistor of 10k and connect to the base of a transistor to drive the fan motor. "remember this should be designed with caution since the circuit is not electrically isolated". for isolation use an optocoupler like PC817.
     
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