how to connect IR led to 555...

Discussion in 'General Electronics Chat' started by TNT, May 26, 2005.

  1. TNT

    Thread Starter Member

    Nov 21, 2004
    11
    0
    Hello.

    I don't know how to connect IR led and a resistor to the output of 555 (pin 3).
    where to put the resistor before or after the IR led?
    should I connect the out pin to VCC or ground?

    what is the best connection?
    can someon explain it to me?

    Thanx.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Useful trick.....

    If you need to determine that the IR-LED is operating, you should be able to take any digital camera and aim it at the LED and the IR-LED light output will be rendered visible on the digital camera's display.

    hgmjr
     
  3. haditya

    Senior Member

    Jan 19, 2004
    220
    0
    how does a digi cam pic up IR and display it...arent these supposed 2 be invisible rays
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Excellent Question, haditya.

    It turns out that the CCD (charge coupled-device) that is the basis of the image capturing system in a digital camera responds to the wavelength referred to as infrared.

    We are so use to chemical film photography that we forget that the imaging system in a digital camera is silicon-chip based.

    hgmjr

    P.S. A simple experiment is to take your digital camera and a TV remote control and while pointing the business end of the tv remote at the camera lens take a look at the camera monitor. Press any key on the tv remote and you will see what I mean. The first time I did it I almost fell out of my chair. Digital Cam-corders will work also.
     
  5. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    Assuming you want the l.e.d. activated when the 555's output is high.
    Connect the resistor to pin 3, the other end of the resistor to the l.e.d's anode, and the l.e.d's cathode to 0V. (But it doesn't matter which is "first", the resistor or the l.e.d.)

    If you want the l.e.d. activated when the 555's output is low, connect the R to the positive supply line, its other end to the l.e.d. anode, and the cathode to pin 3.
     
  6. TNT

    Thread Starter Member

    Nov 21, 2004
    11
    0
    I want to transmit a square wave. so which one to use?



    Thanks.
     
  7. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    Connect the l.e.d. and resistor from pin 3 to 0V.
     
  8. TNT

    Thread Starter Member

    Nov 21, 2004
    11
    0
    Ok. Thanks
     
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