IR Leds

Discussion in 'General Electronics Chat' started by FroceMaster, Feb 21, 2015.

  1. FroceMaster

    Thread Starter Active Member

    Jan 28, 2012
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    Hi,
    Will have some IR-LEDS on a board.
    connected as house number , ex 62.

    Have heard that the LEDS will have to be pulsed, at 15-20 kHz.
    for brighter light ?

    Is that correct, or can i just hook up straight to 5v with resistor ?

    Rgds ForceMaster
     
  2. #12

    Expert

    Nov 30, 2010
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    You don't have to flash LEDs. You only do that to send information or get a bright pulse with an average power that won't smoke the LED.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
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    k7elp60 likes this.
  4. FroceMaster

    Thread Starter Active Member

    Jan 28, 2012
    420
    4
    Ok.
    If i connect the IR led as follow.
    Will the Resistor R1 be ok with 120 Ohm ?
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    How could you connected 6 IR leds?
    If the IR led is 2V/20mA, then it only can connected 5 piece.
     
  6. FroceMaster

    Thread Starter Active Member

    Jan 28, 2012
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    The LED use 1.5 v 100 ma each
     
  7. ScottWang

    Moderator

    Aug 23, 2012
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    If using 80% of 100mA.
    R=(12V-9v)/80mA=37.5 Ω, you can use 39Ω.
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @FroceMaster
    Note: 39 ohms makes 80 mA and a 3V drop.
    3V x 0.08 amps is 0.24 Watts. Too close for comfort on a standard 1/4 watt resistor.
    If you already bought a pack of 120 ohm resistors, you can put 3 in parallel to make 40 ohms of resistance and you get 3/4 watt of power handling ability (assuming you are using the common 1/4 watt resistor).
     
    Last edited: Feb 21, 2015
    ScottWang likes this.
  9. ian field

    AAC Fanatic!

    Oct 27, 2012
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    I'm sort of wondering; why IRLEDs for a house number?
     
  10. wayneh

    Expert

    Sep 9, 2010
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    So you can't see it without night vision goggles, of course.
     
  11. ian field

    AAC Fanatic!

    Oct 27, 2012
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    Maybe the postman checks all the door numbers through the viewfinder of a digital camera.
     
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