IR Leds

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

  1. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    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
    16,283
    6,795
    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
    4,854
    767
    k7elp60 likes this.
  4. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    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
    4,854
    767
    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 Member

    Jan 28, 2012
    400
    4
    The LED use 1.5 v 100 ma each
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    If using 80% of 100mA.
    R=(12V-9v)/80mA=37.5 Ω, you can use 39Ω.
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,031
    3,801
    @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

    Distinguished Member

    Oct 27, 2012
    4,415
    783
    I'm sort of wondering; why IRLEDs for a house number?
     
  10. wayneh

    Expert

    Sep 9, 2010
    12,115
    3,041
    So you can't see it without night vision goggles, of course.
     
  11. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    783
    Maybe the postman checks all the door numbers through the viewfinder of a digital camera.
     
Loading...