IR LED circuit question.

Discussion in 'The Projects Forum' started by jeffjohnvol, Oct 15, 2008.

  1. jeffjohnvol

    Thread Starter Member

    Oct 15, 2008
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    I have a security system that I would like to increase the visibility of the IR camera. I was going to get about 30 jumbo IR LEDs and build a driver circuit.

    With a 12 v power supply, if I have a 1.2 v drop LED and wanted to run 100ma through them, could I put 8 LEDs in series for a 9.6 volt drop and a 24 ohm 0.5 watt resistor?

    Thanks in advance.

    Jeff
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    It will work fine if the LEDs do not get too hot.
     
  3. jeffjohnvol

    Thread Starter Member

    Oct 15, 2008
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    0
    Thanks.
    Jeff
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Be careful what wavelength of emitter you use.. ie. 950nM is very poor and will not be easily visible, where 850s are better.

    Steve
     
  5. jeffjohnvol

    Thread Starter Member

    Oct 15, 2008
    27
    0
    Ah. I didn't know that. Good to know. A friend sent me a link to a 4x7 array, which is what I was going to try to make. It doesn't say what wavelength it is though. I assume it would be geared towards the 800 range, but can't be sure.

    http://www.mcmelectronics.com/product/28-6418&CAWELAID=220326105

    I may order one of these and see if it does the trick. It would save me quite a bit of soldering.
     
  6. karthik_dm

    Member

    Oct 16, 2008
    27
    0
    -----------
    100mA thru a LED is not wise...led current rating is not safe above 40mA..u can use three LEDs in series through a 180-ohms 0.5W resistor..for 12volts...u connect such series combination in parallel for getting more power....
     
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    These LEDs are 1.2V IR ones, not 3.5V white ones.
    At 100mA they dissipate only 120mW. The white LED dissipates 120mW at a current of only 34mA.
     
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