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Thread: USB IR LED circuit

  1. #1
    Senior Member RHCP's Avatar
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    Default USB IR LED circuit

    I know very little about electronics and just wanted to make sure this circuit is correct and will work before ordering the parts.

    I'm trying to drive 8 IR Leds from a usb power source (5v max 100ma).
    Code:
                 R=V/I  = (5-4(1.2)) 
                          __________
                            .02
    
                          =10
    Since there are two groups of LEDS in parallel, the total current being drawn is 20 ma + 20 ma = 40 ma?

    I have read that even if all the LED's are the same, it's good practice for each LED in parallel to have its own resistor (instead of 1 for each lot) - is this one of those BS statements, in reality it's not going to make any difference in this circuit?





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    Senior Member BCNZ's Avatar
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    Default

    The idea that each LED should have its own current limiting resistor is in fact correct.
    Not all LEDs are created equal - some will draw more current than others, thereby making some LEDs run dimly and some bright = inconsistent brightness from all LEDs.

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