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  1. #1
    300+ Forum Addict NicD's Avatar
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    Advice on LEDs and resistors

    Just about to buy a stack of resistors for annunicator LEDs (B737) and I'm after some advice on what size resistor would be best to get to give a realistic level of brightness. We're using 5v power supply with 20mA for the LEDs...

    thanks!
    Nic D'Alessandro
    737NG builder (Hobart, Australia)
    http://simsation.com.au

  2. #2
    75+ Posting Member Olympic260's Avatar
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    Take a look here

    http://www.kpsec.freeuk.com/components/led.htm

    It explains how the resistor can be calculated very easily.

    Hope it helps

    Chris

  3. #3
    1000+ Poster - Fantastic Contributor Bob Reed's Avatar
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    Hey NicD. I am using a 330ohm resistor on every led. My leds are 3 volt max and I am feeding them with 5volts from a computer power supply. Reading at the led, with my meter, is right around 3 volts. Been doing it his way for some time with no problems. My leds are in wired in parallel.
    Bob Reed

  4. #4
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    Quote Originally Posted by Olympic260 View Post
    Take a look here

    http://www.kpsec.freeuk.com/components/led.htm

    It explains how the resistor can be calculated very easily.

    Hope it helps

    Chris
    Excellent reference Chris.... Thanks

  5. #5
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    brianwilliamson's Avatar
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    Here is another link that is quite useful:
    http://metku.net/index.html?sect=vie...calc/index_eng

    Personally I do not use resistors at all. It is too much work installing them !
    I use a regulated power supply with a potentiometer to vary the voltage to suit the intensity required. I actually use a couple of power supplies, one at 3.5 volts for the bright leds, and a 2.1 volt supply for the lesser leds on the backlit switches. If you connect up an external potentiometer in parallel to the one that sets your voltage in the power supply, you then can vary the intensity of all your leds down and actally turn them off.
    Cheers..............Brian W.

  6. #6
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    [quote=brianwilliamson;7596]Here is another link that is quite useful:
    http://metku.net/index.html?sect=vie...calc/index_eng
    quote]

    WOW... that's impressive. We need to stick this in our "Builders Links"

  7. #7
    25+ Posting Member
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    Brian, Could you show me how you incorporate the pots into the circuit?
    My setup:
    pc 1: MSI K9NSli, onboard sound and lan, LC AMD 6400X2, 4096mb corsair 800ddr2, Pcie 7600GT with 32" lcd@1360x768
    pc 2:Asus mobo, onboard sound and lan, Athlon xp2800, 1.5gb pc4200, agp 4200Ti and 10.4" touchscreen lcd@1024x768
    pc 3:generic mobo, Athlon xp2400, 1gb 133 ram, agp Radeon 9200, pci Radeon 9250 with dual psone vga lcds @768x576
    Cougar, f16u, 7.1 sound, 4.1 sound, Trackir 4pro and vrf tfs seat pack.

  8. #8
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    brianwilliamson's Avatar
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    OK I will try to explain. Hard to do without being able post a picture and a circuit diagram !
    Basically I use a kit to build a variable power supply, which is fairly simple and available at most electronic shops. In the setup they have a variable pot to set whatever voltage you need between 1 to 30 volts. All you need to do is connect another pot in parallel to the one in the kit and run a legth of 2 wires with that external pot connected to the one in the power supply and then set the maximum voltage you require. The external pot is then used to vary the voltage downwards.
    Hope this helps.....................Brian W

  9. #9
    300+ Forum Addict NicD's Avatar
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    Thanks for the advice guys - very useful info.
    Nic D'Alessandro
    737NG builder (Hobart, Australia)
    http://simsation.com.au

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