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  • Need help with leds

    Anyone know a bit bout leds or resistors?
    I am trying to get a resistor value of 440 Ohms, but i only have 220k-Ohm, 10-Ohm, and 2.2k-Ohm resistors, what can i combine to get the value?
    My supply voltage will be 12volts and my leds are 3.2v and I got 5 of them with a 20mA current.
    2009 Altima 2.5S CVT Dark Slate

  • #2
    that is not possible with those values.!
    __1__
    1 + 1 = Rtot
    R1 R2
    Sorry for the english

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    • #3
      with the resistors i have?
      Should i just stop being a lasy *** and go out and get a 440 resistor?
      or do you mean i calculated wrong, if so, i did it with one of those led caculators but it said something about a 470 resistor, is that what you mean?
      2009 Altima 2.5S CVT Dark Slate

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      • #4
        5 2.2k resistors in parallel will give you exactly 440 ohms.
        2004 4runner

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        • #5
          the calculation is Correct.!

          but it is not possible to get the correct value with those resistors..!
          is it in use in a car..?

          cos then you should set the leds to aprox. 560 Ohm (20mAMPS at 14,4 Volt)
          cause when the altenator is running, you car will produce aprox. 14,4 Volt
          Sorry for the english

          CarPC Specs.

          Via Epia MII 12000 \\ 512 Mb Ram \\ 200 GB Western Digital \\ PCmcia asus wi-fi
          Xenarc 7" Touchscreen \\ Usb Bluetooth \\ Carnetix P-1280

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          • #6
            hehe
            randu
            U think he got more than 1 of each..?
            damn, then i misunderstood..!
            Sorry for the english

            CarPC Specs.

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            • #7
              Originally posted by Mcnovy
              hehe
              randu
              U think he got more than 1 of each..?
              damn, then i misunderstood..!
              It's not clear if he does or not, but typically they come in bulk so I just thought I'd throw that out there for him. Personally I can't imagine using 5 resistors to get the value I need. Out of those values, I'd probably just toss 2 2.2k resistors in parallel and leave it at that. That should safely turn on most LEDs using a supply between 5V-20V.

              So in his case, he'll get about a 9V drop across the 1.1K resistor combo or about 8mA through the LED. I believe 20mA is the maximum current, not the turn-on current. 8mA should work fine unless he's going for maximum brightness.
              2004 4runner

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              • #8
                Well this is what i am looking at, Can i just use 2 10ohm resistors?
                cause it looks like i need a 16ohm resistor.
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                2009 Altima 2.5S CVT Dark Slate

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                • #9
                  Wait, the 16ohm thing is for hooking the LED to an opto isolator. If you're powering it directly you need a much larger value. The 10 ohm resistors will be nearly useless in that case. If you really just need the 16 Ohm setup, then put two 10 ohm resistors in series. That'll give you 20 ohms and should be close enough.
                  2004 4runner

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                  • #10
                    You can get the 470 ohm resistor at any radio shack.
                    2004 4runner

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                    • #11
                      I have 4 of each resistor i listed. So should i just do two 2.2ks in parallel?
                      2009 Altima 2.5S CVT Dark Slate

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                      • #12
                        2 - 2,2k will bring you to 1,1k
                        that will surely make you led's shine..!
                        but if you want fully output, then it isnt enough,!
                        Sorry for the english

                        CarPC Specs.

                        Via Epia MII 12000 \\ 512 Mb Ram \\ 200 GB Western Digital \\ PCmcia asus wi-fi
                        Xenarc 7" Touchscreen \\ Usb Bluetooth \\ Carnetix P-1280

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                        • #13
                          Should i just stop being a lazy *** ***** bum and go out and buy a 470 one? or a 440 one?
                          2009 Altima 2.5S CVT Dark Slate

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                          • #14
                            thats up to you!

                            you could easily but 2 2.2k parrallel, but you wont get full light output, but u will increase lifetime of the leds..! (but that would normaly not be the problem as they "live" in aprox 10.000 - 100.000 hours)
                            Sorry for the english

                            CarPC Specs.

                            Via Epia MII 12000 \\ 512 Mb Ram \\ 200 GB Western Digital \\ PCmcia asus wi-fi
                            Xenarc 7" Touchscreen \\ Usb Bluetooth \\ Carnetix P-1280

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                            • #15
                              Wait, so how do i wire the resistors in parallel?
                              2009 Altima 2.5S CVT Dark Slate

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