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Thread: LED Query

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    LED Query

    Ive got my watercooling system setup and running now, and ive noticed that on my res and cpu block there are some indented holes for mounting some LEDs in, im thinking about mounting a UV LED in each of these (5mm).

    Ive got one already in Red thats connected to a molex which came with the kit, but was wondering where abouts i could get two UV leds which are connected to molexs, or how would i go about making them myself?

    Ive looked on the bay and theres nothing on there at all, and ive looked at other places, and they just sell the seperate, but i want to be sure before i go making them myself.

    Any help would be appreciated.
    ECS RS482-M, A64 4400+ X2 @ 2.6Ghz,
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    Seething Cauldron of Hatred TheAnimus's Avatar
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    erm its very easy to connect up 2 UV leds to a 5v power line. All you need to do is determine the resistor, which is calculated by the specifications of the LED.

    LEDs can be thought of as greedy, they will try to take so much current that they will burn out and explode. As such we need to put them on a diet, we do this with a resistor. So you will need one LED, one molex plug, and a resistor determined by the LED.
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    • Butcher's system
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    Typical LED wants about 10-20 mA. They have a voltage drop of about 2V, so you want a resistor for the desired current (lets say 10mA) at 3V (5-2).
    Ohm's law gives the resistor:
    R = V/I = 3/0.01 = 300 ohms.

    So you want the positive wire from the molex going to a 300 ohm resistor, then connect that to the anode of the LED, then connect the cathode of the LED to the negative wire. The cathode is usually indicated by a flat on the body of the LED.

    For 2 LEDs either use two resistors, or wire them in series and double the voltage drop (i.e. use a 100 ohm resistor.) Note that you won't be able to power more then two LEDs in series off the 5V line.
    Last edited by Butcher; 16-03-2006 at 03:12 AM.

  4. #4
    Seething Cauldron of Hatred TheAnimus's Avatar
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    quick thing to note, most UV led's use about 3.6V, a physist friend of mine tried to explain why its higher than standard red types once, my eyes melted, all the principle butcher gave was 100% bang on, just that V should = about 1.4V. So a 300ohm resistor would work, but it would limit the current a bit more than needed, so it would be dim, a 100ohm would let it be brigther!

    its important to check the specifications of the LEDs you get... come to mention it, i might have some UV ones nocking around, i'll have a look this weekend, save you wasting money just ordering two.

    nice pictureful link on the matter:
    http://www.lsdiodes.com/shop/index.php?main_page=page_4
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