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Thread: Another "how do I run my led hot" thread

  1. #1
    Board Lurker tankhog's Avatar
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    Default Another "how do I run my led hot" thread

    I've been looking at some older posts about over driving and could use some clarification. I'm well aware life spans and danger blah blah yakity smakity...

    So the options you have are:

    Constant current driver
    The other driver in the store (I forget what it was listed as but you can set the output)
    Or using two buck pucks.

    Since current and voltage are relational, would using a smaller rated resistor have a similar affect or would it just fry the LED?
    For example: if I were to use a 1ohm 2w resistor when having used ohms law to calculate 1.1ohms 2.17w as per the luxeon3 red /o

    I understand there's a lot of other factors we can't control ( the luck of the draw right) but in a perfect world and the led runs to it's listed specs...

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    Is this a question?

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    Board Lurker tankhog's Avatar
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    Yes?

    Since current and voltage are relational, would using a smaller rated resistor have a similar affect or would it just fry the LED?
    For example: if I were to use a 1ohm 2w resistor when having used ohms law to calculate 1.1ohms 2.17w as per the luxeon3 red /o

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    Council Member Novastar's Avatar
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    The difference is negligible, so... I think you'd be fine. As it is... don't forget that your multimeter itself has its own resistance.

    But really... when you're talking about a 0.01 difference regarding ohms, volts, watt-capability... it's generally not a problem. It's still POSSIBLE that you'd "kill" the LED (as it only takes a certain amount "out of spec" to cause an LED to possibly die)... but... it's pretty remote.

    The main thing is... don't give an LED that has a fwd voltage of ~4v... uh (for example)... 8v.
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    Jedi Knight cannibal869's Avatar
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    Default

    It would also help to know what are you trying to achieve with what resources...

    i.e. what is your setup?
    Power pack - type and voltage
    soundboard?
    LED driver (if any)
    LED - is the Lux3 red what you're really asking about?
    (and what's the end goal? - i.e. are you trying to overdrive it and asking how best to achieve this?)

    Also, FYI, this is going to sound a bit snarky, but when I read the title of your thread, I thought, "well, if you want to run the LED hot just don't use the heatsink..."
    Last edited by cannibal869; 02-11-2011 at 12:25 AM.
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    Thanks For the reassurance Nova, I sort of figured it wouldn't amount to much difference but better safe than sorry.

    -------
    I'm running a lux 3 red/orange with 4.5V (3xAAA) and the 2010 obiwan cheap hasbro, no drivers aside from the obi board.
    What I'm trying to achieve is as anyone to get the LED it's brightest as I can, but at the same time making sure using the smaller resistor won't damage my components. * I was just curious if there were other(cheaper) methods aside from the drivers in the store or using two buck pucks to do that. Up the current as it were.

    I used the term running the led "hot" based on info from this URL regarding what happens when you overdrive an LED.
    "...*LED will have a spec that represents a typical point along the operating curve. That would look something like “3.3V @ 20mA typical.” Driving this LED above that point will shorten the useful life. You may also get a maximum rating for either current or forward voltage. Exceeding those ratings will dramatically shorten the useful life, generally ending it suddenly in the process. ***But driving an LED “hot” will make it burn more brightly for a shorter time***..."
    http://led.linear1.org/what-happens-...rdrive-an-led/

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    Jedi Council Member cardcollector's Avatar
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    I have found a led colors (except for reds) can take about .5v mOre than they are rated for without any long term side effects. Voltage does not make the led brighter though, it Is current that does that.I have driven some LEDs twice their rated current. Sure it cuts the life of the led by a couPle hundred hours, but considering LEDs have alifespan of more than 100000 hours, I don't worry about it.
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    Q. How far can I overdrive a power led?

    Since high power leds have a thermal lug you can push them about as far as your thermal solution will handle. Normally from 25% to up to 45% of the max rating. Heat is what kills these leds for the most part. The leds with lower thermal resistance are the ones that can be pushed further.

    Direct drive is sacrilege imo. If you want it bright then why have it dim with battery voltage?

    calculator

    http://led.linear1.org/1led.wiz

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    Using my PC, can I run a rebel royal blue on 1.5a? Or would that be to much? If so what value should I use?

  10. #10

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    Quote Originally Posted by Darth Scorn View Post
    Using my PC, can I run a rebel royal blue on 1.5a? Or would that be to much? If so what value should I use?
    That actually might be too much, depending on your blade flicker settings. I have run my Rebels in the 1250ma range with a light blade flicker on the PC and they seem to handle that just fine. I believe the value for that is 58.

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