Increase voltage to an SMD LED.

Discussion in 'The Projects Forum' started by cobaltsmith, Nov 3, 2010.

  1. cobaltsmith

    Thread Starter New Member

    Nov 3, 2010
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    I mod Xbox's and now XBOX 360's. The new system uses SMD LED's, these babies have a completely different power consumption then what I am used to dealing with which are *3mm 5000mcd bulb type led's*. Not to mention the different power supply to the wireless controllers.

    On the ring of light it's easy enough to replace the SMD LED's with the color of your choice. However, the replacement LED's are usually much dimmer then they should be given the voltage they are supplied with. What I want to do is increase the power to these LED's thus making them brighter.

    What I've come up with so far is jumping power from the batteries, or battery pack to each of the four LED's. This will keep them on at all times, and hopefully make them much brighter. The problem is the rechargeable battery pack provides only 2.4v of power where the batteries *two AA batteries* provide 3v max.

    What I think I need is a capacitor to increase the voltage from the battery pack, or batteries to the LED's. What I can't figure out threw reading MANY different forums is what kind, or even if this will truly work.

    I know the power I want to reach the four LED's is equivalent to a 9v battery with a 100Ohm resistor. The LED's are MUCH brighter when powered like this. I'm not sure what that equates too, and the combination of these issues has brought me here. ANY help on this issue would be greatly appreciated. Thank you for your time.

    Please let me know if you need more info, and as I'm quite new to this field, please use layman's terms. Ready and willing to learn, so, figured I would try here.
     
  2. campeck

    Active Member

    Sep 5, 2009
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    3
    What kind of LED's are you trying to replace the stock ones with?

    With 9v and a 100ohm resistor, assuming the best case scenario you are using the highest voltage drop LED with a 3.8v drop and a transistor (.7v) to turn it on thats 45mA through the SMD LED which is probably rated at only 20mA.

    the voltage drop and current specs are way more important than this=
    "3mm 5000mcd bulb type led's"
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    DC drive at the max input current will work to make them brighter, but I hope you like replacing them, because their lifespan will be much shorter than any 50,000 or 100,000 hour specs might mention. Look for LED's with higher lumen output than the ones you're using if you want them brighter. Don't max out the drive current to brighten them.
     
  4. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Wow, mate... you seem to be completely ignoring Ohms Law and the LED specifications.
    Arbitrarily deciding on how bright an LED will be will result in a "ring of light" that will result in a "ring of certain death".

    First you must know the Specifications of the LED's you have and intent to use as replacements. If the If = 20mA and the Vf = 3.0V then you can not push those numbers and expect to have your LED's last very long. If they are not bright enough at the "Typical" spec ratings, then you need to look for different LED that will be brighter at
    their specified ratings. At that point you can see if the supply voltage to the current LED's
    will be able to maake the new LED's function as desired.

    For a little help on determining the correct resistors for a particular LED array try the calculator on at the following site.

    http://led.linear1.org/led.wiz
     
  5. cobaltsmith

    Thread Starter New Member

    Nov 3, 2010
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    Below are the specs for the led's I'm using. I know they are not as bright as they could be. I just want to get their brightness to their standard, maybe a bit above for a sustained period of time. I don't want to burn them out 100x faster, or fry the battery in 1/4 the time.

    As I stated I'm new to these, and as such I know nearly nothing of their specs or how to manipulate a power supply to make them do what I want.

    NOTE: I cannot find SMD LED"S in blue with a higher MCD rating. *Not the required size at any rate*.

    The calculator seems to be helpful, thank you.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  7. Audioguru

    New Member

    Dec 20, 2007
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    You listed the typical characteristics of the LEDs but did not list the absolute maximum allowed current. Their tested current is 20mA so their maximum allowed current might be 30mA.
    Ohm's Law says that with a 9V supply, a 100 ohm resistor and a "typical" forward voltage of 3.4V then the current is 56mA which will kill the LEDs very soon. If the LED is at its lowest forward voltage of only 3.0V then its current is 60mA.

    Brighter LEDs will simply have the light focussed into a narrow beam that will not be seen if it doesn't point directly towards you.

    Have you tried bright green LEDs? Your vision is much more sensitive to green than to blue.
     
  8. iONic

    AAC Fanatic!

    Nov 16, 2007
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