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Travis King
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 Posted: Wed Jun 06, 2007 6:21 am Post subject: Case LED |
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One of the LEDs of the "headlight" of my Apevia X-Infinity is starting to
burn out as it is much dimmer now and it's flickering. I've been looking
around on the Internet for information about LEDs, but I'm not finding a
lot. Would it be possible to replace the blue LED without replacing the
whole case and if so, how? Thanks. |
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Paul
Guest
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| Posted: Wed Jun 06, 2007 11:28 am Post subject: Re: Case LED |
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Travis King wrote:
| Quote: | One of the LEDs of the "headlight" of my Apevia X-Infinity is starting
to burn out as it is much dimmer now and it's flickering. I've been
looking around on the Internet for information about LEDs, but I'm not
finding a lot. Would it be possible to replace the blue LED without
replacing the whole case and if so, how? Thanks.
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The LED might be soldered to a small piece of PCB. But
before I replaced one, I'd want to check to see what
conditions the manufacturer was applying to it. That
is not the first time I've heard of some super-bright
case LEDs burning out.
It could also be a bad connection. A cold solder joint,
cracked PCB, heat-damaged current limiting resistor and
so on. You'd need to pull the module and have a look.
A LED circuit consists of:
1) power source
2) current limiting resistor
3) the LED
The higher the resistance value, the weaker the LED output. The
LED has a maximum current it can take, listed in the datasheet.
LEDs are now available that can take 1 ampere of current (and
years ago, I had in my possession, a LED that took 2 amps, but
you cannot buy those any more). But devices taking that much
current, need a heatsink attached to them. Ordinary LEDs might
use anywhere from 10 milliamps to 50 milliamps or so. Some
examples here - the second link is a page from the Digikey catalog.
You can see in the catalog page, that 3.5V to 4V of forward
bias has to be applied, before you get any blue light. So either
the 5V or the 12V rail of your PSU would be needed to power a
blue LED circuit, and the 5V is a bit safer. LEDs have a maximum
reverse voltage you can apply, and typical dime-store LEDs are
good for 5V in reverse (which is why hardly anyone ruins the LEDs
on their computer case, by reversing the two pin cable).
http://rocky.digikey.com/WebLib/Lite-on/Web%20Photos/LTL2T3TBK2,LTL2T3TBK3,LTL2T3TBK4,LTL2T3TBK5,LTL2P3TBK5.jpg
http://dkc3.digikey.com/PDF/T072/P2192.pdf
More trivia here, including polarity determination (so you can
figure out which is the plus and minus lead). The most reliable
info can be obtained from the device datasheet, if you can track
one down.
http://en.wikipedia.org/wiki/Led
Have fun,
Paul |
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kony
Guest
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| Posted: Wed Jun 06, 2007 1:04 pm Post subject: Re: Case LED |
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On Wed, 06 Jun 2007 02:28:12 -0400, Paul <nospam@needed.com>
wrote:
<snip>
| Quote: | Ordinary LEDs might
use anywhere from 10 milliamps to 50 milliamps or so.
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Generally speaking, the typical case LEDs can be driven at
up to 30mA, with good heatsinking via leads that are short
and soldered to a large copper plane. Even so, it should
have still lasted longer than this unless the case is fairly
old and continuously powered. A more conservative estimate
for a typical superbright LED is 20mA. However if there
are more than one LED creating some visual effect, it might
require driving the LED to the same brightness level as the
others so it *matches* the others' output instead of being
brighter or dimmer, which would hopefully be accomplished by
the drop-in replacement LED, but not necessarily.
| Quote: | Some
examples here - the second link is a page from the Digikey catalog.
You can see in the catalog page, that 3.5V to 4V of forward
bias has to be applied, before you get any blue light.
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That seems pretty high, often the forward drop is closer to
about 3.2 - 3.6V. Often the resistor used is 470 Ohm on 12V
rail or 68-120 Ohm if powered by 5V rail.
To the OP - Take out the LED and describe the circuit
*around* it. Probably a resistor going to a molex 4-pin
plug? If so, follow the circuit board traces if on a board,
and tell us the color stripes on the LED. However, "odds"
are that if you picked a typical general ultrabright blue
LED, it would be a drop in replacement.
This is unless the problem is not the LED, it might be
damaged wiring. In particular on some cases the wiring is
so high gauge (fragile) that the wire breaks off, typically
right at the point where it is soldered to the LED.
Do you have a soldering iron? It would certainly make the
repair more reliable. To start out with a plan to replace
it, it would help us to know what skills and related tools
you have as it's not necessarily likely you can just buy an
exact replacement - though you might try contacting Aspire
as you never know, they might rise to the occasion and send
you the assembly.
Do you *require* blue? You could (within some limits, red
would probably require changing the resistor as it has a
lower forward voltage drop than most) pick a different color
like purple or aqua. Here's one place that has a blue and
unlike Digikey and many electronics houses, might just drop
it in a first class envelop for minimal shipping cost if you
asked them nicely (they used to do this, YMMV if they still
will), but otherwise it'll be a crazy overhead practically
anywhere to pay $6+ for shipping a < $1 LED.
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=11757
In that case it could end up cheaper to just take the LED
out of something like this,
http://www.svc.com/lzled3blu.html
and I link SVC specifically because they will ship small
items at a USPS, First Class Mail rate is about $3 in the
US. There might be other even cheaper blue LEDs on SVC's
site, I didn't look for very long. |
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kony
Guest
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| Posted: Wed Jun 06, 2007 1:56 pm Post subject: Re: Case LED |
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On Wed, 06 Jun 2007 04:04:36 -0400, kony <spam@spam.com>
wrote:
<snip>
| Quote: | If so, follow the circuit board traces if on a board,
and tell us the color stripes on the LED.
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.... stripes on the resistor, not LED. |
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kony
Guest
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| Posted: Thu Jun 07, 2007 1:23 am Post subject: Re: Case LED |
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On Wed, 06 Jun 2007 16:33:57 GMT, "Travis King"
<Anonymous@none.com> wrote:
Since this is one LED out of 4, you might find the
replacement doesn't quite match in hue or intensity. If
having it match is important, I would buy at least 4 of the
same replacement LED then after having replaced the one, if
it doesn't match then replace the others as well.
| Quote: | The case is two years old, and it is almost continuously on. I will have to
look to make sure, but I believe all the blue LEDs are connected together,
and then there's a place to plug in a y-splitter where you plug your 4-pin
molex connector into. Then there's another one for the digital temperature
monitor.\
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Two years is nothing for an LED, it should last many years
longer unless they had overdriven it (too much current) to
produce more light and/or use a lower grade (cheaper) LED
for the same amount of light. It might just be flawed, but
if they had overdriven it, if you find it later fails again,
you might use a slightly large value of resistor than they
did (and accept the associated decrease in brightness,
except that if you chose an LED with a higher MCD value then
it might still be more or less bright regardless of a little
lower current). Then again while it looks like an LED
failure it might be wiring, I'd take it apart and examine it
before ordering anything.
There's lots more to picking LEDs but it might be overkill
to mention things like viewing angle as it's likely a
typical (most common) 30' or less type, not wide-beam.
| Quote: | I would rather stay with a blue LED or else I'd have to change all of my
LEDs in my case to a different color. My case fans, digital temperature
display, and all the LEDs that light up the "X-Infinity" thing and the
headlights are blue. The case looks almost like a BMW towards the top, and
each headlight consists of two LEDs.
I have a soldering iron, and I know how to get to the front panel and remove
the LEDs. I am up for alternatives besides replacing the LEDs such as
putting different kinds of lights in there that might produce the same
effect.
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LEDs are the best bet. Mounting anything else could be
fiddly and would (normally, ignoring this odd failure you
have) be shorter lived and potentially produce more heat and
would make it harder to achieve the same color, brightness
level, and semi-focused output without a lens and a current
control method. |
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