anyone have experience with changing cdrom LEDs?

[shocksyde]

yeah i know, i ask too many questions about LEDs, but anyone have experience with changing cdrom LEDs?

shock

[Roy]

Of course. http://sysopt.earthweb.com/forum/wink.gif Things like that all are the same. And they're all different. If someone put the unit together, someone can take it appart. Then the mounting method is discovered and the replacement process is evident. Piece of cake. http://sysopt.earthweb.com/forum/wink.gif http://sysopt.earthweb.com/forum/wink.gif

[shocksyde]

but i cant just any LED can I? dont i have to find out what the voltage drop is across the current LED so that i can find one with the same values?

shock

[Roy]

Most LEDs are generally interchangeable. Many units use a FET "driver" off the 5V or 12V supply to limit the current without regard to voltage. Although blue LEDs have a higher voltage drop spec, it's the current that really matters. If you replace a "reglular" LED with a blue, it still will seem very bright because our vision is much more sensitive at that end of the spectrum. For example, when you see 100 unit (the max) white level on a color TV screen, the blue portion of the signal is at 10 units.

So, what are you really trying to accompllish?

[Graham]

Shock,
Let me guess .... blue again ??

You must post some pictures of your room when all the blue LED's are on, gotta see it.

If you must dismantle your CD, be carefull it is delicate.

G

[shocksyde]

LOL graham, right on the money. oh believe me i will post picks when all the LEDs are in place. lets just say they look like headlights and i'm not even done yet. i accidentily blew 2 of them today (stupid mistake), so i'm set back a little.

add the LEDs to the blue neon and people think i'm being abducted every night or something, an erie blue glow emits from my room http://sysopt.earthweb.com/forum/smile.gif

also, i already had to take the cover off of the cd to paint it, so it wont be so hard. if all goes well, my puter shall be brighter than the sun itself! (well let's not get carried away here...)

shock

[Graham]

Shock,
Watch out for the 'brownout' when you power it up http://sysopt.earthweb.com/forum/wink.gif , better warn the neighbours.

G

[This message has been edited by Graham (edited 12-04-2000).]

[shocksyde]

well the good thing is LEDs take so little power. I still have a large Nine Inch Nails logo made of 50 or so LEDs in the works, lets see how that turns out.

shock

[Daemoniumm]

:-0 Wow, Shock! That should look KEWL! As graham said: You have to post a pic once you finish it. http://sysopt.earthweb.com/forum/smile.gif

[shocksyde]

let me ask you guys somethin....for my large NIN logo, can i just use one resistor and then attach all the LEDs together in a huge series?

or would it be more efficient to run maybe 5 LEDs in parallel and have 10 sets? (meaning i would need 10 reisitors instead of one).

shock

[Graham]

Shock,
yes you could use a single resistor, but.. it would need to be quite a high power rating.

Say 40mA per led x 50=2A, with 3V across the diodes thats about 9V across the resistor, power=IxV, or 2X9=18watt, just as an example the little resistors, about 1/3 in long, are about 1/2 watt.
There is another but, the leds will not all draw the same current (nothings perfect), so it would be best to use individual resistors.

G

[shocksyde]

so essentially you mean i should run each LED individually from the power supply? 50 resistors and 50 LEDs?

like this:

5V-----------------------------------------
| | | | | | | |
R R R R R R R R
| | | | | | | |
L L L L L L L L

where R is a resistor and L is an LED.

i didnt add it in, but of course they will all be grounded somehow.

(if my little schematic doesnt show up right, sorry)

shock

[Graham]

Shock,
Thats the way I would do it, resistors are cheap, with care you could make a neat job of it.

G

[shocksyde]

alright, this friday i get paid, so i'll order a bunch of LEDs! i'll post pics when its done, i swear!

shock

[justy]

Shock with that number of LED's I'd say you could probably just run them series without any resistor's.

I installed a floor lighting system that run of a 15v A/C transformer unrectified and unregulated, connected to 200 standard LED's in series.

The mains voltage here ( Ireland ) is 220 A/C 50Hz.
The LED's half wave rectified the 15 v supply, so no flicker was seen at 25Hz. The current was the same through them all because they were in series, and they handled the voltage okay, because of the individual voltage drop across each LED.

Just a thought, save you alot of soldering! and would definetly put less load on the PSU.

All the best, Justy.

[This message has been edited by justy (edited 12-05-2000).]

[Roy]

Depending on the specs for the specific LEDs you get ~ I know, blue = higher voltage drop ~ it would be easiest to put them in series groups of four- to six across the 12V supply.

As a test, I would try six to start and work my way down towards 4, checking the drop across one in the string each time to make sure I wasn't exceeding the spec.

[shocksyde]

well i have decided that getting that many blue LEDs would be way too expensive, so i have decided to go with green. the ones that i am looking at have a 2.2 voltage drop at 20 mA. at that voltage drop, would you think rows of 5-6 would work ok?

also, this means i would only need one resistor for each string right?

i keep getting 3 opinions no matter where i look....some of the people say just run em in parallel with resistors and the 5 volt line, others say just use the 12 volt line with no resistors (i dont see how that would work at all unless i was using only 5 or 6 LEDs), yet others (such as roy) suggest that i run them in parallel strings with 4-6 LEDs in each string on the 12 volt line.....which is best!?

as you can i am anxious to start this project http://sysopt.earthweb.com/forum/smile.gif

shock

[johnqp]

Oops - never mind

[Graham]

And you thought it would be easy !!!!

G

There are many ways to skin a cat.

G

[shocksyde]

i guess roy's way seems to be the way to go.

shock