LED Help

unklerosco

Right Ladees.... I'm starting my new project. A desktop case(u heard right, i'm goin oldskool!!!) I'm new this sort of thing, I'm handy when it comes to the physical side of modding but as for electrics im fooked. I've stripped the case down n I want to change the hard drive n power leds(ie. change the colour) They're small square leds(great discription). I know that when u buy leds one prong? is longer than the other... Is this the + connection? or the other way round? Also what kind of led do i need and where can I get them...(i'm looking for blue/white/red)

cheers

Rosco

CombatCow

well first of all :



And secondly, id bring the led you want to replace into peats or maplin to find a diff colour replacement
Btw if you did connect up the led the wrong way round, the only thing that would happen is it wouldn't light up.

What else does your new project entail ?


CombatCow

ARGINITE

also you will need to attach current limiting resistors to your new leds.
so if you get the rail voltage that you will be running them of and do the following.

{rail voltage(ie 12V)-voltage drop accross led(if buying from maplin this will be in the catalogue)}/current drawn by led(also in maplin catlogue)=resistor value.

po0k

Originally posted by Combatcow
well first of all :



And secondly, id bring the led you want to replace into peats or maplin to find a diff colour replacement
Btw if you did connect up the led the wrong way round, the only thing that would happen is it wouldn't light up.

If it's a 3.3V LED and you try running it off 5V in reverse polatiry it'll break down and won't work.

ARGINITE's right about the resistor in series with the LED. But you should only need to run them off 5V at the most. Prehaps look at hooking up a variable resistor to to it instead, you could adjust the brightness then, or even a 2-way switch to switch between bright and dull (or night and day). Handy if you want to sleep with your machine on in the room.

unklerosco

I understand combatcow... As for the rest

Surely I can just swap the led for one the same without any resistors switchs etc.

elmer

yeah if the voltage of the leds you're getting is the same as the ones you've got then you won't need any resistors - if you can get a hold of a multimeter you can be sure of what the voltage is

Nige

unklerosco

My dad found one in work but i've no idea how to use it, any help???

Multimeter that is

Explosive_Cornflake

Here's how to work out your LED resistors
http://www.metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
Its a calculator so no maths skills needed!

elmer

you should be able to find a v setting 20 should do that trick - then just put the contacts one on each leg of the led. if you're not sure you're doing ti right then try putting the contacts one on each end of a normal aa battery

unklerosco

forgive me if i'm being thicker than a village idiot but do i do this to an unplugged led r a led thats plugged in??? I tried it unplugged n the v kept changing...

elmer

sorry when the led is plugged in and has power going to it - you're actually trying to measure the power supplied by the connection it's plugged into rather than the led itself but it's probably handiest to do it off the led legs

unklerosco

Cheers m8, i'll give it a try

unklerosco

Right, i cant read my hd drive led voltage cause its to hard so i just looked up the specs of the mobo... It seems to be 5v

The lads in peats said its quite hard to get blue leds in the style that i want and they're expensive so i might give them a miss...

What i did find was a led light that i bought for my case a while back but dont use no more. It runs off 12v and consists of 3 blue leds in series with no resistors(that i can see) Could I use these???

ARGINITE

just connect it up if it frys it frys they are cheap, but if you dont get any light dont leave it connected all day and it still should be fine they are pretty hardy as has been shown in many labs! then just turn it around and try it that way

elmer

you could get normal 3mm or 5mm ones and sand the sides of them down until they're flat. 2 main options if it's a 5v feed - either get 5v LEDS or get 3.3v and around a 100 ohm resistor

best bet is to buy the leds online if you're looking for blue ones - peats charge a fortune for them. I've got blue, white, uv and red 3mm 3.3v ones if you want a small quantity send me a pm

Nige

Michael Collins

Did you buy your LEDs online elmer? If so any chance of a URL?

Cheers