My brother wants to put a total of 6 bright white LED's in a display box inside his computer case. The LED's themselves have to be in two rows of three, and in each row have the 3 LED's be one inch apart from the next (in other words, they're not that very close together).

How can he wire the LED's to be turned on by their own switch? And should he wire them all into a molex connector from the power supply, or should he use a separate battery pack to power just the lights? I'm just getting started learning about wiring (I can sauter and I have spare wire and we have replaced the other LED's already in his system), but I don't think this should be that hard, right?



Thanks.

assuming the use of 3.7 volt leds,the setup he wants couldn't be better.run two groups of 3 in series (+ connected to -) and the two clusters in parallel( + connected to +).
the reason for using 3.7v leds is that 3.7x3=11.1v.meaning there is no need for a resistor in the circut,and a switched 12v molex connection is all that is needed.
here's a calculator for finding the proper resistor in other configurations.http://www.bit-tech.net/article/68/

I can tell you how to do it, but I learned from this guy:

http://www.dansdata.com/caselight.htm

So, I will just let him teach you too!

Thanks, pisci, but would you mind elaborating a little bit? Like I said, I've only done a few things with wiring and I don't exactly know HOW to switch a molex connector (just extend the 12V and ground lines?) and I don't know if you're trying to say the LED's should actually be touching one another? The problem with the link above is that the LED's in this case need to be far apart, not just sitting on a board. But thanks.

Connect the leds with wire. Int the guide above they are joined with sloder on the back of the pcb board.

Follow the guide exactly, but use wire instead of solder traces.

Greydawg this is what they're sayn' yo

Attached Files

led hook up.zip (8.8 KB, 97 views)

They are actually the 2.5-3 volt white LED's found on Xoxide.com

How about installing a switch? Where is the best place in the circuit to put it?

I know I sound like a rookie who shouldn't be doing this, but I really want to get into this stuff and I need all the HELP I can get. Can I not just link the LED's end to end with a few short peices of wire and then through an exposed yellow 12v wire coming from my power supply with a switch in there somehow? I have an "Electronics Learning Lab" from Radioshack with a breadboard and switches and stuff that I could test stuff out with, but I'm still not sure if I shouldn't just use a couple batteries---what would happen to the rest of the computer if I wired the circuit wrong into the 12v line or something?

Seriously, I need all the help I can get and we're trying to get this done by Monday. If anyone wants to PM me or email me I would be grateful for their help.


Thanks.

for those LEDs xoxide says their forward voltage is 3.5 volts so you can fit a maximum of 3 to stay within the 12 volts you want to run them on. then their nominal current is 20milliamps. so with ohms law you need a 600 ohm resistor
you need a 600 ohm resistor for each string of 3. simple math. and despite what some may argue use a resistor even if the total forward voltage is higher than the supply voltage.
the attached pic is how your 6 LEDs should be layed out. the resistors are 600 ohms. yes in this apllication the resistors should be after the LEDs something about current sinking blah blah (because current flows towards positive)

Attached Thumbnails

 

I'm not sure I entirely understand your diagram, but I guess I just don't know enough about the design of wiring. It looks to me like in that picture the 12V line is connected to the Ground? And what's that bottom-most arrow pointing down? Seriously, I'm a rookie--I've only ever replaced LED's and extended power wires and added switches--I've never DESIGNED my own circuits.

Quote: Originally posted by Greydawg And what's that bottom-most arrow pointing down?

The arrow pointing down is the symbol for ground.

That is two 3 LED series arrays, wired in parallel.

Did you read the guide I linked above? It covered everything including wiring in series and parallel, as will as mixed arrays.

It really covers everything you need to know in order to do this project!

Ok--thanks. Sorry, no, I haven't read the attachment yet because I can't open zips from here (work) but I will when I get home. You've always been very helpful too, so THANKS in advance! I'll let you know what I think later.

Oh, yeah, sorry--I DID read the guide. It was a little bit over my head (a lot, actually), but it did fill in a few gaps. We've decided we will only need 4 LED's or perhaps just a laser LED array (if I can find one in white). I'll let you know what we come up with--I'm sure to need more help!

Thanks!

I am not talking about the zip.

I am referring to the "How to Build an LED Caselight" article that I linked you to above.

Like I said, I read it, but it was pretty much over my head for the most part. I had actually read it before. It's a pretty good article, but I gotta figure out a lot more before it makes much sense, methinks...

OK, so I've got two LED's that say 3.3V and 20mA

So if I wired them into the 12V line in a series, I would need a 270 ohm resistor?
(12V - (3.3V x 2 LED's)) / .02 amps) = 270 ohm




So I would wire the 12V + wire to the "ON" for my switch and the ground to the "OFF" switch, then a 270 ohm resistor from the ground terminal on the switch ("OFF"), and the LED's in series wired from the anode to the 12 V+ terminal on the switch ("ON")? Is that right?

Or would I wire the 12V+ to the "ON" terminal, then from the "OFF" terminal run the LED series, then the 270 ohm resistor, then the ground wire from the power suplly?

I bought a multimeter today, if that will help me (although I haven't learned to use it yet)...

The latter would be the correct order.

Just make sure that the polarity of the LEDs is correct and you will be golden.

Congratulations on DIY and muddlong through the topic!

Which wires from the power supply should I use for my ground and 12V+? I have a spare floppy drive power connector, but it's joined at the molex connector for my CD-R/W drive. Is it allright to use those wires from the floppy power connector? Or do molex joints make a parallel circuit?

You can wire it to any yellow wire (12v), and any black wire (ground).

AWESOME!!!

We got it to work flawlessly and I have learned a BUNCH of useful information about circuits and electricity and I have basically nobody else to thank but pimprig! So...THANKS to everyone that tried to help me out. Now that I know how to do some of this circuit stuff, I love it even more. I'm therefore going to do a lot more of it, which means I'll probably need more help in the future, and I know just where to go. And not a single person called me out for being a rookie. So thanks again for helping a newbie to DIY wiring! I'll be posting pictures soon of the final (for now) product...

And a special thanks to putwig and ZENNZZO for your patience and knowledge.

Glad to hear it worked