what kind of LED do I need?

[MPTech]

I'm working on a Jukebox project and wanted to light a panel with indirect lighting from 2 blue LEDs.

I picked up 2 - 12v blue LEDs from MicroCenter with a tail & plug to connect to the mobo, I think they were intended for the on/off or HDD LEDs.
I connected & mounted them. They work, but the problem is that the lighted area is very narrow / focused.
I remembered reading something a long time ago that LEDs have projection ranges(?) (ie: in degrees, so a 20 is very intense on a very small area, compared to like an 80 on a much larger area (I'm just making thos numbers up).

Does this make sense? Can anyone point me in a direction or link that would have 12v LEDs, I could connect to a power lead from my PSU, that would light a larger area?

[saloonstudios]

www.superbrightleds.com has some 12v strips, not exactly single LEDs but they'd give you a larger spread. Not sure how much space you have though-

[Dr Zero]

I got some 12v wedge base led for my coin doors from here
http://www.dealextreme.com/products.dx/category.799~search.led

[MPTech]

I'd like to install a few led's like this:
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2FB12120_specs.htm
in my juke project.

Can I run them in parallel off of the 5v from my PSU or would I have to run some kind of resister to drop the voltage a little? (can you tell me what kind of resister I'd need? (i'm not too familar with running led's and could really use the help. thanks!)

[releasedtruth]

I often use flat top leds for very wide dispersion, 120 degrees or so. Works nicely in buttons without the blinding focus of the standard version.

[matsadona]

I will try to sort this out. If it gets to technical, please let me know and I'll do a second try

First of all, what matters when it comes to LEDs is the current.
As you can see in the specifications (IF / Continuous Forward Current) it is rated to 35mA. By the way, 35mA = 0,035 A.
Another value that is critical here is the voltage (VF / Forward Voltage) that is 3,3V.

I Assume that you have a ordinary PSU with 12V, and since you talked about multiple LEDs, I think it is a better idea to go with that, not the 5V.
We can have an 5V example also later on.

The normal way is always try to keep the current as low as possible, and in the case of LEDs that means connecting in series - not paralell.
The current will always be 35mA no matter how many LED's you put there. The only thing that will change is the voltages.

If we have 3 LEDs in series, which all have a voltage drop of 3.3V, then it will be 2.1V left over the resistor (3,3+3,3+3,3 = 9,9 -12 = 2,1).
Now we end up at Ohms law - which says that U=I*R (U= voltage, I= current & R=resistance).
Since we know U and I here, we can easily determine what resistor we need. R = U/I - 2,1/0,035 = 60.
Resistors are not made in any size, so the closest value there is in the standard series (E12) is 68ohm. That is close enough.
For resistors you also need to know the power used, or else you can blow it up. The power, W, you get by multiplying the current with the voltage.
W=U*I - 2,1*0,035 = 0,0735. That says you can safely use a standard 1/4W resistor. 1/4W = 0,25W

[MPTech]

yeah, I worked all of this out a few years ago when I installed some lit flipper buttons on my MAME cab. I knew it wouldn't be easy, I guess that's why a lot of guys go for the 12v PC leds or buy car leds.  I hate wiring stuff in series.

Ok, I followed most of what you said and I think I have enough information to be dangerous.

question on wiring in series, if I had 2 or 3 blinking leds in series, wouldn't that screw things up with the flow?

I never learned the whole amps, watts, volts, ohms thing (and I consider myself resonably smart anyway)

so couldn't I start with 5v, run a resistor to get it to  3.3v, run to a terminal, then run several in parallel?  (I'm sure that's too simple AND WRONG).

[matsadona]

Yes, the principle is the same for one LED.

You have a supply voltage of 5V. That leaves 1,7V over the resistor. That gives you a resistor of 48,6. The closest you have is a 56 Ohm resistor.

[matsadona]

If you want to do it parallel, here is two ways of doing that (refer to the picture attached).

Parallel and series circuits behave a little different.
As you can see the total current is a sum of all parallel currents, since it is multiplied with every parallel load you add.

The voltage is the same over all parallel loads - compare to the previous example were all voltages was added to get the total.

A funny behaviour with resistors is that the total resistance of a parallel curciut is all resistors divided (Rtot=1/(1/R1)+(1/R2)+(1/R3)...).
This goes for speakers too. I.e. if you have two 8 ohm speakers in parallel, the amplifier sees it as a 4 ohm speaker. If you put three 8ohm speakers in parallel the total resistance is 2ohm (2.6667 to be exact).
But putting two 4 ohm speakers in series give a total of 8 ohm.

Remember that having parallel resistors always give total resistance that is less than the smallest resistor.
So if you have one 1000 ohm and one 5 ohm resistor in parallel, the total resistance will be less than 5 ohm ( Rtot = 1/(1/1000)+(1/5) = 4.9751).

Back to the example of your parallel LEDs at 5V. I would recomend that you put one resistor to every LED. Then you don't need to think about the power/watts.
In the first example (picture) the total watts is 0.179. Still safe with a 1/4W resistor. But if you put 5 in parallel it takes a 10 ohm 1/2W resistor since the total power is 0,298.

I hope you get a better picture now, and feel confident to add a couple of LEDs to your project.

If you, or somebody else, has any further questions - please don't hesitate to ask.

[BobA]

It is generally recommended not to put LEDs in parallel with a single resistor.  This may work but the chances are the more LEDs you use the greater the chance of cascading failure of the circuit.  So if your LEDs are in parallel each LED should have its own resistor.

http://members.misty.com/don/ledd.html
Do not put LEDs in parallel with each other. Although this usually works, it is not reliable. LEDs become more conductive as they warm up, which may lead to unstable current distribution through paralleled LEDs. LEDs in parallel need their own individual dropping resistors. Series strings can be paralleled if each string has its own dropping resistor.

http://www.kpsec.freeuk.com/components/led.htm
Avoid connecting LEDs in parallel! Connecting several LEDs in parallel with just one resistor shared between them is generally not a good idea. If the LEDs require slightly different voltages only the lowest voltage LED will light and it may be destroyed by the larger current flowing through it. Although identical LEDs can be successfully connected in parallel with one resistor this rarely offers any useful benefit because resistors are very cheap and the current used is the same as connecting the LEDs individually. If LEDs are in parallel each one should have its own resistor.

http://www.otherpower.com/otherpower_lighting_leds.html
It's important that each string has its own resistor.... putting them in parallel with a single resistor is bad practice. We didn't know this when this article was first written....thanks to all the folks that pointed this out!

[BobA]

On the original topic.   If the LEDs can be filed a bit on the rounded top you can probably get more dispersion out of them with the loss of the lens shape and a bit of roughness.  Use a flat file and give the leds a touch.

[orchidius]

On the original topic.   If the LEDs can be filed a bit on the rounded top you can probably get more dispersion out of them with the loss of the lens shape and a bit of roughness.  Use a flat file and give the leds a touch.

I 2nd that. Most leds are made from clear plastic if you buy them. Like that there is almost no light lost, the light is not broken and will be emitted in the projection range it was intented to, but of course with the potential problem of a hotspot. A very easy and safe solution for this is sanding down the surface of the plastic (be it round or flat) a bit with very fine grit sanding paper. Be gentle though, the purpose here is not to sand away too much plastic, just to roughen it up a bit so the emitted light is broken and gives more of a "glow" effect rather then a hotspot effect. A good comparison would be the way translucent happ pushbuttons work and the way electric-ice pushbuttons from GGG work.

Here's a nice picture "before-and-after"

http://www.google.be/imgres?imgurl=http://www.gerrelt.nl/LED/LED_sanded.jpg&imgrefurl=http://www.gerrelt.nl/LED/index.htm&usg=__kL2E0LHeSeoU6GYqhhZ0Vcbuzp8=&h=400&w=312&sz=32&hl=nl&start=0&zoom=1&tbnid=usRh9w6gEyHHsM:&tbnh=124&tbnw=92&prev=/images%3Fq%3DLED%2Bsanding%26um%3D1%26hl%3Dnl%26client%3Dsafari%26rls%3Den%26biw%3D1280%26bih%3D669%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=118&vpy=42&dur=4875&hovh=254&hovw=198&tx=103&ty=136&ei=ZgyWTICCFYOROIaRuYgJ&oei=ZgyWTICCFYOROIaRuYgJ&esq=1&page=1&ndsp=28&ved=1t:429,r:0,s:0

[Eddie_Brock]

I got some 12v wedge base led for my coin doors from here
http://www.dealextreme.com/products.dx/category.799~search.led

I bought similar LED lights from a local auto parts store. LORDCO here in canada has them.
They are 161 bulbs, but I believe that 194 is a 'universal' that also fits.
Much cheaper in the store.