Wiring LEDs

[Nataku]

I can't figure this out and Radio Shack is of no help. I want to wire 3 LEDs to a 12v battery. First, is this possible or do I need more power? Second, what type of resistor do I need?

Thanx.

 

[Darth Lars]

This LED calculator is a good help.

 

[jackdoud]

What's the voltage rating of the LED's and/or what color are they? Do you want them in series or parallel? 12v should be more than enough to power them.

 

[Nataku]

I'm going with white LEDs in a series.
The calculator says that I can use a 1/4w, 120ohm resistor, is that the ONLY resistor I can use or are there others? RadioShack doesn't seem to have those in stock. :/

THanx for the calculator by the way, the one I was using kept saying in wasn't enough power.

 

[Darth Lars]

You can connect two or more resistors in series, and add the resistor values together.

 

[Nataku]

Forgive me but I know nothing about this stuff.
So for example, two 1/4w, 60ohm resitors?

 

[masterjedi322]

That should work assuming the calculator is correct. Resistors add in series, so two 60 ohm resistors in series is equivalent to one 120 ohm resistor.

Sean

 

[exoray]

assuming you plugged the right numbers in you can also just go up in value to the next common value, a 150 ohm will work as well and the difference won't be that much... Also you can use higher rated resistors like 1/2 watt as well without issues...

 

[jackdoud]

Most white LED's require either 5 volts or about 3.5 volts for maximum brightness, depending on which ones you buy. You're only going to be able to get 2 or 3 of them in series before you start under-driving them (having less voltage available than the LED's want). You can do that without problems but they will be dimmer than they could be. 2 5volt or 3 3.5volt in series could use a 68ohm 1/2 watt resistor no problem and even the notoriously under-stocked Radio shack should have a 5-pack in stock for under $1. If you need more than 2 or 3 LED's then you'll have to start getting creative with series and parallel connections. The calculater can show you some good options.

 

[Nataku]

I hooked up 1 100ohm and 2 10 ohms and it worked perfectly, almost perfectly. The variety pack of light that I bought came with a few green, a few red, a few yellow and a couple whites. After 45 minutes of putting it together I find out that the whites are actually yellow too. Out of an entire pack that contained about 12 bulbs, I can use one.
I hate Radio shack.

 

[jackdoud]

yeah, LED's of all colors come in "clear" so you can't tell what color they are unless you light them. You won't find any white LED's in mixed bags from Rat Shack, they're too expensive and too new. The "clear" colored LED's are high-intensity varieties as opposed to the obviously colored LED's. They're good for throwing light instead of glowing a color.