lighting project using 44 leds

Hello.

I'm looking to get help in designing a simple circuit to run 44 LEDs off of a 12v power supply.

I have very little experience in electronics, and from the little I've read/found out this is pretty simple.

This is what I'm trying to do:

I have 44 LEDs purchased from superbright leds

10 RL5-R12008 red LEDs @50 mA

The LEDs are divided between 15 different groups:

1) 7 reds

5) 4 yellows

8) 1 blue

10) 1 yellow

11) 1 red

15) 1 green

These colors (LEDs) are being displayed through two to three different types of plastic, therefore yeilding a different glow/intensity.

What I'm trying to accomplish is to have a potentiometer per group. Thus 15 different potentiometers. The potentiometers will be used to equalize (dim) the different colors/groups so that all the leds glow at about the same intensity. Wired in parallel.

Aside from the LEDs, I have a 12v .21A computer power supply.

I'm looking at using a separate resistor per LED (excluding the BA9s-G since it's already protected). The reason being is that once the LEDs are in place, they won't be easy to access. If a resistor should fail, I rather replace its respective led rather than the group.

1) What resistors do I get -all 44 separate 470 ohm resistors or does the value of resistor change per different LED color?

I really don't want to trouble anyone, and I hope I'm in the right place for some help. If someone just wants to give me a formula, I can give it a shot with the math and just post what I came up with before I buy all the parts. Aside from the leds, resistors, potentiometers, and power supply, It was also recommended that I buy an in line regulator so I don't have to keep messing with the potentiometers  once I have the intensities set where I want them, but my understanding is that the power supplys used with computers are already regulated. I don't mind buying other things to make the circuit more effecient -i.e. a better power supply or making substitutions in the event that what I have isn't adequate. I'm free to suggestions.

I understand that your time is valuable and I'm under the assumption that some of you can probably map this out in your sleep.

thanks advance

sincerely,

R

Hello.

Pretty new at this sort of thing. I posted a while back, but I think my question was too vague.

This is what I'm trying to do.

I have seven green 13000 mcd (30 mA each) leds purchased from Superbright Leds who recommend that I use 470 ohm resistors with their leds. I wired the leds in parallel running off a 12v power supply.

The Leds are behind a green opaque panel but I couldn't get the leds to shine through  enough. What I had to do was group the green leds into clusters of three (instead of single leds) and step down the resistance to 220 ohms.

It works great! The 3 cluster leds running off the 220 ohm resistor give me the brightness I need. 

I was hoping to use  just one led with a 220 ohm resistor, but I figure the led won't handle the load for long, and added the other 2 leds to share the load.

Here is the problem:

Will I eventually burn out the 3 led cluster by stepping by using a 220 ohm resisitor instead of 470 ohms?

Thanks in advance!

Thanks Hotmik

I'm curious however on how  you got the 3.3 volts for the LED? This is how I worked the math. Odds are, that I'm wrong and you're right!

The ones that I'm primarily concerned with are the green leds. The specs are a continous forward current of 30 mA. The max foward voltage is listed as 4.0 and the typ (I guess that means typical foward voltage??) is listed as 3.5. I subtracted the max forward voltage from 12 volts (the pwr supply) to get 8 volts. I then divided by .03 (amps) to get 266 for the resistor to be used. But you mentioned that I was in a certain range. That I could actually go lower on the resistance to get a brighter glow.

The only problem that I have, is that the 3 green leds need to be tied together. That's why I thought it would be easier to just distribute the load among three leds using one resistor, but you mentioned that I could get a better result by using an individual resisitor per led.

what do you think?

Ok, i use 3.3 volts as a standard voltage for LED's they normally range from 3.3 volts - 3.6 volts.

Normally you would use a 470 ohm resistor on a LED because the average specs on a LED is:

Very kind of you Hotmik. I really appreciate it.

What I'm trying to do here is prolong the life of the led, keep the operating environment cool (since it won't really be all that accessible once I close it up, and get the brightness I need all at the same time.

OK. I WON"T use the max voltage. What about the TYP voltage as per the spec sheet? For instance: the specs for the green leds I'm using are found here: http://www.superbrightleds.com/specs/g5_specs.htm. You'll see that the green leds Max voltage is 4.0 and the typ is 3.5

The red leds max volatage is 2.5 and the typ is 2.0

orange leds max volatage is 2.6 max voltage and the type is 2.2

yellow leds max voltage is 2.5 max and the typ is 2.2

blue leds max voltage is 4.0 and the typ is 3.5

The spec sheet however doesn't address what typ is. I guess it means typical or average. Could I use those typ numbers as per the spec sheet  or am I good to go with the figure that you posted, 3.5?

Just trying things out as per the spec sheet so I don't go buying the wrong resistors.

Thanks again!