Multiple coloured leds

Sven · Post by **Sven** » Fri Feb 04, 2011 5:19 am

How does one put together a multitude of leds, all different colours and voltages? This is my first led attempt and i wish to use 2 reds, a green and a blue on the one power source. Not sure how to calculate it!

USS Atlantis · Post by **USS Atlantis** » Fri Feb 04, 2011 5:30 am

Sven wrote:How does one put together a multitude of leds, all different colours and voltages? This is my first led attempt and i wish to use 2 reds, a green and a blue on the one power source. Not sure how to calculate it!

The easiest way is to take them separately

From your power source you'll have 3 different wires - one runs to the reds, one to the green and one to the blue

Now calculate for the different LEDs as if they were the only ones

Put a resistor after each LED (pair for the reds) then join the runs back up at the other end of the power source

Simply - run each color as a parallel run, with the pair of reds in series - simplifies the calculations

http://led.linear1.org/led.wiz for an LED calculator

Sven · Post by **Sven** » Fri Feb 04, 2011 6:30 am

Awesome, i had a feeling that would be the way to do it! Thanks for the reply.

Sparky · Post by **Sparky** » Sat Feb 05, 2011 1:30 am

The only thing to remember for daisy chained LEDs is that current in a loop must be equal through each element in the loop, that is you can mix LED's that want different voltages so long as they want all the same current. This is for serial LED connections (aka daisy chains).

parallel does not have this requirement, each LED loop is its own loop and can be treated as independent from the rest.

Also:
if battery power or power drain is of concern remember every resistor used is consuming power that is not generating light (generates heat)

USS Atlantis · Post by **USS Atlantis** » Sat Feb 05, 2011 6:06 am

There's the Sparkster - having fun digging out over there?

Anyway, what he says is the total truth - which is why you also try to keep the source voltage as low as you can, this makes the resistors as low in value as possible, and reduces the heat generation

Based on standard values - note that your LED's might have different values than what I have listed here

Red 1.8-2.2v @20ma
Green 2.8-3.4v @25ma
Blue 2.8-3.4v @25ma

So our runs would have
1) 3.6-4.4v @20ma
2) 2.8-3.4v @25ma
3) 2.8-3.4v@25ma

Using standard power sources, our best bet would be 3xAA batteries - supplying 4.5v

Using our calculator

1) 2x Red LED's; 27ohm resistor
2) 1x Green LED; 68ohm resistor
3) 1x Blue LED; 68ohm resistor

On all runs, the values are fairly low (under 100 ohm), so there will be low power loss and low heat buildup

Madman Lighting · Post by **Madman Lighting** » Sat Feb 05, 2011 10:00 am

You could just buy one of my cards and it will just do it for you.

Actually thats good advice from the guys above. Took me long enough to learn about all this electronics stuff. How about this: If you've got a few $$ buy a book called "The Art of Electronics". Its a huge thick tome of how to do lots and lots of stuff from the very simple to the more advanced stuff. Best of all, its written in English so you can understand it and you wont get all the complicated mathmatical devivations you find in college texts. There is enough math to explain whats going on and use the stuff. Well worth it.

USS Atlantis · Post by **USS Atlantis** » Sat Feb 05, 2011 12:33 pm

Ya, the Madman makes some good stuff - I'd I couldn't do it on my own, his is what I'd buy

Couple other books for really basic info

"Electronics for Dummies" (ya, they got a 'Dummies' book for that too) - it has a quick blurb on LED's and the formula for figuring out the resistor values

"Starting Electronics" by Keith Brindley - more good basic info, he also does some stuff on oscillating circuits - to make blinky lights - and how to mix up resistor/capacitor values to change the timing

Sven · Post by **Sven** » Mon Feb 07, 2011 9:01 pm

Cool, thanks for all the help guys. I made a parallell circuit with a 9v battery(only power source on hand at the moment) Used what resistors i had on hand (close enough, the reds may run a little hot but ill only light this one to take some photo's then turn them off again and move on to the next model ) Twas easy!

USS Atlantis · Post by **USS Atlantis** » Mon Feb 07, 2011 9:10 pm

I would be careful of running LED's "hot"

Sometimes you luck out, others POOF - insta-burnout

When in doubt - always put MORE resistor on the LED circuit than it says - all it will do is dim the LED a bit - run a lower resistor value and you chance blowing the LED

Glad to be of help

Madman Lighting · Post by **Madman Lighting** » Tue Feb 08, 2011 7:48 pm

Ditto what Ken says.

LEDs should not run hot, unless they're the new high power ones and then you need a good heatsink which should take the heat, not the LED.

USS Atlantis · Post by **USS Atlantis** » Tue Feb 08, 2011 8:01 pm

Uh, John

I was talking "hot" as in "over powering" - he was using less resistor than he should have for the 9v circuit

Always over-resistor rather than under-resistor - your LEDs will last longer

Sparky · Post by **Sparky** » Tue Feb 08, 2011 8:01 pm

I think the 'running hot' he referred to is the electronics idiom for running with slightly higher power (current and or voltage) then specified.

USS Atlantis · Post by **USS Atlantis** » Tue Feb 08, 2011 8:02 pm

{Brian the Brain voice}

SIMULTANEOUS!!!

{/Brian the Brain voice}

Sven · Post by **Sven** » Sat Feb 19, 2011 7:43 pm

Well, as it turned out, i knew i was using the wrong resistors, cant remember what i used, but i believe they were underpowered as the overall lighting effect turned out pretty lackluster! Then a friend came over to look at it and immediately grabbed it and broke it! Live and learn i guess...live and learn...

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Multiple coloured leds

Multiple coloured leds

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