RGB LED Array

Discussion in 'General Electronics Chat' started by seesoe, Jun 10, 2011.

1. seesoe Thread Starter Active Member

Dec 7, 2008
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hello im trying to figure out the best wiring for multiple common cathode rgb led arrays

im using a 24 channel controller that handles 1 amp or 1 watt dissipation per channel (50 20ma leds max?), my power supply is 12 vdc 15 amps.

im trying to make a rectangle rim of 40x16 rgb leds, each color and each side will have its own channel.

i started off with this, but i just realized that its not going to work because the leds are common cathode and i wouldn't be able to wire them in series correct?

the best solution would be a single resistor per led or would it be safe to wire each side in parallel?

if single
reds = 510 ohm
greens/blues = 430 ohm

if parallel
16 reds = 33 ohm
40 reds = 13 ohm
16 greens/blues = 27 ohm
40 greens/blues = 11 ohm

thanks
seesoe

2. ErnieM AAC Fanatic!

Apr 24, 2011
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My first question would be how do these LEDs turn on? All together at once or one at a time or what?

3. seesoe Thread Starter Active Member

Dec 7, 2008
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The controller will pwm a minimum of 4 channels at a time, this is for a display so there should be at least one color on for the whole frame

4. ErnieM AAC Fanatic!

Apr 24, 2011
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1,842
OK, gotcha now. Best to parallel the LEDs AND the resistors, each LED get a resistor so you need 40+40+16+16 resistors.

As your max load is 40*20mA = 800 mA, one channel should drive even the largest side. 4 sides x 3 colors = 12 controllers, so you have some spares! <grin>

5. SgtWookie Expert

Jul 17, 2007
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1,807
Wait a minute - you can't parallel LEDs unless you match them for Vf (forward voltage) at the rated current.

You can't use just a single resistor per RGB LED in the common cathode either, as turning the red portion on will prevent the blue or green from coming on.

You'll need three resistors per RGB LED.

6. seesoe Thread Starter Active Member

Dec 7, 2008
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0
hows this look?

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