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LED Wiz - RGB LEDs 3.3v/2v bank select
Franco B:
I have three LED Wiz's to wire up shortly with RGB LEDs. I was thinking about powering the banks with 3.3v from an ATX PSU to avoid having to use resistors for the blue and green cathodes as the operation voltage of them is 3.0-3.4v
The red cathodes require 1.8-2.3v so I would have to use a 68Ω resistor on each of those to bring it down to 2v but at least I would only have to wire a 1/3 of the resistors compared to using the standard 5v supply.
It would have been nice to have provided some of the banks with 2v to avoid using resistors all together but I think it would end up being a PITA keeping track of the RGB port positions rather than going 1R 2G 3B 4R 5B 6G etc etc.
Would there be any problems with using the 3.3v from the PSU for the blue and green cathodes?
BobA:
AFAIK there are slight differences in the internal resistance of the LEDs when in operation. This makes the resistor in series with them a necessity to properly provide voltage to the LED. I do not think that providing voltage to the 2 colors without a resistor is a safe solution.
drventure:
On a related note, I just received my LED wiz and noticed in the docs that they show wiring the resistor to the CATHODE (-) side instead of the anode (+) side.
I'd have thought it should be the other way around. But I'm definitely no electrical engineer.
Anyone know why the resistors should be wired to the - side? I'm curious more than anything and a few searches here didn't turn up any info on the subject.
Dudeman:
It can be wired to either side. Think of the resistor as a choke. It will restrict flow from point A to point B so placement doesn't matter.
Franco B:
Cheers BobA, maybe Randy could confirm.
drventure, you do need to solder the resistor to the cathode and then connect that to the numbered terminal.
On a side note if you are using RGB LEDs you need to buy common anode so that you have a cathode for the red, green and blue elements.
I actually wired my 1st LED Wiz up the same way as you thought using the anode. What a complete waste of time that was :laugh:
Are you sure Dudeman? It didn't work for me.
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