Newbies stupidity? RGB LED Troubleshooting

Forum 2005-2010 (read only) Hardware Interfacing
1

Hey Guys,

I've been lotering around for a while, there's some really cool stuff happening here :slight_smile:

Anyway, enough brown nosing :slight_smile:

I'm trying to get a RGB led working
ttp://seeedstudio.com/depot/images/product/rgbled3.jpg

It goes against my judgement, but I believe that diagram implies the common pin works both as an anode and cathode.

Logic tells me that a resistor should be put on each pin (except the common), and the final ping should be grounded.

Now what I'm actually seeing is that it ONLY works if the common pin recieves VCC and the colour pin [Red|Green|Blue] is grounded.

Does anyone have any thoughts?

2

So you got the common anode type LED. They are easier to hook up to transistors than common cathode ones. The illustration shows the pin mapping for both.

3

That's sort of what I gathered. I assume I can control it via PWM like I would a servo.

Do you have any linkage which maybe helpful - this is driving me up the wall!

4

What the diagram is trying to say is that the LED comes in two varieties, one common anode, the other common cathode.

You could put a single resistor on the common. I've done that when playing around. But you really want to put one on each color, so that you can vary the current flowing to each independently, and thus "level" the brightness of each color.

5

Hey Gorilla,

I've tried inversly putting a resister on the 3 alternate pins going into ground but I have no idea how to control that.

[Edit]

Ah! Stupidity resolved itself!
FYI any other idiots: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1228874758/5

As the Arduino can sink power, we can add a resister that way!

[Edit2]
Thanks guys for poitning that out