I am in a situation almost identical to this guy : http://arduino.cc/forum/index.php/topic,58302.0.html
Normally, I would have replied in that thread instead of creating a new thread, but OP didn't post back with the status of the proposed solution. And i have a few questions about the schematic proposed there.
and it has a single ground for the 3 colours. I found out the hard way that i can't use my normal N channel mosfet to control this guy because of the common ground instead of the common anode!
So, I did some research and built a schematic that should allow you to use an arduino to control each of the RGB channels. Here's a schematic i created that should work for this. Hopefully somebody here can confirm / deny if it will work :). [it's similar to OP's but used different / cheaper Digikey parts )
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Parts: IC1: mosfet - http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=869-1052-ND&x=0&y=0 IC2: transistor - http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=2N3904TFCT-ND&x=0&y=0 R1/2: resistors - http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=CF14JT10K0CT-ND&x=0&y=0
Now, the questions I had about my schematic and the proposed schematic (from linked thread)
1) will that schematic work? 2) P channel mosfets require that the source be more positive than the drain, and therefore require a negative voltage on the gate pin? 3) Even though the mosfet i want to use is a Logic Level device, i cant (or can?!) drive it directly with the arduino because the arduino can not output a negative voltage (needed to switch the Gate pin). The reason I ask is because the data sheet says that V(GatetoSource) is + or - 20 volts. Does this mean that i can trigger Drain to Source with a positive voltage?
Thanks for your time! It's appreciated!