I'm trying to control 3x 5m RGB LED strips using an Arduino Mega's PWM pins. Building off ladyada's tutorial: http://www.ladyada.net/products/rgbledstrip/. I created a 3x3 bank of N-channel mosfets, each being supplied by a seperate 12V, 5a power supply. As a diagram if each P is its own 12V DC power supply (P1 powering led strip 1, etc.) , and M is a mosfet:
R G B
P1 - M -M -M (per mosfet: left leg pwm, middle leg to led rgb power strip, right leg ground)
P2 -M -M -M
P3 -M -M -M
I can't seem to get each row to be controlled by pwm when supplying power directing to the mosfets.
To test, I powered P1 with DC power and had the arduino plugged into USB. The colors remained fixed blue despite a script that was to cycle colors. When I powered the same row through the Vin and ground through the arduino, everything worked fine.
Why is this? Is there any way to power each row without utilizing the arduino Vin? Can I use 3 seperate power supplies and one Arduino Mega to do this? Or do I need to get 3 arduino unos or equivalents?
Here are two schematics. The first the arduino is plugged into a USB, and each bank of mosfets is connected to its own power source. The second the arduino Vin is powering one of the banks but not the other two.
(Because I'm a new user I can't upload photos, but they can be found here: http://www.flickr.com/photos/80053489@N06/7165312673/ http://www.flickr.com/photos/80053489@N06/7165313015/