I am using breadboard version of arduino to drive 2meters of RGB LED strip whit 3x STP16NF06LFP N-CHANNEL MOSFTETs. I long on modified blink that blinks each color at 1s interval. And when i plug on around 20cm of led strip it works great(draws around 170mA per color), but when i connect on 1meter or more the delays get all messed up, blue color doesnt even turn on and red and green are turning on/off randomly(current draws around 700mA per color). I am using 70watt power supply.
According to datasheet the mosfets are more then capable of running this current and also i get steady 5v suppls for my MCU whit common ground whit 12v source.
How do you power the LEDs ?
Blue missing... you need more power. The drop may be caused by a too weak powersource.
I hope u've got the N-channels on low-side
Check the Gate voltage, make sure you're getting a good 4.5 to 5V on it.
And definitely wire the MOSFET with Drain to - (cathode) of LEDs and Source to Gnd.
http://www.st.com/content/ccc/resource/technical/document/datasheet/66/f2/4e/c4/ee/dc/45/e4/CD00002848.pdf/files/CD00002848.pdf/jcr:content/translations/en.CD00002848.pdf
You may also need to feed in power to more than 1 place on the strip, like both ends and maybe even the middle.
I have the mosfets wired corectly, and a 70watt power suplly. It is also strange that when i write program to turn each color on for 1 seconds it works. Now i also added a pulldown resistor to ground and a diode on gate to direct any stray capacitance on mosfet gate to ground and now the led strip works but colors are kinda messy.
I changed mosfets for bipolat TIP122 whit series resistor to limit current draw from atmega pin and it works like a charm. But still wanna figure out the problem i had whit original circutry.