So I was trying to dim two different LED strips using two different pots on A0 and A3 ADCs, setting different duty cycles for my PWM.
I'm currently using pins 9 and 11 do to so. The LED strip connected to pin 9 dimmers properly, however, the one connected to pin 11 doesn't. Note that I've switched the LED strips, and already validated the electronics around it (non-inverting push-pull with BJTs for my IRF540s).
I'm suppyling my +5V with the USB port that's used for burning the code into the ATmega328. My guess is that pin 11 is being used for communication and so it won't work as a PWM port.
However, I'm not really experienced with microcontrollers and so I'm not really knowledgeable about the protocols and whatnot the Arduino UNO uses when connected to a USB port.
How many LED's ?
Type of LED's ?
Copy of the sketch ? (use code tags to post it ( </> )
Maybe a half decent schematic ?
From what you said you are using the same 5 volt supply as the USB provides but that is always limited in current to around 500 mA.
Arduino pins are also limited to around 40 mA each.
We see similar issues when people are trying to drive relays where the board cannot supply enough current at some point and relays may not operate as expected.
In almost all those cases using a proper power supply for the external components with just a shared ground back to the Arduino often fixes things.
If you switch what's connected to pins 9 and 11, what happens? Does the problem move with the connection? If so, that indicates hardware flaw. If it stays with a specific pin, that indicates that the issue is in the sketch.
Assuming above test shows it's a sketch problem:
Are you using any libraries that take over timer2? Pin11's PWM is done using timer2 (OC2A), while pin 9 is on timer1 (OC1A).
Are you doing anything with SPI? Pin11 is used for SPI MOSI. If you are using SPI, it will take over the SPI pins and other pin functions won't work.