I want to create a small LED strip driver/controller with 2 channels (Cold/Warm white) using Arduino Pro Mini (5V/16MHz). I have connected the parts per the following diagram I have pins 5 and 6 setup as output, control them via analogWrite, and it all works great on Arduino UNO.
The problem comes with Arduino mini pro. When one channel is set to 255 and the other is 0, the LED strip does light only in one color, which is OK and when I swap the PWM channel's values, the other light color starts to shine. So far so good. When I set both to 0, the strip keeps on shining at about 30% (I don't have a scope, so I can't tell what the pwm signal is doing). Varying the channels' pwm in the range 0-255 does affect the light somehow but it never goes down to a complete off.
Looking at the arduino uno and pro mini I can't see anything obvious that should make them act differently from the hardware perspective so I'm guessing there's a problem in the libraries or perhaps my arduino pro mini (a clone) is somehow messed up.
Has anyone observed this kind of behavior in Arduino pro mini and has a solution for it?
Edit: Added some measurements per @Abel's request. I measured both DC and AC with and without the LED strip connected.
Connecting the LED strip really does mess things up, but WHY? UNO can handle it, but the pro mini can't! I thought mini was basically just shrunk down arduino uno (both have the same SMD version of MEGA328P), but apparently there are some differences.