I have a group of 8 blue LEDs (Vf 3.2V @ 20 mA) currently powered up in parallel by a resistors (one for LED) and a 4.5V power source (3xAA batteries). I've been playing with fade in/out effects and 555 circuits.
What would be a simple circuit to randomly (or-pseudo randomly) fade in and out them independently? I mean, when some LEDs are increasing in intensity others could be decreasing following no specific pattern (the fade in/out cycle time could be different as well).
Ideally, I'd like the fade-out effect not to be complete. In other words, more than a fade in/out effect what I'm looking for is a circuit that can slightly affect the light intensity if each LED randomly (e.g. fluctuating the current from 3mA to 20mA).
I would appreciate any hints or pointers. A detailed explanation or circuit diagram is now necessary (but it would be awesome!).