/diy/ - Do It Yourself

I'd like to make a logic circuit for a lighthouse. At first I thought about using a simple 4017 counter driven by a 4049 oscillator to light up one of ten leds sequentially, emulating the rotating light beam of a light house.

But how could I make a version where the on/off transitions of the leds would have gradual slope instead of distinct on/off states? That would give a much nicer effect. Any ideas? Is this feasible to implement with logic ics?