This is one of my favorite projects
The diameter of the drum is based on an A4 format
Because the length of a A4 format is 29.7 mm, the diameter of the drum is 92.30 mm and the height is 25 mm so that you can make 8 strips of an A4 size.
The software is simple, 2 ATtiny85 serves as mini 9g servo engine control and another for flashing the white led, both with a 10K potmeter
The 3 leds are in parallel with a 100 ohm resistor in series with the power supply
As a power supply I use 3x AA 1.5volt batteries that are mounted underneath
See also https://www.instructables.com/id/Mini-Zoetrope/

The Clock must 8MHz