Design of Knob is simple. There is protrusion for showing and touching the volume level.
Inner side, there is space to attach the knob of potentiometer.
As I acquired large FoV(wide angle of 160) Raspberry Pi Camera, I need to shorten the space between camera and top table. Using trigonometric function, I calculated appropriate height of camera stand that can take picture of entire space of top table by 160 FoV.
Calculated height to the surface of top acrylic table is 62.5mm. By experimenting physical focal point, real FoV angle looks a little tinier than specification. So, I decided to shorten the calculated height of camera stand to 45mm.
Firstly, I made 4 legs stand with keeping space to tighten 2.6mm screw.
However, the narrow legs were too weak to be printed by ABS. Therefore I changed the design to 1 thick leg with keeping a space to 2.6mm screw hole x 4 at the bottom and top side.