Alternative 1:conveyor

Alternative 2: Arm mechanism

Alternative 3: Rotation tray

Alternative 4:button and ejector

Alternative 5: Tube & tray/slide

Alternative 6: pulley & box

Alternative 7: Mini deliver robot

Conclusion:
From these 7 alternative prototype ,we entirely have choosen Alternative 5: Tube & tray/slide as our primary design hitherto refer to pugh diagram..

Possible circuit:

There are two ways of constructing the voltage divider,with the LDR at the top,or with the LDR at the bottom

Below is the circuit for IR sensor

The basic design of the infrared proximity sensor