Materials used- 

1. Arduino UNO
2. Ultrasonic sensor
3. LCD Display 16x2
4. Bread Board
5. Jumper Wires
6. box with cover ( mobile phone packing box and same cover used by me )



Working-

When the white side is down,
the ultra-sonic sensor senses the distance (less then x=4.5cm i.e. slightly higher then the height of box)
and the black counter starts decreasing. When black side is  down, 
the distance gets higher then 'x' and white timer stats decreasing.



More work to do - increment in time