You will need:
9 large plastic cups
A marker pen
A pinch of binary logic
Join the cups together as shown in the picture, they will need to turn, this can be made easier by lining up the joins on the cups.
Across the top row write the Binary Values, 1,2,4,8,16,32,64,128. Underneath each value write a zero. The trick here is to be neat and line up the digits.
Under the zeros add a row of ones. Again neatness and equal spacing is essential to ensure that the digits will all be lined up when the cups are turned.
The final step is the add the two indicators as shown in the picture. The first is the read here, which i where the user lines up the binary values. The binary where the user reads the binary code.
To read the binary code simply turn the Binary Values until you have the total value that your want, for example 41 (32 +8+1)
Then read the Binary Code from the third line. The process can be reversed and students can create a Binary Code and then work out the decimal value.