Make a code wheel

Make a code wheel

Spy science!

You need to get a message to a friend, but you can't let anyone else know what it says. What do you do?

You can make a code wheel!

If you have a code wheel, you and a friend can send each other secret messages.

What you need:

  • 2 x 10cm circle of paper
  • 2 x 12cm circle of paper
  • Ruler
  • Scissors
  • 2 x split pins
  • Pen

How to:

1. In the 10cm circle of paper, cut a 1cm2 window, about 3cm from the centre of the circle.

2. Use the split pin to attach the two circles together at the centres, with the small circle on top of the larger circle.

3. Write the alphabet around the edge of the large circle.

4. Draw an arrow on the small circle, pointing to one of the letters on the large circle.

5. To make your code, turn the small circle until the arrow points to the letter A. Write the letter which you want to represent A in your code in the centre of the window e.g. N. Make a note on another piece of paper to say this letter has been used up.

Code wheel_1

6. Then turn the wheel so the arrow points to B. Write another letter in the centre of the window e.g. Y. Write a note on another piece of paper to say that this letter has been used up.

7. Repeat for all the letters in the alphabet.

8. Make a second code wheel, which is exactly the same as the first. Give this code wheel to your receiver.

9. To write a coded message, first write it out in English. Then, encode your message. Every time there is an A in your message, replace it with an N. Every time there is a B in your message, replace it with a Y. Repeat for all the letters in the alphabet.

Code wheel_!

10. For your friend to decode the message, they need to use the second code wheel. Turning the small circle to get the letter N, they will realise that it stands for the letter A. They do this for all the letters in your message.

What's happening?

You've just made a simple code! People still use code to send secret messages. Often the code is very complicated and it needs a computer to crack it.

Anyone who wants to buy or sell something on the internet is using code. When information is sent over the internet only people who have the key to unlock the code can see the real data. Everyone else sees a string of numbers and letters that don't make any sense.

Sign up for the newsletter
Sign Up For The Newsletter
Want to get the latest science news from Planet Science straight to your inbox? Sign up now!