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Pattern Machine

Computing · Year 2–Year 5

Build a unit, repeat it, and find the unit in a pattern.

About the pattern machine

Tap beads to build a short unit, choose how many times to repeat it, and press Go. The machine draws the unit over and over along the strip, a unit at a time, so the repeating is something a class watches rather than a finished row that appears all at once.

The strip is worked out from the unit and the count, never stored, so the machine cannot draw a pattern that disagrees with the programme that made it. Change a bead or the count and the strip comes off: you have altered the programme, so the machine has to be run again.

The second board turns the question round. It gives you a finished pattern and asks where the unit ends, which is the harder half and the one a scheme actually sets. Tap a bead and the board draws the lines that split the pattern into blocks of that length: blocks that all look the same are a class’s own eyes telling them they were right, and a short last block says so without anybody being marked wrong.

Each bead is a shape as well as a colour, because hue on its own is a poor channel on a classroom projector and a pattern is exactly the picture two similar colours ruin.

This is the repetition objective without a repeat inside a programme: Program the Robot deliberately has no REPEAT command, because a repeat there needs a count and a scope inside the strip of instructions. Here the repeat is the whole tool, so it can be one stepper.

How to use it on your whiteboard

  1. 1Tap beads at the bottom to build the unit. Up to four.
  2. 2Use the plus and minus to choose how many repeats.
  3. 3Press Go and the machine draws the pattern.
  4. 4Ask the class how many beads there will be before you press it.
  5. 5Switch to Find the unit and tap the bead where you think the unit ends.

Questions

What is the unit of a pattern?
The bit that repeats. In red, blue, red, blue the unit is red then blue, and everything after that is the same two beads again. Finding the unit is the skill: once a class can name it they can carry any pattern on as far as they like.
Why does the pattern disappear when I change a bead?
Because the strip is what the programme says, and you have changed the programme. A strip left up after the unit changed would be a picture of a pattern that no longer exists. Press Go and the machine draws the new one.
How many repeats can I have?
As many as the strip can draw with the beads still big enough to count, which depends on how long your unit is: a unit of two goes round more times than a unit of four. Nothing is capped at a number somebody picked.
Is this the same as a loop in Scratch?
It is the idea behind one. A loop says “do this, this many times”, which is exactly the unit and the count here. The difference is that this board shows you the whole result at once, which is what makes it worth doing before anybody writes a repeat block.