Here is a simple idea that I often use when I need a quick challenge for speedier teams to work on while they are waiting for the rest of the class. For example, when I've asked all teams to make a standard build such as the Robot Educator Model.

The challenge

Program a robot to drive around four chair legs in a "figure 8" pattern.

Equipment required

A four-legged chair or equivalent.

As can be seen in the photo, I usually use a few pieces of tape to mark the starting line and the position of the chair legs.

Teacher notes

Although this is of course a fairly straight-forward challenge, I find it useful for exploring different ways of making a two-wheeled robot turn, including:

• turning on the spot (with both wheels turning in opposite directions),
• one wheel fixed, or
• both wheels moving forward but at different power levels.

Having successfully completed a single "figure 8", I like to challenge teams to see how many times their robot can perform the circuit without intervention. This raises questions of reliability and repeatability, and leads nicely into a discussion around the limitations of dead reckoning. For more on this topic, see Why Doesn't My Robot Drive Straight?