Discussion Points


Acting on Information from a Touch Sensor

Whole Class Activity


Before students build a bumper: Remind students of a problem they have already solved: making Roverbot move forward and then stop when it hits something (i.e., when the touch sensor is pressed). Tell them that in this activity they will be sending Roverbot on its own. Explain that their job is to program Roverbot to move until it hits something, then stop, go backwards, turn a bit and continue going forward. Their program has to be written so that Roverbot can do this repeatedly.


If needed, review the Wait Until and Sensor Watcher sensor blocks. Remind students of the main difference between these blocks: the first checks the state of the sensor once, the second checks it over and over again. Suggest keeping that idea in mind when working on a solution to the above problem.


Decide whether to use Transparencies # 5a-d now or whether to let students work on their own first. The activity sheet gives them enough information to get started, but in their attempts to solve the problem, students may miss important nuances about the way a program flows. Discussing the examples in this transparency will help students relate a robotís behavior to the instructions given in a program.


Small Group Activity


Building a single bumper : Have students work in small groups, following Constructopedia bumper building instructions, pages 26-29. Give each student a copy of the activity sheet. As they build, talk to students in their groups, showing them the touch sensor hidden in the bumper. When they have finished building, encourage them to press on the bumper lightly and observe the state of the sensor on the RCX display window. It might be helpful to connect the short connector wire from the bumper to port 1 and to check the state of the sensor when the bumper is pushed.


Have the students follow the activity sheet giving them enough time to work on solving the above problem (which is also the first RCXtra problem in their activity sheet). If you notice that some students experience difficulties, suggest breaking the problem into smaller chunks. For example, suggest programming it to reverse direction as it hits something, download and test it that far. Once they solve this part, they can add the next step of turning in place.


The following Programming Highlights section is somewhat different from the same section in previous activities. Instead of introducing new command blocks, the focus here is on several possible solutions to the problem, pointing out important issues in studentsí programming attempts.


Single Bumper from Constructopedia pages 26-29

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