Be on the lookout
It is critical that the sensor be connected to the same port as the one selected in the program. By default, port 1 is selected in sensor blocks, unless it’s already taken by another sensor. It sometimes happens that students connect a sensor to ports 2 or 3, but forget to change it in the program. They are then puzzled when their robot doesn’t do what they expected it to do.
What you can do: Students are likely to be away from their computer when testing a program. If the above problem comes up, suggest they go back to look at their program and check their sensor selection.
Sometimes students attach a stack of commands to a Stack Decision Maker, losing sight of the condition they are trying to satisfy. This is likely to come up especially with the Wait Until, Repeat Until and Repeat While blocks because these blocks do not have any iconic indication of the desired sensor event.
Tell students to open the wizard by clicking the wizard tab and to go to the sensor event box. Pointing to the sensor event, ask the students, “What is the question the program is asking here?” Have students translate the iconic representation to a question. Then tell them the program is going to stop waiting once the answer to this question is “Yes.”