EV3 Multiple conditions: wait sensor activation for N seconds or

Question

How to program EV3 to wait for a sensor activation for at most X seconds? If the sensor is activated in the given time, begin sequence B. If it is not activated in X seconds, begin sequence A.

Explanation: My robot arrives at point X, then it waits for the ultrasonic sensor activation (if a hand arrives near the sensor - < 7 cm), but must wait only for 10 seconds. If nothing triggers the ultrasonic sensor within 10 seconds the robot must continue with sequence A. If, for example, a hand is placed in front of the ultrasonic sensor (<7CM) within 10 seconds the robot must continue with sequence B. Then when sequence B is terminated, the robot should continue with sequence A.

I have tried using loops, switches and asking Gandalf for help but with no success.

Answer 1

Here's some pseudocode that does what you need:

Reset timer
Loop block:
    Sensor block, output logical TRUE when condition is reached
    Timer block, output logical TRUE when X seconds have passed
    Logic block, outputs logical TRUE if sensor OR timer is true
End loop when it receives TRUE from the Logic block.
Switch block:
    if sensor = condition, SEQUENCE B
End switch
SEQUENCE A

The sensor and timer blocks' logical data wires are connected to the logic block. The logic block is set to "OR", which ends the loop if either one is true. Then you use a switch to decide whether or not to execute SEQUENCE B, and after that, SEQUENCE A happens regardless.

Answer 2

One way would be to use a loop with a counter and a built-in waiting period. In each iteration check the sensor readings: if the value indicates the presence of a hand, exit the loop and start sequence B. Otherwise increment a counter and wait for some time. Finally, if the value of the counter indicates that the 10 seconds have passed, execute sequence A.

Answer 3

In EV3 the pseudocode looks like:

Always surprises me how complex it is to represent simple ideas.