Day Two: A Tale of Two Trains

Friday we modified our night bus train so that it would demonstrate two different concepts of triggering. The wheels no longer function for the night bus. Our turning set of wheels now grace two more muggle motives. Here is a clip of our modified train.

The story that goes along with the movement is that our train driver begins her day's work driving the train/subway in a local city. She goes forward, off to do great things, in the morning. When the sun sets and darkness comes, she goes backward, returning home, where she finds peaceful rest until she rises with the sun the next day and begins her journey all over again.



In this version of our train, the light and motor are both triggered with "edge" triggering. When the light sensor detects darkness, the colors will change into the sunset. When it detects light, the reverse will happen. The motor will start when the button is pushed, reverse when pushed again, and then pushed a third time, the motor will stop. In both of these processes, the action happens when the button is pushed.  Here's a look at what our blocks looked like.

The left column was nicknamed SqW for Squeaky Wheels and is the sequence that turns the motor on and off.
The second column is the Day and Night column.

Now we then also modified our train to show a different kind of triggering, "level" triggering.  Unfortunantly, we did not take a movie of this train, but here is the story (that you can picture in your head) of our level triggered train.



Now we have a train driver that does cross country train driving. She starts in the morning going to her destination, driving until it get darks. When the sun retreats from the sky, she will continue a while longer before stopping to rest. When the sun rises, she continues on her way.



In this cross-country train driver, we have the same color changing system of light detection, but our motor is now triggered by levels. When the button is pushed the train will move, but when the button is released, the train will stop. Unless the button is pushed, our train driver is stuck.  Here's what these blocks looked like and you can notice the difference between this on/off motor sequence and Squeaky Wheels.

The is aptly named the Level sequence, demonstrating level triggering.

So in recap. In "edge" triggering, the button is pushed and the action comences. If the button is released or held down, the action will still happen at the instant the button is pushed. In "level" triggering, the button needs to be pressed down in order for the train to move. The motor is either on or off.



Our train driver would probably like the "edge" triggering system better, otherwise her thumb could get tired holding that button down, the whole day.