VEX Workcell - Using an End Effector - Lab 6 - Build and Test the Triangles Project

Teacher Toolbox - Facilitating the Build and Test the Triangles Project Page

What the Teacher Will Do:

Instruct students that they will continue to work in their groups to follow the steps on this page.
Circle the classroom as students work through the steps on this page and answer any questions that arise.
Students will let you know when they are ready for their check in. Guidance for this check in is provided in a Teacher Toolbox at the bottom of this page.
Once all groups have finished testing their projects and have drawn two triangles, bring the groups together for a whole-class discussion. Guidance for this discussion is provided in a Teacher Toolbox at the bottom of this page.

Now that all ten triangle coordinates have been added to the 2D list, you will need to keep track of the order that the arm draws each of them. To do this, the Index variable will be created and its initial value will be set to ‘1’ for the starting location of triangle coordinate point 1, or row 1 of the 2D list.

Next, a [Repeat] block will be used. The [Repeat] block will repeat the same number of times as the number of rows in your 2D List. This will ensure that the arm will move to all ten points in the 2D List.

The Index variable can be changed after each iteration of the [Repeat] block to keep track of which triangle coordinates have already been drawn, and which one should be drawn next. To do this, a [Change variable] block will be used.

In VEXcode V5, follow the steps in this video to create the Index variable and add the [Set variable] block to the project.

Ensure you are using your mastering and triangle coordinate values, and not the ones displayed in this video.

Follow the steps in this video to add a [Repeat], (Length of 2D List), and [Linear move] block to the project.

The [Repeat] block is used to move the arm to all ten points in the 2D list.
The (Length of 2D List) block is used to tell the [Repeat] block to repeat ten times, the same the length of the 2D list.
The [Linear move] block is used to tell the arm the (x, y, z) coordinates of the ten points in the 2D list.

Follow the steps in this video to add the Index variable and (Item of 2D list) block to the project.

The first parameter of the (Item of 2D List) block for the x, y, and z-values is the Index variable.
The second parameter of the (Item of 2D List) block for the x-value is set to ‘1’ to indicate the first column of the 2D List.
The second parameter of the (Item of 2D List) block for the y-value is set to ‘2’ to indicate the second column of the 2D List.
The second parameter of the (Item of 2D List) block for the z-value is set to ‘3’ to indicate the third column of the 2D List.

Follow the steps in this video to add a [Change variable] block to the project. The [Change variable] block is used to change the Index variable by one each time the [Repeat] block executes. This ensures that all ten coordinates in the 2D list are executed in the project.

Download and run the project. The arm will draw two triangles on the whiteboard.

If your arm did not draw two triangles on the whiteboard, notify your teacher.

Once you have finished coding the arm to draw two triangles on the whiteboard, stop the project and check in with your teacher.

Teacher Toolbox - Troubleshooting

If groups are finding that the arm does not draw the two triangles when they run their project, try the following troubleshooting techniques.

Change the z-value in the third column of the 2D list.
1. The dry-erase marker may not reach the whiteboard at some of these points. Have students set lower z-values, like 1.5 or 1, for the Points 2 through 5 and 7 through 10, and test the project.
Check the mastering values.
1. Instruct students to check that the mastering values they recorded in their engineering notebook during Seek match what is in the [Set mastering] block.
2. If the problem still persists, have students follow the steps in Seek to rerecord their mastering values.
Check the VEXcode V5 project.
1. Have students compare their project to the video on this page and ensure the order of the blocks match. Make sure students are re-downloading their project each time they make a change and before they run the project
Check the build.
1. There may be a mechanical issue with your Workcell. Instruct students to look at the Lab build instructions first and verify that the additions to their Workcell match.
2. Have students go back to the Lab 1 build instructions for a complete look at the build and check that all elements match. Even one small detail being wrong can affect the movement of the arm on the Workcell.

Teacher Toolbox - Check in

Review the following with the group during their check in:

Ensure groups added the additional blocks to the correct places in the project. Use the videos in the steps for reference.
Make sure groups do NOT erase their whiteboard so they can share their triangles during the whole-class discussion.

Extend Your Learning

If groups finish early, have them add to their project so the arm on the Workcell draws a third triangle.

Groups will need to follow the steps to obtain the additional points and create a new 2D list with the additional rows.

Teacher Toolbox - Discussion

After groups have coded the arm to draw two triangles on the whiteboard, engage the class in a discussion about their experience coding and their observations.

Begin by asking groups to share with the rest of the class what the triangles on their whiteboards look like. If time allows, ask groups to run their project to show the arm drawing the triangles for the rest of the class.
Then ask groups to share any observations they had while exploring the z-axis, using a variable, 2D list, and the [Repeat] block. Ask students questions such as:
- How does the arm move along the z-axis? Students should explain that when the z-value decreases, the arm will move down and make contact with the whiteboard. When the z-value increases, the arm will move up into the air. This is important to ensure that the marker is picked up in between drawing the two triangles.
- How was a variable used in this project? Students should note that the Index variable was used to keep track of which triangle coordinate is bring draw, or has been drawn, in the project.
- How and why was a 2D list used in this project? Students should note that the 2D list is used to store the ten triangle coordinates. The number of columns will represent the x, y, z-axis values of the coordinates and the number of rows will represent the number of stored (x, y, z) points. This is used to iterate though all ten points to draw the two triangles.
- How was the [Repeat] block used in this project? Students should explain that the [Repeat] block is used to repeat the linear movement of the arm to all ten points in the 2D list.