Assessment: EV3 - 'Move until Color' w. Line Counting
As students progress through, have them document their milestones in the attched Task Assignment sheet. This assignment sheet also defines the challenge for students.
Line Counting
The Line Counting exercise requires students to use the Sound block and Display block in order to audibly count the lines and smile upon completion.
This lesson will also introduce the students to the rich help files system within EV3-G.
Have students use EV3 Help to learn how to display an image on the brick and to make a sound.
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If students are avoiding using the Color sensor and relying on fixed duration Move blocks, lay out the challenge with varying line spacing and require the solution to work in both directions:
- This will require students to use the Color sensor to detect the lines
- A classic issue you are likely to see is that students using the light sensor will have their robot move forward to the first line, stop, count "1" and then stay on the first line and count "2,3,4" This is due to the nature of the Move-On block preceding the the Wait-for-Color block. It is important the students understand the Move-On block only takes a few milliseconds to run, and then proceeds to the next block in the program. So, if the robot is already sitting on a black line, the next Wait-for-Light may run before the robot moves off the first black line. The students need to move the robot off of the black line.
To increase the level of the challenge, make one or more lines much thicker than the others:
- If students are relying on a fixed duration Move block to get off the line in order to solve the above Move-On issues, varying line thickness will make this solution inadequate.
- If students instead use the Color sensor to detect when they are off the line, then line thickness will not impact their solution.
Students may also struggle with the "4 for 5 seconds" at the end of the program.
- Students may insert several Sound blocks to attempt to meet this requirement - but this will not result in a precise 5 seconds.
- If student select the repeat parameter in a Sound block at the end of the program, the robot may appear not to say anything. This is because, like a Move-On, a repeating Sound block only takes milliseconds to run and then proceed to the next block in the program - which in this case is the end of the program, so the sound stop. In order to here the "4" repeat for 5 seconds, a Wait-for-Time=5s block must be inserted after the repeating Sound block.
The teacher has the final sign-off on this sheet. Key learning to check for during your sign-off includes:
Understanding the concept of a threshold
Calculating a light sensor threshold
- You may want to provide additional examples during your sign-off to ensure student mastery understanding each parameter in the Wait-for-Color block
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Particularly how to set the threshold and the "Mode" (using the sensor's LED light: When and Why?)
- Reflected Light Intensity Mode (LED on)should be used when the sensor is close to a surface
- Ambient Light Intensity Mode (LED off) should be used when sensing the light in the surrounding environment
- If uncertain, trying both ambient/reflected in View mode and selecting the one that gives the largest difference between light and dark readings for the required conditions always works
Understanding their program
- Ensure each team member can explain the program
- How did they solve the counting aloud, line width and repeating sound at end requirements
- Good use of comments in program
