Fri.+Feb.+20,+2009

Last week I made the mistake of using pink and red paper for a course that was supposed to allow us to test the light sensor's ability to respond differently to rolling over light and dark surfaces. Bryce discovered that the light sensor could detect only a relatively minor difference between the intensity of reflected light between these two colors. This week I will again use the white surface with "borders" outlined in black tape. Remember that our light sensors are not actually detecting colors. Instead they are "reading" all colors as differing shades of gray.

For today, please continue to develop a program that will enable your robot to stay within a border, and remove any obstacles that it finds within the borders. I did have a fourth grader at one of my other schools succeed at this with just twenty minutes of programming, and about fifteen seconds of "run" time for his robot. What he did was just what I showed you last week:

Place a LOOP on the sequence beam. Drag a SWITCH inside the loop. Configure the SWITCH to operate by LIGHT SENSOR, instead of the default setting of operate by TOUCH SENSOR. Place one MOVE block on the "light" side (top) of the SWITCH, configured to go forward "Unlimited". On the "dark" side (bottom path) inside the SWITCH, drag two MOVE blocks. Make the first go backwards for some limited number of rotations, and the second execute some kind of turn. At this point, the instructions should exit the SWITCH, and LOOP around to begin again.

Some might wish to continue to tweak the "compare" slider inside the SWITCH until it can react appropriately to the contrast between pink and red, or use one of the two black and white obstacle courses you will find just inside my office. The really ambitious among you might want to construct a course with a dark inside, and a light border....?

Have fun. We will work at using a different sensor next week.

Mr. W.

[|Can I see what a sensor is reading directly on the NXT brick?]

Yes. On the NXT you can see sensor values on the brick's display. Go to the View option. Then select whichever sensor you want to read and in what units (such as inches or cm for the Ultrasonic sensor). Then select which port the sensor is plugged into and the NXT will display the current value of the sensor. It will update as the sensor value changes. This Answer courtesy of LegoEngineering.com and the Tufts University Center for Engineering Educational Outreach (CEEO)

[|What is engineering design?] Engineering Design is the process of applying creativity and math and science knowledge to the solution of human problems. What are the steps of the engineering design process? i. Identifying a problem ii. Researching possible solutions iii. Picking the best solution iv. Building a prototype v. Testing the prototype vi. Repeating any steps needed to improve the design