ME456 Experiment Hardware Checkoff

Transcription

1 Name: ME456 Experiment Hardware Checkoff Robotics with the Boe-Bot v3.0 Fall 2012 Chapter #6: Light Sensitive Navigation with Phototransistors With your Boe-Bot s phototransistors looking down in front of it, develop a program that makes your Boe-Bot recognize the difference between black and white. The BoE-Bot should turn away from black surfaces and towards white ones. Find a large white surface and place dark-black sheets of paper on it. Hints: Make sure to test and understand what the Boe-Bot sees when it is focused on a black sheet of paper and what it sees when it is focused on a white background. Use example programs from the last three activities in this chapter. The RC decay time circuit and programs will be much more helpful for making the program work than the phototransistor divider techniques. Also, make sure this obstacle course is in a uniformly lit area. Bright sunlight from windows, and shadows cast by onlookers can make the demonstration fail. This project functions: Date: Note: STAPLE to this coversheet, all your answers to all 1) Questions (From pg. 217, plus the attached additional questions), 2) Exercises (From pg. 218, plus the attached additional exercises), 3) Activities in this chapter, and 4) Projects (From pg. 218, plus the chapter project above)

2 You are responsible for knowing the answers to Chapter 6 Questions 1-9, Exercises 1-9, Projects 1-3 on pg of Robotics with the Boe-Bot. This material, plus this additional material, will be covered in Quizzes. Chapter 6 Additional Questions 1. How does the conductance of a phototransistor respond to bright and dim light? 2. What happens if the light levels are between bright and dim? 3. Does an I/O pin have any effect on the circuit when it s set to input? 4. What causes the input register for an I/O pin to hold a 1 or 0 when it s set to input? 5. What does threshold voltage mean? 6. What s the threshold voltage of a BASIC Stamp I/O pin?

3 7. What s a voltage divider? 8. Referring to Figure 6-4 on page 173, what electrical effect causes potential voltage at P6 to rise above or fall below a BASIC Stamp I/O pin s threshold voltage? 9. What is it about the circuit that causes potential voltage at P6 to change value? 10. What adjustment can you make to the circuit in Figure 6-4 to make it operate better in a more brightly lit area? 11. How about in a relatively dark area? 12. What are the minimum changes you can make to RoamingWithWhiskers.bs2 to make it work with phototransistors? 13. What s the difference between a farad and a microfarad? 14. Referring to Figure 6-11 on page 184, what does HIGH 6 do to the voltage across the capacitor? What does PAUSE 3 do? What does the RCTIME command do?

4 15. What is a constant declaration? What does it do? How can you use one in a program? 16. How are math expressions evaluated in PBASIC? 17. What s the difference between using a number in an IF THEN condition and using a constant? 18. What s the difference between using an RCTIME measurement in an IF THEN statement and using the value of an I/O pin input register? 19. You can use these modifiers: Bit, Nib, Byte, and Word when declaring a variable, but can you declare one variable name to refer to another variable that has already been declared? If so, how does it work? If not, why can t you?

5 Old Quiz Questions 1. A phototransistor voltage divider circuit is used to detect High/low light levels. a) ls the relative light level that yields P6 = 1 (very high / very low) b) What photoresistor resistance value yields 1.4 volts at pin P6? 2. The photoresistor is also used in the RC circuit shown below. If the code below is executed, time VAR Word HIGH 6 PAUSE 3 RCTIME 6,1,time What current through the photoresistor yields time = 100? 3. In Lecture 17, The last slide shows the diagram What was stated is the most crucial element to the function of the feedback loop above? a) the Controller, b) the Plant or c) the Measurement (Circle one)