This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: ME456 Solutions Robotics! V 2.2 Chapter 6 Questions: 1. What does LDR stand for? Light dependent resistor. 2. How does the resistance of a photoresistor respond to bright and dim light? The resistance is small, a few ohms, if the light is bright. The resistance is large, around 50 kOhm, in dim light. What happens if the light levels are between bright and dim? Then its resistance will be somewhere between the bright and dim values. 3. Does an I/O pin have any effect on the circuit when it’s set to input? No. The I/O pin just quietly listens without any actual effect on the circuit. What causes the input register for an I/O pin to hold a 1 or 0 when it’s set to input? The value of the applied voltage. If the applied voltage is less than 1.4 volts it stores a 0. Otherwise it stores a 1. 4. What does threshold voltage mean? The threshold voltage is a value above which is a logic 1, below which is a logic 0. What’s the threshold voltage of a BASIC Stamp I/O pin? 1.4 Volts. 5. What’s a voltage divider? A voltage divider is a circuit with resistors connected in series, to set a voltage at Vo. See schematic in Figure 6-4. 6. Referring to Figure 6-4 on page 187, what causes Vo to rise above or fall below a BASIC Stamp I/O pin’s threshold voltage? The value of Vo is determined by the ratio of the resistors. What is it about the circuit that causes Vo to change value? Vo changes value because the resistor, R, changes value. R is a photoresistor which changes value depending on the amount of light falling upon it. 7. What adjustment can you make to the circuit in Figure 6-2 to make it operate better in a more brightly lit area? Use a lower value resistor instead of the 2 kOhm. Perhaps 1 kOhm or 470 Ohm. How about in a relatively dark area? Use a larger value of resistor, maybe 4.7 kOhm or even 10 kOhm. 8. What are the minimum changes you can make to RoamingWithWhiskers.bs2 to make it work with photoresistors? Adjust the IF…THEN statements so they monitor IN6 and IN3, instead of IN7 and IN5. 9. How does the program ShadowGuidedBoeBot.bs2 differ from the program RoamingWithPhotoresistorDividers.bs2? It checks the sensors between each pulse, instead of having fixed maneuvers of many pulses. What does this change in the Boe-Bot’s performance? It makes the Boe-Bot much more responsive. 10. What’s the difference between a farad and a microfarad? About a million ;-) A microfarad is one millionth of one farad. 11. Referring to Figure 6-10 on page 198, what does HIGH 6 do to the voltage across the capacitor? What does PAUSE 3 do? What does the RCTIME command do? HIGH 6 applies 5V across the capacitor, thus charging it. PAUSE 3 gives the HIGH command enough time to charge the capacitor....
View Full Document
This note was uploaded on 07/25/2008 for the course ME 456 taught by Professor Radcliffe during the Fall '07 term at Michigan State University.
- Fall '07