Builders guide robot pacman.pdf

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Figure 21. GP2D12However, it also has a significant drawback. The accurate sensing range isbetween 80cm to 10cm with the output gradually increasing as the obstacle getscloser. Once the distance is closer than 10cm, the output begins to drop. Thisposes a serious problem since our <strong>robot</strong> will not be able to distinguish between astraightaway (wall beyond 10 cm), and a wall 1cm away.After extensive research, we decided that a sensor design using a pair of CdSphoto-resistor and a LED is best suited for our needs. Figure 22 illustrates itsoperation and Figure 23 is the circuit drawing for the sensor.LEDpowerV15V+VD1LED1CdS10k 40%OutputR1100R247kFigure 22. Wall SensorFigure 23. Wall Sensor CircuitThe resistance of the CdS photoresistor is inversely related to the surroundinglight intensity. As the light intensity increases, the resistance of the CdS resistordrops. We therefore incorporate the photoresistor in a voltage divider, creating avarying voltage level at the output node as shown in Figure 23. As the sensorapproaches the wall, the LED lights up the wall surface. Depending on theamount of light reflected into the CdS cell, the output voltage gradually increasesas the sensor moves closer to the wall.17
Initial testing of the Figure 22 set-up showed promising results: the voltage outputvaried from 2.5V when sensor was right in front of the wall to around 1.2V whenthere was no wall in front of it. However upon further testing, we discovered thatvarying ambient light intensity on the maze wall resulted in a 0.5V outputdeviation at the desired stopping distance (wall clearance) of 3 cm. To reduce theinterference from the ambient light, we decided to replace the original red LEDwith a super white LED which has a much greater intensity. Testing revealed thatat the desired stopping distance the sensor output already reached 3V, whichmeans that the ambient light now contributes to much less of the overall reflectedintensity. Testing also showed that although the output is now consistent withdifferent wall lighting, the output at the desired range still varies around 0.3Vfrom one sensor to another due to the slight differences in the photoresistors. Inorder to make the sensing distance more accurate across all sensors, softwarecalibration is performed before each round of the game. To reduce the currentconsumption of the LEDs we decided to modify the circuit to allow modulation tothe LED power supply. Instead of leaving the LEDs on all the time, themicrocontroller only turns them on right before it polls the sensor data.5.2 Dot Counting SensorDot counting is an important feature for the Pac-Man game. It allows Pac-Man todetect the dots, which are red LEDs, on the maze and to keep score of the numberof dots that it has collected. The circuit is simple and consists of one sensor,which is a photoresistor, three resistors and an op-amp as shown in Figure 24 inthe following.Figure 24. Dot Counting CircuitThe sensor placed at the bottom of Pac-Man, approximately 3cm away from thefloor of the maze. When there is no light, the voltage measured across thepositive terminal is around 0.6V (see connection diagram above). When a redLED shines to the sensor, the measured voltage is approximately 1.1V.Therefore, the reference voltage is set to 0.96V by connecting a 20kΩ resistor anda 4.7kΩ resistor as shown in the diagram above. Since the LEDs emit a narrowbeam of light, the sensor in the center of Pac-Man sometimes cannot detect the18
Page 1 and 2: PAC-MANEECE 474 - Team 1July 24, 20
Page 3 and 4: Table of ContentsList of Tables ...
Page 5 and 6: List of TablesTable 1. Encoding sch
Page 7 and 8: AbstractThe EECE474 Pac-Man project
Page 9 and 10: 2.0 ChassisThe design objective of
Page 11: casters in the back. For any two wh
Page 14 and 15: Figure 10. 55M048B2U 12VDC Unipolar
Page 16 and 17: 4.0 Radio Frequency ApplicationSinc
Page 18 and 19: Table 1. Encoding schemeUp 100Left
Page 20 and 21: is held for several clock cycles an
Page 22 and 23: Figure 20. Receiver Block DiagramTh
Page 26 and 27: ed LED on the maze. Therefore, the
Page 28 and 29: Since the beacon signal needs to co
Page 30 and 31: 6.0 Microcontroller and SoftwareOur
Page 32 and 33: Figure 31. Pin assignments for Pac-
Page 34 and 35: Table 2. RF signal format for Pac-M
Page 36 and 37: We know that the timer counts at 1
Page 38 and 39: Figure 40. Pin assignments for the
Page 40 and 41: The measurements for the right and
Page 42 and 43: 7.0 MazeThe maze is the area in whi
Page 44 and 45: Table 4. Truth table of the Memory
Page 46 and 47: 8.4 RegulatorsRegulators were added
Page 48 and 49: 9.0 RecommendationsRFIn order to re
Page 50 and 51: 10.0 ConclusionThe design and imple
Page 52 and 53: APPENDIX A: Photo GalleryPac-ManGho
Page 54 and 55: APPENDIX B: PCB LayoutsPac-ManBotto
Page 56 and 57: GhostBottom Layer (PIC, motor, cont
Page 58 and 59: MazeLEDs and sensor circuit
Page 60 and 61: APPENDIX D: Gantt chartWeek 1(May 6
Page 62 and 63: Pac-Man Source Code/***************
Page 64 and 65: }}}next_turn = NONE;turn_ready = 0;
Page 66 and 67: MIN_RIGHT += read_adc();}output_bit
Page 68 and 69: if ( (ob_left > MAX_LEFT) || (ob_ri
Page 70 and 71: Ghost Source Code/*****************
Page 72 and 73: }case S:}go_forward();break;}curren
Page 74 and 75:
}if ( walls & SOUTH )return 0;elser
Page 76 and 77:
}queue_count = 0, queue_index = 0,
Page 78 and 79:
}}}turn_enable = 0;turn_180 = 0;tur
Page 80:
{// Look for Pac-Man's beacon signa
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