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In the fall of 1996 at Texas Tech University a class of 32 EE students was asked to build a mobile robot vehi- cle It would under Region 3 Student Conference robotics competition guide- lines 1) complete three laps around a wooden track and 2) at the beginning of each lap drop a coin in a toll slot in an order specified to the vehicle at the starting line
Building a mobile robot in six weeks was an extremely challenging task for this class of sophomore EE laboratory students They were divided into eight groups of four people The groups were assigned the identical task of building this robot vehicle but each developed a unique design Weekly presentations by all groups allowed for time to discuss problems and obtain possible solutions from other groupsrsquo members
The competition required the vehicle to follow a reflective white line around the center of an oval wooden track and complete three laps At the start of each lap the vehicle was supposed to deposit
40
a quarter into one of three toll slots in an order spec- ified by the Lap Instruc- tion LEDs (hght emitting diodes) These were em- bedded in the track at the starting line The vehicle had to scan the LEDs to obtain the Lap Instruction Data before starting
The Lap Instruction Data were interpreted by a three bit binary code In binary code a zero (0) means the LED is ldquoOFFrsquo and a one (1) means the LED is ldquoONrdquo (See Table 1 for the Lap Instruction Data) For example if the
binary code is (010) then the interpreta- tion is (132) Thus in lap 1 the vehicle should drop a quarter in slot 1 in lap 2 drop a quarter in slot 3 and in lap 3 drop a quarter in slot 2
This vehicle was made up of four different subsystems 1) the power sup- ply (the heart of the vehicle) which powered the entire vehicle 2) the sen- sors 3) the microcontroller (the ldquobrainrdquo of the vehicle) and 4) the mechanics (ie the quarter depositing mecha- nism) Each of these subsystems was designed and built separately but inter- connected to make a complete vehicle
The power supply-the source of strength for the system-was essential Several parts of the vehicle required 5 volts to work well A voltage regulator supplied a constant voltage to the micro- controller sensors and servo motors
A 72-volt Ni-Cad rechargeable bat- tery with a capacity of 12 Ah (Ampere hour) supplied power to the motor Another 72-volt battery with the same specifications ran the servos and sen- sors (The only difference was that this battery was regulated to 5 volts) The
0278-664898$1000 0 1998 IEEE
microcontroller required a 9 volt battery rated at 65 mAh Since the motor pro- duced a lot of noise the use of a sepa- rate battery pack eliminated the need for an optical isolator
A linear voltage regulator supplied a constant voltage to different parts of the car A regulator circuit and two filter capacitors were also used The capaci- tors which were both connected paral- lel to each other and the power supply filtered out 1) noise that may have been caused by coupling from other cir- cuits 2) noise from the motor or servos and 3) high frequency transient from the crystal clock in the microcontroller board The voltage regulator ckcuit is shown in Fig 1
Front sensors These sensors con- tained an infrared emitter and a photo- transistor pair that were built into a single plastic casing They were sepa- rated by a thin black plastic housing This prevented detection of the light given off by the emitter before it was reflected off the white line The emitter and detector pair was set at a particular angle so that only the detector recog- nized the reflected beam of light
Five sensors were used three were placed on the white stripe and two were placed outsidea the white stripe on either side (Placing two sensors on either side of the white stripe gave an accurate position of the car to the microcontroller) As soon as the car went off the white stripe the sensors
IEEE POTENTIALS
Fig I Regulafor circiiifry gave a signal to the niicrocontroller to get the car back on the track These sen- sors worked optimally at a height of 05 inches above the reflective surface
The output from the sensors was passed through a Schmitt trigger (The Schmitt trigger was used to eliminate any ambiguity to the microcontroller that might result from the different out- put voltages of the sensors) The voltage threshold for the Schmitt trigger was between 16V and 19V The circuit shown in Fig 2 displays the sensors connected to a Schmitt trigger
Starting block f ensors Three infrared photo transistors were used to detect the LEDs at the starting block This signal was converted by the micro- controller into a binary code that was used to drop the quartlzrs into the right slots in the right sequence
Distance measurement sensor A simple circuit (similar to the circuit in Fig 5) using a reflective object sensor was built to measure the distance trav- eled by the car It was placed approxi- mately one-half of an inch away from the right rear wheel
A circular cardboard disk which had four equal divisions was pasted on the outer surface of this wheel Each divi- sion was painted black and white alter- nately The sensor gave a high signal when it read the white area and a low signal when it read the black area (Fig 3) By measuring the circumference of the wheel and depending on the high and low values given to the microcon- troller by the sensor tlhe distance trav- eled by the car was determined
These sensors also read the white line They required a forward current of 40 mA (milli Amp) an output voltage of 41 volts for the whi Le region and 16 volts for the black region The input voltage again was 5 vcilts
Arm sensor Infrared LED and infrared phototransistor sensors which
Emitter
Disc
Detector I
Fig 2 Sensor circuif fo sense fhe white line were mounted at the end of the arm were used to detect the white circle around the toll slots When the white circle was detected a high signal was given to the microcontroller in order to move the servo motor and release the quarters Thus the quarters would roll out and be deposited into the toll slots
Programming the microcontroller
The microcontroller used as the cen- tral control system for the vehicle was the Motorola 68HC11 It has many fea- tures including five IO ports five internal independent timers that can be programmed to provide pulse width modulation and an on-board analog to digital converter The 68HC 11 can also be easily interfaced with different external circuits
The program for the microcontroller used in this project could be broken into five parts Figures 4 and 5 show flow- charts of this program
The starting code was the key to depositing coins in the correct toll slots This code read three LEDs then jumped to one of six subroutines (These subrou- tines stored the values of the correct slot in which to deposit the coins during the right lap) The starting code then entered a loop where it awaited a ldquoGOrsquo signal before jumping to a subroutine that set all the desired flags and registers
The steering driver was based on output compares (mechanisms used to produce a pulse with a set pulse width) The speed of the car was a set value at the start of the program The microcon- troller board read input from the five front sensors if a sensor deviated from the line the steering turned slightly in the direction required bringing the sensor
sors turned high the microcontroller started an interrupt that counted how far the robot had traveled When it had trav- eled a desired distance the program then jumped to the distance subroutine
The distance subroutine changed the counting flags so it would no longer count the pulses created by the distance sensor This decreased the speed of the motor The program then continued to slow the motor by feeding the speed control circuit a smaller pulse The pro- gram then jumped back into the steering
Fig 3 Disfance measurement circuif
Fig A Flowchart I
FEBRUARYIMARCH 1998 41
Fig 5 Flowchart 2
loop in order to increase the speed of the motor The toll slot released the quarter Input from the Lap Instruction Data helped the robot decide where and when to deposit the quarter Input from the five front sensors told the program in which direction to turn The arm sen- sor would find the toll slots and transfer the information to the toll slot code
Once the toll slot subroutine was called the position of the correct slot was compared to the position of the cur- rent slot If the current slot was not the correct slot the program performed a two-second delay to skip that toll slot so it was not sensed twice At the correct slot the program cut the pulse to the speed control circuit thus stopping the motor The subroutine used the other output compare to create a pulse width modulation that moved the servo to release a quarter The program then sent a pulse to the speed control so the car could begin accelerating
The f inish line code counted the amount of distance covered by the car The finish line subroutine was called if all five sensors were high This subrou- tine updated the lap count and deter- mined the slot in which to deposit the coin The program then checked to see if the robot was in lap 4 If so it would stop once the robot had crossed the finish line If the robot was not in lap 4 the program would use a delay so that the finish line was read only once Once this entire subroutine was complete the pro- gram jumped back into the steering loop
The body of the car contained two major parts the chassis and the arm The entire vehicle had to fit into a 12 inch by 12 inch square that was no more
42
than 14 inches high (Complete- ly assembled the robot was 12 inches tall)
The chassis was made up of an upper stage and a lower stage The upper stage was made of clear Plexi- glas which was cut to fit a 12 inch by 12 inch square (per IEEE Region 3 Com-
petition regulations) The upper stage contained the arm and most of the elec- trical controls such as the speed of con- trol and the power regulator The lower stage was host to the sensors steering servo batteries and motor
The indirect drive sew-used as the steering servo-required a pulse width of 14 ms for full left 18 ms for full right and 16 ms for the center position
The wooden arm mounted on the upper stage was 1625 inches in length and 8 inches in height This arm was mounted atop a servo motor that swung the arm out to deposit the coins (To swing the arm out at 90deg it required a pulse width of 084 ms)
The release mech- anism had a servo motor connected by two metallic rods When pulled back once the mechanism loaded the quarter into the chute and moved the servo for- ward to release the coin A fully extend- ed arm is displayed in Fig 6
The motor and the speed control worked together to start stop and regu- late the carrsquos speed The motor had a maximum stall cur- rent of 45 amps and a no-load cur- rent of 024 amps The maximum speed of the motor with a no-load current was
16900 revolutionslminute whereas the stall torque was 00762 Newton meters
The speed control consisted of an N- Channel enhanced mode power MOS- FET (metallic oxide semiconductor field-effect transistor) and a flyback diode connected to the motor and the battery The purpose of the flyback diode was to protect the MOSFET from high inductive currents produced when switching the motor Figure 7 shows the speed control circuit
The major handicap in programming this microcontroller was that it had only 512 bytes of memory available The software used for this vehicle was very condensed and fit exactly in that avail- able memory
Front sensors with better white line sensing capabilities (ie sensing the white line from a distance of more than 05 inches) would considerably improve the handling capability of the vehicle on the track There was also an occasional problem of quarters get- ting jammed side by side in the quarter release mechanism Making the quarter arm slot approximately 00625 inch narrower would help improve this
Fig 6 Quarter arm assembly
Fig 7 Speed control circuit
IEEE POTENTIALS
regulator circuit w a 5 volt regulator used in the linear voltage regulator 1 Radio Shack LM780j
chassis steering servo
N-Channel enhanced mode power speed control
front sensors I Obiect sensors I distance measurement sensors
starting block sensors microcontroller
Digi-Key QSDl23QT Infrared Photo Transistors
The program could also be improved to allow the car to stop right in the center of the toll slots However this would probably take great time and experimentation
The results A vehicle was built on a modified
radio-controlled car chassis rigged with optical sensors and a Motorola 68HC 11 microcontroller This vehicle completed three laps and deposited one quarter in the correct toll slot The vehicle stopped at the other two toll slots in the correct order but missed them by about one third of an inch
when shooting the quarter each time After the third lap the car stopped within three inches of the finish line after crossing it
All eight groups demonstrated their cars and their performance at a campus event All teams were able to make their vehicles complete three laps although some of them were not able to deposit quarters in the toll slots The class has also continued showing their robots to local elementary and Junior High Class- es As a result the class satisfactorily answered questions regarding oper- ation construction costs and engineer- ing as a potential career
Papers for Potentials IEEE Potentials invites manuscripts of interest
to engineering students and recent graduates to be submitted for possible publication
Manuscript should be typed double-spaced If you can please also send it on a disk (Mac)
A manuscript should equal two to four pages when published including illustrations
Technical articles should be relevant with only a few if any equations The content should not talk down to or be over the heads of the intended audience
Manuscripts are reviewed by Student members Members Potentials staff and others as appropriate before a final deck ion to publish is made
For more info visit our web site at
httphrvwwczsumredupotentials
Please send your manuscript to IEEE Potentials 445 Hoes Lane PO Box 1331 Piscalaway NJ 08855-1 331
Robots AK Peters Wellesley Massa- chusetts 1983
Motorola Inc H C l l M 6 8 H C l l Reference Manual Motorola Inc 1991
1 1996 Texas Tech University
01 Rohit DSouza is a senior electrical
engineering student at Texas Tech Uni- versity He worked as a co-op at Alca- tel Network Systems in Richardson TX in the summer of 1997 and will be doing his second co-op term in the summer of 1998
He is an Engineering Ambassador for the College of Engineering and will assist in recruiting new students for the college He is also a Peer Mentor for incoming freshmen This year he was elected as the Director of Activities for the IEEE at Texas Tech University He intends to pursue a Masters degree in electrical engineering specializing in Image Processing
Johns Hopkins University
Graduate Studies in Electrical and Computer Engineering
Founded in 1876 Johns Hopkins was the first University to offer graduate education as its known today in America with emphasis on creative scholarship Today graduate study in the Department of Electrical and Computer Engineering is oriented toward the PhD with emphasis on scholarship and research rather than formal coursework In addition the Department offers a MSE degree program Departmental financial aid is available to qualified students We offer concentrations in the following areas
Communications and Signal Processing Computer Engineering
Language and Speech Processing Nonlinear and Quantum Optics
Solid-state Electronics Systems and Control Theory
For more information please contact ECE Departmenflhe Johns Hopkins University
3400 N Charles St1105 Barton Hall Baltimore MD 21218
gradadmecejhuedu httplwww ecejhuedu
(410) 516-4808
FEBRUARYMARCH 19198 43
Fig I Regulafor circiiifry gave a signal to the niicrocontroller to get the car back on the track These sen- sors worked optimally at a height of 05 inches above the reflective surface
The output from the sensors was passed through a Schmitt trigger (The Schmitt trigger was used to eliminate any ambiguity to the microcontroller that might result from the different out- put voltages of the sensors) The voltage threshold for the Schmitt trigger was between 16V and 19V The circuit shown in Fig 2 displays the sensors connected to a Schmitt trigger
Starting block f ensors Three infrared photo transistors were used to detect the LEDs at the starting block This signal was converted by the micro- controller into a binary code that was used to drop the quartlzrs into the right slots in the right sequence
Distance measurement sensor A simple circuit (similar to the circuit in Fig 5) using a reflective object sensor was built to measure the distance trav- eled by the car It was placed approxi- mately one-half of an inch away from the right rear wheel
A circular cardboard disk which had four equal divisions was pasted on the outer surface of this wheel Each divi- sion was painted black and white alter- nately The sensor gave a high signal when it read the white area and a low signal when it read the black area (Fig 3) By measuring the circumference of the wheel and depending on the high and low values given to the microcon- troller by the sensor tlhe distance trav- eled by the car was determined
These sensors also read the white line They required a forward current of 40 mA (milli Amp) an output voltage of 41 volts for the whi Le region and 16 volts for the black region The input voltage again was 5 vcilts
Arm sensor Infrared LED and infrared phototransistor sensors which
Emitter
Disc
Detector I
Fig 2 Sensor circuif fo sense fhe white line were mounted at the end of the arm were used to detect the white circle around the toll slots When the white circle was detected a high signal was given to the microcontroller in order to move the servo motor and release the quarters Thus the quarters would roll out and be deposited into the toll slots
Programming the microcontroller
The microcontroller used as the cen- tral control system for the vehicle was the Motorola 68HC11 It has many fea- tures including five IO ports five internal independent timers that can be programmed to provide pulse width modulation and an on-board analog to digital converter The 68HC 11 can also be easily interfaced with different external circuits
The program for the microcontroller used in this project could be broken into five parts Figures 4 and 5 show flow- charts of this program
The starting code was the key to depositing coins in the correct toll slots This code read three LEDs then jumped to one of six subroutines (These subrou- tines stored the values of the correct slot in which to deposit the coins during the right lap) The starting code then entered a loop where it awaited a ldquoGOrsquo signal before jumping to a subroutine that set all the desired flags and registers
The steering driver was based on output compares (mechanisms used to produce a pulse with a set pulse width) The speed of the car was a set value at the start of the program The microcon- troller board read input from the five front sensors if a sensor deviated from the line the steering turned slightly in the direction required bringing the sensor
sors turned high the microcontroller started an interrupt that counted how far the robot had traveled When it had trav- eled a desired distance the program then jumped to the distance subroutine
The distance subroutine changed the counting flags so it would no longer count the pulses created by the distance sensor This decreased the speed of the motor The program then continued to slow the motor by feeding the speed control circuit a smaller pulse The pro- gram then jumped back into the steering
Fig 3 Disfance measurement circuif
Fig A Flowchart I
FEBRUARYIMARCH 1998 41
Fig 5 Flowchart 2
loop in order to increase the speed of the motor The toll slot released the quarter Input from the Lap Instruction Data helped the robot decide where and when to deposit the quarter Input from the five front sensors told the program in which direction to turn The arm sen- sor would find the toll slots and transfer the information to the toll slot code
Once the toll slot subroutine was called the position of the correct slot was compared to the position of the cur- rent slot If the current slot was not the correct slot the program performed a two-second delay to skip that toll slot so it was not sensed twice At the correct slot the program cut the pulse to the speed control circuit thus stopping the motor The subroutine used the other output compare to create a pulse width modulation that moved the servo to release a quarter The program then sent a pulse to the speed control so the car could begin accelerating
The f inish line code counted the amount of distance covered by the car The finish line subroutine was called if all five sensors were high This subrou- tine updated the lap count and deter- mined the slot in which to deposit the coin The program then checked to see if the robot was in lap 4 If so it would stop once the robot had crossed the finish line If the robot was not in lap 4 the program would use a delay so that the finish line was read only once Once this entire subroutine was complete the pro- gram jumped back into the steering loop
The body of the car contained two major parts the chassis and the arm The entire vehicle had to fit into a 12 inch by 12 inch square that was no more
42
than 14 inches high (Complete- ly assembled the robot was 12 inches tall)
The chassis was made up of an upper stage and a lower stage The upper stage was made of clear Plexi- glas which was cut to fit a 12 inch by 12 inch square (per IEEE Region 3 Com-
petition regulations) The upper stage contained the arm and most of the elec- trical controls such as the speed of con- trol and the power regulator The lower stage was host to the sensors steering servo batteries and motor
The indirect drive sew-used as the steering servo-required a pulse width of 14 ms for full left 18 ms for full right and 16 ms for the center position
The wooden arm mounted on the upper stage was 1625 inches in length and 8 inches in height This arm was mounted atop a servo motor that swung the arm out to deposit the coins (To swing the arm out at 90deg it required a pulse width of 084 ms)
The release mech- anism had a servo motor connected by two metallic rods When pulled back once the mechanism loaded the quarter into the chute and moved the servo for- ward to release the coin A fully extend- ed arm is displayed in Fig 6
The motor and the speed control worked together to start stop and regu- late the carrsquos speed The motor had a maximum stall cur- rent of 45 amps and a no-load cur- rent of 024 amps The maximum speed of the motor with a no-load current was
16900 revolutionslminute whereas the stall torque was 00762 Newton meters
The speed control consisted of an N- Channel enhanced mode power MOS- FET (metallic oxide semiconductor field-effect transistor) and a flyback diode connected to the motor and the battery The purpose of the flyback diode was to protect the MOSFET from high inductive currents produced when switching the motor Figure 7 shows the speed control circuit
The major handicap in programming this microcontroller was that it had only 512 bytes of memory available The software used for this vehicle was very condensed and fit exactly in that avail- able memory
Front sensors with better white line sensing capabilities (ie sensing the white line from a distance of more than 05 inches) would considerably improve the handling capability of the vehicle on the track There was also an occasional problem of quarters get- ting jammed side by side in the quarter release mechanism Making the quarter arm slot approximately 00625 inch narrower would help improve this
Fig 6 Quarter arm assembly
Fig 7 Speed control circuit
IEEE POTENTIALS
regulator circuit w a 5 volt regulator used in the linear voltage regulator 1 Radio Shack LM780j
chassis steering servo
N-Channel enhanced mode power speed control
front sensors I Obiect sensors I distance measurement sensors
starting block sensors microcontroller
Digi-Key QSDl23QT Infrared Photo Transistors
The program could also be improved to allow the car to stop right in the center of the toll slots However this would probably take great time and experimentation
The results A vehicle was built on a modified
radio-controlled car chassis rigged with optical sensors and a Motorola 68HC 11 microcontroller This vehicle completed three laps and deposited one quarter in the correct toll slot The vehicle stopped at the other two toll slots in the correct order but missed them by about one third of an inch
when shooting the quarter each time After the third lap the car stopped within three inches of the finish line after crossing it
All eight groups demonstrated their cars and their performance at a campus event All teams were able to make their vehicles complete three laps although some of them were not able to deposit quarters in the toll slots The class has also continued showing their robots to local elementary and Junior High Class- es As a result the class satisfactorily answered questions regarding oper- ation construction costs and engineer- ing as a potential career
Papers for Potentials IEEE Potentials invites manuscripts of interest
to engineering students and recent graduates to be submitted for possible publication
Manuscript should be typed double-spaced If you can please also send it on a disk (Mac)
A manuscript should equal two to four pages when published including illustrations
Technical articles should be relevant with only a few if any equations The content should not talk down to or be over the heads of the intended audience
Manuscripts are reviewed by Student members Members Potentials staff and others as appropriate before a final deck ion to publish is made
For more info visit our web site at
httphrvwwczsumredupotentials
Please send your manuscript to IEEE Potentials 445 Hoes Lane PO Box 1331 Piscalaway NJ 08855-1 331
Robots AK Peters Wellesley Massa- chusetts 1983
Motorola Inc H C l l M 6 8 H C l l Reference Manual Motorola Inc 1991
1 1996 Texas Tech University
01 Rohit DSouza is a senior electrical
engineering student at Texas Tech Uni- versity He worked as a co-op at Alca- tel Network Systems in Richardson TX in the summer of 1997 and will be doing his second co-op term in the summer of 1998
He is an Engineering Ambassador for the College of Engineering and will assist in recruiting new students for the college He is also a Peer Mentor for incoming freshmen This year he was elected as the Director of Activities for the IEEE at Texas Tech University He intends to pursue a Masters degree in electrical engineering specializing in Image Processing
Johns Hopkins University
Graduate Studies in Electrical and Computer Engineering
Founded in 1876 Johns Hopkins was the first University to offer graduate education as its known today in America with emphasis on creative scholarship Today graduate study in the Department of Electrical and Computer Engineering is oriented toward the PhD with emphasis on scholarship and research rather than formal coursework In addition the Department offers a MSE degree program Departmental financial aid is available to qualified students We offer concentrations in the following areas
Communications and Signal Processing Computer Engineering
Language and Speech Processing Nonlinear and Quantum Optics
Solid-state Electronics Systems and Control Theory
For more information please contact ECE Departmenflhe Johns Hopkins University
3400 N Charles St1105 Barton Hall Baltimore MD 21218
gradadmecejhuedu httplwww ecejhuedu
(410) 516-4808
FEBRUARYMARCH 19198 43
Fig 5 Flowchart 2
loop in order to increase the speed of the motor The toll slot released the quarter Input from the Lap Instruction Data helped the robot decide where and when to deposit the quarter Input from the five front sensors told the program in which direction to turn The arm sen- sor would find the toll slots and transfer the information to the toll slot code
Once the toll slot subroutine was called the position of the correct slot was compared to the position of the cur- rent slot If the current slot was not the correct slot the program performed a two-second delay to skip that toll slot so it was not sensed twice At the correct slot the program cut the pulse to the speed control circuit thus stopping the motor The subroutine used the other output compare to create a pulse width modulation that moved the servo to release a quarter The program then sent a pulse to the speed control so the car could begin accelerating
The f inish line code counted the amount of distance covered by the car The finish line subroutine was called if all five sensors were high This subrou- tine updated the lap count and deter- mined the slot in which to deposit the coin The program then checked to see if the robot was in lap 4 If so it would stop once the robot had crossed the finish line If the robot was not in lap 4 the program would use a delay so that the finish line was read only once Once this entire subroutine was complete the pro- gram jumped back into the steering loop
The body of the car contained two major parts the chassis and the arm The entire vehicle had to fit into a 12 inch by 12 inch square that was no more
42
than 14 inches high (Complete- ly assembled the robot was 12 inches tall)
The chassis was made up of an upper stage and a lower stage The upper stage was made of clear Plexi- glas which was cut to fit a 12 inch by 12 inch square (per IEEE Region 3 Com-
petition regulations) The upper stage contained the arm and most of the elec- trical controls such as the speed of con- trol and the power regulator The lower stage was host to the sensors steering servo batteries and motor
The indirect drive sew-used as the steering servo-required a pulse width of 14 ms for full left 18 ms for full right and 16 ms for the center position
The wooden arm mounted on the upper stage was 1625 inches in length and 8 inches in height This arm was mounted atop a servo motor that swung the arm out to deposit the coins (To swing the arm out at 90deg it required a pulse width of 084 ms)
The release mech- anism had a servo motor connected by two metallic rods When pulled back once the mechanism loaded the quarter into the chute and moved the servo for- ward to release the coin A fully extend- ed arm is displayed in Fig 6
The motor and the speed control worked together to start stop and regu- late the carrsquos speed The motor had a maximum stall cur- rent of 45 amps and a no-load cur- rent of 024 amps The maximum speed of the motor with a no-load current was
16900 revolutionslminute whereas the stall torque was 00762 Newton meters
The speed control consisted of an N- Channel enhanced mode power MOS- FET (metallic oxide semiconductor field-effect transistor) and a flyback diode connected to the motor and the battery The purpose of the flyback diode was to protect the MOSFET from high inductive currents produced when switching the motor Figure 7 shows the speed control circuit
The major handicap in programming this microcontroller was that it had only 512 bytes of memory available The software used for this vehicle was very condensed and fit exactly in that avail- able memory
Front sensors with better white line sensing capabilities (ie sensing the white line from a distance of more than 05 inches) would considerably improve the handling capability of the vehicle on the track There was also an occasional problem of quarters get- ting jammed side by side in the quarter release mechanism Making the quarter arm slot approximately 00625 inch narrower would help improve this
Fig 6 Quarter arm assembly
Fig 7 Speed control circuit
IEEE POTENTIALS
regulator circuit w a 5 volt regulator used in the linear voltage regulator 1 Radio Shack LM780j
chassis steering servo
N-Channel enhanced mode power speed control
front sensors I Obiect sensors I distance measurement sensors
starting block sensors microcontroller
Digi-Key QSDl23QT Infrared Photo Transistors
The program could also be improved to allow the car to stop right in the center of the toll slots However this would probably take great time and experimentation
The results A vehicle was built on a modified
radio-controlled car chassis rigged with optical sensors and a Motorola 68HC 11 microcontroller This vehicle completed three laps and deposited one quarter in the correct toll slot The vehicle stopped at the other two toll slots in the correct order but missed them by about one third of an inch
when shooting the quarter each time After the third lap the car stopped within three inches of the finish line after crossing it
All eight groups demonstrated their cars and their performance at a campus event All teams were able to make their vehicles complete three laps although some of them were not able to deposit quarters in the toll slots The class has also continued showing their robots to local elementary and Junior High Class- es As a result the class satisfactorily answered questions regarding oper- ation construction costs and engineer- ing as a potential career
Papers for Potentials IEEE Potentials invites manuscripts of interest
to engineering students and recent graduates to be submitted for possible publication
Manuscript should be typed double-spaced If you can please also send it on a disk (Mac)
A manuscript should equal two to four pages when published including illustrations
Technical articles should be relevant with only a few if any equations The content should not talk down to or be over the heads of the intended audience
Manuscripts are reviewed by Student members Members Potentials staff and others as appropriate before a final deck ion to publish is made
For more info visit our web site at
httphrvwwczsumredupotentials
Please send your manuscript to IEEE Potentials 445 Hoes Lane PO Box 1331 Piscalaway NJ 08855-1 331
Robots AK Peters Wellesley Massa- chusetts 1983
Motorola Inc H C l l M 6 8 H C l l Reference Manual Motorola Inc 1991
1 1996 Texas Tech University
01 Rohit DSouza is a senior electrical
engineering student at Texas Tech Uni- versity He worked as a co-op at Alca- tel Network Systems in Richardson TX in the summer of 1997 and will be doing his second co-op term in the summer of 1998
He is an Engineering Ambassador for the College of Engineering and will assist in recruiting new students for the college He is also a Peer Mentor for incoming freshmen This year he was elected as the Director of Activities for the IEEE at Texas Tech University He intends to pursue a Masters degree in electrical engineering specializing in Image Processing
Johns Hopkins University
Graduate Studies in Electrical and Computer Engineering
Founded in 1876 Johns Hopkins was the first University to offer graduate education as its known today in America with emphasis on creative scholarship Today graduate study in the Department of Electrical and Computer Engineering is oriented toward the PhD with emphasis on scholarship and research rather than formal coursework In addition the Department offers a MSE degree program Departmental financial aid is available to qualified students We offer concentrations in the following areas
Communications and Signal Processing Computer Engineering
Language and Speech Processing Nonlinear and Quantum Optics
Solid-state Electronics Systems and Control Theory
For more information please contact ECE Departmenflhe Johns Hopkins University
3400 N Charles St1105 Barton Hall Baltimore MD 21218
gradadmecejhuedu httplwww ecejhuedu
(410) 516-4808
FEBRUARYMARCH 19198 43
regulator circuit w a 5 volt regulator used in the linear voltage regulator 1 Radio Shack LM780j
chassis steering servo
N-Channel enhanced mode power speed control
front sensors I Obiect sensors I distance measurement sensors
starting block sensors microcontroller
Digi-Key QSDl23QT Infrared Photo Transistors
The program could also be improved to allow the car to stop right in the center of the toll slots However this would probably take great time and experimentation
The results A vehicle was built on a modified
radio-controlled car chassis rigged with optical sensors and a Motorola 68HC 11 microcontroller This vehicle completed three laps and deposited one quarter in the correct toll slot The vehicle stopped at the other two toll slots in the correct order but missed them by about one third of an inch
when shooting the quarter each time After the third lap the car stopped within three inches of the finish line after crossing it
All eight groups demonstrated their cars and their performance at a campus event All teams were able to make their vehicles complete three laps although some of them were not able to deposit quarters in the toll slots The class has also continued showing their robots to local elementary and Junior High Class- es As a result the class satisfactorily answered questions regarding oper- ation construction costs and engineer- ing as a potential career
Papers for Potentials IEEE Potentials invites manuscripts of interest
to engineering students and recent graduates to be submitted for possible publication
Manuscript should be typed double-spaced If you can please also send it on a disk (Mac)
A manuscript should equal two to four pages when published including illustrations
Technical articles should be relevant with only a few if any equations The content should not talk down to or be over the heads of the intended audience
Manuscripts are reviewed by Student members Members Potentials staff and others as appropriate before a final deck ion to publish is made
For more info visit our web site at
httphrvwwczsumredupotentials
Please send your manuscript to IEEE Potentials 445 Hoes Lane PO Box 1331 Piscalaway NJ 08855-1 331
Robots AK Peters Wellesley Massa- chusetts 1983
Motorola Inc H C l l M 6 8 H C l l Reference Manual Motorola Inc 1991
1 1996 Texas Tech University
01 Rohit DSouza is a senior electrical
engineering student at Texas Tech Uni- versity He worked as a co-op at Alca- tel Network Systems in Richardson TX in the summer of 1997 and will be doing his second co-op term in the summer of 1998
He is an Engineering Ambassador for the College of Engineering and will assist in recruiting new students for the college He is also a Peer Mentor for incoming freshmen This year he was elected as the Director of Activities for the IEEE at Texas Tech University He intends to pursue a Masters degree in electrical engineering specializing in Image Processing
Johns Hopkins University
Graduate Studies in Electrical and Computer Engineering
Founded in 1876 Johns Hopkins was the first University to offer graduate education as its known today in America with emphasis on creative scholarship Today graduate study in the Department of Electrical and Computer Engineering is oriented toward the PhD with emphasis on scholarship and research rather than formal coursework In addition the Department offers a MSE degree program Departmental financial aid is available to qualified students We offer concentrations in the following areas
Communications and Signal Processing Computer Engineering
Language and Speech Processing Nonlinear and Quantum Optics
Solid-state Electronics Systems and Control Theory
For more information please contact ECE Departmenflhe Johns Hopkins University
3400 N Charles St1105 Barton Hall Baltimore MD 21218
gradadmecejhuedu httplwww ecejhuedu
(410) 516-4808
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