74*245
Motor Driver
H-Bridge
Driver
Simple
PWM Gen.
Handy
Method Measuring RPM
Measuring
RPM via Photo reflector
Introduction
to Robotic
DC,
Stepper,and Servo Motor
Microcontroller
Tutorial
Computer
Interface
Tutorial
.............more
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void getHomeFromRoom1(void), void getHomeFromRoom2(void),
void getHomeFromRoom3(void), void getHomeFromRoom4(void)
These functions maneuver the robot from the position it deploys the
cup back to the home area using the line sensors and the encoder. Each
is called only once by cupPlacement. Each getHomeFromRoom function is
fundamentally identical to its corresponding room function. The only
difference is that at the beginning of this function, the car is still
located inside the room the candle is in. Subsequently, this function
backs the robot up until the white line in the doorway is detected.
After this, the robot continues to move in reverse a specified distance
to get itself into a better position to make a 90 degree turn to orient
itself parallel with the white line in the hallway. It then makes the
aforementioned 90 degree turn (either right or left depending on the
room it traveled to) and commences following the line in the manner
the functions room1, room2, room3, and room4 do. Finally, once this
distance is achieved, the motors are turned off and the code enters
a forever loop (this is because there is no no-op instruction on the
89c51RD2) and no further instructions execute. One important fact we
would like to mention is that the official rules for the IEEE hardware
competition state that the robot is considered to be in the home area
as long as some part of it has crossed over the tape enclosing the home
area. As a result, there is a large margin for error on the trip back
to the home area, the robot can stop short or go past the home area
as long as some portion is inside the tape enclosing the home area.
Watchdog Timer
If the encoder interrupt does not occur in approximately 13 seconds,
the watchdog timer backs the robot up slightly and makes a right or
left turn. The direction of this turns alternates and gets increasingly
larger each time the interrupt occurs. This keeps the robot from getting
trapped against the wall for more than about 13 seconds and gets it
into a better position complete the run.
void SetMotor(unsigned char, int) and void AllStop(void
) These two functions are used to control the speed and the rotation
direction of the two DC motors. SetMotor sets up the Pulse Width Modulation
in the PCA. It initializes the PCA and by accepting the unsigned char
value between 0 and 255 it sets up the length of the time interval of
the pulse sent to the DC motors. This determines the speed of the motor.
AllStop simply sends zeros to both of the motors, which does not send
any pulses to the motors. This stops their rotation.
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