It is based on 8 bit Microcontroller. This Robot follows the black line which is drawn over the white surface or it follows the white line which is drawn over the black surface. The infrared sensors are used to sense the line. When the infrared signal falls on the white surface, it gets reflected and if it falls on the black surface, it is not reflected this principle is used to scan the Lines for the Robot. All the above systems are controlled by the Microcontroller. Microcontroller gets the signals from the infrared sensors and it drives the motors according to the sensor inputs. Two stepper motors are used to drive the robot.
THEORY OF OPERATION-: How to sense a black line The sensors used for the project are Reflective Object Sensors, 0PB710F that are already ready in the Electronic Lab. The single sensor consists
of an infrared emitting diode and a NPN Darlington phototransistor. When a light emitted from the diode is reflected off an object and back into the phototransistor, output current is produced, depending on the amount of infrared light, which triggers the base current of the phototransistor. In my case, the amount of light reflected off a black line is much less than that of a white background, so we can detect the black line somehow by measuring the current. (This current is converted to voltage.) ii) How to control a DC motor
Instead of applying a constant voltage across a DC motor, we repeat switching on and off the motor with a fixed voltage (Vcc) applied to the motor. This is done by sending a train of PWM (Pulse Width Modulation) pulses to a power MOSFET in order to turn it on and off. Then, the motor sees the average voltage while it depends on duty cycle of PWM pulses. The speed of rotation is proportion to this average voltage.
By PWM method, it's easier to control the DC motor than by directly controlling the voltage across it. All we have to do is to modulate pulse width, in order
No comments:
Post a Comment