Due to the digital nature of the circuit a 5V regulated power supply was needed. To provide the supply two Batteries of 9v were used one for the motors and one for the circuit. Earlier it was found that the one battery was easily depleted in a few minutes of operation and low battery resulted in processor reset leading to erratic behavior.
A common ground was given to both supplies for there coexistence. The Power supply was simply fabricated on an all-purpose PCB which made the assembly easy. Two pin connectors were used to identify positive and negative so as to avoid mixing of the negative and positive terminals for the various modules as simple switch switches the supply on and off accordingly. The two 9V batteries are joined together by a tape and then there input is given to the power supply the status of the power supply is denoted by a simple green LED telling weather it is on or off.
The H-bridge is responsible for taking appropriate logic signals from the MICROCONTROLLER, and power from the power controller, controlling both of motors accordingly. The motor controller is capable of independently controlling each motor, in a stopped condition, forwards or backwards optionally at different speeds using the onboard commands from the uC.
This circuit can control the two small DC motors, in the Pioneer. When both the points A & B are "HIGH" Q1 and Q2 are in saturation. Hence the bases of Q3 to Q6 are grounded. Hence Q3, Q5 are OFF and Q4,Q6 are ON . The voltages at both the motor terminals are the same and hence the motor is OFF. Similarly when both A and B are "LOW" the motor is OFF. When A is HIGH and B is LOW, Q1 saturates, Q2 is OFF. The bases of Q3 and Q4 are grounded and that of Q4 and Q5 is HIGH. Hence Q4 and Q5 conduct making the right terminal of the motor more positive than the left and the motor is ON. When A is LOW and B is HIGH, the left terminal of the motor is more positive than the right and the motor rotates in the reverse direction.
The diodes protect the transistors from surge produced due to the sudden reversal of the motor. Two such circuits are required to control the robot.
These are the following action that the robot would result on the requisite motor status.
OF: On Forward
OB : On Backward
OFF : Switched Off
Motion of the Pioneer according to the signal of uC.