NEX ROBOTICS FIREBIRD V ATMEGA 2560 Hardware Manual page 29

Pulse Width Modulation for velocity control:
Pulse width modulation is a process in which duty cycle of constant frequency square wave is
modulated to control power delivered to the load i.e. motor.
Duty cycle is the ratio of 'T
wave. Power delivered to the motor is proportional to the 'T
PWM the motor reacts to the time average of the signal.
PWM is used to control total amount of power delivered to the load without power losses which
generally occur in resistive methods of power control.
Figure 3.19 shows the PWM waveforms for motor velocity control. In case (A), ON time is 90%
of time period. This wave has more average value and hence more power is delivered to the
motor. In case (B), the motor will run slower, as the ON time is just 10% of time period.
For the Fire Bird V ATMEGA2560 version, logic level for the motor direction control is given in
the table 3.4.
Microcontroller Pin
PL3 (OC5A)
PL4 (OC5B)
PA0
PA1
PA2
PA3
© NEX Robotics Pvt. Ltd. and ERTS Lab, CSE, IIT Bombay, INDIA
/ T'. Where 'T
ON
Figure 3.19: Pulse Width Modulation (PWM)
Pulse width modulation for the left motor (velocity control)
Pulse width modulation for the right motor (velocity control)
Left motor 1 direction control
Left motor 2 direction control
Right motor 1 direction control
Right motor 2 direction control
Table 3.3: Pin functions for the motion control
Fire Bird V ATMEGA2560 Hardware Manual
' is ON time and 'T' is the time period of the
ON
' time of the signal. In case of
ON
Function
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