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Brushed DC Motor is the most widely used motor due to its simplicity. Its application ranges from toy, small electrical appliances to industrial automation machine and robotics. In most of the applications, we do not want to run the motor at fixed speed and variable speed control is essential. Controlling the motor speed is pretty straight forward as the speed of brushed DC motor is proportional to the applied voltage. What we need to do is just varying the voltage of the power supply.
This is a companion discussion topic for the original entry at https://community.robotshop.com/index.php/blog/show/fundamental-of-pwm-speed-control-for-brushed-dc-motor-1