The Insides: Motor Shell with Permanent Magnet Ring -- Rotor -- End Bell with Brushes

Brushed DC motors have an affinity for direct current, engineered to spin in proportion to the level and polarity of the applied DC voltage. For example, a miniature 6-volt DC motor runs at its full rated speed when supplied with power from four AA batteries (four times 1.5 volts equals 6 volts). The motor will run slower with three AA batteries (4.5 volts) or even slower with two AA batteries (3 volts). When the speed of a robot's DC motor needs to be controlled by software, swapping batteries in and out just won't do. 

To control the motor with software like CircuitPython, a special signal called Pulse Width Modulation (PWM) is used. Microcontrollers such as the Feather M4 Express send software-controlled PWM signals to an external breakout board in order to regulate motor speed. To cause the motor to spin, the microcontroller furnishes the external motor controller board a pulsing signal which in turn sends a high-power pulse to the attached motor. The PWM signals control the motor’s direction, speed, and available torque.

A typical PWM signal used for a brushed DC motor consists of three primary characteristics, duty cycle, decay mode, and frequency. Let’s get to know each aspect of the PWM signal better.

This guide was first published on Apr 11, 2021. It was last updated on May 15, 2024.

This page (PWM and Brushed DC Motors) was last updated on Mar 08, 2024.

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