DC electric motors have been popular for the better part of two centuries. In this article, learn the basics and explore the circuitry needed to drive them. Also, get an introduction to newer brushless DC motor designs.
Brushed DC Motor Basics
Through the use of magnets and a bound wire, DC motors convert electricity into motion. They are composed of four main components: stationary magnet (stator), rotor, commutator, and brushes. When power is sent through the rotor, it generates an electrical field that acts against the magnetic field generated by the stator, creating rotational motion.
Brushless DC Motor Basics
Rather than using brushes to transmit power to the rotor, brushless motors use transistors and a more complex drive circuitry. Compared to brushed motors, they tend to have higher torque-to-power ratios and better efficiency. Additionally, since there aren’t any brushes to wear out, they last longer.
Drive Circuits for Brushed Motors
A simple electric motor can be driven simply by applying power. However, for more complex needs, a drive circuit is needed. To control a motor’s speed, a pulse-width modulation (PWM) setup is used. This contains a transistor and a flyback diode, and serves to rapidly switch the current to the motor on and off, effectively reducing its speed. An H-bridge circuit, using 4 transistors, can control the direction of the motor by reversing the current direction.
Conclusion
Brushed motors, though simple, are relatively inexpensive and durable. With the right type of drive circuit design and high-quality components, such as those from Diodes, Inc, it’s easy to integrate these workhorses into modern designs.