What Is a DC Motor?
A DC motor is the most basic motor type that runs on direct current (DC), converting electrical energy into rotational motion. The classic type contains brushes and a commutator.
How Does It Work?
The current through the winding inside it creates a magnetic field; interacting with a fixed magnet, the rotor turns. The brushes and commutator keep the motion going by switching the current direction as rotation continues.
Speed and Direction Control
Speed is proportional to the applied voltage; in practice the average voltage is set with PWM. Direction is reversed by changing the current direction, usually with an H-bridge circuit.
| Property | DC Motor |
|---|---|
| Supply | Direct current (DC) |
| Speed control | Voltage / PWM |
| Direction | Current direction (H-bridge) |
Driving
The motor current is more than most MCU pins can give; a motor driver or transistor is placed in between. Being a coil, it needs a flyback diode against the reverse voltage spike.
Where Is It Used?
Toys, fans, robot wheels, power tools and everywhere speed/direction adjustment is needed. If a linear push/pull motion is needed instead of rotation, a solenoid is preferred.
The Brush Problem
Brushes wear over time and produce sparking/noise; this shortens the life and creates electrical interference. This disadvantage led to the birth of brushless (BLDC) motors.
Common Mistakes
- Direct drive: an MCU pin can't handle the motor, a driver is essential.
- No flyback: the reverse voltage burns the driver transistor.
- Startup current: the high current drawn at the first instant must be accounted for.
Frequently Asked Questions
How is the speed set?+
How does the direction change?+
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