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Robotics
Robot Motors Explained
DC, servo, and stepper motors with real uses
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Robot motors turn electrical energy into motion, which lets a robot drive, lift, grab, point, and position parts. Choosing the right motor matters because each type is best at a different kind of motion. A wheel needs smooth continuous spinning, while a gripper may need to stop at a set angle. Understanding DC motors, servo motors, and stepper motors helps students design robots that move reliably.
Key Facts
- DC motors spin continuously when powered, and reversing the voltage polarity reverses the spin direction.
- Servo motors move to a commanded angle, often from 0° to 180°, using internal feedback.
- Stepper motors move in fixed angle steps, so position can be controlled by counting steps.
- Rotational speed is often measured in revolutions per minute, rpm.
- Power = voltage x current, or P = VI.
- Gear reduction increases torque but decreases output speed.
Vocabulary
- DC motor
- A DC motor is a motor that spins continuously when connected to direct current electricity.
- Servo motor
- A servo motor is a motor with control electronics and feedback that moves to a specific angle.
- Stepper motor
- A stepper motor is a motor that turns in small fixed steps for precise positioning.
- Torque
- Torque is the twisting force that helps a motor turn a wheel, arm, or gear.
- Gear ratio
- A gear ratio compares input turns to output turns and shows how gears trade speed for torque.
Common Mistakes to Avoid
- Using a DC motor for exact arm angles, which is wrong because a basic DC motor does not know its own position without extra sensors and control.
- Assuming a servo can spin like a wheel motor, which is wrong because most hobby servos are designed for limited angle motion such as 0° to 180°.
- Ignoring torque when choosing a motor, which is wrong because a motor with enough speed may still stall if it cannot produce enough twisting force.
- Powering motors directly from a microcontroller pin, which is wrong because motors usually need more current than the pin can safely provide and should use a motor driver.
Practice Questions
- 1 A robot wheel uses a DC motor spinning at 120 rpm. How many full rotations does the wheel make in 10 seconds?
- 2 A stepper motor has a step angle of 1.8°. How many steps are needed to turn exactly 90°?
- 3 A school robot needs one motor for drive wheels, one for a gripper, and one for a small precise sliding platform. Choose DC motor, servo motor, or stepper motor for each job and explain your choices.