PUBLISHED ENGINEERING · FIELD GUIDE · 15 MIN

Choosing a motor

How to choose the right motor, and understand how that one decision shapes the power, control, performance and cost of everything built around it.

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Mohammed Riaz

RESEARCH · AUTHOR

Compiled the four motor classes, their specs and the manufacturer directory.

Eleazar Asase

PROJECT DIRECTOR · REVIEWER

Peer-reviewed the guide for accuracy and clarity.

Why it matters

Choosing the right motor is one of the most important decisions in robotics, because it determines how fast, strong, accurate and efficient the final system can be. It also drives the choice of battery, motor driver, gearing, frame, control method and overall cost. Understand the strengths and limits of each motor type and you can choose with confidence, and give the project the best chance to perform the way you imagined.

The four classes

Brushed DC motor

A simple, affordable, dependable workhorse · easy to control, ideal for continuous rotation.

Torque

~0.01-5 Nm stall in small-medium robotics motors. More via gear reduction, at lower output speed.

RPM

~3,000-20,000 no-load. Geared versions ~10-2,000 rpm at the output shaft.

Voltage

~3-24 V DC

Current / stall

No-load ~0.05-3 A. Stall from <1 A (tiny motors) to >100 A (large high-power).

Control method

PWM through a brushed DC driver; an H-bridge reverses direction by flipping polarity.

Feedback

Usually none. An optional encoder adds position/speed for closed-loop control.

Weight

A few grams (miniature) up to ~1 kg (larger gearmotors).

Best forWheels, conveyors, rollers, pumps, fans, continuous rotation with simple speed/direction control. With a gearbox + encoder, also robot drivetrains and controlled motion.

Watch out forBrushes wear and create electrical noise. Speed drops as load rises; accurate position needs an encoder + closed loop. A stalled motor can draw dangerous current and overheat fast.

Examples: CIM Motor, 12 V (AndyMark) · 5203 Yellow Jacket 19.2:1, 312 rpm w/ encoder (goBILDA)

Brushless DC (BLDC) motor

Efficient, powerful, low-maintenance · excellent power-to-weight, but requires electronic control.

Torque

~0.01-10 Nm

RPM

~1,000-30,000 rpm

Voltage

~6-60 V DC

Current / stall

No-load ~0.1-5 A; continuous ~5-70 A; peak/stall can exceed 200 A in high-power motors.

Control method

Needs an ESC / three-phase driver that switches current through the phases. Commands via PWM, CAN, or serial.

Feedback

Sensorless (back-EMF estimate) or sensored (Hall / encoder). Encoders preferred for accurate low-speed, position or torque control.

Weight

~20 g to several kilograms

Best forDrones, robot drivetrains, electric propulsion, high-speed fans/pumps/spindles, anything needing high efficiency, high power-to-weight, long life, or rapid speed changes.

Watch out forCan't run directly off a battery or microcontroller, needs a compatible controller. Sensorless control is weak at very low speed; Kv, voltage, current, controller, cooling and load must be matched. Poor cooling overheats windings, controller or magnets.

Examples: NEO 2.0, 12 V w/ Hall encoder (REV Robotics) · MN3110 Navigator KV700 (T-MOTOR)

Stepper motor

A precise low-speed positioner that moves in repeatable steps and holds place · but loses strength as speed rises.

Torque

~0.02-12 Nm

RPM

Best below ~1,000 rpm (many below 600). Some reach 2,000-3,000 under light load, but weaken sharply.

Voltage

Windings ~1-12 V; the current-regulating driver commonly runs on a 12-48 V DC supply.

Current / stall

~0.3-6 A per phase. No separate stall rating · the driver controls the current.

Control method

A stepper driver: the controller sets direction and step count. Faster step commands = faster rotation; step count = distance.

Feedback

Most are open-loop with no built-in feedback.

Weight

~50 g to 5 kg

Best for3D printers, CNC machines, camera sliders, positioning systems, lead screws, dosing pumps, accurate, repeatable movement at low-to-moderate speed.

Watch out forAdvertised torque is usually measured stopped, so it delivers less while moving. Overload it and it misses steps and loses position. Steppers run hot even while holding, and always need a compatible driver.

Examples: 17HS19-2004S1 NEMA 17 · iCL57-13 NEMA 23 closed-loop, 1.3 Nm (STEPPERONLINE)

Servo motor (closed-loop actuator)

An all-in-one motion controller: moves to a commanded position and uses feedback to stay there.

Torque

~0.05-15 Nm stall

RPM

~30-200 rpm no-load output

Voltage

Standard servos ~4.8-8.4 V; smart servos ~6-24 V. Always use the maker's rated range.

Current / stall

No-load ~0.1-0.5 A; stall ~0.5-10 A or more.

Control method

Hobby servos: three wires (power, ground, signal); the signal sets the angle. Smart servos take digital commands over serial, often daisy-chained. The driver is built in.

Feedback

Basic servos use a potentiometer internally; advanced use an encoder. Smart servos report position, speed, load, voltage, temperature.

Weight

~5 g to 1 kg

Best forRobot arms, grippers, steering, pan-tilt mounts, RC control surfaces, valves, anything that must move to and hold a specific angle.

Watch out forStall torque is a short-term maximum, not safe continuous torque. A stalled servo draws large current, overheats, strips gears, or resets the microcontroller if the supply is too weak.

Examples: Hitec HS-422 analog sport servo (Hitec) · DYNAMIXEL XL430-W250-T smart servo (ROBOTIS)

How to choose for your project

Criterion	Ask yourself
Type of motion	Continuous rotation, movement to a specific angle, or small repeatable steps?
Torque & speed	How much turning force and speed must the motor provide while moving the real load?
Accuracy & feedback	Must it know and hold its exact position, or is simple speed control enough?
Power & control	What voltage and current can your supply provide? Which driver / ESC will you use?
Practical limits	Limits on size, weight, price, running time, heat, noise and maintenance?

Manufacturers directory

Company	Known for	Region
AndyMark	Brushed DC motors, gearboxes, drivetrains, wheels for educational/competition robots	Kokomo, IN, USA
goBILDA	Modular components, planetary gearmotors, servos, structural & motion hardware	Winfield, KS, USA
REV Robotics	Educational/competition parts, incl. NEO brushless motors and SPARK controllers	Carrollton, TX, USA
T-MOTOR	High-performance BLDC motors, ESCs, propellers and propulsion for drones/UAVs	Nanchang, China
STEPPERONLINE	Stepper motors, drivers, closed-loop stepper systems, gearboxes	Nanjing, China
Hitec RCD USA	Hobby & robotic servos, radio-control equipment and accessories	San Diego, CA, USA
ROBOTIS	DYNAMIXEL smart servos, integrated actuators, educational kits, research platforms	Seoul, South Korea

Glossary

PWM: Pulse Width Modulation controls a motor by switching its power on and off very quickly. More on-time usually means faster.
Encoder: A sensor that measures how far and how fast a shaft has moved, a step counter for the motor, letting the controller check actual movement.
Kv rating: A BLDC motor's approximate no-load rpm per volt. A 700 Kv motor at 10 V nears 7,000 rpm no-load. Not kilovolts, not a torque/power rating.
No-load: Running with nothing attached. No-load speed is higher, and no-load current lower, than during real use.
Stall torque & stall current: When power is applied but the shaft can't turn: stall torque is the max turning force, stall current the very high draw. Short-term limits, not safe continuous values.
Motor driver / ESC: The power-control device between the microcontroller and the motor: takes a small command and switches the large current safely. An ESC is the type used with BLDC motors.
H-bridge: A circuit that reverses current direction through a brushed DC motor, letting it run forward or backward.
Gear ratio / reduction: A gearbox trades speed for torque. 20:1 means the motor turns 20× per output rotation, slower output, greater force.
Hall-effect sensor: Detects magnetic fields to find the position of a motor's rotating part; BLDC controllers use it to switch phases at the right time.
Back EMF / sensorless control: A spinning motor generates a small voltage (back-EMF). A sensorless controller measures it to estimate position without a separate sensor.
Feedback / open- vs closed-loop: Feedback is information about what the motor actually did. Open-loop commands without checking; closed-loop measures the result and corrects, like checking a map while driving.
Phase: One of the separate winding circuits inside a motor. A driver powers the phases in sequence to make a BLDC or stepper rotate.
Potentiometer: A simple position sensor whose value changes as it turns. Basic servos use one to measure the output-shaft angle.

Image credits

Figures for this guide are drawn from Wikimedia Commons and will be added with these credits:

Figure	Credit
Brushed DC motor assembly	“Brushed DC Motor Assembly” by Ilia Krivoruk (Iliakriv), Wikimedia Commons
BLDC spindle motor	“Floppy Drive Spindle Motor Open” by Sebastian Koppehel (SKopp), Wikimedia Commons
Stepper motor	“Stepper Motor MICROCON SX17-1705” by Dolly1010, Wikimedia Commons
Servo motor internals	“Inside a Servo Motor” by Jstapko, Wikimedia Commons

Cite this

Riaz, M. (2026). Choosing a motor.
Spartan Autonomous Robotics, Michigan State University. Reviewed by E. Asase.
https://msusar.org/research/choosing-a-motor

Sources

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