Choosing the right DC motor can make or break your maker project. Whether you're building a robot arm that needs precise positioning, a drone that demands efficiency, or a simple fan that just needs to spin — understanding motor types and specifications is essential.
In this guide, we'll break down the three main types of DC motors, explain the critical torque-speed relationship, and give you a simple decision framework to pick the perfect motor.
Understanding Motor Specifications
Before comparing motor types, let's understand the three key specifications you'll encounter:
RPM (Speed)
Revolutions Per Minute — how fast the motor shaft rotates. Higher RPM = faster rotation.
Torque
The rotational force the motor can provide. Measured in N·m or kg·cm. Higher torque = more pushing power.
Voltage
The electrical potential that drives the motor. Must match your power supply (3.3V, 5V, 12V, 24V, etc.).
The Three Types of DC Motors
1. Brushed DC Motors
The most common and affordable motor type. Uses carbon brushes that make physical contact with the commutator to transfer electrical current.
- Pros: Cheap, simple to control (just apply voltage), widely available
- Cons: Brushes wear out over time, generate electrical noise, less efficient
- Best for: Toys, simple robots, fans, low-budget projects
2. Brushless DC Motors (BLDC)
Uses electronic commutation instead of physical brushes. The magnets are on the rotor and the coils are on the stator.
- Pros: High efficiency (85-90%), longer lifespan, less noise, compact and powerful
- Cons: Requires an ESC (Electronic Speed Controller), more expensive, complex control
- Best for: Drones, electric vehicles, high-performance robotics, cooling fans
3. Geared DC Motors
A brushed or brushless motor with an integrated gearbox that trades speed for torque.
- Pros: Very high torque output, precise positioning possible, slow and controlled movement
- Cons: Lower maximum speed, heavier, potential gear backlash
- Best for: Robotic arms, conveyor belts, actuators, heavy lifting applications
Motor Type Comparison
Use this comparison to quickly identify which motor type fits your needs:
The Torque vs Speed Trade-off
This is the most important concept to understand: Torque and Speed are inversely related. When a motor operates under load:
🔑 Key Concepts
- Stall Torque: Maximum torque when the motor is stopped (0 RPM). This is when you're trying to start moving a heavy load.
- No-Load Speed: Maximum speed when there's no resistance. The motor spins freely with no work to do.
- Operating Point: Your actual use case will be somewhere between these extremes.
Rule of Thumb: If you need more torque than your motor provides, add a gearbox. It will reduce speed but multiply torque.
Decision Flowchart: Finding Your Motor
Use this simple flowchart to narrow down your motor choice:
🤖 Motor Selection Guide
Practical Examples
Summary
Selecting the right DC motor comes down to understanding your project's requirements:
- Need it cheap and simple? → Brushed DC
- Need efficiency and long life? → Brushless DC (BLDC)
- Need high torque for heavy loads? → Geared DC
🚀 Key Takeaway
Always calculate your torque requirements first. If your motor can't provide enough torque, your project will stall. When in doubt, add a gearbox — it's easier to reduce speed than to increase torque!