A Guide to Choosing Motors and Drivers for Robotics Projects
What makes a robot move is its motors; but choosing the right motor is only part of it — choosing a matching driver and power source is just as critical. A mismatched motor-driver pair either gives insufficient torque, overheats, or doesn't work at all. In this guide we cover motor and driver selection for your robotics projects step by step.
Define the need first
Motor selection starts with "what you want it to do." Will it rotate continuously or move to a specific angle? How much torque and speed do you need? Is position feedback essential? Your answers to these questions directly determine the motor type. First clarify the nature of the motion, then choose the part.
Motor types and where they're used
| Motor | Characteristic | Typical use |
|---|---|---|
| DC motor | Simple, continuous rotation, easy speed control | Wheel, fan, pump |
| Servo motor | Positions to a specific angle, built-in feedback | Robot arm, steering, wing/flap |
| Stepper motor | Precise step-by-step rotation, open-loop position | 3D printer, CNC, precise positioning |
| BLDC (brushless) | High efficiency, long life, high speed | Drone, electric vehicle, high performance |
Choosing the motor driver
Microcontroller pins can't drive a motor directly; a motor driver is needed in between. When choosing a driver, the two most critical criteria are the motor's operating voltage and the current it will draw (especially the peak current at start/stop). The driver's current capacity must be above the motor's peak current. For DC motors an H-bridge that provides direction control (for example the L298N or more efficient MOSFET-based drivers), for stepper motors step drivers, and for BLDC dedicated three-phase drivers are used. Servo motors usually come with a built-in driver and are controlled directly with a PWM signal.
Power and supply
Motors are among the highest current-draw parts in electronics and can draw several times the nominal current at startup. That's why it's good practice to separate the motor supply from the logic (MCU) supply: the noise and voltage drops the motor produces could otherwise reset the microcontroller. Choose a source that can deliver enough current, add filter capacitors on the supply line, and keep the wires between motor and driver short.
Feedback: knowing the position
If a robot needs to know where it's going, feedback is essential. Servo motors provide this internally. For DC and BLDC motors, an encoder is added for position/speed information. Stepper motors know their position roughly by counting steps in open loop, but if they miss a step they can't detect it; in precise applications an encoder is added to the stepper too (closed loop).
Torque, gears and gearboxes
Most small motors rotate at high speed but low torque; robotics applications usually need the opposite. A gearbox (reducer) solves this by lowering the speed and increasing the torque. When choosing a motor to move a wheel or arm, look not only at the rpm but at the torque you'll get after the gears; insufficient torque is the most common reason a robot can't move.
Protection features to look for in a driver
A good motor driver doesn't just deliver current; it also protects itself and the circuit. Overcurrent protection prevents the driver from burning out when the motor stalls; thermal shutdown temporarily stops the circuit on overheating; and reverse-voltage (flyback) protection absorbs the motor's inductive spikes. Where possible, choose a driver with these protections; otherwise you'll need to add these safeguards yourself. Especially when a robot hits an obstacle and locks the motor, these protections save the circuit.
Example: a line-following robot
Consider a simple line-following robot: two small geared DC motors are enough for the two wheels. The voltage and peak current of these motors are determined, and a suitable dual-channel H-bridge driver is chosen. If precise speed matching isn't needed, you can start without encoders; if there's a drift problem on a straight line, encoders are added. The motor supply comes from the battery pack, and the MCU supply from a separate regulator. This simple selection logic works directly on most beginner robots.
Common mistakes
- Choosing an underrated driver: a driver that doesn't meet the motor's peak current heats up and fails.
- Sharing a single supply: powering the motor and MCU from the same line can reset the microcontroller.
- Not calculating torque: looking only at speed and skipping the gearbox results in a robot that can't move.
- Lack of feedback: using an encoderless motor where position is needed loses precision.
- Forgetting flyback protection: a motor is an inductive load; if the driver has no protection, voltage spikes burn the circuit.
Frequently asked questions
Which motor for a wheeled robot?
A geared DC motor (gearmotor) is usually the most practical and economical choice; if precise position is needed, an encoder version is preferred.
Servo or stepper motor?
A servo for precise position over a limited angle; a stepper for continuous, repeatable stepped motion (printer, CNC).
Is the L298N enough?
It's common and cheap for small DC motors, but it has a noticeable voltage drop and heating; if efficiency matters, modern MOSFET-based drivers are better. We also covered this IC in the 8 classic ICs article.
Conclusion
The right choice for robotics comes from first defining the nature of the motion and the suitable motor type, then determining together a driver that meets its voltage and peak current and a gearbox that provides enough torque. Don't forget to separate the power supply and add feedback where needed. You can review supplier offers for the motors and drivers you need with search and the comparison tool.