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Actuators & Drive Systems
Three types of motors do nearly all the work in robotics. Each below is interactive — adjust the inputs and see what they do.
⚡ DC Motor + PWM
A DC motor's speed is roughly proportional to voltage. Microcontrollers can't easily vary voltage — they vary the duty cycle of a fast on/off signal (PWM). The motor's inertia smooths the pulses into average power.
Controls
Live state
🎯 Hobby Servo
A servo is a DC motor + gearbox + potentiometer + small controller, all in one. You command an angle, the servo's internal controller drives the motor until the pot matches.
Command
PWM pulse width: 1500 µs — typical servos accept 1000 µs (0°) to 2000 µs (180°) at 50 Hz.
Live state
⚙️ Gearbox Trade-off
A gearbox is a trade: multiply torque by N, divide speed by N. There is no free lunch (minus a few percent friction loss).
Gear ratio
Output
For your Pi car: typical 1:48 gear motors give ~150 RPM @ 6V — enough torque to climb a small ramp, slow enough to control.
How they combine in the Pi car: two DC gear motors (one per side, differential drive) controlled by an L298N H-bridge. The Pi sends two GPIO signals per motor (forward/reverse) plus one PWM (speed). A single servo, optionally, can sweep an ultrasonic sensor side-to-side to scan for obstacles.