A servo motor is a closed-loop positional actuator. An internal potentiometer measures shaft angle and a control circuit drives the motor until the measured angle matches the commanded angle. The position command arrives as a PWM pulse: 1ms = 0°, 1.5ms = 90°, 2ms = 180°, repeated at 50Hz.
| Operating voltage | 4.8 – 6V |
| Stall torque | 1.8 kg·cm @ 5V |
| Speed | 0.1 s / 60° @ 5V |
| Pulse width | 1000 – 2000 µs |
| Frequency | 50 Hz |
| Angle range | 0 – 180° |
The MCU outputs a PWM signal at 50Hz. Pulse width (1–2ms) encodes the desired angle. Inside the servo, a comparator subtracts the potentiometer voltage (proportional to shaft angle) from a ramp waveform derived from the PWM pulse. The difference drives the motor until the error is zero.
Limited to 180° range (continuous rotation servos exist but lack position feedback). Holding torque draws current even when stationary. Jitter increases under electrical noise on the PWM line. Not suitable for high-speed rotational applications.