Servo Motor Symbol
Definition: The Servo Motor symbol represents a closed-loop actuator that uses pulse-width modulation (PWM) position commands to drive a DC motor with internal gear reduction and feedback potentiometer, used in schematic diagrams to denote a component that rotates to a precise angular position in response to a PWM signal on its Signal pin, with VCC (typically 5 V) and GND power connections.
Also known as: RC servo, PWM servo, hobby servo, position servo, servo actuator, SG90 compatible.
What the Servo Motor symbol means
The Servo Motor symbol represents a self-contained positional actuator that combines a DC motor, a reduction gearbox, a position-feedback potentiometer, and a control circuit in one housing. It receives a PWM command signal and drives its output shaft to the corresponding angular position and holds it there against an external load torque.
In electronic circuit diagrams the servo symbol is drawn with three pins: Signal (the PWM control input), VCC (the 4.8 V–6 V power supply), and GND (the common ground reference). The servo is the standard angular actuator in robotics, RC models, and embedded-systems projects because it requires only one GPIO pin for position control and no external motor driver.
How to identify the Servo Motor symbol
The Servo Motor symbol appears as a labelled rectangular block with a motor/actuator graphic, showing three pins on one side (or the bottom): Signal (PWM in), VCC (power), and GND (ground). Some representations include a small output-shaft circle or gear icon. In simplified block diagrams it may be shown as a labelled box with the three-wire colour code (orange/red/brown for signal/power/ground) noted.
Function and usage boundary
A servo motor converts a PWM signal (typically 50 Hz, with 1 ms–2 ms pulse width corresponding to 0°–180°) into a proportional shaft angle. The internal feedback potentiometer measures actual shaft position and the onboard control circuit drives the motor to eliminate any difference between the commanded and actual positions. Most hobby servos provide 0°–180° of angular travel, delivering 1.5 kg·cm to 25 kg·cm of torque depending on size.
Standards: IEC vs ANSI
| IEC 60617 | No dedicated IEC 60617 symbol exists for a servo motor. IEC 60617 uses a general motor symbol for the DC motor element and a functional block symbol for the closed-loop servo actuator module. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 does not define a unique servo symbol. In IEEE-compliant schematics a servo is represented as a labelled functional block (rectangle) with annotated PWM input and power pins, consistent with IEEE 315 block-diagram conventions. |
| Key difference | Both IEC and ANSI use the same generic labelled block for servo motors at the schematic level. Servo motor specifications are governed by the RC servo industry standard (pulse width 1–2 ms at 50 Hz) rather than by IEC or ANSI electrical symbol standards. |
The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.
Logical terminals
| Logical ID | Editor terminal name |
|---|---|
| signal | Signal |
| vcc | VCC |
| gnd | GND |
Where the Servo Motor symbol is used
- Robotics: servo motors drive robotic arm joints, gripper mechanisms, and leg joints in servo-based walking robots
- RC model aircraft: ailerons, elevators, rudders, and throttle control using PWM signals from a radio receiver
- Pan-tilt camera mounts: two servos (pan axis + tilt axis) controlled by a microcontroller track subjects for surveillance or photography
- Automated valve control: servos actuate ball valves or butterfly valves in liquid dispensing and flow-control systems
- 3D printer bed levelling: servo-actuated probes replace fixed z-limit switches for automatic bed compensation
- Microcontroller educational projects: the servo is the simplest closed-loop actuator to demonstrate PWM control with minimal wiring
Key facts
- The servo motor symbol has three pins: Signal (PWM control input), VCC (power supply 4.8 V–6 V), and GND (ground reference) — no separate motor driver chip is needed.
- The standard servo PWM protocol runs at 50 Hz (20 ms period) with pulse widths from 1.0 ms (0°) to 2.0 ms (180°); 1.5 ms commands the centre position (90°).
- A servo motor is a closed-loop device: the onboard feedback potentiometer continuously measures shaft angle and the internal controller corrects position errors, unlike a stepper motor which is open-loop.
- SG90 is the most widely used micro servo (9 g weight, 1.5 kg·cm torque, 4.8 V–6 V supply) and its pinout and PWM specification are the de facto industry standard for hobby and educational servo applications.
- The wire colour code for a 3-wire servo connector is: orange or white = Signal, red = VCC, brown or black = GND — this is a non-standard but universally adopted convention among RC and hobby servo manufacturers.
- Continuous-rotation servos are servo motors modified so that the feedback potentiometer is replaced with a fixed centre resistor; they respond to the same PWM signal but rotate continuously at a speed and direction proportional to pulse width rather than stopping at a position.
- The stall current of a servo motor can reach 2 A–3 A; a microcontroller's 3.3 V or 5 V I/O pin cannot supply this current, so servo VCC must be connected to an external power supply or adequate bulk capacitance, not to the microcontroller's VCC rail.
Diagrams that use this symbol
Frequently asked questions
What does the servo motor symbol look like in a schematic?
The servo motor symbol is a labelled rectangular block with three pins: Signal (PWM input), VCC (power), and GND (ground). It may include a small motor or gear icon inside the block to distinguish it from other module types. The three pins typically appear on one side or the bottom of the symbol.
What does the servo motor symbol mean in a circuit diagram?
The servo motor symbol represents a closed-loop PWM-controlled positional actuator. It means the component accepts a PWM signal on the Signal pin and rotates its output shaft to an angular position proportional to the pulse width, holding that position against external loads.
What PWM signal does a servo motor use?
A servo motor uses a 50 Hz PWM signal (20 ms period). Pulse width controls position: 1.0 ms = 0°, 1.5 ms = 90° (centre), 2.0 ms = 180°. Most microcontrollers generate this using a timer or servo library function.
What voltage and current does a servo motor need?
Standard hobby servos require 4.8 V to 6.0 V. Current ranges from 200 mA (no-load) to 2 A or more at stall. The power supply for servo VCC should be separate from the microcontroller supply to avoid voltage drops from servo current spikes disrupting microcontroller operation.
What is the difference between a servo motor and a stepper motor in a schematic?
A servo motor symbol shows three pins (Signal/VCC/GND) and represents a closed-loop PWM-controlled actuator with internal position feedback. A stepper motor symbol shows four or more pins (coil pairs) and represents an open-loop device that advances by discrete angular steps in response to sequential coil energisation pulses.
What is the designator for a servo motor in a schematic?
Servo motors use the designator M (motor) in most schematics, e.g. M1 or SRV1. Some diagrams use the prefix SERVO or SV to distinguish servo actuators from regular DC motors and stepper motors.
Can a servo motor turn 360 degrees continuously?
A standard servo motor rotates 0°–180° and is a positional actuator. A continuous-rotation servo has its position feedback replaced by a fixed resistor so it spins continuously; speed and direction are controlled by pulse width, with 1.5 ms being the stop point, values above 1.5 ms for one direction, and values below 1.5 ms for the other.
Related symbols
- Ceiling Fan symbol
- DC Motor symbol
- Garage Door Opener symbol
- 3-Phase Motor symbol
- Pool Pump symbol
- Stepper Motor symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
Place the Servo Motor symbol directly on a wiring diagram or schematic in the free online editor — no download required.