TECHNICAL SUPPORT
Published 2026-04-11
When selecting aservomotor for a robotics project,CNC machine, or remote-controlled vehicle, understanding its technical specifications is the first and most critical step. The performance, precision, and reliability of your entire system depend on choosing aservowith the right parameters. This guide provides a complete, authoritative breakdown of every essentialservomotor specification, using real-world examples to help you make an informed decision.
Torque is the rotational force a servo motor can produce, measured inkg·cm(kilogram-force per centimeter) oroz·in(ounce-force per inch). The most critical value isstall torque– the maximum torque the servo can exert when its output shaft is not moving.
Common example:A standard 9g servo used in small RC planes typically provides 1.6 kg·cm at 5V. In contrast, a medium-sized servo for a robotic arm might require 15 kg·cm to lift a 1.5 kg object at a 10 cm distance from the shaft.
Key rule:Always choose a servo with stall torque at least 1.5 times your calculated load torque to ensure reliable operation and prevent stalling.
Speed indicates how fast the servo rotates its output shaft, measured inseconds per 60 degrees(s/60°). This is the time required for the servo to turn 60 degrees under no load.
Real-world scenario:For a fast-moving RC car steering servo, a speed of 0.10 s/60° is typical. For a slow, precise camera panning servo, 0.25 s/60° might be perfectly acceptable. A 0.05 s/60° servo is considered high-speed but usually comes with lower torque.
Trade-off alert:Higher speed almost always means lower torque for a given servo size and voltage. Always balance speed against torque based on your application’s priority.
Servo motors are designed to work within a specific voltage window, typically4.8V to 6.0Vfor standard servos, and up to7.4V or 8.4Vfor high-voltage (HV) servos. Therated voltage(e.g., 6.0V) is where the manufacturer guarantees the listed torque and speed.
Critical note:Running a servo below its minimum voltage causes sluggish response and lower torque. Exceeding the maximum voltage can instantly burn the control board inside. Always check the datasheet: a servo rated for 4.8–6.0V must never be connected directly to a 2S LiPo battery (7.4V) without a regulator.
All standard analog and digital servos use aPWM (Pulse Width Modulation)signal to determine shaft position. The standard parameters are:
Neutral position:1.5 ms pulse
Minimum position (0°):1.0 ms pulse
Maximum position (180°):2.0 ms pulse
Refresh frequency:50 Hz (20 ms period) for analog servos; digital servos can handle 200–300 Hz.
Important distinction:Some continuous rotation servos use the same pulse widths but interpret 1.5 ms as stop, 1.0 ms as full reverse, and 2.0 ms as full forward – no positional feedback.
Deadband is the smallest change in the control pulse width that will cause the servo to move. Measured inmicroseconds (µs). A smaller deadband means higher precision.
Typical values:
Standard analog servo: 5–8 µs deadband
Hobby digital servo: 2–3 µs
Precision industrial servo:
Practical impact: A servo with a 2 µs deadband can respond to a 0.36° command change (assuming 2 µs corresponds to about 0.36° of rotation on a 500 µs range for 180°). A 8 µs deadband servo will ignore small command changes, leading to noticeable “slop” in precise positioning tasks.
The gears inside a servo transfer motor torque to the output shaft. Common materials from lowest to highest durability:
Plastic/nylon – Cheap, quiet, but wears quickly under high load. Example: basic 9g servos.
Carbon/plastic composite – Better wear resistance, still lightweight.
Metal (brass, aluminum, steel) – Highest strength and durability, essential for high-torque applications (over 10 kg·cm). Metal gears are noisier but survive crashes and heavy loads.
Case example: In a 10 kg robotic arm joint, a metal-geared servo lasted 3 years of daily use, while an identical plastic-geared servo failed within 3 months.
The output shaft support affects longevity and radial load capacity.
Plain bushing – Simple brass or oil-impregnated sleeve. Adequate for lightweight, low-torque servos under 3 kg·cm.
Ball bearing (single or dual) – Provides smooth rotation and handles higher radial loads. Dual ball bearings are standard on all quality servos above 5 kg·cm.
Rule of thumb: If your application involves side forces (e.g., a wheel or arm pulling sideways on the shaft), always choose a servo with at least one ball bearing.
Servo size is standardized around common categories:
Micro/sub-micro: 20–25 mm length, 8–12 g weight, torque
Standard: 40×20×40 mm, 45–60 g, torque 4–10 kg·cm
Large/giant: 60×30×60 mm, 150–300 g, torque > 20 kg·cm
Check physical fit: Always verify the mounting hole pattern (commonly 3 mm holes at 48 mm centers for standard servos) and overall height including spline.
Standard servos rotate 90° to 180° total (often ±45° or ±90° from center). Some “sail winch” servos rotate up to 3–5 full turns. Continuous rotation servos have no angle limit – they spin freely.
Critical for precision: A 180° servo gives you about 0.1° resolution with a 10-bit controller (1024 steps). A 90° servo gives double the effective resolution for the same control steps.
High-end servos (often called “smart servos” or “serial servos”) provide position and temperature feedback via a digital bus (I²C, UART, or CAN). Standard hobby servos have no feedback – they simply try to reach the commanded position without reporting if they succeeded.
When you need feedback: Robotic arms that must detect a stall, or any system requiring safety monitoring (e.g., a gripper that needs to know if it closed on an object).
To ensure your project succeeds, follow this step-by-step decision process:
1. Calculate your load torque – Multiply the weight (in kg) by the arm length (in cm). Then add 20% safety margin. Example: 2 kg × 5 cm = 10 kg·cm → choose a servo rated at least 12 kg·cm stall torque.
2. Determine required speed – Measure how fast the load must move. For a 90° movement, if you need it in 0.2 seconds, look for a servo with 0.15 s/60° or faster.
3. Select voltage based on your power system – If you have a 5V USB supply, choose a 4.8–6.0V servo. For 2S LiPo (7.4V), choose an HV servo rated to 8.4V.
4. Prioritize metal gears and ball bearings for any load over 5 kg·cm or any application subject to shock or vibration.
5. Check deadband if you need precision below 1°. Look for ≤ 2 µs deadband (typically digital servos).
Final core takeaway: The five most critical parameters you cannot ignore are stall torque, speed at your operating voltage, gear material, bearing type, and deadband width. Master these, and you will reliably select the correct servo for any application – from a small robotic gripper to a heavy-duty CNC machine. Always consult the manufacturer’s datasheet and verify specifications under your actual load conditions.
Update Time：2026-04-11
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