How to Check if a Servo Motor Is Working or Not: Your Complete Guide

Understanding the Basics of a Servo Motor

Servo motors are the heart of precision control in robotics, automation, RC vehicles, and industrial machinery. Unlike regular motors, which only spin continuously, servo motors are designed for accurate position control—they rotate to a specific angle, hold that position, and respond precisely to control signals. This capability makes them indispensable for applications requiring dexterity and fine movement.

Before diving into how to check whether your servo motor is working, it’s good to understand what makes a servo tick. Most servo motors consist of a small electric motor, a gear train, a position sensor (usually a potentiometer), and a control circuit. When the servo receives a signal, it compares the target position with the actual position from the sensor, then adjusts accordingly—until the desired position is reached or maintained.

Knowing this, the essential question arises: How do you determine if your servo motor is functioning correctly? The process involves a combination of visual inspection, electrical testing, and operational assessment. Each method provides insight into different potential faults—whether it’s electrical, mechanical, or control-related.

Preparing for the Test

Before you start testing, gather your tools and take a moment to prepare. Here’s what you’ll need:

A compatible power supply that matches your servo’s voltage requirements. A servo tester or a microcontroller (like Arduino, Raspberry Pi) to send control signals. Multimeter or voltmeter for electrical checks. A physical setup to observe the servo’s movement—this can be a mounting arm or holder. Optional: Oscilloscope for detailed signal analysis.

Once you've assembled your tools, ensure your workspace is safe. Disconnect power when connecting or disconnecting wires to prevent shorts or damage. Always confirm the specifications of your servo motor—voltage, current, and signal types—to avoid underpowering or overloading it.

Common Signs of a Faulty Servo

If your servo isn’t working, you might notice:

No movement at all when powered and commanded. Jerky, unsteady motion. Excessive noise or overheating. Continuous spinning or failure to reach the target position. Overly loose or tight movement, indicating mechanical issues.

Recognizing these symptoms is vital because they guide your troubleshooting process, saving you time and preventing unnecessary replacements.

Basic Electrical Tests

The first step in checking a servo is to verify its electrical connections and signals. Here’s how:

1. Visual Inspection

Inspect the wires and connectors for any damages, corrosion, or loose connections. Sometimes, a simple fix like reconnecting a loosened plug can resolve the issue. Check the motor’s casing for signs of burns or physical damage.

2. Power and Ground Verification

Using a multimeter set to measure voltage, connect your black probe to ground and the red probe to the power line. Turn on the power supply—your servo should receive voltage matching its specifications (e.g., 4.8V, 6V, 7.2V, etc.). If no voltage is present, trace back through your wiring and power source.

3. Control Signal Check

For digital servos, control signals are typically pulses ranging from 1 ms to 2 ms at certain frequencies (often 50 Hz). Use an oscilloscope or a signal tester to verify that the control line receives the correct PWM pulses. No signals or inconsistent signals indicate a control issue.

4. Resistance Checks

Set your multimeter to resistance mode and measure across the motor terminals. Initial resistance reading varies by model, but a very high or infinite reading suggests open windings—likely a burnt-out motor. Conversely, very low resistance might indicate a short.

Operational Testing with a Servo Tester or Microcontroller

Once electrical checks are satisfactory, you can proceed to test the servo’s operation:

Using a Servo Tester:

A servo tester is a simple device that generates the PWM signals typical of RC controllers. Connect your servo to the tester and power it up. Adjust the calibration knobs or digital settings to command different angles. Watch how the servo reacts—smooth, accurate, and responsive movement indicates a functional motor. If it refuses to move or moves erratically, further investigation is needed.

Using a Microcontroller:

If you have an Arduino or similar microcontroller, connect the servo’s control wire to a PWM-capable pin. Load a simple sketch (a standard servo sweep program, for example) and observe the movement. Listen for any unusual sounds or sparks, and examine whether the shaft reaches the intended positions.

Interpreting Results and Next Steps

If your servo responds correctly to tests, smooth movement, and maintains position, it’s likely in good health. However, if you observe erratic behavior, lack of response, or mechanical issues, further troubleshooting or replacement may be necessary.

In the next part of this guide, we’ll cover advanced diagnostics, common failure modes, how to repair a faulty servo, and recommended maintenance tips to keep your servo in top shape.

Leveraging innovations in modular drive technology, Kpower integrates high-performance motors, precision reducers, and multi-protocol control systems to provide efficient and customized smart drive system solutions.