Why Your Servo Motor Stutters (And How to Fix It)

You write the code. You upload it. The servo moves — but not smoothly. It jerks. It twitches. It stops mid-sweep and vibrates in place.

You check the wiring. It looks right. You check the code. It looks right. You try a different servo. Same problem.

The issue is almost never the servo itself. It is almost always one of three things: power, signal timing, or mechanical load.

The Three Most Common Causes

Cause 1: Insufficient Power

Most servos operate at 4.8V to 6V. When powered from an Arduino's 5V rail, the servo and the Arduino are competing for the same power supply. The Arduino's onboard regulator can deliver maybe 200-500mA total. A servo under load can draw 1A or more during movement.

When the servo stalls or tries to move against resistance, the voltage drops. The Arduino's voltage regulator compensates, but the voltage to the servo fluctuates. The servo's internal controller sees this as an invalid signal and responds erratically.

The fix: power the servo from a separate 5-6V power supply with at least 1A capacity. Connect the grounds together. Never power a servo from the Arduino's 5V pin if the servo draws more than 200mA.

Cause 2: Signal Timing Interference

Servos expect a PWM signal with specific timing: a 1ms pulse for full counterclockwise, 1.5ms for center, 2ms for full clockwise, repeated every 20ms.

The Servo.h library handles this correctly on most Arduino pins. But if you are generating the PWM manually — or if your code is disabling interrupts during the pulse — the timing gets disrupted.

The delay() and millis() functions disable interrupts. So does Serial.print(). If you are calling these inside a servo control loop, you are creating gaps in the PWM signal. The servo interprets these as corrupt commands and twitches.

Photo via circuits-diy.com — basic servo motor Arduino setup

Cause 3: Mechanical Overload

Every servo has a torque rating. When you push a servo beyond its rated torque, the motor stalls. The internal controller keeps trying to reach the target position, drawing maximum current, heating up, and producing the characteristic vibration or buzzing sound.

This is the servo protecting itself. It is not malfunctioning. It is telling you that the mechanical load exceeds its capacity.

The fix: either reduce the mechanical load or upgrade to a servo with higher torque. For interactive installations where users might push against the mechanism, always use a servo rated at 2-3x the expected load.

How to Debug Systematically

When your servo stutters, test in this order:

1. Power first. Remove the servo from the mechanism. Connect it to a dedicated 5V 1A power supply. Run the basic sweep example from Servo.h. If it moves smoothly, the problem is power.

2. Signal second. With the servo still on the bench power supply, check your code for delay(), Serial.print(), or any operation that blocks interrupts. Move all blocking calls outside the servo control loop.

3. Load third. Reconnect the mechanism. If stuttering returns, the mechanism is demanding more torque than the servo can deliver. Measure the force required to move the mechanism with a scale. Compare to the servo's rated torque.

Via Arduino Forum — servo jitter caused by mechanical overload and power issues

For Interactive Installations

In interactive art contexts, servos are often used where users can touch or push the mechanism. The worst thing you can do is let the servo fight the user.

Use a servo with a torque rating high enough that it cannot be stalled by reasonable force. Or implement a current-limiting circuit that detects stall and releases the servo.

The Servo.attach() function in Arduino lets you set angle limits. Use them. Setting min(600) and max(2400) gives you the full range. But if your mechanism only needs 30 degrees of motion, limit the servo to 30 degrees. This reduces the mechanical stress and prevents the violent jerk when the servo hits a physical stop.

The Next Step

Before buying a more powerful servo, try powering the current one from a dedicated battery or bench power supply. Most servo stuttering problems are power problems in disguise.

If the smooth sweep on bench power still stutters when connected to your circuit, the problem is mechanical load — and no amount of code adjustment will fix it.

Product recommendations for reliable servo projects:

MG996R High Torque Servo Motor — 10kg/cm torque, metal gears, suitable for interactive installations where users might push against the mechanism. (Amazon)

SG90 Micro Servo — 1.8kg/cm torque, cheap and reliable for light-duty applications. Good for learning and prototyping. (Amazon)

Dedicated 5V 2A Power Supply — If your servo stutters, the Arduino's 5V rail is not enough. Get a separate supply. (Amazon)

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Article #006, 2026-04-18. Content Farm pipeline, Run #006.