TECHNICAL SUPPORT
Published 2026-04-18
This guide provides a practical, field-tested method to convert a standard positionalservomotor into a continuously rotatingservo. Whether you need a low-cost drive wheel for a small robot or a simple winch, this modification removes the internal mechanical stop and disables the feedback potentiometer, allowing theservoto spin freely in either direction. The instructions below are based on common hobbyist servo models and have been repeatedly verified by robotics builders and makers. No brand-specific components or proprietary tools are required.
A standard servo is designed to rotate only within a limited arc (typically 90° to 180°), then stop. By modifying it, you gain:
Unlimited rotation in both directions
Speed control proportional to the input signal
Simple integration into mobile robots, conveyor belts, or pan-tilt mechanisms
A cost-effective alternative to a dedicated DC motor with encoder
One standard analog servo (size 9g, 20g, or standard – all work similarly)
Small Phillips screwdriver
Needle-nose pliers
Wire cutter/stripper
Soldering iron and solder
Small flat-head screwdriver or a hobby knife
Heat-shrink tubing or electrical tape
Remove the four screws on the bottom of the servo. Carefully lift the bottom cover. Inside you will see:
The DC motor
A small printed circuit board (PCB)
A feedback potentiometer (usually a round component with three wires)
The output shaft with a set of gears
Common observation:In most servos, the potentiometer is directly attached to the final output gear via a small plastic tab.
On the final output gear (the large gear connected to the output shaft), you will find a small plastic protrusion – this is the mechanical stop. It limits rotation by hitting against a fixed pin inside the case.
How to remove it:
Use a hobby knife or small flat-head screwdriver to carefully cut or break off the stop.
Alternatively, if the gear has two stops,remove both.
Ensure the gear surface is smooth after removal. Test by rotating the gear fully by hand – it should spin continuously without obstruction.
> Real-world example:Many hobbyists have found that on common 9g servos, the stop is a tiny 1mm ridge. Removing it with a sharp blade takes less than two minutes and instantly allows the gear to rotate past the original limit.
The potentiometer tells the servo control board the current shaft position. For continuous rotation, we need to “trick” the board into thinking the shaft is always at the center position.
Method A – Fix the potentiometer at center (recommended for beginners):
1. Turn the potentiometer shaft to its electrical center using a small screwdriver.
2. Apply a drop of super glue or hot glue to lock it in place. Do not let glue enter the resistive track.
Method B – Replace with a fixed voltage divider (more reliable):
1. Desolder the three potentiometer wires from the PCB.
2. Solder two resistors (2.2kΩ to 4.7kΩ) in series across the power and ground pads.
3. Connect the center tap to the signal pad. This provides a constant 2.5V reference (for 5V servos).
Important:After disabling the pot, the servo will no longer hold a specific angle. Instead, the input pulse width determines only the direction and speed.
Place the gears back carefully. Ensure the output gear spins freely. Close the case and tighten screws.
Test signal guide (using a standard 5V microcontroller or servo tester):
1.5 ms pulse → motor stops
1.7 ms → full speed clockwise
1.3 ms → full speed counter-clockwise
Values between 1.5 ms and the extremes produce proportionally slower speeds.
Common test result:When powered, the modified servo should hum softly at the stop position. If it rotates slowly without a signal, adjust the potentiometer (if still accessible) or resistor values until it stops at 1.5 ms.
This modification is irreversible for most servos. Keep an original servo for angle‑control applications.
The modified servo draws slightly less current than a standard DC motor at stall, but still use proper power supply (4.8–6V for most analog servos).
Do not exceed the servo’s original torque rating – continuous rotation does not increase power.
Modifying a servo for continuous rotation is a straightforward, well-documented procedure that requires only basic tools and about 15 minutes of work. By removing the mechanical stop and locking the feedback potentiometer, you transform a limited‑angle actuator into a fully rotational drive unit ideal for small robots, winches, or automated turntables.
Repeat of the core principle: The two essential modifications are (1) eliminating the physical rotation limit and (2) providing a constant center-position signal to the control board. Master these two steps, and any standard servo can become a continuous‑rotation servo.
Immediate action steps for your project:
1. Select a spare analog servo – practice on an inexpensive unit first.
2. Follow the three steps in order: open case → remove stop → disable potentiometer.
3. Test with a 1.5 ms pulse to verify stop, then vary pulse width to confirm speed/direction control.
4. Mount the modified servo in your robot or mechanism, ensuring the output shaft is not mechanically blocked.
With this guide, you have a reliable, repeatable method used by countless makers. Proceed with confidence – your servo is now ready for continuous motion.
Update Time：2026-04-18
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