TECHNICAL SUPPORT
Published 2026-04-06
Sometimes you need a compact, geared DC motor for a DIY project, but all you have is a standard radio-control (RC)servo. A regularservohas three wires (power, ground, signal) and requires a pulsed control signal. By converting it to a two-wire setup, you turn theservointo a simple, powerful geared DC motor that runs directly from a battery or power supply – forward when polarity is one way, reverse when swapped. This guide walks you through the exact steps to rewire any common hobby servo (e.g., the widely available 9gMicro Servoor a standard-size unit like MG995) into a two-wire drive, using only basic tools.
A standard servo contains three main parts inside: a DC motor, a gear train, a control board, and a feedback potentiometer. The three wires are:
Red– positive power (typically 4.8–6.0V)
Brown/Black– ground
Orange/Yellow– PWM signal
To make it work as a two-wire device, you remove the control board and potentiometer, then connect directly to the motor’s two terminals. The result is a high-torque geared DC motor that responds instantly to DC voltage – no signal generator needed.
One standard 3-wire servo (any size, but a 9gMicro Servois easiest for practice)
Small Phillips screwdriver
Wire cutters/strippers
Soldering iron and solder (optional but recommended)
Two pieces of flexible wire (about 10cm each, red and black for polarity)
Heat shrink tubing or electrical tape
Multimeter (to identify motor wires – helpful but not mandatory)
Remove the four screws on the bottom of the servo. Carefully lift off the bottom cover. You will see the control circuit board with the three wires soldered to it, plus the potentiometer (a small round component with three legs) attached to the output shaft.
Using your soldering iron, desolder the three external wires (red, brown, orange) from the circuit board. Then desolder the potentiometer wires (usually three thin wires connecting the potentiometer to the board). Lift out the entire circuit board and the potentiometer. Keep only the DC motor and the gear train inside the case.
Inside the servo, you will see a small DC motor (typically a 130-size or smaller). The motor has two metal tabs or solder points where the original control board connected. These are the motor’s positive and negative terminals. Use a multimeter in continuity mode to confirm – they show low resistance (a few ohms) across them.
Solder one length of your new red wire to one motor terminal, and one black wire to the other motor terminal. It does not matter which terminal gets red or black at this stage – reversing polarity later will reverse the motor direction. Use heat shrink tubing to insulate each solder joint.
Feed the two new wires through the original cable exit hole. Place the bottom cover back on and screw it closed. Make sure the wires are not pinched and that the gears rotate freely.
Connect the red and black wires to a DC power source (e.g., a 4.8–6V battery pack or a regulated 5V supply). The motor will spin in one direction. Swap the wires – it will spin the opposite way. Do not exceed 6V for standard servos; higher voltage may damage the motor or gears. For larger servos (like standard size), 6V is safe; 7.4V may be acceptable for short periods but check the motor’s rating.
A 9g micro servo is often used in small RC planes and robots. After removing the circuit board, the internal DC motor is about 10mm in diameter. Solder two 30AWG silicone wires to its terminals. When powered with 5V, the output shaft (via the gear train) provides approximately 1.5 kg·cm of torque at about 60 RPM – perfect for a small winch or robotic finger. The two-wire conversion eliminates the need for an Arduino or servo controller.
Do not reverse polarity for more than a few seconds on some small motors– while DC motors handle reversal fine, continuous reversal at high speed may increase brush wear. This is normal for brushed DC motors.
Current draw: A converted servo motor can draw 200–500mA at no load, and up to 1.5A when stalled. Ensure your power supply can deliver that.
Removing the potentiometer completelyis essential – if left connected, it will create a short or erratic behavior.
Gear lubrication: After conversion, add a tiny amount of lithium grease to the gears if they seem dry.
The entire conversion boils down to one key fact:a servo is a DC motor with a control board. Remove the board, and you have a two-wire geared motor.All you need to do is open the case, discard the electronics, and connect your own wires directly to the motor terminals. This works for any brand or size of standard servo.
1. Start with a cheap, broken servo– If you have a servo that no longer responds to PWM signals, it is perfect for this conversion. The motor and gears are usually still functional.
2. Label your wires– Use red for one terminal and black for the other. Even though polarity is reversible, consistent labeling helps during project assembly.
3. Add a diode for back-EMF protection– If you will be reversing the motor frequently using relays or H-bridges, solder a 1N4007 diode across the motor terminals (cathode to positive, anode to negative) to protect your switching components.
4. Test before final assembly– Always connect the two wires to your power source briefly to verify that the motor spins freely and the gears turn smoothly. Then reassemble permanently.
5. Never exceed the original voltage– The internal motor is rated for the servo’s specified voltage (usually 4.8–6.0V). Using 12V will burn out the motor windings quickly.
By following these steps, you can repurpose any standard servo into a reliable, two-wire DC geared motor for custom robots, winches, animatronics,or any project where you need torque and compact size. Remember: the three original wires are gone – now only two wires control everything. Forward, reverse, stop – all by simply connecting or swapping DC power.
Update Time：2026-04-06
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