What Is an RC Servo Motor?
RC servo motors are compact devices primarily used in radio-controlled (RC) vehicles and various control applications. They allow for precise control in response to specific command values, making them ideal for steering mechanisms and similar tasks.
Uses of RC Servo Motors
Originally, RC servo motors were developed for controlling radio-controlled vehicles. However, their use has broadened to include robot motion control, where precise movements are essential. They offer more accurate control compared to stepping motors, thanks to their internal feedback mechanism. This mechanism adjusts movements based on real-time feedback from an encoder, ensuring precise alignment with commanded values.
Principle of RC Servo Motors
RC servo motors operate by responding to pulse signals, which dictate their rotation position and direction. Typically, these motors require pulses with a cycle of 15 to 20 ms and a width of 0.5 to 2.5 ms. The process of sending commands through pulse width modulation (PWM) aligns the pulse width with the desired motor angle. The servo’s circuit board processes the input command and the potentiometer’s angle measurement, adjusting the DC motor’s voltage via a motor driver to achieve the target position.
Structure of RC Servo Motors
An RC servo motor integrates a DC motor, gear head, drive circuit, and an angle-command type servo controller into a compact package. Typically, they feature three parallel wires for signal input, allowing for movement to any specified angle. These connectors often use a female connector with a 2.54mm pitch.
1. Signal Line
The signal line carries pulse-shaped inputs to control the motor. It’s usually colored white, blue, yellow, or orange. Some models require a pull-up resistor to ensure compatibility with microcontroller signal inputs.
2. Power Supply Line
Comprising two lines, one for the power supply (+) and the other for the ground (GND), the power line is typically red, while the ground line may be black or brown. This color coding helps prevent incorrect connections.
Other Information for RC Servo Motors
1. Potentiometer
In RC servo motors, potentiometers measure rotation or movement as a change in voltage. Connected directly to the servo’s output shaft, they function as displacement sensors, enabling the microcontroller to calculate the motor’s position based on voltage output.
2. PWM
PWM control in RC servo motors can employ the triangular wave comparison method. This method involves comparing a desired sine wave frequency with a triangular carrier wave in an operational amplifier. The comparison dictates the switching control signal’s ON or OFF state, producing the necessary pulse wave for motor control.