Servo, DC, and Stepper Motors- The Motors to Satisfy Your Robotics Needs
When choosing motors to satisfy your robotics needs, you are likely to come across types like servo, DC, and stepper motors. But which type of motor should you get? Each motor has unique features. Use this guide to differentiate each so you can choose the right motor for your robotics project:
A servo motor is made up of a DC motor, a control circuit, gearing set, and a position sensor, which is typically a potentiometer. The position of a servo motor can be more precisely controlled (compared to a standard DC motor). The three wires (ground, control, and power) play a critical role. Power must be constantly applied to servo motors, and the servo control circuit regulates the draw to make the motor run. Hence, servo motors are ideal for applications where the position must be accurately defined, such as moving a robotic leg or arm within a pre-defined range. Servo motors cannot freely rotate the way conventional DC motors can. Their angle of rotation is limited to 180 degrees.
Direct current motors consist of continuous rotation motors and two wires: ground and power. When power is supplied, the DC motor will spin until you remove that power. DC motors like the ones required in radio controlled wheels and cooling fans in computers commonly run at high revolutions per minute. Their speed can be controlled with pulse width modulation, which rapidly pulses the power on and off. The speed of the motor is determined by the percentage of time spent cycling the on and off ratio.
A stepper motor is an electromechanical device for mechanical movements using the conversion of electrical pulses. These motors work via digital pulses instead of continuously applied voltage. Stepper motors step or rotate in fixed angular increments, making them ideal for applications that require position control. A stepper motor can follow digital instructions as long as the system has a stepper motor/driver/controller design. Stepper motors lack feedback to maintain the control of position as they are open loop systems.
Stepper motors are made up of a shaft, stator laminations and rotor, bearings, magnets, lead and copper wires, front and end covers, and washers. Their shaft is usually made of stainless steel, and the stator and rotor laminations are often made of silicon steel for better electrical resistivity and lower core loss. Magnets allow for multiple construction applications. The bearings may depend on the size of the motor, and the housing materials are usually resistant to heat.
This article is written by Jack Wang who is associated with GEMS Motor. Jack got his Bachelor's degree in Mechanical Engineering and Master's degree in Electrical Engineering, specialized in electric motor design.