NEMA 17 Stepper Motors

ATO Nema 17 stepper motor is a hybrid bipolar stepper motor with an end face size of 1.7 inches x 1.7 inches (42mm x 42mm). 2 phase permanent magnet stepper motor draws 0.8 to 2 amp, allowing for holding torque of 0.16N·m to 0.65N·m, simple structure, small size and easy to mount. 2A closed loop electric stepper motor allows for holding torque of 0.40N·m to 0.72N·m. The high torque motor has four color-coded wires, a 1.8 degree step angle and a 5mm shaft at factory price. These low cost stepper motors can be controlled by AC or DC digital stepper drivers for precise position control. Widely used in 3D printers, CNC routers, robot arms, sewing machines, engraving machines, film cutting machines and other equipment.

3 drive modes of Nema 17 stepper motor

The Nema 17 stepper motor has three basic drive modes, including full-step, half-step, and subdivision. The main difference lies in the control accuracy of the motor coil current, that is, the excitation method. Usually, stepper motors have the characteristics of low-frequency vibration, and the balance of low-speed operation of the motor can be improved through subdivision and coordination.

Full-step drive

In full-step operation, the same stepper motor can be equipped with either full or half-step drivers or subdivision drivers, but the operating effects are different. The stepper motor driver cyclically excites the two coils of the two-phase stepper motor according to the pulse or direction command (that is, the coil is charged to set the current), and each pulse of this driving method will move the motor by a basic step angle, that is, 1.80 degrees (a standard two-phase motor has a total of 200 step angles in one revolution).

Half-step drive

During single phase excitation, the motor shaft stops at the full-step position. After the driver receives the next pulse, if it is excited to another phase and remains in the original excitation state, the motor shaft will move half a step angle and stop in the middle of two adjacent full-step positions. A single phase and then 2 phase excitation of the 2 phase coil in this manner will rotate the stepper motor in half steps of 0.90 degrees per pulse. Compared with the full-step mode, the half-step mode has the advantages of twice the accuracy and less vibration during low-speed operation, so the half-step mode is generally used when the full/half-step driver is actually used.

Subdivision drive

The subdivision drive mode has two advantages of extremely small low-speed vibration and high positioning accuracy. For stepper applications that sometimes require low-speed operation (that is, the motor shaft sometimes works below 60rpm) or where the positioning accuracy is required to be less than 0.90 degrees, subdivision drives are widely used.

The basic principle is to perform precise current control on the two coils of the motor according to sine and cosine steps respectively, so that the distance of a step angle is divided into several sub-steps to complete. For example, the driving method of sixteen subdivisions can make a stepping motor with 200 standard steps per revolution achieve the running accuracy of 200*16=3200 steps per revolution (i.e., 0.1125°).