Stepper Motor: Bipolar, 200 Steps/Rev, 20×42mm, 4.3V, 0.8 A/Phase

This small NEMA 8-size hybrid bipolar stepping motor has a 1.8° step angle (200 steps/revolution). Each phase draws 800 mA at 4.3 V, allowing for a holding torque of 300 g-cm (4.2 oz-in). With a weight of 80 g, this is one of the smaller stepper motors we carry.

Bipolar stepper motor wires are terminated with bare leads.

Bipolar stepper motor wiring diagram.

Overview

This small hybrid bipolar stepping motor has a 1.8° step angle (200 steps/revolution). Each phase draws 800 mA at 4.3 V, allowing for a holding torque of 300 g-cm (4.2 oz-in). The motor has four color-coded wires terminated with bare leads: black and green connect to one coil; red and blue connect to the other. These leads connect to the stepper motor through a removable JST-ZHR-5 connector. The motor can be controlled by a pair of suitable H-bridges (one for each coil), but we recommend using a bipolar stepper motor driver or one of our Tic Stepper Motor Controllers. In particular, the Tics make control easy because they support six different interfaces (USB, TTL serial, I²C, RC, analog voltages, and quadrature encoder) and are configurable over USB with our free configuration utility.

Our 4 mm universal mounting hub can be used to mount objects on the stepper motor’s 4 mm-diameter output shaft. For a slightly less powerful motor in the same NEMA size but a shorter length, consider Stepper Motor: Bipolar, 200 Steps/Rev, 20×30mm, 3.9V, 0.6 A/Phase. A comparison between these two motors can be seen in the image below.

SY20STH30-0604A (top) and SY20STH42-0804A (bottom).

Specifications

• Size: 20 mm square × 42 mm, not including the shaft (NEMA 8)
• Weight: 80 g (2.8 oz)
• Shaft diameter: 4 mm “D”
• Steps per revolution: 200
• Current rating: 800 mA per coil
• Voltage rating: 4.3 V
• Resistance: 5.4 Ω per coil
• Holding torque: 300 g-cm (4.2 oz-in)
• Inductance: 1.5 mH per coil
• Lead length: 30 cm (12″)
• Output shaft supported by two ball bearings

More specifications are available in the datasheet (28k pdf).

Dimensions

The following diagram shows the stepper motor dimensions in mm. The dimension labeled “Length” is 30 mm. The output D-shaft has a length of 15 mm and a 4 mm diameter with a section that is flattened by 0.5 mm. This shaft works with our 4 mm universal mounting hub.

The inside of a bipolar stepper motor (SOYO NEMA 14-size).

Stepper Motor Applications

Stepper motors are generally used in a variety of applications where precise position control is desirable and the cost or complexity of a feedback control system is unwarranted. Here are a few applications where stepper motors are often found:

• Printers
• CNC machines
• 3D printer/prototyping machines
• Laser cutters
• Pick and place machines
• Linear actuators
• Hard drives

Pololu’s assortment of stepper motors.

Note: This stepper motor is SOYO part number SY20STH42-0804A.