Stepper Motors

A stepper motor is used as an output in electronic circuits. The motor is a brushless DC electric motor that divides a full rotation into a number of equal steps.

The motor’s position can then be made to move and hold at one of these steps without any position sensor for feedback as long as the motor is carefully sized to the application in respect to torque and speed.

Multiple coils are organised in phases (groups). By energising each phase in sequence the motor will rotate, one step at a time.

Why and when to use a Stepper Motor?

With a computer controlled stepping you can achieve very precise positioning and/or speed control.
•Steppers move in precise repeatable steps, they are perfect to use where precise positioning is needed such as 3D printers, CNC and camera platforms.

•Some disk drives use stepper motors to position the read/write head.

•Precise increments of movement also allow for excellent control of rotational speed for process automation and robotics.

•A Stepper motor has maximum torque at low speeds, so they are a good choice for applications where low speed with high precision is needed.

Stepper motor types
•Bipolar drivers use H bridge circuitry to reverse the current flow through the phases. By energising the phases with alternating the polarity all the coils can be put to work turning the motor.

•Permanent magnet motors use a permanent magnet in the rotor. They operate based on the principle that minimum reluctance occurs with minimum gap, meaning the rotor points are attracted towards the stator magnet poles.

•Unipolar drivers always energise the groups in the same way. The common lead will always be negative. They can be implemented with simple transistor circuitry.

Advantages of step motors
•Low cost

•High reliability

•High torque at low speed

•Full torque at standstill

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Description Price Step Angle Holding Torque Number Of Wires Voltage Rating Frame Size Stepper Motor Type Shaft Diameter Current Rating Winding Arrangement Shaft Length Depth Number of Pole Pairs Resistance Per Phase Detent Torque
RS Stock No. 122-4621
Mfr. Part No.ADM1220S-2R-V3-83 + M2X0.2X15 + 2.8000.08.353
18° 2.4mNm - 3 V - Disc Magnet 1.5mm 220 mA Bipolar 3.85mm 0mm 10 10.4Ω -
RS Stock No. 921-1341
Mfr. Part No.AM1524-2R-V-12-150-05
15° 6mNm 4 12 V dc - Bipolar, Unipolar 1.5mm 75 mA Bipolar 6.5mm 19.5mm 2 138Ω 0.9mNm
RS Stock No. 921-1347
Mfr. Part No.AM0820-V3-18-08 C06.072A 08/1 256:1
18° 0.65mNm 4 3 V dc - Bipolar, Unipolar 2.34mm 150 mA Bipolar 3.85mm 16.75mm 2 18Ω 0.17mNm