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hardware

28BYJ-48 Stepper Motor Brackets

28BYJ-48 Stepper motors are really inexpensive and I have had been experimenting with them for some time. As-supplied they only have two attachments lugs that seem to be inconveniently positioned for most of the applications in which I want to using them.

About this Motor

One of the most common hobby stepper motors is the 28-BYJ48 Stepper motor.

The motor has a four 5V rated coils in an unipolar arrangement, making it easy to control with basic microcontrollers. They provide 64 steps per revolution of the motor (5.625° per step) and in most cases are also geared down by a factor of 64 to give 1024 steps per revolution, giving a fine resolution and high level of control.

However, these motors run on low voltages (5 or 12V depending on the rating) and don’t provide high torque.

These motors are really inexpensive and often bundled with a ULN2003 ‘stepper driver’ board (really just high voltage, high current darlington transistor IC) that need 4 digital I/O pins to drive the motor (shown below).

Designing a Bracket

These motors are an awkward shape, and the only attachment points are the two lugs located on the side of the round body. Despite my best efforts I could not find a ready-made solution that would allow me to easily and elegantly connected the motors to a platform (either above or below), so I decided to design my own.

The first step was to obtain a mechanical datasheet with the motor dimensions.

I then modelled the motor in Fusion360 as a starting point for the bracket design. This model is available on Thingiverse.

Using this model, an appropriate bracket was designed. This bracket is symmetrical (ie, the same component can be used for left or right). This design allows the motor brackets to be attached flush to a surface (above or below) with the motor attached to the brackets.

This is shown below.

The motor lug holes are designed for threading with a M4 tap or clearance drill with a nut on the far side. The top holes are sized for M3 threading.

The finished motor mounts in use are shown below.

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