Exercise: Motor Music

Note: this exercise is not yet final and may be still slightly revised.

In this exercise we will design and fabricate a simple musical instrument driven by an electric DC gearmotor. The overall project objective is sound-producing device which combines autonomy and user interaction. The technical objective is creating a reliable actuation scheme using a gearmotor.

There are several directions you might consider.

  • enabling the user to control the motor vs directly actuate sound

  • using a motor as a source of energy

  • using a motor to create timing

  • an elaboration of the manually-operated music box to use motor actuation

Objectives

The overall objective of this exercise is to design and fabricate a freestanding device which actuates a sound-producing process using a DC gearmotor.

The goals of this exercise are that you should be able to:

  1. Design and fabricate an object which can create sound.

  2. Design a structure to support the sound element while allowing one or two degrees of freedom.

  3. Reliably mount a DC gearmotor in an assembly.

  4. Design a motion transmission to couple motor shaft rotation to the sound process via mechanism.

  5. Design a multi-part assembly including joinery.

  6. Laser-cut parts, assemble, test, and iterate.

Gearmotors

A principal technical objective is gaining design experience with gearmotors. These actuators can provide continuous rotation in either direction at variable speed and are useful for energy input and motion control. In this exercise we are simply powering them for for constant rotation.

Please do not glue anything to your motor shafts. The Pololu 1997 hub is the most practical way to mount an element on the motor shaft. For mounting your element it features four M3 threaded holes on a half-inch diameter bolt circle (6.35 mm radius, 12.7 mm diameter). The M3 x 10 mm button-head cap screws are a good length for attaching 6 mm plywood to the hub.

Please note that unlike the hobby servos, gearmotors do not have any position sensing, so moving them to specific positions will require the use of additional sensing, usually in conjunction with microcontroller programming and a digital motor driver.

Deliverables

  1. Live in-class demo of your device

  2. A short report posted to the shared drive including:

    1. a short text statement reviewing your intent and outcomes

    2. one or more photos

    3. a brief video

    4. your SolidWorks files