Probeware (sensors combined with data-analysis software) is a well-established part of physics education. In engineering and technology, sensors are frequently paired with actuators—motors, heaters, buzzers, valves, color displays, medical dosing systems, and other devices that are activated by electrical signals to produce intentional physical change. This article describes how a 20-year project aimed at better integration of the STEM disciplines (science, technology, engineering and mathematics) uses brief actuator activities in physics instruction. Math Machines “actionware” includes software and hardware that convert virtually any free-form, time-dependent algebraic function into the dynamic actions of a stepper motor, servo motor, or RGB (red, green, blue) color mixer. With wheels and a platform, the stepper motor becomes LACI, a programmable vehicle. Adding a low-power laser module turns the servo motor into a programmable Pointer. Adding a gear and platform can transform the Pointer into an earthquake simulator.

Topics
History of science, Data analysis, Earthquakes, Stepper motors, Transducers, Mathematical modeling, Lasers, Education, Teaching, National Science Foundation
1.
Stepper motors are similar to standard DC motors but without internal circuitry to turn magnets on and off. Instead, their motion depends on external circuitry and logic to specify which magnets are active at any time. Each change in the external signal specifies an angular displacement, either a “step” or a “half-step.” We use a double-shaft stepper motor, Soyo model SY42STH38-0806B (available from Robot Shop), with a half-step resolution of 0.9°.
2.
Hobby servo motors are widely used to move rudders, steering wheels, elevators, and other controls of model boats, cars, and airplanes. They contain internal logic and feedback systems such that the width of each signal pulse corresponds to a specific angular position. The servo motor we use is HiTec model HS-7975HB with a resolution of 0.1°.
3.
LACI is a “Linear Algebraically Controlled Implementer.”
4.
We use a Class II diode laser module (< 1 mW) from OnPoint Lasers. The power output is in the low range of handheld laser pointers. It remains important, however, to follow good laser safety procedures. In lab, this includes restricting the range of motion of our servo to within 50° of center and using a screen that covers this target field. With appropriate precautions, the laser can also project onto a classroom whiteboard.
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Although Math Machines workshops frequently engage teachers in building hardware, we rarely expect students to build hardware. Students generally design and test dynamic processes such as the motion of a motorized cart, rather than designing or building the cart itself.
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Here “v” is the instantaneous velocity and the dependent variable, “t” is time and the independent variable, the constant “v0“ is the initial velocity and the y-intercept, and “a” is a constant acceleration and the slope for this linear relationship.
14.
Current hardware consists of the LACI vehicle and the servo motor Pointer with an RGB LED, each controlled through a Digilent chipKIT WF32, a variant of the popular Arduino boards.
15.
Although not part of NSF’s original STEM concept, many schools have added an “A” for art, creating STEAM programs.
16.
Available for download at http://www.mathmachines.net.
17.
Download software at TPT Online under the Supplemental tab at https://doi.org/10.1119/1.5018695 .
© 2018 American Association of Physics Teachers.
2018
American Association of Physics Teachers

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