Oscillations and resonance are essential topics in physics that can be explored theoretically and experimentally in the classroom or teaching laboratory environments. However, one of the main challenges concerning the experimental study of resonance phenomena via forced oscillations is the control of the oscillation frequency, which demands an electronic circuit or a fine tuned coupled mechanical system. In this work, we demonstrate that, in what concerns the physics teaching, such demanding accessories are not necessary. The forced oscillations can be implemented by the teacher's hand guided by an oscillating circle displayed in a web application loaded in a smartphone. The oscillations are applied to an ordinary spiral toy. Qualitative, as well quantitative, proposals are explored in this work with excellent results.

We present a device, created by us and named Stellector, composed by a laser pointer which is precisely guided by two step motors with the purpose to explore and teach astronomy concepts having the real night sky in the background. The electronic part is made of low cost items and the mechanical part is 3D printed. The controller software was written in HTML/Javascript language in order to run in any portable communication device, such as smartphones and tablets. Communication with the Stellector hardware is via Bluetooth standard. These characteristics ensure the necessary portability and autonomy for outdoor astronomy teaching activities. In this work, we sketch the Stellector design and its mode of operation. We also illustrate some teaching activities involving basic night sky observations and astronomy concepts. Finally, we discuss the device limitations, its accuracy and further improvements.