Our team is developing a levitating sound system that uses PID control, Arduino, Pulse-Width-Modulation, and a custom electromagnet that levitates a portable speaker in free space. The sound system analyses the frequency content of playing music to detect and oscillate integrated lights to the beat of the music. (Just another one of my over-the-top gifts for a friend)
Project inception: December 20th, 2018. Status: Work in Progress. The following titles illustrate work we have already done as of January 14, 2019, but the work has not been expanded upon in this portfolio yet due to the fact that the project remains in development.
Input Constraints Used to Design Our System
Maximum Levitating Speaker Mass, Maximum Distance of Speaker, Maximum Electromagnet Diameter, Electromagnet Height, j = 1000 for Max Current Calculations.
Examples of Plots Prepared/Used in System Design
Beat Detection & Digital Signal Processing
Microphone & Preamplification / DC Offset /Automatic Gain Control
In order to perform beat detection, the team had to implement a microphone into the sound system that could detect and normalize audio. While the team explored the possibility of designing preamplification, DC Offset, and automatic gain control circuits from scratch, the Electret MAX9814 performed all these tasks at a lower expense than the team could achieve ourselves. This chip was used for signal detection.
Physical Low-Pass Filter
In early stages of the prototyping process, a simple RC low pass filter was designed to process low-frequency beats from playing music. This filter was applied over the signal produced from the MAX9814, and transmitted through a single LED. The proof-of-concept beat detection can be seen in the following video.
Fast Fourier Transform
The signal output by the MAX9814 chip was visualized on an oscilloscope, and a Fast Fourier Transform analysis was applied to the signal. The purpose of this was to further refine the cutoff frequencies of the physical filter, and to determine the possibility of implementing a digital filtration scheme to refine signal processing.
Digital Band-Pass Filter
Operational Amplifier & LED Panel Design
In the future, I will elaborate further on the process taken to get here. However, the following is a short clip with beat detection being performed successfully and displayed on an LED strip. This scheme required the use of an Operational Amplifier to provide the LED strip enough power to light up.
Speaker Design & Acoustics
Bluetooth Transmission / Reception
Tonewood Acoustics vs. Cost
Details will come when the project is complete. For now, enjoy this nice video of us cutting out a frame for prototyping.
A Hilpert correlation scheme was implemented to model and predict the impact of cooling on the electromagnet temperature. (Technical details will be released upon completion of the project). Three temperature change tests were performed; the predicted and determined steady state values are listed for each test setup, and two plots are displayed.
- Electromagnet running at 32V with no cooling
- Electromagnet running at 32V with cooling, but partial contact on fins (Predicted Steady State: 50 C, Actual Steady State: 49 C)
- Electromagnet running at 32V with cooling and full contact on fins. (Predicted Steady State: 37 C, Actual Steady State: 38 C)
The following three images illustrate parts of the test setup.
PID Controller Design
PWM / MOSFET Control
As the team has progressed from an initial concept to designing aspects of the system around various physical constraints imposed by our objectives, the design of the levitating speaker setup has changed. As of January 14, 2019, the following images display the various iterations of the levitating speaker design, where the bottom right blue setup is the current design we are exploring.