Tangible Electricity: Audio Amplifier and Speaker John Miller, Brandon Herrera Baylor University John_Miller1@baylor.edu Self introduction Goal for this presentation: present an example project that might spark your own ideas Welcome feedback

Course Overview First-semester students for all majors Per section: 32 students, 1 TA Introduction to Engineering Want to do? Practice Useful tools/skills Broad content Motivation Is this something they want to do? What’s involved in the practice of engineering? What’s it like? Design process, teamwork, communication Fundamental skills and tools – units conversions, Excel Content from both ME and EE Motivate them for future learning

Project Criteria A project needs to: Not involve programming Be cheap Pique their curiosity, make them ask how it works. Being open-ended is part of that. Be simple and manageable both for the students and instructors! Work within time and space constraints. Be fun so they are engaged Be something they can take home and show off in order to establish that identity Be an application of theory that we’re discussing

Project Overview Two parts: Individual 3 lab sessions, 75 min each Solder & test amplifier Build speaker Individual 3 lab sessions, 75 min each Amplifier soldering Amplifier testing and start speaker Speaker testing

Amplifier Design Done by faculty Small – 1x2 in 12 components – 6 thru-hole, 6 SMD

Week 1: Soldering First time for most Watch 2 videos (YouTube) “Reading” assignment Regular classroom Worked in pairs (1 iron per 2 students) TA evening “lab hours” See Lab 1 assignment Had TA’s hold evening lab hours

Supplies Components Safety Tools Regular classroom, brought in: Power strips Soldering kits with iron, pliers, tweezers Provide components & PCBs Safety equipment (mats and glasses)

Week 2: Amplifier Testing Tested for operation with commercial speaker Help them troubleshoot Start working on speakers

Week 3: Speaker Testing Provided magnets and coils of wire Otherwise household materials Lots of examples (YouTube) Bring completed speaker to lab

Student Examples

Testing Procedure DC supply MATLAB script Eliminate difference in batteries Measure power (V&I) to get sensitivity MATLAB script Sensitivity = efficiency Played tones and recorded microphone FFT of that 2 tests: Fixed-frequency tone test to determine sensitivity Sweep to get average SPL in 3 frequency regions (low, mid, hi) and overall

Student Feedback Positive student comments: Enjoyed learning to solder Surprised at the simplicity of a speaker Overcoming failure or improving performance by iterating their design Seeing a wide variety of solutions to the same problem Experiencing the technical evaluation of a prototype Accessibility of simple construction materials We gave the following post-assignment: Write a short (1-2 page) report that contains the following: Two paragraphs summarizing your experience with the lab. Write about what you learned, things you did that worked well, things you would have changed or done differently, etc... Also provide some comments on the lab itself (if there are ways to improve the lab or things that were good and shouldn't change). Picture of your speaker without the enclosure or a view inside of it Picture of your speaker and enclosure (i.e. the outside) Table of measurement data. Of those who took survey (44%), 88% said “Yes” or “Very much” to enjoying EE activities and 89% said the same to the activities helping them better understand EE.

Cost One-time = $5-50 per student Recurring = $10-20 per student Tools (irons, pliers, tweezers, mats, etc.) Test equip (mics, mixer, PSU) Recurring = $10-20 per student Electrical components PCBs Magnets & wire For us, both were $10/student

Lessons Learned Hot glue is great! Magnet wire can tangle Need more lab time Speaker testing became repetitive Questions?