Analog Circuits Lab (EE122) was my first electronics lab class. The course was primarily about filters, so one obvious application that occurred to my lab partner and me was to build a music tuner. We called our little breadboard contraption “A Tuner”, deliberately making a pun off of the musical note at 440 Hz (both he and I played a musical instrument; I played the violin while he played the saxophone). Our tuner’s input was a microphone and its output was an LED bar graph that displayed the pitch.
Because the breadboard belonged to the lab, we had to disassemble it to return the breadboard. I was so attached to the thing that I measured the exact values of every component with the intention of replicating the tuner at a later time. Looking back, that was kind of silly, seeing how chips vary so much that even if I were to find the exact resistance values, I would still have to recalibrate the tuner.
Download A Tuner Schematic (115 KB).
Download A Tuner Block Diagram (517 KB).