Mechanical Design Portfolio
A circuit diagram, above, for the 6th order Bessel filter implemented to isolate the song's bass drum. Below is the circuit implementation using a quad op-amp.
A scope readout from the testing of the programmable gain amplifier. The green trace shows the output of the low pass filter. In blue is the output of one of the comparators of the amplifier, which goes low when the volume of the song is above the lowest set threshold; in the operational range for the circuit. The output of the amplifier is in yellow, with the magnitudes of the peaks nearly constant within a certain volume range.
Analog Metronome
As part of ENGS 32: Introduction to Linear and Digital Circuits, a partner and I developed a project to incorporate the signal processing focus of the course's standard final project as well as integrate a mechanical system. We created a "reverse" metronome to take an audio input from a headphone jack and move a lever in time.
We decided to use the bass drum of the song as the beat, so we first implemented a low pass filter to attenuate all frequencies above 50 Hz, using a sixth-order Bessel filter with Sallen-Key topography. We then created a programmable gain amplifier to normalize the voltage output (volume) of the song, using analog switches to adjust the gain of an inverting amplifier. We also included LEDs to indicate if the volume was too low or too high for the amplifier. To determine the beat, we used a peak detector and took all voltages above a certain threshold. The signal was passed through digital logic gates to control an H-Bridge, which enabled a motor and determined its direction. Finally, we implemented position sensors using infrared emitting LEDs and infrared sensing BJTs to limit the range of motion of the motor.
While most of the project work was done together, my significant individual design contributions were the programmable gain amplifier and the position sensor. The schematics in OrCAD were evenly divided.