Lab 4 - Working with MIDI

The Team:
Lisa Perez
Amit Ranjan
Andrew Rohr
Eric Sihite

Our Goals for This Lab:
During the first part of this lab, we aimed to minimize quantization error by switching out our hall effect sensor from the last lab with a more sensitive hall effect sensor and maximizing the output range by the sensor by putting it in circuit with on op amp. After minimizing error, we aimed to obtain a velocity reading by differentiating the position signal with another op amp. We planned to integrate the improved settings with our virtual environments from the last lab.

The second part of lab entailed integrating a haptic environment of our motor with a MIDI interface to create a haptic instrument. For this, we aimed to understand how to send information from the Arduino to PD, our software synthesis interface, and what to program in PD to be able to get a noise and force feedback just from manipulating the motor armature.

What We Accomplished:
We were excited to use the new hall effect sensors to obtain better settings. However, shortly after soldering the terminals, one of the terminals broke, and we were not able to solder it back on. Instead, we obtained one of the older hall effect sensors and completely our work with that. We were able to get a larger output range from the op amp, with serial ouput ranging from 0 to 815 (in contrast to the approx. 500-600 range).

Even though the hall effect sensor was the same model that we had used in the last lab, we had to tweak the programming slightly to account for a difference in behavior. Once we did this, however, we were able to resimulate our virtual environments.

After we did this, we did a search on how to integrate the Arduino with PD, an interface that allows software synthesis. We learned that we could download preexisting patches for both the Arduino and PD, and altered these patches for our needs, such that the information from the hall effect sensor would transfer correctly from the Arduino to the PD interface, and consequently to the speakers.

After a few hours of looking at programming in Arduino and PD, we were able to get tones from the speakers by moving the armature back and forth. We tweaked the numbers to make it so that the armature only played if displaced from center, with higher notes being further away from center. We included a virtual spring so that the users would feel more force further away from center (and thus with a higher note).