Practice Pedal
Inspiration
We were inspired by guitar pedals from the 70s and 80s, which we found very retro. We were also interested in modern-day motivation products, such as the iPhone lock cage. The objective of Practice Pedal is to motivate children and others to play guitar by rewarding them for how long they practice.
What does it do?
Practice Pedal reads a voltage generated from an electrical guitar and measures how long the player has played in minutes. A certain amount of time played on the instrument for a consistent amount of time rewards players with candy.
How was it built?
The project began with an old guitar pedal that was not working so we wanted to repurpose it. We gutted the old electronics of the case, and instead fitted an op amp, full-wave rectifier, and Arduino Nano. The voltage (audio) connects to the op amp which amplifies it by a factor by 100 (power gain of 4.5V). It is given a smoothing rectifier with a significant capacitor, which essentially converts AC voltage to DC voltage. This was done to make programming a task of reading HIGH and LOW. Connect the rectifier’s output to the analog pin (A0) on the Arduino Nano. Conditional statements are used to determine if voltage is high, which indicates that the player is playing the guitar. If so, a “totalTime” variable is incremented accordingly. No time will be added if the input is LOW, meaning the player is not playing.
Another conditional is used to control the servo. If the totalTime is above a certain number (e.g. 25 minutes), the servo is activated, allowing candy to fall and reward the player. After rewarding the player, the LCD screen on the box displays a congratulations message to the player and the Arduino stops counting time.
Challenges we ran into
Main challenges:
None of our group members had a guitar on campus, so getting a guitar for testing was very difficult. Fortunately, someone at the Hive allowed us to test for a few hours, but we could not take it with us after the Hive closed.
We worked non-stop at Hive, from opening to closing. However, we were still limited by time. 20 minutes before the Hive closed, we ran into a bug with the op-amp circuit. Without the oscilloscopes, guitar, soldering irons, and other tools found at the Hive, we were unable to continue progress with the analog circuits.
We tested the op-amp circuit multiple times - and it worked every time except right until the Hive was about to close. We asked for help and debugged until the Hive closed, but we couldn’t solve the problem in time. Thus, we had to adapt to an unfortunate fate and scrap the rectifier and op-amp, even though we spent a lot of time building it. Because of this, we had to changeWe still have the circuits and videos of them working for evidence.
We overestimated the laser cutter’s accuracy. It was unreliable because the leveling was not ideal, thus causing problems for sections requiring high-precision, like small holes.
Other challenges:
Noise issues with the oscilloscopes. The Hive is very noisy when it comes to electrical signals. This buffered our efficiency in general.
Strange communication error with the Arduino serial monitor and the limitation of cycles in PCs. We thought the Arduino wasn’t working, but it was. More or less, a challenge with all of us using Arduino Nano for the first time.
Arduino misleading API for millis(), which is said to measure how much time occurred since the program started. It did not actually do this, so we had to use another library.
Dimensioning challenges
These are challenges with a technical project which integrates multiple different disciplines: firmware/embedded systems, mechanical, and electrical engineering.
Accomplishments that we’re proud of:
Have executed the main purpose and goal of our vision Learned a lot about general electronics and signal processing in the real world. Integrate IO devices on Arduino and having it work was really nice. Learned a lot about Arduino
What's next for Practice Pedals
Apply different algorithms to determine types of practice (e.g. musical playing)
Implement portable battery
Buy a guitar! Why not?
