Blog - Sketching with Hardware

Team 3 – Graff-O-Phon Technical Documentation

Published on: | Author: Florian Lehmann | Categories: 2017a, Projects

Concept

We started with a brainstorming phase after Bernhard announced the topic on day two of this “MIDI-Madness — creating a musical instrument”. Therefore we collected several ideas and picked the most promising:

Using old graffiti cans with different fill levels to produce sounds in analogy to a drum set.

Based on this theme we sketched first ideas on how to build the instrument and experimented with electronic actuators to test sound generation with graffiti cans, e.g. with servos and solenoids. We decided to use a solenoid to “shoot” on the plain metal surface of the cans to generate sounds. In total we used six graffiti cans and hit them along the vertical axis on two different position to generate twelve sounds.

graff-o-phon-td6graff-o-phon-td1

Technical Construction

First, we had the idea of cans hanging down from a wooden construction but went on with a less complicated construction. We arranged the cans semicircular around the actuators, mounted with a self-designed construction made of acrylic glass. The cans are kept in place with two laser cut acrylic glasses: A base plate and a second plate with holes in it to hold the cans in their position. We used thread rods to align the plates properly.

graff-o-phon-td2graff-o-phon-td3

In the center of the graffiti cans, we placed the stepper motor with the servo motor and the solenoid attached to it. Therefore, we glued the solenoid to the servo motor to control the vertical positioning and attached the servo with an offsetting wood construction on top of the shaft of the stepper motor. The whole construction, including the electronics, is screwed on two wooden plates.

From an creative perspective we chose an industrial look with strong links to the graffiti culture. We painted the wooden base with black graffiti ink and dripped color splashes on them.

graff-o-phon-td4graff-o-phon-td7

Electronic Components

  • Arduino Duemilanove Micro controller Board
  • Bipolar Stepper Motor
  • Servo Motor 5V
  • Solenoid 12V (Push)
  • Pololu md18a H-Bridge Motor Driver Module
  • L298 Dual Motor Driver Module
  • MIDI In/Output Module
  • 2200uF 16V Radial Electrolytic Capacitor
  • Computer Power Supply (2 x 5V DC)
  • 18V DC Power Supply
  • 6V DC Power Supply

Circuit

graff-o-phon-fritzing

Core component in our circuit is the Arduino Duemilanove microcontroller board (we show a Arduino Uno, but it should work as well). The Arduino communicates with the MIDI I/O module on GPIO pins 2 and 3. In our case we only use the MIDI output functionality, which is the input for our instrument. On pin 6 we attached the servo motor directly and on pin 4 the L298N h-bridge that drives our solenoid. Pins 8 – 11 are connected with the Pololu md18a h-bridge that drives our stepper motor.

To supply sufficient power, we used a computer power supply with independent 5V DC supplies for each motor. Another 18V DC power supplies the solenoid. The Arduino gets supplied by a 6V DC power supply. All supplies share the same GND.

Source Code

Our source code is well commented and publicly available on GitHub: Graff-O-Phon Gist.

Final Graff-O-Phon

graff-o-phon

In Action

graff-o-phon-animated

linked categories 2017a, Projects

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