Dania González Sanabria

And of sublime pains.)

José Martí. “Versos Sencillos”, Fragment. ( José Julián Martí Pérez (Havana, 1853 - Dos Ríos, 1895) was a Cuban politician, diplomat, poet, essayist, journalist and philosopher, founder of the Cuban Revolutionary Party and organizer of the Cuban War of Independence, during which he died in combat. He is considered the initiator of literary modernism in Latin America. He is considered the national hero of the Republic of Cuba, and his ideals of independence and anti-colonialism have been used by the Cuban regime to politically indoctrinate the Cuban people. But these same ideals of nationalism and independence also serve as a guide and inspiration to the opposition that desires a Cuba without repression, a just country and a republic “with everyone and for the good of everyone”).

Concept development

The lemon tree is a resilient plant that bears fruit even when it is dying.

In this project, the lemon tree is a symbol of the members and generations of my Cuban family, it is an inheritance of sentimental and moral values in it.

The death of that plant also speaks about the Cuban context in general, its history, and its current socio-political crisis that generates physical and sentimental ruptures of its most vulnerable families. It has affected especially the humble elderly people who were the working generations who created and supported the revolutionary Cuban process that became corrupted and negligent to them. Now, those persons are the most affected by the crisis, being abandoned by the system to which they gave their faith and the effort of their lives.

The piece is a tribute to them.

Technical implementation

Embedded systems development

Embedded systems development

During our project, we used Visual Studio Code and Arduino to program and control motors based on sensor data.

Technology

• Arduino Nano
• capacitive soil sensor
• 15g Servo

Code

For the platformio.ini:

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
lib_deps = roboticsbrno/ServoESP32@1.0.3
monitor_speed = 9600

Fort he main.cpp:

#include <Arduino.h>
// include the servo library
#include <Servo.h>

//  timing 
unsigned long currentTime = 0;

unsigned long lastTimeA = 0;
unsigned long lastTimeB = 0;
unsigned long lastTimeC = 0;
unsigned long lastTimeD = 0;
unsigned long lastTimeE = 0;
unsigned long lastTimeF = 0;

const int baseServoDelayTimeA = 17300;
const int baseServoDelayTimeB = 11020;
const int baseServoDelayTimeC = 15400;
const int baseServoDelayTimeD = 12800;
const int baseServoDelayTimeE = 8400;
const int baseServoDelayTimeF = 6300;

float randMultiplier = 1.0;

long randNumber; 

//sensors 
const float sensorTriggerValueA = 700;
const float sensorTriggerValueB = 520;
const float sensorTriggerValueC = 650;
const float sensorTriggerValueD = 880;
const float sensorTriggerValueE = 950;
const float sensorTriggerValueF = 1100;

float getSensorValuePpm (int sensorPin);

const int sensorA = 36;
const int sensorB = 39;
const int sensorC = 34;
const int sensorD = 35;
const int sensorE = 32;
const int sensorF = 33;

float gasValueSensorA = getSensorValuePpm (sensorA);
float gasValueSensorB = getSensorValuePpm (sensorB);
float gasValueSensorC = getSensorValuePpm (sensorC);
float gasValueSensorD = getSensorValuePpm (sensorD);
float gasValueSensorE = getSensorValuePpm (sensorE);
float gasValueSensorF = getSensorValuePpm (sensorF);

//servos 
const int servoPinA = 19;
const int servoPinB = 18;
const int servoPinC = 05;
const int servoPinD = 17;
const int servoPinE = 16;
const int servoPinF = 04;

Servo servoA;
Servo servoB;
Servo servoC;
Servo servoD;
Servo servoE;
Servo servoF;

boolean isLeftA;
boolean isLeftB;
boolean isLeftC;
boolean isLeftD;
boolean isLeftE;
boolean isLeftF;

//function declarations 
void playSound(unsigned long &lastTime, int sensorPin, Servo &servo, float &gasValueSensor, boolean &isLeft, int baseServoDelayTime, float sensorTriggerValue);

float getSensorValuePpm (int sensorPin);

void setup() {
  analogSetAttenuation(ADC_11db);
  Serial.begin(9600);

  servoA.attach(servoPinA);
  servoA.write(30);
  isLeftA = true;

  servoB.attach(servoPinB);
  servoB.write(30);
  isLeftB = true;

  servoC.attach(servoPinC);
  servoC.write(30);
  isLeftC = true;

  servoD.attach(servoPinD);
  servoD.write(30);
  isLeftD = true;

  servoE.attach(servoPinE);
  servoE.write(30);
  isLeftE = true;

  servoF.attach(servoPinF);
  servoF.write(30);
  isLeftF = true;
}

void loop() {
  currentTime = millis();

  playSound(lastTimeA, sensorA, servoA, gasValueSensorA, isLeftA, baseServoDelayTimeA, sensorTriggerValueA);
  playSound(lastTimeB, sensorB, servoB, gasValueSensorB, isLeftB, baseServoDelayTimeB, sensorTriggerValueB);
  playSound(lastTimeC, sensorC, servoC, gasValueSensorC, isLeftC, baseServoDelayTimeC, sensorTriggerValueC);
  playSound(lastTimeD, sensorD, servoD, gasValueSensorD, isLeftD, baseServoDelayTimeD, sensorTriggerValueD);
  playSound(lastTimeE, sensorE, servoE, gasValueSensorE, isLeftE, baseServoDelayTimeE, sensorTriggerValueE);
  playSound(lastTimeF, sensorF, servoF, gasValueSensorF, isLeftF, baseServoDelayTimeF, sensorTriggerValueF);
}

//functions

void playSound(unsigned long &lastTime, int sensorPin, Servo &servo, float &gasValueSensor, boolean &isLeft, int baseServoDelayTime, float sensorTriggerValue){
  
  //generate multiplier and adjust delaytime 
  randMultiplier = 0.7 + (random(0, 341) / 100.0);
  int adjustedDelayTime = baseServoDelayTime * randMultiplier;

  if (currentTime - lastTime >= adjustedDelayTime){
      // check if timing works
      Serial.print("Random delayTime");
      Serial.println(adjustedDelayTime);
      Serial.println("Triggering sensor reaading");
      gasValueSensor = getSensorValuePpm(sensorPin);
      // check sensor value 
      Serial.print("Sensor Value: ");
      Serial.println(gasValueSensor);

        if (gasValueSensor > sensorTriggerValue){
          Serial.println("Triggering servo");
          // move servo to play sound
            if (isLeft == true){
              servo.write(0);
              isLeft = false;
              Serial.println("right");
            }
            else{
              servo.write(30);
              isLeft = true; 
              Serial.println("left");
            }
            Serial.println("Servo moved. Last Time updated.");
          }
          // update lastTime
          lastTime = currentTime;
        }
}

float getSensorValuePpm (int sensorPin) {
  float voltage = analogRead(sensorPin) * (5.0 / 1023.0);
  float RS_air = 10.0;
  float RL = 2.0;
  float ratio = RL / RS_air;
  float RS = ((5.0 / voltage) - 1.0) * RL;
  float ppm = 1000.0 * pow((RS / RS_air), ratio);
 return ppm;
}

Manual construction

I was responsible for the structural and mechanical implementation of the project since my strengths lie far more in this area than in writing computer code. Additionally, unlike Hanna, I have the necessary resources at home to craft.

We needed a mount that would allow the servo motors to hover above the guitar strings so they could pluck them individually. The servo motors had to be positioned at a certain distance from each other to avoid interfering with one another when striking the strings. We had already identified this issue through a cardboard prototype. Since guitar picks were to be attached to the motors, increasing the radius of the strike, it made sense to always leave two strings between those being played.

I decided to attach two motors to one bar. The construction sketch can be seen here:

Since I couldn’t guarantee millimeter-precise construction, and factors like the surface, variations in the way the picks were attached, or different motor models could create height differences, it was necessary to allow for fine adjustments to the height of the mount. For this, I used special adjustment screws that allow the height of the mounting beams to be individually adjusted on both sides. Unlike regular screws, these have two types of threads: the upper thread remains fixed in the wood, while the lower thread can be screwed in and out like a standard screw. This enables precise millimeter-level height adjustments to fit the conditions.

Additionally, the sensors had to be connected to the breadboard. To do this, I soldered cables—each consisting of three wires—of sufficient length to each of the six sensors. I then soldered a connector to each wire to facilitate easy attachment to the breadboard.

The Plants

• Hyacinth
• Euphorbia
• Fern
• Begonia
• Peperomia
• Alocasia

Exhibition

Concept

The idea was to place the guitar on a table, with a clothing rack positioned behind it, from which the six plants would hang. These included a hyacinth and an alocasia in bags, a fern and a pepper plant in small greenhouses, as well as a begonia and a moldy euphorbia in screw-top jars.

The cables and the breadboard were intentionally installed with minimal cable management, keeping them clearly visible to emphasize the DIY aesthetic.

The lighting needed to be bright enough to provide sufficient light for the plants without being too harsh. Hanna brought her grow lights, which perfectly illuminated the exhibition niche where our work was displayed.

We chose the niche as our exhibition space because it allowed us to maintain a necessary distance from other sound-based projects. Additionally, this setup ensured that the work could only be viewed from the front, preventing visitors from accidentally bumping into it and disturbing any components.

Preparations and setup

Hanna and I met in Weimar on the Saturday before the exhibition to attach the picks to the motors and test the interaction of all components. This allowed us to check the overall functionality of both the code and the construction. Fortunately, everything worked as intended, with only a few minor tasks remaining.

Our plan was to hang the plants from a clothing rack. However, since two of the plants were potted in jars, suspending them proved to be a challenge. To solve this, I crafted wooden discs with holes through which we could thread wire, ensuring that the jars could be securely hung. Hanna also made some minor adjustments to our code.

On the Thursday before the exhibition, we finalized our setup. We darkened the window, adjusted the lighting, secured all components to the table to prevent any shifting during the exhibition, connected the sensors and motors, plugged in the power supply, set the timers, and fine-tuned the height of the mounting structure to ensure that each pick could strike its string and produce a pleasant sound.

(written by Fiene)

Winterwerkschau

The Winterwerkschau was a great success for our project. Contrary to our initial concerns, the adhesive held up perfectly, keeping the picks securely attached to the motors for both days of the exhibition. As a result, all the strings could be continuously played without any issues.

When Hanna and I took our turn overseeing the exhibition, we were met with an incredible amount of interest and enthusiasm. Visitors were fascinated by our work, showering us with questions and curiosity. It was an incredibly rewarding experience that filled us with pride and reinforced our excitement about what we had created.

All the hard work had truly paid off, and seeing our project resonate with others made the effort even more worthwhile.

(written by Fiene)