Carly Robin | Sensors + Actuators

For our concept, we explored specific pressure sensors and sound actuators that attempt to relieve awkwardness in a public space, such as a bus stop. Though we are not settled on the exact context yet, we are still interested in getting people together to make simple beats from a drum kit. 

The first exploration is using a Parallax Ping code, which senses the distance from an object. Once a certain proximity is reached, a beat would be output. Here is a sample of the code:

unsigned long echo = 0;

 int ultraSoundSignal = 9; // Ultrasound signal pin

 unsigned long ultrasoundValue = 0;

 void setup()

 {

 Serial.begin(9600);

 pinMode(ultraSoundSignal,OUTPUT);

 }

 unsigned long ping(){

 pinMode(ultraSoundSignal, OUTPUT); // Switch signalpin to output

 digitalWrite(ultraSoundSignal, LOW); // Send low pulse

 delayMicroseconds(2); // Wait for 2 microseconds

 digitalWrite(ultraSoundSignal, HIGH); // Send high pulse

 delayMicroseconds(5); // Wait for 5 microseconds

 digitalWrite(ultraSoundSignal, LOW); // Holdoff

 pinMode(ultraSoundSignal, INPUT); // Switch signalpin to input

 digitalWrite(ultraSoundSignal, HIGH); // Turn on pullup resistor

  echo = pulseIn(ultraSoundSignal, HIGH); //Listen for echo

  ultrasoundValue = (echo / 58.138) * .39; //convert to CM then to inches

 return ultrasoundValue;

 }

 void loop()

 {

 int x = 0;

 x = ping();

  Serial.println(x);

  delay(250); //delay 1/4 seconds.

 }

The next exploration is using direct pressure to make sound.

http://www.youtube.com/watch?v=LQ21lXr6egs

Other methods to achieve this would be using a load cell sitting inside a digital weight. 

Then rehooking it to the arduino.

Here is the schematics:

And the arduino + shield:

// Arduino as load cell amplifier

// by Christian Liljedahl 

// christian.liljedahl.dk

// Load cells are linear. So once you have established two data pairs, you can interpolate the rest.

// Step 1: Upload this sketch to your arduino board

// You need two loads of well know weight. In this example A = 10 kg. B = 30 kg

// Put on load A 

// read the analog value showing (this is analogvalA)

// put on load B

// read the analog value B

// Enter you own analog values here

float loadA = 10; // kg

int analogvalA = 200; // analog reading taken with load A on the load cell

float loadB = 30; // kg 

int analogvalB = 600; // analog reading taken with load B on the load cell

// Upload the sketch again, and confirm, that the kilo-reading from the serial output now is correct, using your known loads

float analogValueAverage = 0;

// How often do we do readings?

long time = 0; // 

int timeBetweenReadings = 200; // We want a reading every 200 ms;

void setup() {

  Serial.begin(9600);

}

void loop() {

  int analogValue = analogRead(0);

  // running average - We smooth the readings a little bit

  analogValueAverage = 0.99*analogValueAverage + 0.01*analogValue;

  // Is it time to print? 

  if(millis() > time + timeBetweenReadings){

    float load = analogToLoad(analogValueAverage);

    Serial.print("analogValue: ");Serial.println(analogValueAverage);

    Serial.print("             load: ");Serial.println(load,5);

    time = millis();

  }

}

float analogToLoad(float analogval){

  // using a custom map-function, because the standard arduino map function only uses int

  float load = mapfloat(analogval, analogvalA, analogvalB, loadA, loadB);

  return load;

}

float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)

{

  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;

}

We then finally found the actual drum kit setup for our actuator:

http://spikenzielabs.com/SpikenzieLabs/DrumKitKit.html

So ultimately, we want to combine the weight/distance sensor and drum kit actuator for our piece. We still are looking for the right stage to install this design.