Published April 16, 2021 © GPL3+

Laser harp-like sound making instrument prototype

Make a laser harp with a phototransistor and a laser module, that play a random note.

BeginnerWork in progress624

Laser harp-like sound making instrument prototype

Things used in this project

Hardware components

Arduino UNO

Laser Module KY-008

Vishay phototransistor BPW77NB

LM386 amplification module

speaker 1W 8 ohms

Rotary potentiometer (generic)

1k potentiometer

Resistor 220 ohm

Breadboard (generic)

Jumper wires (generic)

both male-male and male-female

9V battery (generic)

9V to Barrel Jack Connector

USB-A to Micro-USB Cable

used with smarphone power supply to power the laser module separately

Story

This project is dedicated to make a kind of laser harp with an arduino board, a laser module, a phototransistor, and a speaker.

I'm more and more interested in sound generation using hardware and coding. This is part of my investigations.

In this first version, the laser module points toward the phototransistor, allowing to detect any cut of this light "chord". Each time such an event appears, a random frequency sound with a random duration is generated via arduino tone( ) function. I used a 8 Ohm speaker through a LM386 amplification module to play the sound.

The phototransistor outputs a current intensity growing with the amount of received light. Using a resistor, we obtain an output voltage growing with the amount of received light that can be read by an arduino board.

I choosed to capture phototransistor voltage output signal as analog input of my arduino board rather than digital input. There is two reasons for this:

to anticipate further evolutions where I could take advantage of the voltage level in sound generation

to ensure that voltage level doesn't exceed 5 V I kept the maximum level around 3-4 V.

I dedicated the first 5 seconds of execution to calibration and get the maximum level of input signal, corresponding to phototransistor illuminated by the laser. Then, each time the level of input signal decrease too much, the tone( ) function is called.

Next step is to add chords and use more interesting sound pieces.

Code

Laser Harp Version 1

// Laser Harp Project V1.0 
// Olivier E
// 12/04/2021

int maxBrightness = 0;    //calibration of max detected brightness

void setup() {
  //Serial.begin(9600);   //uncomment to show analog input values on serial m.
  pinMode(9,OUTPUT);      //speaker

  //calibration during first 5000 ms
  long startTime = millis(); 
  while (millis()-startTime < 5000) {
     int brightness = analogRead(A0);
     if (brightness > maxBrightness) maxBrightness = brightness;
  }
  //Serial.print("maxBrightness = "); //uncomment to show analog input values
  //Serial.println(maxBrightness); //uncomment to show analog input values
  tone(9,110,100);        //make a sound when calibration done
  delay(100);
  noTone(9);     
}

void loop() {
  int brightness = analogRead(A0);      //read phototransistor output voltage
  if (brightness < maxBrightness*0.1) { //if low brightness: asked to play!
    //Serial.println(brightness); //uncomment to show analog input values     
    tone(9,random(50,600),random(100,2000)); //play random note
    delay(250);
    noTone(9);               
  }
  delay(10);
}

Laser harp-like sound making instrument prototype

Things used in this project

Hardware components

Story

Schematics

Laser Harp Schematic

Code

Laser Harp Version 1

Credits

oliviere

Comments

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Laser harp-like sound making instrument prototype

Laser harp-like sound making instrument prototype

Things used in this project

Hardware components

Story

Schematics

Laser Harp Schematic

Code

Laser Harp Version 1

Credits

oliviere

Comments

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