Electronics Club, IIT Madras

Difficulty Level: Easy

Concept

We will duplicate a similar sound as that of a Theremin, digitally using a buzzer controlled by Pulse Width Modulations and a Light Dependent Resistor (LDR), for reading the hand movements over it which will be considered as inputs to control the sound coming out of the buzzer.

Prerequisites

Arduino IDE

Components

Electronics Club Custom Development Board (CDB)
Light-Dependent Resistor (LDR)
Buzzer
Resistor - 10k
Jumpers
Breadboard

Schematic

Buzzer Pin 1 --> 4 of CDB
Buzzer Pin 2 --> GND
LDR Leg 1 --> 10k Resistor --> 5 of CDB
LDR Leg 1 --> VCC
LDR Leg 2 --> GND

(Note: Leg 1 and Leg 2 are named arbitrarily)

Code

int photopin = 5; // Pin where the photo resistor is connected to
int photValue; // The analog reading from the photoresistor
int buzzerPin = 4; // Connect Buzzer to Pin 4
long buzzerFreq; // The frequency to buzz the buzzer
// You can experiment with these values:
long buzzMAX = 2500; // Maximum frequency for the buzzer
long photoMAX = 1023; // Maximum value for the photoresistor
void setup() {
    pinMode(buzzerPin, OUTPUT); // set a pin for buzzer output
}
void loop() {
    // read the values of the photoresistor
    photValue = analogRead(photopin); // Values 0-1023
    // normalize the readings of a photoresistor to that of the buzzer and photoresistor
    buzzerFreq = (photValue * buzzMAX) / photoMAX;
    buzz(buzzerPin, buzzerFreq, 10);
}
void buzz(int targetPin, long frequency, long length) {
    long delayValue = 1000000/frequency/2;
    long numCycles = frequency * length/ 1000;
    for (long i=0; i < numCycles; i++){
        digitalWrite(targetPin,HIGH);
        delayMicroseconds(delayValue);
        digitalWrite(targetPin,LOW);
        delayMicroseconds(delayValue);
    }
}

Follow-up Problem Statement

Can you use the capacitive touch pins and Aluminium foil to change the frequency of the buzzer as you slide your finger over the foil??

References

Simple Theremin with ESP32

Theremin using Light-Dependent Resistor