In this tutorial, we simulate a theremin musical instrument’s action: we change the sound’s height in a non-contact way, closing the photoresistor more or less from the light.
The original instrument was invented back in 1920 by Leon Theremin, a man with a difficult and intense fate. And now we have the opportunity to reproduce the invention with the help of simple electronics.
1x piezo squeaker (a capacitor that sounds when charging and discharging)
6x male wires
1x 10 kOhm resistor
The Scheme on the Layout
In this diagram, we use a new rated resistor, look at the marking table to find a 10 kOhm resistor, or use a multimeter.
The polarity of the photoresistor, like a conventional resistor, does not play a role. It can be installed on either side of the photoresistor.
In this exercise, we collect a simple version of the piezodynamic circuitry.
The piezo’s polarity does not matter: you can connect any of its legs to the ground, any of them to the microcontroller port.
On Arduino Uno, the use of the tone function prevents PWM usage on ports 3 and 11. However, you can connect it to one of the following ports.
Remember how the voltage divider is arranged: the photoresistor is placed in position R2 – between analog input and ground. This is how we get a resistive photosensor.
// give names for piezo pins and photo -
// Light Dependent Resistor or simply LDR)
#define BUZZER_PIN 3
#define LDR_PIN A0
// pin with a piezo - exit...
// ...and all other pins are inputs initially,
// every time the microcontroller is powered up or reset.
// Therefore, we don't really need to
// configure LDR_PIN to enter the login mode: it is already there
int val, frequency;
// read the illumination level in the same way as for
// potentiometer: as a value from 0 to 1023.
val = analogRead(LDR_PIN);
// calculate the frequency of the squeaker in hertz (note),
// using the projection function (English map). It displays
// value from one range to another, building the proportion.
// In our case [0; 1023] -> [3500; 4500]. This is how we will get
// frequency from 3.5 to 4.5 kHz.
frequency = map(val, 0, 1023, 3500, 4500);
// make the pin with the squeaker "vibrate," i.e., sound
// (English tone) at a given frequency of 20 milliseconds.
// At next loop passes, the tone will be called again and again,
// and in fact, we will hear a continuous sound with a tonality that
// depends on the amount of light hitting the photoresistor
tone(BUZZER_PIN, frequency, 20);
The map(value, fromLow, fromHigh, toLow, toHigh) function returns an integer value from the [toLow, toHigh] interval, which is a proportional display of the value content from the [fromLow, fromHigh] interval.
The map’s upper limits do not have to be larger than the lower ones and may be negative. For example, you can display the value from the interval [1, 10] in the interval [10,-5].
If a fractional value is formed in calculating the map value, it will be discarded, not rounded.
The map function won’t discard values outside the specified ranges and scale them by the specified rule.
If you need to limit a lot of acceptable values, use the constrain(value, from, to) function, which will return them:
– value, if this value falls into the range [from, to].
– from, if the value is less than it
– to, if the value is greater than it
The tone(pin, frequency, duration) function causes the piezo squeaker connected to the pin port to produce a sound with frequency hertz over a duration of milliseconds.
The duration parameter is optional. If it is not transmitted, the sound will turn on forever. To turn it off, you will need the noTone(pin) function. It needs to pass the port number with the squeaker to be turned off.
Only one squeaker can be operated at a time. If you call tone for another port during the sound, nothing will happen.
Invoking tone for an already sounding port will update the frequency and duration of the sound.
Useful Video: How to Build an Arduino Theremin