Keyboard are great way to let user interacts with your project

In this tutorial,you will be constructing something called a resistor ladder.


This is a way to read a number of switches using the analog input. It’s a helpful

technique if you find yourself short on digital inputs. You’ll hook up a number of

switches that are connected in parallel to analog in 0. Most of these will connect

to power through a resistor. When you press each button, a different voltage level

will pass to the input pin. If you press two buttons at the same time, you’ll get a

unique input based on the relationship between the two resistors in parallel.This can be use for door bell

Wire up your breadboard with power and ground. Connect one end of the piezo to ground.

Connect the other end to pin 8 on your Arduino.

Place your switches on the breadboard as shown in the circuit.

The arrangement of resistors and switches feeding into an

analog input is called a resistor ladder. Connect the first one

directly to power. Connect the second, third and fourth switches

to power through a 220-ohm, 10-kilo ohm and 1-mega ohm resistor,

respectively. Connect all the switches’ outputs together in one

junction. Connect this junction to ground with a 10-kilo ohm

resistor, and also connect it to Analog In 0. Each of these acts as

a voltage divider.


Arduino Uno

Full Size Breadboard – 1

Piezzo buzzer – 1

Switches – 4

220-Ohms resistor — 1

10K ohm resistor – 2

1M ohm resistor – 1

Jumper wires

const byte KEYBOARD  = A0;                  // connect keyboard to A0
const byte PIEZO_PIN =8;                   // connect buzzer to 8
// Global constants
const int NOTES[] = { 262, 294, 330, 349 }; // C, D, E, F frequencies
const unsigned int BAUD_RATE = 9600;        // serial monitor's baud rate
// Global variables
unsigned int key_val;
void setup() {
    Serial.begin(BAUD_RATE);    // start the serial monitor
    pinMode(PIEZO_PIN, OUTPUT); // set PIEZO_PIN as OUTPUT
void loop() {
    // read and print KEYBOARD value
    key_val = analogRead(KEYBOARD);
    Serial.print("key_val = ");
    if (key_val >= 1019) {
        tone(PIEZO_PIN, NOTES[0]); // first switch ~ key C
    } else if ((key_val >= 990) && (key_val <= 1010)) {
        tone(PIEZO_PIN, NOTES[1]); // second switch ~ key D
    } else if ((key_val >= 505) && (key_val <= 515)) {
        tone(PIEZO_PIN, NOTES[2]); // third switch ~ key E
    } else if ((key_val >= 5) && (key_val <= 10)) {
        tone(PIEZO_PIN, NOTES[3]); // fourth switch ~ key F
    } else {
        noTone(PIEZO_PIN);         // no switch ~ no sound


Keyboard schematics
And that’s how you should wire it, standing to the code















We hope you enjoyed the tutorial and this little lesson will purport you into great levels. Enjoy yourself in electronics. For more tutorials and questions, please leave your comments in the comment area. See other components on the site Inspiring ingenuity.


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