100+ Switches in a single pin of Arduino

Introduction

Did you run out of input pins? Don’t worry, here is a solution without any shift registers. In this video, we are going to learn about connecting more than 100 switches to a single pin of Arduino.

Working Theory

Take a look at the circuit diagram first, otherwise, you won’t be able to understand what I’m saying. Whenever I press a switch the circuit will be completed through a different number of resistors,

That means the voltage reaching the analog pin A1 will be different for each switch, so we will use analogRead() function to read the values from the pin A1 and then we use an if else if condition to perform different operations for each switch.

Components	DIY Usthad	Amazon.com	Banggood	AliExpress	Utsource
Arduino Nano
Push Button

 Let’s Build

• First, connect five push switches to a breadboard.
• Of course, you can connect a maximum of 1023 switches theoretically to an 8-bit microcontroller like Arduino. 
• Then interconnect resistors in between the push switches as shown in the diagram.
• Connect the other end of all the switches to 5v of Arduino, as you can see here I have connected them in such a way that one end is connected to the blue line of the beard board which is connected to the 5v.
• Then from the end of the final switch connect a wire to analog pin A1 of Arduino.
• Then connect a resistor across A1 and GND of Arduino, which is for pull-down, That is to keep the value to zero when no switch is pressed.

Connect some LEDs

Let’s connect some LEDs to check the functioning of our circuit.

• Connect the LEDs as shown in the circuit using some wires.
• Connect all the positive terminal all LEDs to the 5v.
• Connect the negative terminal of each LED to the digital pin D12 to D8 of Arduino, respectively.
• Practically we have to connect the LEDs through resistors for a good life. 

Coding

Take a look at the program. All the lines are commented properly.  

#define sw A1 //name for analog pin A1
#define led1 12
#define led2 11
#define led3 10
#define led4 9
#define led5 8

void setup() 
{
  Serial.begin(9600);
  pinMode(led1,OUTPUT); digitalWrite(led1,HIGH); //setting led1 pin HIGH ie LED will be off according to our circuit
  pinMode(led2, OUTPUT); digitalWrite(led2,HIGH); //setting led2 pin HIGH ie LED will be off according to our circuit
  pinMode(led3, OUTPUT); digitalWrite(led3,HIGH); //setting led3 pin HIGH ie LED will be off according to our circuit
  pinMode(led4, OUTPUT); digitalWrite(led4,HIGH); //setting led4 pin HIGH ie LED will be off according to our circuit
  pinMode(led5, OUTPUT); digitalWrite(led5,HIGH); //setting led5 pin HIGH ie LED will be off according to our circuit

}

void loop() 
{
  Serial.println(analogRead(sw)); // reading and printing the values from analog pin A1

  if(analogRead(sw) >197 && analogRead(sw) <207 )
  digitalWrite(led1,LOW);// LED will turn ON
  else if(analogRead(sw) >248 && analogRead(sw) <258)
  digitalWrite(led2,LOW);// LED2 will turn ON
  else if(analogRead(sw) >333 && analogRead(sw) <343)
  digitalWrite(led3,LOW);// LED3 will turn ON
  else if(analogRead(sw) >509 && analogRead(sw) <514)
  digitalWrite(led4,LOW);// LED2 will turn ON
  else if(analogRead(sw) >1015 && analogRead(sw) <1023)
  digitalWrite(led5,LOW);// LED2 will turn ON
  

}

Applications

• Keypad
• Full-sized keyboard for Arduino.
• Custom mini keyboard for your Raspberry Pi tablet, etc.

Drawbacks

• Multiple switches won’t work in a single instant.

If you can think of another application post it in the comments. Thanks.

Video

To buy electronic components order from UTSOURCE