Arduino code to control 4 led's from 4 buttons

Question

This is my very first arduino sketch and it's causing me a bit of a headache. Sounds so simple really all I want the sketch to do is digitalread from one of 4 digital input pins and then digitalwrite to one of 4 output pins in essence. So that when button 1 is pressed LED 1 lights up, button 2 pressed led 2 lights up and so on. I've added a serial write so I could check that the buttons are actually working when pressed.

The code I've written:

const int buttonPin1 = 7;     // number of pushbutton 1 pin
int buttonState1 = LOW;       // set the default variable value for pushbutton1 status
const int ledPin1 =  6;       // number of the LED 1 pin
const int buttonPin2 = 8;     // number of pushbutton 2 pin
int buttonState2 = LOW;       // set the default variable value for pushbutton2 status
const int ledPin2 =  9;       // number of the LED 2 pin
const int buttonPin3 = 4;     // number of pushbutton 3 pin
int buttonState3 = LOW;       // set the default variable value for pushbutton3 status
const int ledPin3 =  5;       // number of the LED 3 pin
const int buttonPin4 = 2;     // number of pushbutton 4 pin
int buttonState4 = LOW;       // set the default variable value for pushbutton4 status
const int ledPin4 =  3;       // number of the LED 4 pin


void setup() {                  // Set Pins to Outputs Or Inputs 
  pinMode(buttonPin1, INPUT);   // initialize the pushbutton pins as an inputs:
  pinMode(ledPin1, OUTPUT);     // initialize the LED pins as an outputs:
  pinMode(buttonPin2, INPUT);   // initialize the pushbutton pins as an inputs:
  pinMode(ledPin2, OUTPUT);     // initialize the LED pins as an outputs:
  pinMode(buttonPin3, INPUT);   // initialize the pushbutton pins as an inputs:
  pinMode(ledPin3, OUTPUT);     // initialize the LED pins as an outputs:
  pinMode(buttonPin4, INPUT);   // initialize the pushbutton pins as an inputs:
  pinMode(ledPin4, OUTPUT);     // initialize the LED pins as an outputs:
  Serial.begin(9600);           // initialize serial communication at 9600 baud
}

void loop() {                  

buttonState1 = digitalRead(buttonPin1);  // read current states of the pushbutton value:
  buttonState2 = digitalRead(buttonPin2);  // read current states of the pushbutton value:
  buttonState3 = digitalRead(buttonPin3);  // read current states of the pushbutton value:
  buttonState4 = digitalRead(buttonPin4);  // read current states of the pushbutton value:

// check if the pushbutton is pressed buttonState# == HIGH/LOW
  // if pressed change buttonState == HIGH to turn on ledPin# 
  // else if buttonState == LOW then digitalWrite(ledPin#, LOW) Keeps Led off.

if (buttonState1 == HIGH) {    //check buttonState
digitalWrite(ledPin1, HIGH);  //if HIGH turn LED on:
} else {
digitalWrite(ledPin1, LOW);   // turn LED off:
}
Serial.println(buttonState1); //Print buttonState to serial
if (buttonState2 == HIGH) {   //check buttonState
digitalWrite(ledPin2, HIGH);  //if HIGH turn LED on:
} else {
digitalWrite(ledPin2, LOW);   // turn LED off:
delay(10);
}
Serial.println(buttonState2); //Print buttonState to serial
if (buttonState3 == HIGH) {   //check buttonState
digitalWrite(ledPin3, HIGH);  //if HIGH turn LED on:
} else {
digitalWrite(ledPin3, LOW);   // turn LED off:
delay(10);
Serial.println(buttonState3); //Print buttonState to serial
}
if (buttonState4 == HIGH) {   //check buttonState
digitalWrite(ledPin4, HIGH);  //if HIGH turn LED on:
} else {
digitalWrite(ledPin4, LOW);   // turn LED off:
delay(10);
Serial.println(buttonState4); //Print buttonState to serial
}

The Leds all have a common GND and the buttons all have a common GND. Buttons are connected to +5V & Input pin# so one terminal has got two wires, Led's are connected to digital output pins then resistor and straight to GND. What happens is that ALL of the LED's come on when any one of the 4 buttons in pressed.

I've attempted to edit some of the code in the example sketches to get this to work.

Can anyone suggest anything that I'm doing wrong? Or ammend the code sp that I can see where I'm going wrong.

Answer 1

It is likely you have connected the switches incorrectly. Normally, people use single poll single throw (SPST) switches connected to 5 volts and the input pin of the Arduino. This will pull the input pin to 5 volts when the switch is closed. Then, to pull the input pin to ground when the switch is open, people add a large resistor between ground and the same processor pin.

Almost any large resistor will work here. Consider using 10K ohms (10,000 ohms) or there abouts.

Of course, if you are using a 3 volt Arduino, do not connect the switch to a 5 volt source. Instead connect it to a 3 volt source.

Alternatively, a pull up resistor inside the processor, if available, can be activated. Look at this arduino.cc web page. There this sample code shows how to activate the processor's pull up on pin number 2:

pinMode(2,INPUT_PULLUP); 

Because not all processors have a "pull up" feature on all input pins & because the range of internal to the processor pull up resistances can vary (for example 50,000 ohms to 150,000 ohms), it may be more useful and universal to use an external pull up resistor.

Answer 2

Get rid of the external resistors, use the internal pullup resistor.

In setup():

pinMode (pinX, INPUT_PULLUP);

Wire the button between input pin pinX and Gnd, then test for a LOW to see if the button is pressed in loop():

if (digitalRead (pinX) == LOW){ // button is pressed

// do something

}

else { // button is not pressed

// do something else

}

Answer 3

I would suggest taking the resistor/s off the switches, so the button connects to digital inputs to the 3v/5v line. Then use 470ohm resistors for the leds(to limit the current) on the digital outputs.