Why isn't this pushbutton program working?

Question

Here is my circuit:

and here is my code:

int LED = 13;
int BTN = 7;

void setup() {
pinMode(LED,OUTPUT);
pinMode(BTN,INPUT);
}
void loop() {
if(digitalRead(BTN) == HIGH) {
digitalWrite(LED,LOW);
}
else{
digitalWrite(LED,HIGH);
}
}

When I press the button, the LED is supposed to go low, but it doesn't. What is wrong with this circuit/code?

Answer 1

Your code and schematic both seem to be wrong.

Try out this schematic:

And then code:

const int kPinLed = 6; // LED - Pin 6
const int kPinBtn = 7; // Push Button - Pin 7

void setup()
{
  pinMode(kPinLed, OUTPUT);       // LED as OUTPUT
  pinMode(kPinBtn, INPUT_PULLUP); // Push Button as INPUT wiith pullup
}

void loop()
{
  if(digitalRead(kPinBtn) == LOW)  // When Push Button is pressed
  {
    digitalWrite(kPinLed, HIGH);   // LED ON
  }
  else digitalWrite(kPinLed, LOW); // LED OFF
}

Answer 2

Paul is correct. Your button is wired wrong. The GPIO pin should be connected to the same side as the resistor. Also the button needs rotating through 90 degrees.

Also check how your LED is wired up. At the moment it looks like it's set up so that the GPIO sinks the current (LOW turns the LED on) yet the LED looks like it's connected the wrong way around for that.

In fact, I can't actually find anything right about that circuit...

Answer 3

The Input port is going to always be at Gnd, because you have connected it to ground. Sorry to put it in such basic terms but this is the way I understand it. It needs to be more difficult for the output of the button to get to ground than to get to the BTN pin of your UNO. So put a bigger resistor (1K-10K) in place of your yellow wire between the button and ground.

And your LED is the wrong way round in the diagram.

(And Majenko is a quicker typist than me! :) )

Answer 4

In addition to the answers from Matt and Majenko, you code uses the wrong pin for the LED.

You have int LED = 13; whereas your LED is connected to pin 6.

NB: Pin 13 is connected to an LED soldered on to the Arduino board - as seen in the image below.