How to leave an LED on

Other Hardware LEDs and Multiplexing
1

Hello guys, I am probably gonna get laughed at here but I need help programming an LED. I got the SUPER basic program on turning an LED on when a pushbutton on my breadboard is pressed but the LED only turns on when I press it, and it goes off when I release it. I need a program where I press and release it once and the LED turns (and remains) on. And when I press and release it again the LED goes off. I am using an Arduino UNO.

const int buttonPin = 2; // the number of the pushbutton pin
const int ledPin = 13; // the number of the LED pin

// variables will change:
int buttonState = 0; // variable for reading the pushbutton status

void setup() {
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT);
}

void loop(){
// read the state of the pushbutton value:
buttonState = digitalRead(buttonPin);

// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, LOW);
}
else {
// turn LED off:
digitalWrite(ledPin, HIGH);
}
}

1 Like
2

The key phrase here is:

I need a program where I press and release

You need to detect when the button goes from "pressed" to "not pressed" and simply flip the state of the LED.

3

Normally the button would be between a pin ( set with a pullup in setup ) and ground,

so if you press the button and digitalRead the pin it will be low,

if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, LOW);

Normally the LED is wired from the pin through a resistor to ground ( as is the built in LED on pin 13 ) so you would
digitalWrite(ledPin, HIGH) to switch it on

// check if the pushbutton is pressed.

// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, LOW);
}
else {
// turn LED off:
digitalWrite(ledPin, HIGH);
}

even when you get the logic sorted out, what you are doing is saying " if the buttons is pressed, light the LED' else ( otherwise ) turn it off.

So you might as well wire the LED to the button :slight_smile:

when you have the logic levels sorted search for toggle.

4

Thanks for the help. Hopefully I can figure this out. Kinda confused cos I'm used to programming 8051s on Silicon Labs.

5

8051, PIC, PowerPC or ARM - the principle is identical.

6

Here's a great video tutorial that will show you just what you need :slight_smile:

Towards middle of it it shows how to switch on/off button so it stays lit or unlit.