Trying to get an output(LED lighting up) based off an input(5V)?

Projects Programming
1

I'm new to Arduino coding and have been looking at a lot of references to help me, and while I have been able to get LEDs to light up from a code in an Arduino Uno, I am unable to get the Arduino to send a signal through an LED when i try to give an input. Ive used analog and digital reads and differing inputs but nothing is working.

//define pins for the red LED
#define RED_LED 6
#define RED_input 5

//initial brightness for red LED
int Routput = 0;

//initialized variables
int i = 0;
int red_val = 0;

void setup() {
  //set up pins to output.
  pinMode(RED_input, INPUT);
  pinMode(RED_LED, OUTPUT);
  
  for(i=0; i<20; i++){
    readInput();
    delay(100);
    displayOutput();
    delay(100);
  }
}


  void readInput(){
    red_val = 0;
    Routput = 0;
    red_val = digitalRead(RED_input);
    
    if(red_val = 0){
      Routput = 0;
    }else{
      Routput = 255;
    }
  }


  void displayOutput(){
    analogWrite(RED_LED, Routput);
    analogWrite(RED_LED, 0);
  }

void loop(){

}

I fiddled a lot with different variables and names and it hasn't worked so I'm open to any suggestions.

2

I notice you have your RED_input pinmode set to INPUT rather than INPUT_PULLUP. How is your input wired?

I would recommend getting rid of the for loop and read your input and display your output in the loop() function.

  void loop() {
    readInput();
    displayOutput();
  }

You attempted to do a comparison "if (red_val = 0)". A comparison is done with == like "if (red_val == 0)".

  void readInput(){
    red_val = 0;
    Routput = 0;
    red_val = digitalRead(RED_input);
   
    if(red_val = 0){
      Routput = 0;
    }else{
      Routput = 255;
    }
  }

If you do turn the LED on here you will turn it off so fast you won't see it.

  void displayOutput(){
    analogWrite(RED_LED, Routput);
    analogWrite(RED_LED, 0);
  }
3

Thank you for the feedback! So currently I have 5V set to A5, and an LED in series with a resistor wired to ground from output 6 all on the Arduino.

All I am trying to do currently is have the LED turn on when i plug in the 5V to A5 and turn off when I remove it, I plan having several inputs to the same number of outputs eventually, but wanted to learn on one I/O first so I deal with one section instead of many.

4

Your displayOutput() should just write Routput. You've already decided in your input routine whether Routput should be ON (255) or OFF (0).

And your input pin is DIGITAL pin 5 NOT A5. Different pins. If you leave it using pinMode INPUT and you expect it to be active when it is high(5V) you need a pull-down resistor (about 10K) between the pin and ground to stop it floating and make sure the pin normally stays low.

Steve