If - else statement in Arduino

Question

I'm starting to learn how to use Arduino and I tried to make this code, which is just a simple if else statement; what I want to make is when the input is LOW, LED 1 is HIGH and LEDs 2,3 are LOW, and when the input is HIGH, the LEDs 2,3 are HIGH and LED 1 is LOW. I wrote this code but when I put the switch in LOW, instead having just like what I intended, all the outputs are HIGH.

I try changing the output and I checked all the wiring to the LEDs so my mistake is in the code.

Could you guys tell me what's wrong with the code?

int switchstate = 0;
void setup() {
  pinMode (13,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(3,INPUT);
}

void loop() {
  switchstate = digitalRead(3);
  if (switchstate == LOW) {
    digitalWrite(11,HIGH);
    digitalWrite(12,LOW);
    digitalWrite(13,LOW);
  } else {
    digitalWrite(11,LOW);
    digitalWrite(12,HIGH);
    digitalWrite(13,HIGH);
  }
}

Answer 1

Your code doesn't seem to be the problem. Contrary to what you are saying I think your problem is most definitely in your hardware setup.

Most likely, your digitalRead doesn't register a HIGH input, so it doesn't get 5V. Instead of digitalRead, go for analogRead(A0). So change your circuit and attach it to pin A0.

Use serial.println(switchstate) to print the results to the serial monitor and then decide what your top value (HIGH) and bottom value (LOW) for detection will be. Perhaps include a pull down resistor as well on the A0 pin.

Answer 2

To debug this, as Len has suggested I would recommend putting in some Serial.println("Debug info") commands into your code. This will confirm that you are programming the Arduino as you expect, and that the Arduino is running.

To do this simply include a Serial.begin(9600) command in your setup block, and then a Serial.println("Some text") wherever you want to check if you are reaching a certain part of the code. You can then read these messages via the serial monitor (which you can get to from Tools->Serial Monitor in the Arduino IDE).

For hardware debugging if you have a multi-meter available I would check that you are getting 0V/5V on digital pin 3 when you expect (i.e. when you are / are not pressing the button). Also, to check your LEDs are working, and connected to the output pins you think they are, write a script which just scrolls through them with a short delay (See the Blink example under File->Examples->01.Basics->Blink for an example of how to do that).