I'm having a problem with this Arduino code.

So whenever I press the "button" in port 11, which is supposed to either reset the burglar alarm or stop it, the whole program stops (the void loop() function stops). The wiring is most likely not the problem, because I've tested it on multiple occasions with different codes. The button, too, works perfectly well as a button with different codes.

In the Serial port, it keeps printing "78005", which it should before the button is pressed, until when I press the button, at which it randomly breaks off printing (resulting in 78, 780, 7, 7800, or 78005 as the last line printed).

Can anyone explain why the arduino will behave in this way?

Thank you so much.

int button = 11;
int receiver = 12;
int buzzer = 13;
int frequency = 1000; // frequency of buzzer

bool keepAlerting = false; // toggles Alarm regardless of detected charge
int receiverVal = LOW; // value from port 12
int buttonVal = LOW; // value from button
int oldButtonVal = LOW;

int setupTime = 5000; // time the user has to close the box after toggling alarm

bool alarmOn;
int buttonMode = 0;
const int resetButton = 1;
const int stopButton = 2;
int buttonModeDecider = 0;

void setup() {
  // put your setup code here, to run once:
  pinMode(buzzer, OUTPUT);
  pinMode(receiver, INPUT);
  pinMode(button, INPUT);


void loop() {  
  // put your main code here, to run repeatedly:
  receiverVal = digitalRead(receiver);
  buttonVal = digitalRead(button);

  if(alarmOn == true){


  if(buttonVal == HIGH && oldButtonVal == LOW){
    buttonModeDecider = 1 - buttonModeDecider;

    if(buttonModeDecider == 1){
      buttonMode = resetButton;
    } else {
      buttonMode = stopButton;

    switch(buttonMode) {
      case resetButton:
        alarmOn = true;
      case stopButton:
        alarmOn = false;
  oldButtonVal = buttonVal;

void setAlarm() {
  if(receiverVal == LOW || keepAlerting == true) {
    tone(buzzer, frequency);
    keepAlerting = true;
  • 1
    How is the button wired?
    – Majenko
    Commented Jan 14, 2017 at 15:07
  • You claim "the void loop() function stops", then you say "or 78005 as the last line printed". Can you really confirm this is the last line printed ONCE then nothing, or the last line reprinted forever, which would be much different than "the loop() stops" then.
    – jfpoilpret
    Commented Jan 14, 2017 at 16:56
  • 1
    For your inputs you use INPUT mode not INPUT_PULLUP, this means you added yourself a pullup or pulldown resistor "between" your button and the input pin, can you confirm this wiring? And then the opposite button side is connected to GND (if you use a pullup resistor) or +5V (if you use a pulldown resistor). A bad wiring here could make your program fail unexpectedly.
    – jfpoilpret
    Commented Jan 14, 2017 at 16:58
  • Add debouncing for your mechanical button. Your probably false detecting button press and release caused by bouncing. arduino.cc/en/Tutorial/Debounce Commented Jan 14, 2017 at 19:28
  • jfpoilpret: Yes, I can confirm that the last line printed is definitely the last line. It is not reprinted. Also, I can confirm the 10 ohm resister exists between my button and the input pin, and that the opposite button side is connected to GND. The wiring probably isn't a problem because if I use a different code with the same wiring to do other similar behaviors, it still works.
    – Daniel
    Commented Jan 16, 2017 at 14:13

2 Answers 2


Arduino stops loop randomly whenever a button is pressed

your button is shorting the supply?


A 10 Ohm resistor when switched to ground can cause the power supply to drop below the operating voltage of the Arduino. If you mean to have a pulldown resistor to ground use a 10K value instead.

Note that a 10 Ohm resistor across a 5V supply draws 0.5 Amps of current.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.