Hello All, First time poster here, but I do know the frustration of asking a question that has already been answered. I am new to programming, but trying to build projects as they come and figure it out as I go. I have a project where I have 6 contact switches (Level 1-6) that need to indicate to 6 LED's respectively. I also have a 5v buzzer as an audible alarm that one of the switches has closed. I have that much figured out. Where I am getting into a land of frustration, is that I am trying to add a button as an acknowledge switch that would disable the buzzer for a set duration of time (somewhere between 10-15 minutes), while still allowing the other contact switches to indicate open/close with the LED's during that time . I have ran this code with the delay function successfully , until the blocking does not allow the other led's to operate correctly. I believe I understand the concept of the millis() function, but I am having trouble applying it. As I understand it, If a button was pressed to turn on an LED at the currentMillis of, just say,100, and you programmed a wait time of 500, the LED would turn off at 600. With that logic, if the button was pressed again at 2000, with the same wait time the led would turn off at 2500. Currently the LED's and buzzer operate correctly, With the acknowledge button depressed, the buzzer does turn off With the acknowledge button depressed, other LED's will indicate open/closed When the acknowledge button is released, with a contact switched closed, the buzzer turns back on with no delay. Thank you for the help, const int LED1 = 3; const int LED2 = 4; const int LED3 = 5; const int LED4 = 6; const int LED5 = 7; const int LED6 = 8; int Level1 = A0; int Level2 = A1; int Level3 = A2; int Level4 = A3; int Level5 = A4; int Level6 = A5; int Buzzer = 2; int Button = 9; int buttonState = 0; boolean BuzzerState = false; unsigned long startMillis; unsigned long currentMillis; const unsigned long period = 4000; void setup() { pinMode(LED1, OUTPUT); pinMode(LED2, OUTPUT); pinMode(LED3, OUTPUT); pinMode(LED4, OUTPUT); pinMode(LED5, OUTPUT); pinMode(LED6, OUTPUT); pinMode(Level1, INPUT); pinMode(Level2, INPUT); pinMode(Level3, INPUT); pinMode(Level4, INPUT); pinMode(Level5, INPUT); pinMode(Level6, INPUT); pinMode(Button, INPUT); pinMode(Buzzer, OUTPUT); Serial.begin(9600); startMillis = millis(); } void loop() { Serial.println(digitalRead(Button)); buttonState = digitalRead(Button); digitalWrite(Buzzer, LOW); BuzzerState = false; if (digitalRead(Level1) == HIGH) { digitalWrite(LED1, HIGH); BuzzerState = true; } else { digitalWrite(LED1, LOW); } if (digitalRead(Level2) == HIGH) { digitalWrite(LED2, HIGH); BuzzerState = true; } else { digitalWrite(LED2, LOW); } if (digitalRead(Level3) == HIGH) { digitalWrite(LED3, HIGH); BuzzerState = true; } else { digitalWrite(LED3, LOW); } if (digitalRead(Level4) == HIGH) { digitalWrite(LED4, HIGH); BuzzerState = true; } else { digitalWrite(LED4, LOW); } if (digitalRead(Level5) == HIGH) { digitalWrite(LED5, HIGH); BuzzerState = true; } else { digitalWrite(LED5, LOW); } if (digitalRead(Level6) == HIGH) { digitalWrite(LED6, HIGH); BuzzerState = true; } else { digitalWrite(LED6, LOW); } if (BuzzerState == true) { if (digitalRead(Button) == HIGH) { currentMillis = millis(); if (currentMillis - startMillis >= period) { digitalWrite(Buzzer, LOW); startMillis = currentMillis; } } else { digitalWrite(Buzzer, HIGH); } } }

[image] tward1: a button as an acknowledge switch that would disable the buzzer for a set duration Know when the "silence" button is pressed to record millis(). (startSilence = millis();) Calculate fifteen minutes. (fifteenMins = 15 min * 60 sec/min * 1000UL ms/sec) Set a "silence" flag. (silenceBuzzerFlag = 1) If fifteen minutes time is up, clear the "silence" flag. (if millis() > startSilence + fifteenMins)... (silenceBuzzerFlag = 0;) If the buzzer is to be sounded, examine the "silence" flag (if (soundBuzzer == true)) if the silence flag is clear (over 15 mins), sound the buzzer.(if (silenceBuzzerFlag == 0))

[image] xfpd: If fifteen minutes time is up, clear the "silence" flag. (if millis() > startSilence + fifteenMins)... (silenceBuzzerFlag = 0;) This is a bad advice to OP Never calculate time interval in the future, it is not work while millis overflow. The proper way is using substraction of timer points: if (millis() -startSilence > fifteenMins)... (silenceBuzzerFlag = 0;

[image] xfpd: if millis() > startSilence + fifteenMins Better use millis() - startSilence >= fifteenMins as it handles millis overflow correct.

look this over. #undef MyHW #ifdef MyHW const byte PinLeds [] = { 10, 11 }; // { 3, 4, 5, 6, 7, 8 }; const byte PinButs [] = { A2, A3 }; // { A0, A1, A2, A3, A4, A5 }; const byte PinBuz = 13; const byte PinAck = A1; #else const byte PinLeds [] = { 3, 4, 5, 6, 7, 8 }; const byte PinButs [] = { A0, A1, A2, A3, A4, A5 }; const byte PinBuz = 2; const byte PinAck = 9; #endif const int Nbut = sizeof(PinButs); enum { StOff, StActive, StAck }; int stateBuz [Nbut]; bool stateLed [Nbut]; const unsigned long PeriodMsec = 4000; unsigned long ledMsec [Nbut]; unsigned long buzMsec [Nbut]; // potentially turn back on later enum { LedOff = HIGH, LedOn = LOW }; enum { BuzOff = HIGH, BuzOn = LOW }; char s [90]; // ----------------------------------------------------------------------------- void loop () { unsigned long msec = millis (); for (int n = 0; n = 500) { stateLed[n] = false; digitalWrite (PinLeds [n], LedOff); sprintf (s, " led %d timeout", n); Serial.println (s); } // check for led button press if (! stateLed [n] && LOW == digitalRead (PinButs [n])) { ledMsec [n] = msec; digitalWrite (PinLeds [n], LedOn); digitalWrite (PinBuz, BuzOn); stateBuz[n] = StActive; stateLed[n] = true; sprintf (s, " but %d pressed", n); Serial.println (s); } } if (LOW == digitalRead (PinAck)) { for (int n = 0; n < Nbut; n++) { if (stateBuz [n] != StAck) { stateBuz [n] = StAck; // potentiall turned on later? buzMsec [n] = msec; // capture timeStamp - unused digitalWrite (PinBuz, BuzOff); sprintf (s, " ack %d", n); Serial.println (s); } } } } // ----------------------------------------------------------------------------- void setup () { Serial.begin (9600); Serial.println ("ready"); pinMode (PinAck, INPUT_PULLUP); pinMode (PinBuz, OUTPUT); digitalWrite (PinBuz, BuzOff); for (int n = 0; n < Nbut; n++) { pinMode (PinButs [n], INPUT_PULLUP); pinMode (PinLeds [n], OUTPUT); digitalWrite (PinLeds [n], LedOff); } } don't understand what you have in mind for this,but i added variables to capture when the buzzer was activated for each LED [image] tward1: that would disable the buzzer for a set duration of time (somewhere between 10-15 minutes)

Hi @tward1 ! First of all it would be helpful if you post the wiring of your components! The use of pinMode(...,INPUT) with buttons and switches requires the use of external pullup or pulldown resistors to ensure stable potential while a button/switch is open. In every loop of your sketch you set the buzzer pin to LOW and if BuzzerState is true while the Button pin is LOW the buzzer pin is set to HIGH again. See here for the second observation: if (BuzzerState == true) { if (digitalRead(Button) == HIGH) { currentMillis = millis(); if (currentMillis - startMillis >= period) { digitalWrite(Buzzer, LOW); startMillis = currentMillis; } } else { // This happens when BuzzerState == true and Button state is LOW digitalWrite(Buzzer, HIGH); } } If you use passive buzzer this creates a sound depending on timing of loop(), the quicker loop runs the higher the sound will be. Do you have an active buzzer and does it switch ON when the Buzzer pin is set to LOW or to HIGH? Some hints how to improve readability and traceability of a sketch: Reduce complexity to ease testing and debugging Use functions with parameters to avoid repeating the same code Avoid nested if conditions wherever possible Here is a version closely based on your code but less complex (and should work as intended): constexpr byte LED1 = 3; constexpr byte Level1 = A0; constexpr byte Buzzer = 2; constexpr byte Button = 9; int buttonState = 0; boolean BuzzerState = false; unsigned long startMillis; unsigned long currentMillis; unsigned long period = 0; const unsigned long wantedPeriod = 4000; void setup() { pinMode(LED1, OUTPUT); pinMode(Level1, INPUT); pinMode(Button, INPUT); pinMode(Buzzer, OUTPUT); Serial.begin(115200); startMillis = millis(); } void loop() { buttonState = digitalRead(Button); BuzzerState = false; if (digitalRead(Level1) == HIGH) { digitalWrite(LED1, HIGH); BuzzerState = true; } else { digitalWrite(LED1, LOW); } if (digitalRead(Button) == HIGH) { startMillis = millis(); // This makes sure that the delay will become valid // after the first button press! period = wantedPeriod; } if (millis() - startMillis < period) { BuzzerState = false; } if (BuzzerState == true) { digitalWrite(Buzzer, HIGH); } else { digitalWrite(Buzzer, LOW); } } Feel free to test it on Wokwi: https://wokwi.com/projects/464988089266131969 I separated checking the Button pin evaluating the "silence period" and handling the buzzer If this works as intended there are only a few steps required to add more level switches and leds by using arrays and for-loops ... Good luck! ec2021

I understand your corrections... but... [image] b707: This is a bad advice to OP It is not bad advice, it is conveying a concept. You (in your young life) learned to add before you learned to subtract. "then + 15" is the same point in time as "now - then > 15"... ... and teaching practices addition before subtraction because one is the easier concept. [image] b707: Never Countdown clocks exist. [image] Rintin: handles millis overflow A great concept to teach after watching a working example walk before it runs. I didn't code-dump this time, choosing pseudocode, because this isn't a person wanting "the codes, now," and shows aptitude. Thanks for your understanding.

[image] xfpd: It is not bad advice, it is conveying a concept. the concept is "duration" so you do have to subtract the start time from the current time to get the duration and compare it to see if you waited long enough, more than the threshold. So actually millis() - startSilence > fifteenMins is the way to think about it...

[image] xfpd: Thanks for your understanding. Do you try to put a brave face on it? Given this post, it looks like you need to relearn unsigned arithmetic...

[image] b707: try to put a brave face Mentioning countdown clocks to future date/time is putting on a brave face?

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J-M-L May 25, 2026, 6:06am 5

you might benefit from studying state machines. Here is a small introduction to the topic: Yet another Finite State Machine introduction

Otherwise there are many discussions about managing time and non blocking code - for extra information and examples look at

Using millis() for timing. A beginners guide
Several things at the same time
Flashing multiple LEDs at the same time

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