Elapsedtime variable not resetting

Question

I am new to Arduino programming. Let me describe the application I am working on. I am pressing a button for a certain period of time (30 sec). I can not hold it in a pressed position for all the time. I want to avoid accidental transition from button state going from logic HIGH to LOW. I am trying to drive a solenoid valve only at the end of the event.

The algorithm I am using is if once the system detects a HIGH from the sensor it goes in a loop and looks for transition to LOW. It checks if there is continuous LOW for more than 5 sec. If NO then it resets to start checking LOW again. If YES that means end of event and drives the solenoid valve.

The problem I am facing with the code is although the transition to LOW and remaining in LOW is less than 5 sec, the system is sending pulse to drive the solenoid valve. I have incorporated Serial.print() function to observe the value of the sensor input state and elapsed-time. The elapsed-time variable does not reset and keep increasing even though the button state reverts from LOW to HIGH.

I am incorporating part of the code here which is related to the algorithm. I will greatly appreciate if you kindly take a look at the code and the output file and help me detect the bug.

Thanks again! Niloy.

void loop() {
 buttonstate = digitalRead(button); // read the state of the microswitch value: HIGH "on" or LOW "off"
 if (buttonstate == HIGH ){
 countstart = 1;
 while(countstart == 1) {
 buttonstate = digitalRead(button); // read the state of the microswitch value: HIGH "on" or LOW "off"
 if ( ( buttonstate == LOW ) && ( startFlag == 0 ) ) { //start new time sequence
 startFlag = 1;
 startTime = millis();
 }
 if ( ( buttonstate == LOW ) && startFlag == 1 ){
 endTime = millis();
 elapsedTime = endTime - startTime;
 }
 if ( ( buttonstate == HIGH ) && startFlag == 1 ){
 startFlag == 0;
 endTime = startTime =0;
 elapsedTime = endTime - startTime;
 countstart = 0;
 }
 Serial.print(buttonstate);
 Serial.print("\n"); // Print tab space
 Serial.print(elapsedTime);
 Serial.print("\n"); // Print tab space
 if ( elapsedTime >= 5000)
 {
 delay(2000); //2 sec delay
 solenoid->run(FORWARD);
 delay(40);
 solenoid->run(RELEASE);
 delay(500);
 solenoid->run(BACKWARD);
 delay(40);
 solenoid->run(RELEASE);
 countstart = 0;
 endTime = startTime =0;
 elapsedTime = endTime - startTime;
 buttonstate = LOW;
 delay(15000); //wait for 15 sec
 }
 }
 }
}

• Edgar Bonet: Why don't you use a debounce library?
• Niloy Talukder: @Edgar, Can you please elaborate?
• Edgar Bonet: Your problem looks very similar to button bounce, albeit with longer time scales. The are ready made libraries meant to solve this problem reliably.
• Niloy Talukder: @Edgar, thank you so much for explaining. I am happy to learn about debounce. Let me take a look at that. Happy holidays!

Answer 1

startFlag variable never goes to zero because there is a bug in this part of code:

 if ( ( buttonstate == HIGH ) && startFlag == 1 ){
 **startFlag = 0;**
 endTime = startTime =0;
 elapsedTime = endTime - startTime;
 countstart = 0;
 }

• mikeY: 4 parens on second IF, 3 on third, 3 on fourth.
• Niloy Talukder: @leoc7, yes that was the bug which restrained elapsed-time from resetting. I misplaced an extra equal sign. Thanks a lot for pointing it out. The system is working as expected now! Happy holidays a thanks again!
• leoc7: @user141512 you’re welcome!