New to programming. Help with millis()

Using Arduino Programming Questions
1

I am using a photoelectric sensor to measure the distance between two objects that it passes by. The sensor is going by the objects at a constant speed, so I am trying to determine the time between the objects by using millis(). I can then find the distance from the time and speed data. I am having problems when the millis gets to around 10,000 my board begins to slow and starts to freeze up. How do I fix this problem? I am very new to programming so any help is appreciated! My program is attached.

Thanks!

counting_plants.ino (318 Bytes)

2

I'd love to help, but I can't see your code.
Please post it, between code tags.

3

Sorry. Here is my code.

int inputPin = 2; //digital 2
int counter = 0;
int state;
int laststate = HIGH;
unsigned long time;

void setup(){
  Serial.begin(9600);
  pinMode(inputPin, INPUT);
}

void loop()
{
  int state = digitalRead(inputPin);
  if ( state != laststate) 
  {
     laststate = state;
     counter=counter+1;
     Serial.println(counter);
     time = millis();
  //prints time since program started
     Serial.println(time);
  }
}
4

And what is connected to pin 2?
Aren't you more interested in the differences of time, rather than absolute times?

5

This sketch is not what you want, but it should give you some ideas:

unsigned long currentMillis;
unsigned long pin13Millis;
unsigned long StartMillis;
unsigned long time;

boolean timingMode = false;  //Used to enable/disable parts of the sketch

const byte startSwitch = 2; //pushed = LOW
const byte stopSwitch  = 3; //pushed = LOW

//**********************************************************************

void setup()
{
  Serial.begin(9600);

  pinMode(13,OUTPUT);
  pinMode(startSwitch, INPUT_PULLUP); //pushed = LOW
  pinMode(stopSwitch,  INPUT_PULLUP); //pushed = LOW

} //  >>>>>>>>>>>>>> E N D  O F  s e t u p ( ) <<<<<<<<<<<<<<<<<

void loop()
{
  //Leave this at te top of the sketch
  currentMillis = millis();

  //***********************************
  if(timingMode == false && digitalRead(startSwitch) == LOW)
  {
    StartMillis = millis();
    timingMode = true;
  }
  if(timingMode == true && digitalRead(stopSwitch) == LOW)
  {
    time = millis() - StartMillis;
    Serial.print("Time from Start to Stop = ");
    Serial.println(time);
    timingMode = false;
  }

  //***********************************
  //Some code to check for blocking
  //toggle pin 13 every 200mS
  //has 200ms or more gone by?
  if (currentMillis - pin13Millis >= 200UL)
  {
    //code here runs every 200ms
    //get ready for next iteration
    pin13Millis = pin13Millis + 200UL;
    //toggle pin 13
    digitalWrite(13,!digitalRead(13));
  }

  //*********************************
  //put other non-blocking stuff here
  //*********************************

} //  >>>>>>>>>>>>>> E N D  O F  l o o p ( ) <<<<<<<<<<<<<<<<<
6

The photoelctric sensor is connected to pin 2. Yeah I am more interested in differences than time rather than absolute time. Is there a different way to do that?

7

gaclaassen:
The photoelctric sensor is connected to pin 2. Yeah I am more interested in differences than time rather than absolute time. Is there a different way to do that?

Pretty simple, really. Subtract one time from another. That's really it.