Peak counting in serial Arduino

Question

I want to count peak of photocell data with serial communication in Arduino.

Here is the question. My problem is when I count one of the peaks it continues the counting and doesn't stop counting. My project is count Michelson Morley fringes with a photocell and Arduino.

If somebody can help me with the coding part I would appreciate it.

Here is the code that I used:

int count=0;
int val;
int data;

void setup() {
  Serial.begin(115200);
}

void loop() {
  data=analogRead(A0);
  val=map(data,0,1023,1000,0);
  if(val>700) {
   count++;
  }
  Serial.println(count);
  delay(100);
}

This picture shows what I am trying to achieve:

Example Michelson Morley fringes:

Answer 1

keep in mind that since you used

delay(100)

your 'loop' code runs in 10HZ (10 times a second) So, every time you are lighting on your sensor, if its for longer than 1/10 of a second, you are likely going through several instances of 'loop', in which the condition

(val>700)

is satisfied.

If you know that your peaks are going to take several loops, and only want to count each peak once- a simple way would be to make sure you dropped from the previous peak before incrementing the counter. you can achieve that with something like:

int count=0;
int val;
int data;
bool inPeak = false;

void setup() {
  Serial.begin(115200);
}

void loop() {
  data=analogRead(A0);
  val=map(data,0,1023,1000,0);
  if(val>700) {
     if (!inPeak)
     {
        count ++;
        inPeak = true;    
     }  
  }
  else 
  {
      inPeak = false;
  }

  Serial.println(count);
  delay(100);
}