Issue reading RPM of fan

Projects Programming
1 
HI,

im trying to use a IR Led and receiver to count the rpms of a fan, i have it all wired up but im getting no information through to the infrared photo transistor, im using an elegoo uno R3
ill put my code below






[code]
int photo_i_p = 2;
int loop_no = 0;
int time_sec = 0;
int input_value = 0; // digital input signal either on / off 0 or 1
int currentState = 0;
int previousState = 0; // set up input and count variables, -32768 to 32767
float pot_i_p ;
float voltScaled ;
float period = 2000; // using millis() is mS
float physCount = 0;
float blades_sec ;
float set_rev_sec ;
float fb_rev_sec ; // feed back photo_i_p optic sense
float elapse ;
float start ;
void setup()
{
  pinMode(photo_i_p, INPUT) ; // declare i/p could avoid this set as default
  pinMode(10, OUTPUT);

  Serial.begin(9600) ;
  delay(1000) ; // delay to start
  Serial.println("");
  Serial.println(" Oct 2019 ");
  Serial.println(" ");
  Serial.println(" ");
  Serial.println(" set feed back");
  Serial.println(" sec rev/s rev/s ");
  start = millis(); // mS since program started

} // setup
void loop()
{
  // section 1/ potentiometer input leading to PWM output

  pot_i_p = analogRead(A1); // read volts pin A1 = physical pin #15 (0-5.0 volts)
  voltScaled = (pot_i_p / 665) * 250; // scaled for 0-1023 from 0-5.0 volt
  set_rev_sec = voltScaled / 3.5 + 16.07;
  analogWrite(10, voltScaled);

  // section 2/ measure rotational speed


  // a/ single pulse debounce & count, increments as a result of single cycle input
  input_value = digitalRead(photo_i_p);
  if (input_value == HIGH)
  {
    currentState = 1;
  }
  else
  {
    currentState = 0;
  }

  if (currentState != previousState)
  {
    if (currentState == 1)
    {
      physCount ++;
    }
  }
  previousState = currentState;

  // b/ n-second sampling period, rpm calculation
  elapse = millis() - start ; // elapse = millis(current) – millis(start of programme) mS
  if (elapse > period) // period set in declarations above
  {
    blades_sec = physCount * 1000 / period ; // use thousands as no decimal
    fb_rev_sec = blades_sec / 7.0 ; // true feedback speed from 7 fan
    // blades
    loop_no ++ ; time_sec = loop_no * period / 1000;

    // start = millis(); // reset timer
    physCount = 0; //physical counter reset for new sample period
    displayResult(); // call output routine
  }
} // loop return

// section 3/ display on monitor
void displayResult()
{
  Serial.print(" ");
  Serial.print(time_sec);
  Serial.print(" ");
  Serial.print(set_rev_sec); // from potentiometer scaled
  Serial.print(" ");
  Serial.print(fb_rev_sec);// from photo-diode
  Serial.println(" ");
} // display



thanking you
2

Also putting a schematic or at least a labeled block diagram would be of great help.

Have you verified the IR LED is working?

1 Like
3

Read the forum guidelines to see how to properly post code and some good information on making a good post.
Use the IDE autoformat tool (ctrl-t or Tools, Auto format) before posting code in code tags.

Please go back and fix your original post.

Photos that clearly show your wiring can also be very helpful.

1 Like
4

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