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Tony Scarpelli
Published © GPL3+

Arduino IR Lathe Tachometer

Build a tachometer for your metal lathe using an Arduino Nano, a two line LCD display, and an IR sensor.

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Arduino IR Lathe Tachometer

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Schematics

Arduino Lathe Tachometer

Code

Arduino code for Lathe Tachometer

Arduino
This program was used at one time with a reed relay, for a bicycle cadence counter I was building, but it works all right with the input from the IR sensor. If I need to reuse it, all variables are still in place. You can remove all the references to the cadence counter if you wish.
// Tachometer_For_Lathe_IR
// Display RPM rate of lathe spindle

// Uses:
// Arduino Nano V 3.0
// OSOYOO IR Infrared Sensor (available on Amazon)
// IM162 LCD Display (similar ones available on Amazon)

// Include the LCD and Timer library code:
#include <LiquidCrystal.h>
#include <TimerOne.h>

// Initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 12, en = 11, d4 = 6, d5 = 5, d6 = 4, d7 = 3;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

// RPM values to track
const int IRSensorPin = 2;  // the number of the IR sensor input pin
const int ledPin = 13;          // the number of the LED pin on Nano
int ledState = HIGH;           // the current state of the output pin

// Note: This program was used at one time with a reed relay, for a bicycle cadence counter,
//       but it works all right with the input from the IR sensor. 
//       If I need to reuse it, all variables are still in place.
int inputState;                          // the current state from the input pin
int lastInputState = LOW;        // the previous InputState from the input pin
long lastDebounceTime = 0;   // the last time the output pin was toggled
long debounceDelay = 5;        // the debounce time; increase if the output flickers
long time;
long endTime;
long startTime;
int RPM = 0;
//int lnCount = 0;        // counter for averaging RPM
//int avgRPM = 0;      // averaging total

//long voltage = 0;           // Value read from the pot
//long outputValue = 0;   // Value output to the PWM (analog out)
//int speedVal = 0;
//long rpm50 = 833333;
//volatile unsigned long cadTime = 0;  // use volatile for shared variables
//long timeC, endTimeC, startTimeC;
//int RPMC = 0;
float lnTime = 0;
//int speakerPin = 10;
//int lowRate;
//int hiRate;
//int potPin = A0;               //Analog in pin 0
//int switchValPin = A1;     //Analog in pin 1

// ---------------------------------------------------------------
void setup(void) {
  pinMode(IRSensorPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, ledState);
  
  Serial.begin(9600);
  lcd.begin(16, 2); // Initialize LCD

  // Startup text on display
  lcd.clear();
  lcd.print("LATHE IR.");
  lcd.setCursor(0, 1);
  lcd.print("TACHOMETER");
  delay(2000);

  endTime = 0;
  Timer1.initialize(1000000);  // Set the timer to 60 rpm, 1,000,000 microseconds (1 second)
  Timer1.attachInterrupt(timerIsr);  // Attach the service routine here

}

// ---------------------------------------------------------------
void loop(void) {
  time = millis();
  int currentSwitchState = digitalRead(IRSensorPin);

  if (currentSwitchState != lastInputState) {
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (currentSwitchState != inputState) {
      inputState = currentSwitchState;
      if (inputState == LOW) {
        digitalWrite(ledPin, LOW);
        calculateRPM(); // Real RPM from sensor
        ledState = !ledState;
      }
      else {
        digitalWrite(ledPin, HIGH);
      }
    }
  }
  lastInputState = currentSwitchState;
}

// ---------------------------------------------------------------
void calculateRPM() {
  startTime = lastDebounceTime;
  lnTime = startTime - endTime;
  RPM = 60000 / (startTime - endTime);
  endTime = startTime;
}

// --------------------------
// Custom ISR Timer Routine
// Timer set to rpm, see above
// --------------------------
void timerIsr()
{
  // Print RPM every second
  // RPM based on timer
  Serial.println("---------------");
  time = millis() / 1000;
  Serial.print(time);
  Serial.print(" RPM: ");
  Serial.println(RPM);

  lcd.clear();
  lcd.print("SPINDLE SPEED");
  lcd.setCursor(0, 1);
  lcd.print(RPM);
  lcd.setCursor(6,1);
  lcd.print("RPM");
  delay(500);
  RPM = 0;
}

// ---------------------------------------------------------------

Credits

Tony Scarpelli
1 project • 1 follower
I'm a 76 year old retired programmer and TV engineer. Always been in electronics, and in 1976 started studying computers. Still programming.

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