Arduino IR LCD RPM

Infrared tachometer on Arduino platform

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The tachometer on the Arduino platform uses an infrared obstacle sensor that can detect an obstacle at a distance set by a potentiometer.

      

A secondary use of a similar sensor is basically a counter that can respond to the pulley speed from the crankshaft.

      

A reflective surface (on the order of millimeters, max 1 centimeter) is placed on the pulley - sheet, tape, aluminum foil, which can reflect infrared light from the emitting diode into the receiving diode.

      

The sensor does not respond to the distance as such. It only responds to the reflection of light from the reflective surface.

      

The result is a relatively reliable tachometer that represents the result on a character LCD display with an I2C converter.

      

Can be used to record pulleys (harvesters, tractors), but also for bicycles, car wheel (can also be recalculated to the speed of motion at a known wheel circumference).

      

Project hardware:

Arduino Uno R3

IR Obstacle sensor

LCD 20x4 or 16x2

I2C converter

Result

Schematics

Knižnica / Library

https://github.com/fdebrabander/Arduino-LiquidCrystal-I2C-library

Program (Basic)

//Martin Chlebovec (martinius96@gmail.com)
//Základná implementácia pre otáčkomer na platforme Arduino Uno / Nano (ATmega328P)
//Neobsahuje ošetrenie zákmitov, volatile premenné v interrupt rutine (negarantované obslúženie premennej)
//Verzia zdarma pre orientačné meranie, chybovost meraní do: 30%
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3F, 20, 4);     //alebo 0x27 (najpouzivanejsie I2C komunikacne adresy)
int rev = 0;
int rpm;
unsigned long oldtime = 0;
unsigned long time;

void isr() {
  rev++;
}

void setup() {
  lcd.begin(); //100 kHz I2C speed - Standard Mode
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("-----ZETOR 4011-----");
  attachInterrupt(digitalPinToInterrupt (2), isr, RISING); //interrupt pin
}

void loop() {
  delay(1000);
  detachInterrupt(digitalPinToInterrupt(2));      
  time = millis() - oldtime;    //rozdiel casov
  rpm = (rev / time) * 60000;   //vyrataj otacky/min
  oldtime = millis();           //uloz aktualny cas
  rev = 0;
  lcd.setCursor(0, 1);
  lcd.print(rpm);
  lcd.print(" ot/min   ");
  attachInterrupt(digitalPinToInterrupt (2), isr, RISING);
}