#define CLK_PIN 25 
int counter = 0;
int CLK_state;
int prev_CLK_state;

#include <LiquidCrystal_I2C.h>

int lcdColumns = 16;
int lcdRows = 2;

LiquidCrystal_I2C lcd(0x27, lcdColumns, lcdRows); 

float time1=0;
float time2;
float Times;
float speed;

void setup() {
  pinMode(CLK_PIN, INPUT);
  prev_CLK_state = digitalRead(CLK_PIN);
  lcd.init();                    
  lcd.backlight();
}

void loop() 
{
  
  CLK_state = digitalRead(CLK_PIN);
  if (CLK_state != prev_CLK_state && CLK_state == HIGH) 
  {
    time2=millis();
    Times=time2-time1;
    if (Times<1000)
    {
      speed=(18)/(((Times)*(10^-3))/60); //in degrees per minute
      lcd.setCursor(0,0);
      lcd.print("Speed:");
      lcd.print(abs(speed));
    
    }
    time1=time2;
  }
  if (millis()-time1>1000)
  { 
    lcd.setCursor(0,0);
    lcd.print("Speed:");
    lcd.print(abs(0.000));
  }
  // save last CLK state
  prev_CLK_state = CLK_state;
}