#include <LiquidCrystal.h>
LiquidCrystal lcd(9, 8, 7, 10, 5, 4);
int lcdkontrast = 110;

int pin = 13;
int zeit;
int poti;
int frequenz;
void setup() {
poti = A0;

  lcd.begin(16, 2);
  analogWrite(6, lcdkontrast);
  pinMode(pin, OUTPUT);
}

void loop() {

  zeit = map(poti, 0, 1023, 500, 5);  //bei potiwert 0: 500ms an und 500ms aus also eine sekunde was dann 1 Hz wären,
  digitalWrite(pin, HIGH);
  delay(zeit);
  digitalWrite(pin, LOW);
  delay(zeit);

  frequenz = map (zeit, 500, 5, 1, 100);
  char buffer[7];
            sprintf(buffer,"%4i Hz",frequenz);
           lcd.setCursor(0, 0);
           lcd.print("Frequenz");
           lcd.setCursor(0, 1);
           lcd.print(buffer);
           lcd.setCursor(0, 1);
}