Code van mijn snelheidsmeter (https://www.youtube.com/watch?v=uQMSEfN3kMo)

gui.py

import serial
import tkinter as tk
import threading

# seriele port verschilt per pc/arduino
ser = serial.Serial("/dev/tty.usbmodem21301", 9600, timeout=0.1)

root=tk.Tk()
value = tk.StringVar()
label = tk.Label(root,textvariable=value, font=("Arial", 96))
label.pack()

def read_input():
    while True:
        line = ser.readline()
        if line:
            value.set(f"{line.decode().strip()} km/u")

threading.Thread(target=read_input, daemon=True).start()

root.geometry("600x110") 
root.mainloop()

snelheid_meter.ino

#define LDR1 A0
#define LDR2 A1

const int MIN_LIGHT = 800;
const double DISTANCE = 0.05;

long firstMeasure = 0;
long secondMeasure = 0;

void setup() {
  Serial.begin(9600);

}

void loop() {
  int ldr1 = analogRead(LDR1);
  int ldr2 = analogRead(LDR2);
  if (ldr1 < MIN_LIGHT && firstMeasure == 0) {
    firstMeasure = millis();
  }
  if (ldr2 < MIN_LIGHT && secondMeasure == 0 && firstMeasure != 0) {
    secondMeasure = millis();
    // in seconds
    double timePassed = (secondMeasure - firstMeasure) / 1000.0;

    double speed = (DISTANCE / timePassed);

    Serial.println(speed*3.6);

    firstMeasure = 0;
    secondMeasure = 0;
  }
}