Line Tracking Sensor with Raspberry Pi – Simple KY‑033 Door/Line Detector

Learn how to use a single KY‑033 line‑tracking sensor to detect whether a door is open or to sense a line crossing, all with a Raspberry Pi. The following guide covers wiring, installation, and a ready‑to‑run Python script.

About This Project

This concise example demonstrates how the Elegoo 37‑1 Sensor Kit v2 (or compatible HW‑006 v1.2) can turn a single sensor into a reliable door‑status or line‑tracking detector. It’s perfect for robotics, security, or DIY automation projects.

Connecting the Sensor to the GPIO

The KY‑033 has three pins: Signal (S), +V, and Ground (G). Connect them as follows:

• Signal (S) → GPIO 24 (Pin 18)
• +V → 3.3 V (Pin 1)
• G → GND (Pin 6)

Refer to the schematic for a visual guide.

Installing the Software

Ensure Python is installed on your Raspberry Pi. Then clone the sample code from the following Gist and run it.

git clone https://gist.github.com/2299af0b2fbace8994b9fb9e409bc3f5.git

Navigate to the cloned directory and execute:

python tracer.py

The script will output Line detected whenever a dark line is detected beneath the sensor. You can test this in action here.

Wiring Diagram

Python Code

Below is the complete script. It sets up the GPIO pin, reads the sensor, and prints a message when a line is detected.

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)

# GPIO pin connected to the sensor’s Signal pin
GPIO_PIN = 18
GPIO.setup(GPIO_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)

# Delay between readings (seconds)
delayTime = 0.2

print("#— Hackster project line tracker example —#")

try:
    while True:
        if GPIO.input(GPIO_PIN) == False:
            print("Line detected")
        time.sleep(delayTime)
except KeyboardInterrupt:
    GPIO.cleanup()

Source: Line tracking sensor with RPi