Detecting Motion with an HC-SR501 PIR Sensor on a Raspberry Pi 4B

Step by step

1. Drag Raspberry Pi 4B onto the Canvas.
2. Drag the HC-SR501 PIR Motion Sensor onto the Canvas — a real 3-pin module. It can mount straight into a breadboard, or wire directly to the Pi.
3. Hover over its 3 pins to confirm the labels, left to right: VCC, OUT, GND.
4. Wire VCC → a Pi power pin and GND → a Pi GND pin.
5. Wire OUT → any Pi GPIO pin you'll configure as an input (e.g. physical pin 38) — no voltage divider needed here: unlike the HC-SR04's Echo pin, OUT is a genuine 3.3V-safe digital signal, matching the real HC-SR501 datasheet.
6. Click the sensor to select it, then open its settings panel and set three values: Delay (sec) — how long OUT stays HIGH after a trigger (3–300, default 5); Sensitivity (%) — scales that hold duration from 0.5× at 0% up to 1.5× at 100%, unaltered at the 50% default (a disclosed simulation convenience, not a model of real PIR detection-range physics, since this simulator has no distance/heat-source concept to give Sensitivity its real datasheet meaning); and Retrigger Mode — Repeatable ("H", the common factory-default jumper position) or Non-repeatable ("L").
7. Go to the Code tab and write a script that polls the OUT pin in a loop:

import RPi.GPIO as GPIO
import asyncio
 
GPIO.setmode(GPIO.BOARD)
PIR_OUT = 38   # adjust to match your wiring
 
GPIO.setup(PIR_OUT, GPIO.IN)
 
while True:
    if GPIO.input(PIR_OUT) == 1:
        print("Motion detected!")
    else:
        print("No motion.")
    await asyncio.sleep(0.5)

8. Click Start.
9. Click directly on the sensor's own body on the Canvas — this simulates a real motion event, the same way a person walking in front of an actual HC-SR501 would trigger it.

Watch the Console: it should switch to printing "Motion detected!" for roughly your configured Delay (scaled by Sensitivity), then return to "No motion." — no further clicks needed for the hold itself to run its course.

10. To see the Retrigger Mode setting matter: in Repeatable mode (the default), click the sensor again while it's still reading HIGH — the hold timer restarts at full duration, visibly extending how long "Motion detected!" keeps printing.
11. Switch Retrigger Mode to Non-repeatable and repeat — a second click while already triggered is correctly ignored; OUT still returns to LOW at the original scheduled time, unaffected by the extra click.

What “working correctly” looks like

• Clicking the sensor's body lights its own small onboard status LED (matching a real HC-SR501 board's indicator) and flips OUT HIGH for roughly your configured Delay × Sensitivity scaling, then back to LOW — visible both on the sensor itself and in the Console's own printed output.
• In Repeatable mode, clicking the sensor again while it's still triggered visibly extends the HIGH window past the original duration.
• In Non-repeatable mode, clicking again while still triggered has no effect at all — OUT returns LOW at the original time regardless.
• Clicking the sensor works whether or not a simulation is currently running, but OUT's value only reaches a running Python script while Start is active — matching how every other GPIO-facing component in this simulator behaves.

If something’s wrong

• OUT never reads HIGH → confirm OUT is wired to the exact pin your script configures with GPIO.setup(pin, GPIO.IN), and confirm you're clicking directly on the sensor's own body, not just near it.
• OUT stays HIGH longer than you expected → check the Sensitivity setting — a higher percentage scales the hold duration up to 1.5× the configured Delay, by design (a disclosed simulation convenience, not real PIR detection-range physics).
• A second click during an active hold doesn't seem to do anything → confirm Retrigger Mode is set to Repeatable — in Non-repeatable mode, a click during an already-active hold is correctly ignored, not a bug.