Confirm sustained PIR motion

Distinguish a sustained digital PIR pulse from a pulse too short to pass a 500 ms confirmation rule.

Physics Phoebe: I want you to connect interface type to observable pin behavior and test the duration rule before trusting a motion alert., your practice guide

Physics Phoebe: I want you to connect interface type to observable pin behavior and test the duration rule before trusting a motion alert.
Predict the reading, then compare it with the measurement.

Wokwi ESP32

Third party Tool

Distinguish a sustained digital PIR pulse from a pulse too short to pass a 500 ms confirmation rule.

Tier 1 · Web · No account

Version tested: Compiled and booted by the Wokwi gate (ESP32 Arduino core 3.3.11); captured in the Wokwi web editor on 2026-09-09. Date: 2026-09-09.

Open the ESP32 editor, paste diagram.json, then paste sketch.ino.

Open Wokwi to paste in the files (new tab)

Get the files

Use both prepared files. This is a paste-in setup; saving a project requires a Wokwi account.

diagram.json

721 bytes · Circuit connections

Download

sketch.ino

1,093 bytes · ESP32 program

Download

// Generic esp32 core does not define LED_BUILTIN; DevKit status output is GPIO 2.
const int LED_BUILTIN = 2;

// Add filtering to reduce false triggers
const int PIR_PIN = 13;
const int MIN_TRIGGER_DURATION = 500; // Milliseconds
unsigned long triggerStartTime = 0;
bool confirmedMotion = false;

void setup() {
  Serial.begin(115200);
  Serial.println("PIR warm-up: wait 60 seconds");
  pinMode(PIR_PIN, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
  delay(60000);  // Wait for PIR warm-up
}

void loop() {
  int pirState = digitalRead(PIR_PIN);

if (pirState == HIGH) {
    if (triggerStartTime == 0) {
      triggerStartTime = millis(); // Start timing
    } else if (millis() - triggerStartTime > MIN_TRIGGER_DURATION) {
      // Confirmed motion only if PIR stays HIGH for 500ms
      if (!confirmedMotion) {
        confirmedMotion = true;
        Serial.println("CONFIRMED MOTION");
        digitalWrite(LED_BUILTIN, HIGH);
      }
    }
  } else {
    // PIR went LOW - reset
    triggerStartTime = 0;
    confirmedMotion = false;
    digitalWrite(LED_BUILTIN, LOW);
  }

delay(50);
}

Use the launch button above to open the ESP32 editor in Wokwi.
Select the editor’s diagram.json tab and replace all its text with the supplied diagram.json.
Select the sketch.ino tab, replace all its text with the supplied sketch.ino, then click Start Simulation.

Steps

Screens captured against Wokwi ESP32 Compiled and booted by the Wokwi gate (ESP32 Arduino core 3.3.11); captured in the Wokwi web editor on 2026-09-09 on 2026-09-09; the tool may have moved on — the text steps are the contract.

Step 1
Do
Paste the prepared diagram and sketch into Wokwi ESP32. Inspect the PIR connections.
You will see
PIR OUT connects to GPIO 13, supply to VIN, and ground to GND. The status output uses GPIO 2.
Why it matters
This exercise uses a digital level, unlike the host’s addressed I2C sensors and chip-selected SPI devices.
Step 2
Do
Start the simulation at 115200 baud and let it run for at least 60 simulated seconds.
You will see
PIR warm-up: wait 60 seconds appears immediately. Motion evaluation starts after the original 60-second delay.
Why it matters
The boot marker proves startup only. It does not prove motion detection during the warm-up period.
Step 3
Do
After warm-up, select the PIR sensor and press Simulate Motion.
You will see
A sustained HIGH produces CONFIRMED MOTION after more than 500 ms and switches the GPIO 2 status output HIGH.
Why it matters
The sketch requires a duration, rather than accepting the first HIGH sample.
Step 4
Do
Leave the sensor alone after triggering it.
You will see
The default simulated pulse lasts about five seconds; when OUT returns LOW the status output clears without printing a separate reset message.
Why it matters
Confirmation state resets on LOW, allowing a later pulse to be evaluated independently.
Step 5
Do
Trigger motion again, and trigger once more while the pulse remains HIGH.
You will see
The continuous HIGH interval produces one confirmation; retriggering extends the interval rather than producing a second confirmation immediately.
Why it matters
The confirmedMotion flag suppresses repeated announcements until a LOW resets it.
Step 6
Do
Stop the simulation, change MIN_TRIGGER_DURATION from 500 to 6000, restart, wait through warm-up, and trigger once.
You will see
A single default five-second pulse does not print CONFIRMED MOTION.
Why it matters
A duration threshold longer than the input pulse rejects that pulse; the setting must match the intended behavior.
Step 7
Do
Restore MIN_TRIGGER_DURATION to 500, restart, wait through warm-up, and trigger once again.
You will see
CONFIRMED MOTION returns after a sustained pulse, establishing the original baseline.
Why it matters
Repeatable input and explicit thresholds help separate interface wiring failures from application filtering rules.

Chapter checks

These questions refer to the chapter’s examples. Use the return links to review their answers.

An ESP32 has three I2C sensors: BMP280 (0x76), BH1750 (0x23), and SHT31 (0x44). After adding a second BMP280 for redundancy, both pressure readings return identical values. What is the most likely cause?
Return to the chapter’s knowledge check
You need to read data from an SD card at 2 MB/s and also connect a BME280 environmental sensor. Which protocol combination is most appropriate?
Return to the chapter’s knowledge check

Return to Protocol Diagnostics and Bus Design · Browse Labs

Wokwi ESP32

Get the files

diagram.json

sketch.ino

Steps

1 Step 1

2 Step 2

3 Step 3

4 Step 4

5 Step 5

6 Step 6

7 Step 7

Chapter checks

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7