Example 44: PIR Motion Sensor

Experiment Overview

The HC-SR501 PIR (Passive Infrared) module detects human presence by sensing changes in infrared radiation emitted by the human body. Outputs HIGH when a person is detected, suitable for automatic lighting, security alarms, people counting, and similar scenarios.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
OUT	GPIO4	PIR module output (HIGH when person detected)

HC-SR501 requires 5-20V power, outputs 3.3V HIGH, can connect directly to ESP32.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "pir_01",
      "name": "PIR Motion",
      "type": 11,
      "enabled": false,
      "pins": [4],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario 1: Motion-Activated Light (Polling Trigger)

Feature: Turn on relay when person detected, turn off after 30 seconds

Web UI Configuration Steps

Step 1: Ensure Relay Peripheral is Configured

• Peripheral ID: relay_01
• Type: GPIO Output

Step 2: Create Rule

1. Click Peripheral Execution in the left menu
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Motion-Activated Light
   • Report Data: ✅ Enabled
   • Enable: ✅ Enabled

Step 3: Configure Trigger (Polling Trigger)

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Polling Trigger	Periodic condition check
   Target Peripheral	Select pir_01	PIR motion sensor
   Polling Interval	200	200ms
   Condition Expression	value == 1	Person detected

Step 4: Configure Actions (3 actions required)

Action 1: Open Relay

1. Click Add Action button
2. Fill in:
   • Action Type: Select HIGH
   • Target Peripheral: Select relay_01

Action 2: Delay 30 Seconds

1. Click Add Action button again
2. Fill in:
   • Action Type: Select Delay
   • Delay Time: 30000 (30000ms = 30 seconds)

Action 3: Close Relay

1. Click Add Action button a third time

2. Fill in:

   • Action Type: Select LOW
   • Target Peripheral: Select relay_01

3. Click Save button

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Scenario 2: Security Alarm (Polling Trigger)

Feature: Trigger buzzer alarm when human motion is detected

Configuration Steps:

1. Create rule, name: Intrusion Alarm
2. Trigger configuration:
   • Trigger Type: Select Polling Trigger
   • Target Peripheral: Select pir_01
   • Polling Interval: 500
   • Condition Expression: value == 1
3. Action configuration (2 actions required):
   • Action 1: Select HIGH, target buzzer_gpio
   • Action 2: Select Send Event, type alarm, message Human motion detected!
4. Click Save

PIR Sensor Specifications

Feature	Description
Supply Voltage	5-20V
Output Level	3.3V (ESP32 compatible)
Detection Range	3-7m (potentiometer adjustable)
Delay Time	5s-5min (potentiometer adjustable)
Trigger Mode	L=non-repeatable, H=repeatable (jumper)
Warm-up Time	~1 minute

Notes

1. Warm-up Time: HC-SR501 requires ~1 minute warm-up after power-on to stabilize
2. Delay Adjustment: Module potentiometer adjusts HIGH output hold time (5s~5min)
3. Sensitivity: Another potentiometer adjusts detection sensitivity/range (3~7m)
4. Trigger Mode: L=non-repeatable trigger, H=repeatable trigger (jumper selection)
5. Temperature Dependency: PIR detects temperature difference between human body and environment; sensitivity decreases when ambient temperature approaches body temperature
6. Occlusion: Cannot detect through glass (glass blocks far-infrared)