Example 29: Photoelectric Sensor

Experiment Overview

A through-beam photoelectric sensor consists of a transmitter and receiver pair. When the light path is obstructed, the output signal changes. Suitable for counting, limit detection, conveyor belt item detection, and other industrial scenarios.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
OUT	GPIO4	Photoelectric sensor DO output (LOW when obstructed)

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "photoelectric_01",
      "name": "Photoelectric Sensor",
      "type": 13,
      "enabled": false,
      "pins": [4],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario: Item Pass Counter (Polling Trigger + Script)

Feature: Detect items passing through the light path and automatically count

Web UI Configuration Steps

Step 1: Create Rule

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

Step 2: 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 photoelectric_01	Photoelectric sensor
   Polling Interval	50	50ms (fast detection)
   Condition Expression	value == 0	LOW = light path obstructed

Step 3: Configure Action (Script Counting)

1. Click Add Action button

2. Fill in:

   • Action Type: Select Command Script
   • Action Parameter:

   var c=getVar('count',0);
   c++;
   setVar('count',c);

3. Click Save button

Application Scenarios

Scenario	Description	Detection Range
Item Counting	Conveyor belt item statistics	5-30cm
Limit Detection	Robotic arm position limiting	5-30cm
Safety Protection	Dangerous area intrusion detection	5-30cm

Notes

1. Alignment: Transmitter and receiver must be directly aligned; misalignment causes false readings
2. Ambient Light: Strong light environments may interfere with the receiver; add a light shield
3. Detection Range: Typical effective range is 5-30cm (module type)
4. Response Speed: Photoelectric sensors respond quickly (<1ms), suitable for high-speed counting