Example 8: Stepper Motor Control

Experiment Overview

Control a 28BYJ-48 stepper motor via ULN2003 driver board for precise angle and speed control. FastBee has a built-in STEPPER_MOTOR peripheral type (type: 42), supporting half-step drive mode.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
IN1	GPIO15	ULN2003 Driver Board IN1
IN2	GPIO2	ULN2003 Driver Board IN2
IN3	GPIO0	ULN2003 Driver Board IN3
IN4	GPIO4	ULN2003 Driver Board IN4

ULN2003 module requires external 5V power, 28BYJ-48 stepper motor has 2048 steps per revolution (half-step mode).

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "stepper_01",
      "name": "ULN2003 Stepper Motor",
      "type": 42,
      "enabled": false,
      "pins": [15, 2, 0, 4],
      "params": {
        "stepsPerRevolution": 2048,
        "speed": 8
      }
    }
  ]
}

Parameter Description

Parameter	Description	Default
stepsPerRevolution	Steps per revolution (28BYJ-48 half-step=2048)	2048
speed	Speed (RPM)	8

Peripheral Execution Linkage

Scenario 1: Forward One Revolution (Platform Trigger)

Function: Control motor forward one revolution (2048 steps) via cloud platform command

Web Interface Configuration Steps

Step 1: Create Rule

1. Click left menu Peripheral Configuration → Switch to Peripheral Execution Management tab
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Stepper Forward
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Platform Trigger	Receive cloud platform commands
   Operator	Select Match Pattern	Match command
   Comparison Value	{"cmd":"forward"}	Forward command

Step 3: Configure Action

1. Click Add Action button

2. Fill in action configuration:

   Field	Value	Description
   Action Type	Select Call Peripheral	Call peripheral method
   Target Peripheral	Select stepper_01	Stepper motor peripheral
   Action Params	2048	Forward 2048 steps (one revolution)

3. Click Save button

Execution Flow:

Receive forward command
  ↓
Call stepper_01 move method
  ↓
Forward 2048 steps (one revolution)
  ↓
Action complete (blocking execution)

⚠️ Note: stepper_move action blocks the current rule until motor movement completes

---

Scenario 2: Reverse Half Revolution (Platform Trigger)

Function: Control motor reverse half revolution (-1024 steps) via cloud platform command

Web Interface Configuration Steps

Step 1: Create Rule

1. Click New Rule
2. Fill in basic configuration:
   • Rule Name: Stepper Reverse
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button
2. Fill in:
   • Trigger Type: Select Platform Trigger
   • Operator: Select Match Pattern
   • Comparison Value: {"cmd":"reverse"}

Step 3: Configure Action

1. Click Add Action button

2. Fill in:

   • Action Type: Select Call Peripheral
   • Target Peripheral: Select stepper_01
   • Action Params: -1024 (negative = reverse, 1024 steps = half revolution)

3. Click Save button

Steps to Angle Conversion

Steps	Angle	Description
2048	360°	One full revolution
1024	180°	Half revolution
512	90°	Quarter revolution
256	45°	Eighth revolution
-2048	-360°	Reverse one full revolution

Notes

1. Power: Stepper motor needs 5V independent power, ULN2003 cannot be powered from ESP32 3.3V
2. Heat: Stepper motor still has holding current when stationary, disconnect power when not in use for long periods
3. Speed Limit: 28BYJ-48 max ~15RPM, exceeding will cause missed steps
4. Pin Order: IN1-IN4 order must be correct, otherwise motor will vibrate but not rotate
5. Blocking Execution: stepper_move action blocks the current rule until complete