Overview
The servo node controls servo motors with precise angular positioning using PWM
(Pulse Width Modulation) signals. Standard hobby servos rotate between 0 and 180 degrees, while continuous rotation
servos use the same signal for speed and direction control. Ideal for robotics, pan/tilt cameras, valve actuators,
and automated mechanical systems.
Properties
| Property | Type | Required | Default | Description |
|---|---|---|---|---|
| pin | number | Yes | 18 | PWM-capable GPIO pin (BCM numbering) |
| minPulse | number | No | 1.0 | Minimum pulse width in milliseconds (0° position) |
| maxPulse | number | No | 2.0 | Maximum pulse width in milliseconds (180° position) |
| frequency | number | No | 50.0 | PWM frequency in Hz (standard servo = 50Hz) |
| minAngle | number | No | 0.0 | Minimum allowed angle in degrees |
| maxAngle | number | No | 180.0 | Maximum allowed angle in degrees |
| startAngle | number | No | 90.0 | Initial angle on deploy (center position) |
Inputs
Sets the target angle in degrees (0-180).
0 Minimum position (1.0ms pulse) 90 Center position (1.5ms pulse) 180 Maximum position (2.0ms pulse) Outputs
Outputs current servo position with calculated pulse width.
{
"angle": 90,
"pulseWidth": 1.5,
"pin": 18,
"timestamp": 1709251200000
}Wiring / Connection Diagram
Standard Servo to Raspberry Pi
Raspberry Pi Servo Motor
+-----------+ +----------+
| | | Signal |<-- Orange/White wire
| GPIO 18 |----[PWM Signal]-| (PWM) |
| | | |
| 5V |----[Power]------| VCC (+) |<-- Red wire
| | | |
| GND |----[Ground]-----| GND (-) |<-- Brown/Black wire
| | +----------+
+-----------+
Pulse Width Mapping:
┌─────────┬────────────┬────────────┐
│ Angle │ Pulse (ms) │ Duty Cycle │
├─────────┼────────────┼────────────┤
│ 0° │ 1.0 ms │ 5.0% │
│ 90° │ 1.5 ms │ 7.5% │
│ 180° │ 2.0 ms │ 10.0% │
└─────────┴────────────┴────────────┘Tip: Use an external 5V power supply for servos drawing more than 500mA. Connect grounds together between the Pi and the external supply.
Example Use Cases
Dashboard Slider Servo Control
Control servo angle from a dashboard slider widget (0-180 degrees).
[
{
"id": "angle-slider",
"type": "slider",
"label": "Servo Angle",
"min": 0,
"max": 180,
"step": 1
},
{
"id": "pan-servo",
"type": "servo",
"pin": 18,
"minPulse": 1.0,
"maxPulse": 2.0,
"startAngle": 90
}
]Automated Door Lock
Use RFID input to lock/unlock a servo-driven deadbolt mechanism.
[
{
"id": "rfid-reader",
"type": "rfid",
"pin": 8
},
{
"id": "auth-check",
"type": "function",
"func": "// Authorized card UIDs
var allowed = ['A1B2C3D4', 'E5F6A7B8'];
var uid = msg.payload.uid;
msg.payload = allowed.includes(uid) ? 0 : 90;
return msg;"
},
{
"id": "lock-servo",
"type": "servo",
"pin": 12,
"minAngle": 0,
"maxAngle": 90,
"startAngle": 90
}
]Pan-Tilt Camera Mount
Control dual servos for pan and tilt via MQTT commands.
[
{
"id": "mqtt-camera",
"type": "mqtt-in",
"topic": "camera/position"
},
{
"id": "pan-servo",
"type": "servo",
"pin": 18,
"minAngle": 0,
"maxAngle": 180,
"startAngle": 90
},
{
"id": "tilt-servo",
"type": "servo",
"pin": 12,
"minAngle": 30,
"maxAngle": 150,
"startAngle": 90
}
]Common Use Cases
Robotics
Articulated arms, grippers, and walking mechanisms
Pan-Tilt Cameras
Surveillance and tracking camera mounts
Door Locks
Automated deadbolt and latch mechanisms
Valve Control
Proportional valve actuators for flow regulation