Overview
The pwm node generates Pulse Width Modulation signals for precise analog-like control
of digital pins. Use it to dim LEDs, control motor speeds, position servos, and create variable outputs from
digital GPIO pins.
Hardware vs Software PWM
Hardware PWM (Recommended)
- • Available on GPIO 12, 13, 18, 19 only
- • Zero CPU overhead
- • Precise, jitter-free signal
- • Best for servos and motors
Software PWM
- • Available on any GPIO pin
- • Uses CPU cycles
- • May have slight jitter
- • Good for LED dimming
Properties
| Property | Type | Required | Default | Description |
|---|---|---|---|---|
| pin | number | Yes | - | GPIO pin number (BCM numbering) |
| frequency | number | No | 1000 | PWM frequency in Hz |
| range | number | No | 100 | Range for duty cycle (0-range) |
| mode | string | No | "auto" | "hardware", "software", or "auto" |
| initialValue | number | No | 0 | Initial duty cycle on deploy |
Inputs
Sets the duty cycle (0 to range value).
0 → 0% duty (off) 50 → 50% duty (half brightness/speed) 100 → 100% duty (full on) Outputs
Passes through with current PWM state.
{
"payload": 75,
"topic": "pwm/18",
"pin": 18,
"_pwm": {
"duty": 75,
"frequency": 1000,
"mode": "hardware"
}
}Common Applications
LED Dimming
Smooth brightness control
Frequency: 1000 Hz
Range: 100 (0-100%)
Mode: software (any pin)
DC Motor Speed
Variable speed control
Frequency: 20000 Hz
Range: 100
Mode: hardware (GPIO 18)
Servo Control
Position control (0-180°)
Frequency: 50 Hz
Range: 100 (2.5-12.5% duty)
Mode: hardware (GPIO 12/13)
Example Flows
Breathing LED Effect
Smoothly fade LED in and out continuously.
[
{
"id": "fade-timer",
"type": "inject",
"repeat": "0.05",
"payload": ""
},
{
"id": "fade-calc",
"type": "function",
"func": "var t = context.get('t') || 0;
t += 0.05;
context.set('t', t);
msg.payload = Math.round(50 + 50 * Math.sin(t));
return msg;"
},
{
"id": "led-pwm",
"type": "pwm",
"pin": 18,
"frequency": 1000
}
]Dashboard Brightness Control
Control LED brightness with a dashboard slider.
Servo Control Guide
Standard servos use 50Hz PWM with pulse widths of 1-2ms (2.5-10% duty cycle) for 0-180° rotation.
// Convert angle (0-180) to duty cycle
function angleToDuty(angle) {
// 0° = 2.5% duty, 180° = 12.5% duty
return 2.5 + (angle / 180) * 10;
}
// Usage: Set servo to 90° (center)
msg.payload = angleToDuty(90); // Returns 7.5
return msg;Tip: Use hardware PWM (GPIO 12, 13, 18, 19) for servos to avoid jitter.