node-red-contrib-hysteresis

A Node-RED node for hysteresis (deadband) logic - prevents rapid on/off switching when values hover around a threshold.

Features

• Simple configuration: Setpoint + Hysteresis (±)
• Two modes: High (ON when above) or Low (ON when below)
• Configurable initial state
• Real-time status display in editor
• Live threshold preview while editing

Configuration

| Property | Description | Example | |----------|-------------|---------| | Setpoint | Target value | 22 | | Hysteresis (±) | Deadband range | 1 | | Mode | When to turn ON | High / Low | | Initial State | Starting state | undefined |

Mode: High (Cooling)

Use when output should be ON when temperature is above setpoint.

Setpoint: 22, Hysteresis: 1
→ ON when value ≥ 23
→ OFF when value ≤ 21

Mode: Low (Heating)

Use when output should be ON when temperature is below setpoint.

Setpoint: 22, Hysteresis: 1
→ ON when value ≤ 21
→ OFF when value ≥ 23

How It Works

         OFF zone          Deadband           ON zone
      ◄────────────►  ◄──────────────►  ◄────────────►
                     │                │
  ────────────────── 21 ════════════ 23 ──────────────
                     │   (no change)  │
               Low Threshold    High Threshold
                 (22 - 1)         (22 + 1)

Usage

Input

• msg.payload - Numeric value (temperature, pressure, humidity, etc.)

Output

• msg.payload - Boolean (true or false)
• msg.value - The input value
• msg.previousState - State before evaluation
• msg.setpoint - Configured setpoint
• msg.hysteresis - Configured hysteresis
• msg.mode - Configured mode

Example Output

{
  "payload": true,
  "value": 24.5,
  "previousState": false,
  "setpoint": 22,
  "hysteresis": 1,
  "mode": "high"
}

Example Sequences

Cooling (Mode: High)

| Input | Output | Reason | |-------|--------|--------| | 20 | OFF | Below 21 | | 22 | OFF | Between thresholds, stays OFF | | 24 | ON | Above 23 | | 22 | ON | Between thresholds, stays ON | | 20 | OFF | Below 21 |

Heating (Mode: Low)

| Input | Output | Reason | |-------|--------|--------| | 24 | OFF | Above 23 | | 22 | OFF | Between thresholds, stays OFF | | 20 | ON | Below 21 | | 22 | ON | Between thresholds, stays ON | | 24 | OFF | Above 23 |

Use Cases

• HVAC Control: Prevent heating/cooling from toggling rapidly
• Pump Control: Avoid frequent pump starts when water level fluctuates
• Alarm Systems: Reduce false alarms from sensor noise
• Fan Control: Smooth fan on/off behavior based on temperature

Author

sr.rpo

License

MIT