node-red-contrib-difference

Node-RED Difference Calculator - calculates the difference between two numeric input values.

Features

• Calculates A - B from two input values
• Configurable topic names for inputs
• Absolute value mode (|A - B|)
• Configurable decimal places (0-10)
• Outputs detailed input info

Behavior

• Input A identified by configurable topic (default: "a")
• Input B identified by configurable topic (default: "b")
• Result = A - B
• Output triggered on every new message once both values are known

Example

topic="a", payload=24.5  → stored as A
topic="b", payload=18.2  → stored as B
Output: 24.5 - 18.2 = 6.3

Configuration

| Property | Description | Default | |----------|-------------|---------| | Topic A | Topic name for input A | "a" | | Topic B | Topic name for input B | "b" | | Absolute | Output absolute value | false | | Decimals | Number of decimal places | 2 |

Input

• msg.payload - Numeric value
• msg.topic - Required - Must match Topic A or Topic B

Runtime Override

| Property | Description | |----------|-------------| | msg.reset | true = reset both values |

Output

{
  "payload": 6.3,
  "inputs": {
    "a": { "topic": "a", "value": 24.5 },
    "b": { "topic": "b", "value": 18.2 },
    "result": 6.3,
    "absolute": false
  }
}

Use Cases

| Application | Description | |-------------|-------------| | Temperature | Difference between two sensors | | Energy | Consumption difference between readings | | Level | Water level difference |

Node Status

• a(24.5) - b(18.2) = 6.3 - Result calculated
• Waiting for a... - Input A missing
• Waiting for a and b... - Both inputs missing

Author

sr.rpo

License

MIT