Easy PID Controller Node for Node-RED

The easy-pid-controller is a Node-RED node that provides industrial-grade Proportional-Integral-Derivative (PID) control based on simple-pid-controller v2.0.0. It integrates easily with PLCs, MQTT, and SCADA systems, and supports 0-10V and 4-20mA control signals with safety features like anti-windup, output clamping, and bumpless transfer.

Features

• Easy to configure PID parameters: Kp, Ki, Kd.
• Setpoint (SV) and Process Variable (PV) inputs over msg.topic.
• Outputs full PID status: PV, SV, error, P, I, D, output, scaled Signal, and Value.
• Choice of control signal types: 0-10V or 4-20mA.
• Anti-windup (integral clamping) and output clamping (min/max).
• Deadband support to suppress output when the error is negligible.
• settled handling: stop the loop automatically when within tolerance.
• Manual / Auto mode with bumpless transfer.
• Runtime gain tuning (gains topic) and controller reset (reset topic).
• Real-time status updates via node status text and optional MQTT/InfluxDB integration.

Installation

npm install node-red-contrib-easy-pid-controller

Usage

1. Drag and drop the easy-pid-controller node into your Node-RED flow.
2. Double click on the node to configure:
   • PID gains: Kp, Ki, Kd.
   • Loop interval dt (seconds).
   • Output and integral limits.
   • Deadband and settled tolerance.
   • Signal type (0-10V or 4-20mA) and engineering range.
3. Connect MQTT / Inject / Function nodes to provide SV, PV, auto, and optional advanced topics (gains, mode, manual_output, reset).
4. Deploy and monitor the outputs (output, Signal, Value, mode) in real-time.

Inputs

All control is driven by msg.topic and msg.payload:

• SV (number)
  Desired setpoint value for the controller.

  • msg.topic = "SV"
  • msg.payload = <number>

• PV (number)
  Process variable / current state of the system.

  • msg.topic = "PV"
  • msg.payload = <number>

• auto (boolean)
  Start/stop the PID loop and auto mode.

  • msg.topic = "auto"
  • msg.payload = true → start loop and switch to auto mode
  • msg.payload = false → stop loop and switch to manual mode

• gains (object) — v2.0.0
  Runtime PID gain tuning without restarting the node.

  • msg.topic = "gains"
  • msg.payload = { k_p: <number>, k_i: <number>, k_d: <number> }

• mode (string) — v2.0.0
  Explicitly switch controller mode.

  • msg.topic = "mode"
  • msg.payload = "auto" or "manual"
  • Switching manual → auto uses bumpless transfer (no output jump).

• manual_output (number) — v2.0.0
  Fixed output used in manual mode, also seeds bumpless transfer when returning to auto.

  • msg.topic = "manual_output"
  • msg.payload = <number>

• reset (any) — v2.0.0
  Reset controller internal state (integral, derivative, timestamp).

  • msg.topic = "reset"
  • msg.payload can be any value

Outputs

The node outputs an object on msg.payload with the following fields (from simple-pid-controller v2.0.0):

• PV (number)
  Current process variable.

• SV (number)
  Current setpoint.

• error (number) — v2.0.0
  Current control error: SV - PV.

• P (number)
  Proportional component.

• I (number)
  Integral component (clamped by Integral Min/Max for anti-windup).

• D (number)
  Derivative component (derivative on measurement — no kick on setpoint changes).

• output (number) — v2.0.0
  Raw clamped PID output (P + I + D, limited by Output Min/Max).

• Signal (number)
  Output mapped to the configured signal range:

  • 0-10V → 0 to 10
  • 4-20mA → 4 to 20

• Value (number)
  PV mapped to the signal units for easier UI or Range node usage.

• mode (string) — v2.0.0
  Current controller mode: "auto" or "manual".

Node Configuration Fields (Editor)

• Kp, Ki, Kd: PID gains.
• dt (s): Target loop interval in seconds (controller internally uses dynamic timestamps; dt is a base rate / initial fallback).
• Output Min / Output Max: Clamp bounds for output.
• Integral Min / Integral Max: Anti-windup clamps on the integral accumulator.
• Deadband: If |error| is below this value, output is forced to 0 (disable with 0).
• Settled Tolerance: When |error| falls below this value, the controller emits a settled event and the node stops the loop; restart with auto: true.
• Signal Type: 0-10V or 4-20mA.
• Range Min / Range Max: Engineering range for mapping PV and output to signal units.

Changelog

v2.0.1

• Updated core to use simple-pid-controller v2.0.0 with:

  • Dynamic dt based on real timestamps (constructor dt used as fallback).
  • Anti-windup via configurable Integral Min/Max.
  • Output clamping via Output Min/Max.
  • Deadband support to suppress small-error output.
  • setTarget() now resets integral and derivative state.
  • Derivative on measurement, avoiding derivative kick on setpoint steps.
  • EventEmitter-based update and settled events internally.

• Inputs

  • Added: gains topic for runtime tuning of { k_p, k_i, k_d }.
  • Added: mode topic to switch auto/manual with bumpless transfer.
  • Added: manual_output topic to set fixed output in manual mode.
  • Added: reset topic to clear internal controller state.
  • Improved: auto topic now also sets mode to auto/manual instead of just starting/stopping the timer.

• Outputs

  • Added: error, output, and mode in the payload.
  • Kept: PV, SV, P, I, D, Signal, Value for compatibility.

• Node behaviour

  • Improved: Node status messages show setpoint, PV, mode, and reset events.
  • Improved: On node close, the controller is reset and the internal timer is cleared.

v1.2.1

• Added: Node status updates during runtime to display relevant information like current PV, PID activation state, and more.

v1.2.0

• Changed: Moved the Setpoint (SV) from node configuration to msg.payload with the topic SV.

v1.1.0

• Added: New output value Value that provides the direct control signal based on the sensor type configuration.
• Improved: Code documentation and error handling for invalid inputs.

v1.0.0

• Initial release with basic PID functionalities.
• Support for 0-10V and 4-20mA signal types.

Contributing

Contributions to improve the node or fix any issues are welcome. Please submit an issue or pull request on the GitHub repository.

License

GPL-3.0 License. See the LICENSE file for details.

Example

See the examples/ directory for sample flows illustrating:

• Basic PID control.
• MQTT-based SV/PV input.
• InfluxDB logging of PID status.
• Runtime gain tuning and mode switching.

Author

Harshad Joshi @ Bufferstack.IO Analytics Technology LLP, Pune