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Common Basic Nodes in IIoT

Beyond the 엣지 category, these are the nodes shipped with vanilla Node-RED that matter most in IIoT flows, ordered by how often they are used.

1. inject — Trigger / Scheduler​

The starting point of a flow. Trigger once with a button, or automatically on a fixed interval or at a set time.

OptionDescription
Repeat: intervalFires every N seconds/minutes/hours (e.g. poll every second)
Repeat: interval between timesFires only during a specific time window (e.g. 09:00–18:00)
Repeat: at a specific timeAt a fixed time each day (e.g. 07:00 daily)
Repeat: cron-likecrontab format (e.g. 0 7 * * * — 07:00 daily)
Inject once afterWhether to fire once right after Deploy, plus a delay

It can also inject msg.payload and msg.topic, so a single node serves as both "schedule" and "input data."

2. debug — Sidebar Log​

Outputs msg or msg.payload to the debug tab in the right sidebar. Switching the output target to "the complete msg object" reveals every field that would otherwise stay hidden — essential for debugging.

3. function — Free-Form JavaScript​

Takes a block of JavaScript code. Transform msg and return msg; it to pass it on to the next node.

// 예: payload 가 숫자라면 100배 해서 출력
msg.payload = parseFloat(msg.payload) * 100;
return msg;

To branch into multiple outputs, raise Outputs: 2 (or more) in the node settings and return an array return [a, b];.

4. change — Set/Copy/Delete Fields (No Code)​

Simple transformations such as msg.topic = "abc" or msg.payload = msg.payload.value are handled by a single change without a function node. Four actions are available: set / change / move / delete.

5. switch — Conditional Branching​

Inspects msg.payload or any other field and routes to a different output port. Options are checking all rules or stop after first match.

            ┌─ ≥ 80 ─▶ Slack 알림
read ──▶ switch ─┤
            └─ < 80 ─▶ 정상 라인

6. join — Collecting Multiple Messages​

Merges the results of several parallel nodes (태그값 읽기 ×3 and so on) into a single array or object. mode manual, count N, key msg.topic.

7. delay — Delay / Rate Limit​

  • Pause: Holds messages for N seconds/minutes (e.g. suppress re-sending for 5 minutes after an alarm)
  • Rate Limit: Caps throughput, e.g. "1 message per second" — protects external API polling and MQTT publishing

8. trigger — Combining State and Timers​

Patterns such as "send a start message when a message arrives, and an end message if nothing updates for N seconds" — frequently used for detecting data dropouts.

9. http request / http in / http response​

NodePurpose
http requestCalls an external REST API (e.g. a weather API, in-house ERP)
http in + http responseCreates a new HTTP endpoint on Node-RED itself (e.g. receiving /myreport POST)

10. file / file in​

  • file (write/append): Saves to a file on disk (CSV logging, etc.)
  • file in (read): Reads file contents

11. csv / json / xml​

String ↔ object conversion. csv offers a rich set of header and delimiter options.

12. template​

Renders a template using mustache syntax. Most convenient for composing emails, Slack messages, and report bodies.

🔥 [경보] {{tag_id}} = {{value}}{{unit}} (한도 {{threshold}})

13. link in / link out​

"Virtual jumps" within the same workspace. Used to clean up a tangle of wires.

14. catch / status / complete​

When an error occurs anywhere in the flow, catch catches it, and status reports node status (e.g. mqtt connected/disconnected). Essential for stable operation.

Next Steps​