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inject

Triggers a flow manually or at regular intervals. Perfect for testing, debugging, and scheduled tasks.

inject
input v1.0.0

Triggers a flow manually or at regular intervals. Can inject timestamps, strings, numbers, JSON objects, or context values.

trigger timer cron schedule
Inputs
0
Outputs
1

Overview

The inject node is one of the most commonly used nodes in EdgeFlow. It allows you to:

  • Manually trigger a flow by clicking the button on the node
  • Automatically inject messages at regular intervals
  • Schedule injections using cron expressions
  • Inject on flow deployment (useful for initialization)
  • Toggle mode: alternate payload between true/false on each tick (perfect for blinking LEDs)

This node is essential for testing and debugging flows, as well as creating time-based automations.

Properties

Property Type Required Default Description
name string - - Display name for this node in the editor.
payload any - timestamp The payload to inject. Can be a timestamp, string, number, boolean, JSON, or flow/global context.
payloadType string - date The type of payload: date, str, num, bool, json, flow, global.
topic string - - The msg.topic value to set on the outgoing message.
intervalType string - seconds Unit for repeat interval: seconds, minutes, hours, days, or months.
intervalValue number - - Numeric value for the repeat interval.
repeat boolean - false Enable automatic repeated injection at the configured interval.
toggle boolean - false Toggle mode: alternates payload.value between true and false on each interval tick. Perfect for blinking LEDs.
crontab string - - Cron expression for scheduled injection (e.g., "0 * * * *" for every hour).
once boolean - false Whether to inject once when the flow is deployed.
onceDelay number - 0.1 Delay in seconds before the first injection after deploy.

Outputs

The inject node has a single output that sends a message with the configured payload:

Output Message Format

{`{
  "payload": ,
  "topic": "",
  "_msgid": ""
}`}

When the payload type is set to timestamp, the payload will be the current time in milliseconds since January 1, 1970 (Unix epoch).

Toggle Mode

When toggle is enabled, the inject node automatically alternates payload.value between true and false on each interval tick. This eliminates the need for a Function node when you just need to blink an LED or toggle a relay.

Toggle Mode Output

Tick 1 
{ "value": true }
Tick 2 
{ "value": false }
Tick 3 
{ "value": true }

Any extra payload fields you configure are preserved alongside the toggling value.

Examples

Basic Timestamp Injection

This simple flow injects a timestamp and displays it in the debug panel. Click the inject button to trigger the flow.

Timestamp to Debug

Injects the current timestamp and displays it in the debug panel.

View Flow JSON 
[
  {
    "id": "inject1",
    "type": "inject",
    "name": "Timestamp",
    "payload": "",
    "payloadType": "date",
    "repeat": "",
    "wires": [["debug1"]]
  },
  {
    "id": "debug1",
    "type": "debug",
    "name": "Output",
    "active": true
  }
]

JSON Payload

Inject a JSON object containing sensor configuration data.

JSON Configuration

Injects a JSON object with sensor settings.

View Flow JSON 
[
  {
    "id": "inject2",
    "type": "inject",
    "name": "Sensor Config",
    "payload": "{\"sensor\":\"dht22\",\"pin\":4,\"interval\":5000}",
    "payloadType": "json",
    "topic": "config",
    "wires": [["debug2"]]
  },
  {
    "id": "debug2",
    "type": "debug",
    "name": "Output"
  }
]

Use toggle mode to blink an LED every second — no Function node needed. The inject node alternates between true and false automatically.

Blink LED Every 1s

Inject with toggle mode drives gpio-out to blink an LED on pin 17.

View Flow JSON 
[
  {
    "id": "toggle1",
    "type": "inject",
    "name": "Toggle 1s",
    "intervalType": "seconds",
    "intervalValue": 1,
    "repeat": true,
    "toggle": true,
    "payload": { "value": true },
    "wires": [["led1"]]
  },
  {
    "id": "led1",
    "type": "gpio-out",
    "name": "LED Pin 17",
    "pin": 17
  }
]

Scheduled Injection

Automatically inject every 30 seconds to poll a sensor or check a status.

30-Second Timer

Injects automatically every 30 seconds.

View Flow JSON 
[
  {
    "id": "inject3",
    "type": "inject",
    "name": "Every 30s",
    "payload": "poll",
    "payloadType": "str",
    "repeat": "30",
    "wires": [["function1"]]
  },
  {
    "id": "function1",
    "type": "function",
    "name": "Process",
    "func": "msg.timestamp = Date.now();\nreturn msg;"
  }
]

Troubleshooting

Inject button doesn't work

Make sure the flow is deployed. Changes to nodes are not active until you click the Deploy button.

Cron expression not triggering

Verify your cron expression is valid. EdgeFlow uses standard 5-field cron format:

minute hour day-of-month month day-of-week

Example: */5 * * * * triggers every 5 minutes.

JSON payload shows as string

Make sure you've set the payload type to JSON (not string). The dropdown next to the payload field lets you select the type.

Related Nodes

schedule input

Advanced cron scheduling with timezone support.
debug output

Display messages in the debug panel.
function logic

Transform messages with custom code.