> For the complete documentation index, see [llms.txt](https://docs.augelab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.augelab.com/function-blocks/blocks-reference/input-output/outputs-exports/led-output.md).

# Led Output

This function block provides a simple visual indicator for boolean signals. Use it to quickly check whether a condition in your scenario is TRUE, FALSE, or undefined.

## 📥 Inputs <a href="#inputs" id="inputs"></a>

`Boolean` This input socket accepts a boolean signal to drive the LED indicator. Connect any logic or condition output here.

## 📤 Outputs <a href="#outputs" id="outputs"></a>

This function block does not have outputs.

## 🕹️ Controls <a href="#controls" id="controls"></a>

`led` Visual LED indicator shown on the block:

* Gray — input is undefined / None.
* Green — input is TRUE.
* Red — input is FALSE.

## 🎨 Features <a href="#features" id="features"></a>

* Real-time visual feedback for boolean signals.
* Clear color coding for three states: undefined, TRUE, and FALSE.
* Lightweight and suitable for dashboards or quick debugging.

## 📝 Usage Instructions <a href="#usage" id="usage"></a>

1. Provide a boolean signal to the `Boolean` input.
2. Observe the `led` color to understand current state:
   * Green for TRUE
   * Red for FALSE
   * Gray when no value is present

Use this block on UI screens where immediate visual feedback is helpful.

## 📊 Evaluation <a href="#evaluation" id="evaluation"></a>

When the scenario runs, the block checks the boolean value arriving at the `Boolean` socket and updates the `led` color accordingly. If no value is present, the indicator shows the undefined state.

## 💡 Tips and Tricks <a href="#tips-and-tricks" id="tips-and-tricks"></a>

* For manual testing, connect a `Logic Input` to the `Boolean` socket so an operator can toggle the LED on the fly.
* Combine condition checks before the LED using logic blocks such as `And`, `Or`, and `Not` to visualize combined conditions.
* Use comparison blocks like `Equals`, `Greater`, or `Smaller` to convert numeric measurements into boolean signals for the LED.
* Use edge detectors such as `Rising Edge` or `Edge Rising` to show event pulses instead of continuous states.
* Add temporal behavior with `Delay Step`, `ON Delay`, or `OFF Delay` if you want the LED to respond only after a sustained condition.
* Use `Set - Reset` to latch a condition and keep the LED on until explicitly reset.
* Integrate with data or communication blocks upstream (for example, use `Data Write Local` / `Data Write Global` or `MQTT Publish` on the logic feeding this block) to reflect remote or network-driven states locally.

## 🛠️ Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* LED stays gray: Check that the previous block is producing a boolean value. Consider using `Is None` or a simple `Logic Input` to test the path.
* LED always red/green but condition seems wrong: Verify the upstream logic (comparisons, merges) with intermediate indicators or debug blocks before connecting to the LED.
* Need persistent indicator for transient events: Use `Set - Reset` or an edge-to-latch pattern so a short pulse becomes a sustained visual state.