Simple illuminance chart card

Who it’s for

Building managers, facilities teams, and greenhouse growers ask “how has the light level changed over time, without the clutter of delta comparisons?” They want to see the current reading and a trend line in one card, nothing more.

What it does

A sensor currently reading 8 lx shows an orange value — Moderate — above a chart that reveals whether illuminance has been rising toward brighter conditions or falling toward darkness over the selected period.

• Large current illuminance value color-coded across five bands from Dark to Very Bright
• Time-series chart of illuminance readings over the selected time window, averaged per interval
• Shows one sensor’s data; it does not compare multiple zones or show period-over-period deltas

How to set up

Data keys

Key	Role	Type	Description
illuminance	Chart series	Timeseries	Illuminance in lx; drives the chart. The Latest value overlay is automatically derived from this same key
Latest	Latest value	Timeseries	The headline figure above the chart. Its own color ranges are where the band colors are edited

The widget ships with a simulated function datasource key labeled Illuminance, so it draws random values until you point the datasource at a device and rename the key.

To point it at your own device: open the dashboard in edit mode, open the widget’s Datasources, pick the entity or entity alias, and replace the function key with the key your device reports.

If the key has never reported for the selected time window, the chart is empty and the value overlay shows no data.

Value ranges

Range (lx)	Level	Color
< 1	Dark	Dark Gray
1–5	Low	Orange
5–20	Moderate	Orange
20–50	Bright	Red-Orange
50+	Very Bright	Red

How to customize

• To use your own illuminance thresholds — edit the color ranges on the Latest data key; adjust the five default bands to match your facility’s targets.
• To hide or show the chart — toggle Show chart in the widget settings.
• To change the chart line color — set Chart color.
• To show min, max, or total in the legend instead of avg — edit the Legend settings.
• To hide the entity name subtitle or the timestamp — turn off Show subtitle or Show date.
• To match your dashboard’s fonts — set the font options under each data key’s appearance settings.

Tips

• Use this card when the trend shape matters more than the exact period-over-period change. Add the full illuminance chart card if you need a delta percentage alongside the chart.
• A gradual downward trend through the day in a greenhouse can indicate cloud cover building up — useful context for automated lighting control systems.