Light Sensor

The Light Sensor is an automation building used to detect ambient light levels and send a signal based on whether a chosen brightness threshold is met. It is especially useful when a colony wants to mix natural sunlight with artificial lighting, since it can keep lamps off while sunlight is sufficient and turn them on only when the area becomes too dim.

This makes it a practical tool for crops and other setups that depend on strong light. Plants such as Gas Grass need extremely high light levels, while other plants only need a small amount of light or are affected by darkness. In a greenhouse or surface farm, a Light Sensor lets players take advantage of sunlight without wasting power during the day. Because sunlight follows a regular day-night cycle, a Cycle Sensor or Timer Sensor can sometimes approximate the same behavior, but the Light Sensor is more direct because it reacts to actual brightness instead of time.

It is also useful anywhere light has a gameplay effect. Any cell with more than 0 lux counts as lit, which affects decor, the Lit Workspace status, and some recreational or duplicant interactions. A Light Sensor can therefore be used to manage lamps in work areas, dining spaces, or other rooms where players want light only when it provides a benefit.

Practical uses include:

• Automatically turning lamps on only when natural sunlight is not enough.
• Supporting light-dependent farming without keeping lights powered all day.
• Preserving the benefits of lit areas, such as the Lit Workspace bonus, while reducing electricity use.
• Coordinating with surface sunlight, which is strongest during the day and absent at night.

When building around sunlight, it is worth remembering that the sun’s light can be intense enough to reach very high brightness levels on exposed surfaces, while shaded areas can quickly fall to darkness. A Light Sensor is therefore most valuable in mixed-light setups, where the goal is to let sunlight do the work whenever possible and fall back to artificial light only when needed.