Daylight harvesting sensors play an essential role in automated lighting control systems by monitoring a room’s ambient light level and transmitting that data to digitally connected load controllers. These controllers then interpret the information and adjust the lighting output based on the configured setpoint and operational mode. This automatic adjustment ensures that electric lighting complements available natural daylight, maintaining a consistent and comfortable illumination level across the space while reducing unnecessary power consumption. The sensors are popular among electrical contractors due to their flexible mounting options and digital pairing methods, which significantly reduce installation time and complexity. An auto-setpoint selection mode simplifies setup by helping calibrate the ideal light level for each environment automatically.
These digital daylight harvesting sensors operate as part of a broader digital communication network using a topology-free, 3-wire data line connection. The wiring system employs standard 18/3 cable and wire nuts, eliminating the limitations and reliability concerns often found in CAT-5-based systems. Each sensor is individually addressable, allowing them to be digitally zoned with load controllers and wall stations through one of three configuration methods: the out-of-the-box single-zone default mode, a push-button pairing sequence for multi-zone applications, or configuration via a mobile application that requires the SWD-940 Advanced Load Controller. Once the devices are paired, each digital control zone can be fine-tuned with multiple operating modes, dimming ranges, and photocell parameters to achieve optimal performance across varied lighting environments.
During standard operation, a daylight harvesting sensor automatically measures the amount of natural light entering a space and adjusts the controlled lighting accordingly. Through an initial auto-setpoint calibration process, the sensor establishes the ambient light threshold required to maintain balanced brightness. When daylight levels are high, the system gradually reduces artificial light output to maintain the target illumination level. Conversely, when daylight decreases, the lighting automatically increases to compensate, ensuring consistent brightness throughout the day. In areas with consistently high daylight contribution, lighting can even be configured to switch off completely for maximum energy savings. The calibration process is easily initiated via a quick push-button command on the photocell, while additional preset values for light thresholds can be selected directly from connected load controllers.
Two primary photocell control modes are available: On/Off Photocell Control and Daylight Harvesting Control. On/Off control is best suited for transitional areas such as hallways or entryways, where abrupt changes in lighting are acceptable and unlikely to disturb occupants. In this mode, the sensor’s photocell output turns lights off when the ambient light level exceeds the defined threshold and turns them back on when the light level drops below it. To prevent rapid on/off cycling, a deadband level—equal to the controlled light’s measured contribution—is automatically maintained, ensuring that lights remain stable and responsive only to meaningful daylight variations.
Daylight Harvesting Control, on the other hand, is ideal for occupied spaces like offices and classrooms where comfort and visual consistency are critical. In this mode, the sensor gradually dims electric lighting as daylight increases, maintaining the desired overall brightness without sudden changes. Once lights reach the designated low trim level, the system can optionally turn them off entirely when natural light alone is sufficient. This functionality maximizes efficiency while maintaining occupant comfort and adherence to lighting standards.
These digital photocell sensors integrate seamlessly with load controllers and remote wall stations within the same network, forming a unified control system that meets modern energy code requirements such as ASHRAE 90.1, IECC, and Title 24. Each unit features a compact, matte-finish housing that complements architectural spaces, and installation is streamlined through contractor-friendly mounting options, including a nipple attachment with an integrated hole saw. Communication occurs through a secure, digitally encrypted proprietary protocol over a 3-wire data line that supports point-to-point distances of up to 1,000 feet and total bus lengths of up to 4,000 feet.
The sensors operate at 15 VDC with a low current draw of approximately 8 mA, supporting reliable long-term performance even in distributed lighting networks. LED indicators on each unit provide visual confirmation of pairing and communication status, while test modes allow installers to verify sensor operation quickly by toggling paired controllers or isolating zones for coverage testing. Each system can be configured for daylight harvesting or On/Off photocell operation through its paired controller, with parameters easily adjusted to match specific environmental and energy performance goals.
With their blend of simple installation, intelligent self-calibration, and secure digital connectivity, these daylight harvesting sensors form a crucial component in modern building automation and lighting control systems. They allow precise daylight integration, flexible zoning, and consistent compliance with energy efficiency standards, all while maintaining a clean aesthetic and minimal maintenance requirement.
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