Photocells
Photocells, Light Sensors for Automatic Dusk-to-Dawn Control
Photocells, also called photo controls or light sensors, automatically switch lighting circuits on or off based on ambient light levels. In industrial and commercial applications, they are commonly used for dusk-to-dawn control of outdoor area lighting, parking lots, security lighting, and signage, helping reduce energy use and ensuring lights operate only when needed. For object presence, part counting, or color/mark detection on machines and conveyors, see our photoelectric sensors, which provide precise, fast-acting optical switching.
A photocell monitors outdoor light and closes or opens its internal contacts when the light level passes a set threshold. Wired in series with a lighting load or control circuit, it can turn fixtures on at dusk and off at dawn without manual intervention or time-clock adjustments. Devices are available in fixed- and adjustable-setpoint versions and are rated for different voltages and load types, including LED and traditional discharge lighting.
Galco's photocell offering includes controls suitable for fixture-mount, junction-box, and panel installations, allowing maintenance and design teams to match voltage rating, mounting style, and environmental protection to each lighting or control application.
Frequently Asked Questions
What is the difference between a photocell and a motion sensor?
A photocell detects changes in light level, such as dusk-to-dawn transitions or beam interruption, without requiring movement. A motion sensor (e.g., a PIR or microwave sensor) detects movement. Photocells are ideal for light-based control, while motion sensors respond only when something moves.
Can photocells operate correctly in direct sunlight?
Some photocells can, but others may become saturated or less accurate when exposed to intense sunlight. For outdoor use, choose a photocell rated for high ambient light levels and ensure it is mounted in a shielded or appropriate orientation.
Can a photocell be connected directly to a PLC?
Yes, if the photocell provides a compatible output such as NPN, PNP, relay, analog, or digital signal. Always verify voltage and current requirements to ensure correct integration with the PLC input module.