A photocell, also known as a photo-sensor or dusk-to-dawn sensor, is a light-sensitive electronic component that automatically turns lights on at night and off again during the day. This simple and reliable device is the key to automating all of your outdoor and security lighting, providing enhanced safety, energy efficiency, and "set it and forget it" peace of mind.
How Photocells Work
The magic of a photocell lies in a tiny component called a photoresistor, which changes its electrical resistance based on the amount of ambient light it detects.
- At Dusk: As the sun sets and the natural light level falls below a certain threshold, the sensor's resistance increases. This change triggers an internal switch, closing the electrical circuit and turning the connected lights ON.
- At Dawn: When the sun rises in the morning, the sensor is exposed to light again. Its resistance drops significantly, which causes the switch to open the circuit, turning the lights OFF.
This simple, automated cycle ensures your lights are only running when they are actually needed, which dramatically reduces energy consumption and extends the lifespan of your light bulbs.
Types of Photocells
Photocells come in a variety of shapes and mounting styles to suit any fixture or application.
- Button Photocells: These are small, discreet, and one of the most common types. They are designed to be mounted directly onto an outdoor light fixture or a junction box through a small drilled hole, providing a clean, integrated look.
- Swivel Mount Photocells: Featuring an adjustable arm or "swivel," these sensors can be aimed with precision. This is useful for positioning the sensor towards open sky while avoiding interference from other artificial lights that could cause it to turn off prematurely.
- In-Wall Switch Photocells: This device combines a photocell with a standard wall switch. It replaces a regular switch indoors and is used to control an entire circuit of outdoor lights, often including a manual override for convenience.
- Plug-In Photocells: The easiest option for temporary or decorative lighting. This portable adapter plugs into any outdoor outlet, and you then plug your string lights or holiday decorations into the adapter for instant dusk-to-dawn automation.
Advanced Control: Dimming and Daylight Harvesting
Beyond simple on/off functionality, advanced photocells are used in commercial and energy-efficient buildings for a strategy called "daylight harvesting."
- Dimming Control Photocells: Unlike a standard photocell that acts like a switch, a dimming photocell acts like a throttle. It provides a variable low-voltage signal (typically 0-10V) to a dimmable LED driver or ballast. Instead of just turning lights on or off, it tells them how bright to be. More daylight results in a lower signal and dimmer lights, while less daylight results in a higher signal and brighter lights.
- Daylight Harvesting: This is the practical application of dimming photocells. The goal is to maintain a consistent, optimal light level in a space by using natural light as the primary source. In an office with large windows, the photocell will detect the abundant sunlight and dim the indoor lights. As clouds pass over, the sensor will instantly tell the lights to brighten to compensate. This process of supplementing natural light with the precise amount of artificial light needed can reduce a building's lighting energy consumption by 20-60%.
Common Applications
Photocells are the standard for automated control in countless outdoor lighting scenarios.
- Security & Area Lighting: For floodlights, wall packs, and barn lights around a home or commercial building.
- Landscape & Accent Lighting: To automatically illuminate pathways, gardens, and architectural features.
- Entryway Lighting: Perfect for porch lights, post lanterns, and garage sconces.
- Commercial & Municipal Lighting: The primary control method for most streetlights, parking lot lights, and building exteriors.
Reliable, Automated Lighting Control
A photocell is a cost-effective and dependable way to ensure your property is always safe, secure, and welcoming after dark. By removing the need for manual switching or complex programming, it provides simple, worry-free automation for any outdoor lighting system. Ensure your property is always well-lit at night and saving energy during the day. Explore our complete collection of durable and accurate photocell sensors at Bees Lighting.
