What Is a Photocell?
Photocell is a light-sensitive electrical control that detects surrounding brightness and switches a connected light on or off. Outdoor lighting commonly uses a photocell to turn fixtures on at dusk and off at dawn. The device supports automatic operation without a wall switch or timer, although placement and wiring affect performance.
Quick Facts About Photocell
Category
Light-sensitive control
Used for
Automatic outdoor lighting
Common confusion
Motion sensor
Also called
Photoelectric Cell, Dusk-to-dawn sensor
Often discussed with
Security Lighting Installation, Lighting Repair
Key Takeaways About Photocell
- Light level, not motion, triggers the control.
- Placement affects when the fixture switches.
- A photocell is not the same as a motion sensor.
How Photocell Works
A photocell senses the amount of visible light around its housing. Its internal control changes electrical state as daylight fades or returns, which allows a connected fixture to operate automatically. The control does not detect movement, sound, or occupancy. A motion sensor responds to activity, while a photocell responds to ambient brightness.
Related glossary terms: Line Voltage, Disconnect Switch, Electrical Load.
Outdoor fixtures often place the sensor where it can read natural light without seeing the fixture's own output. Direct light from a nearby lamp can cause unwanted switching. Shade, dirt, orientation, and surrounding buildings can also affect the reading. During a security lighting installation, the photocell connects to the lighting circuit and is checked during changing light conditions to confirm reliable operation.
From the Center Electric Service team
When we install security lighting, we check the photocell's location, wiring, and view of the sky. We also test the fixture's response after covering the sensor and exposing it to light. Our team looks for nearby lamps or obstructions that could cause cycling or delayed operation.
Photocell in Practice: A Real-World Example
A homeowner wants a side-yard security light to operate automatically after sunset. A photocell mounted where it receives natural daylight can switch the fixture on in the evening and off after daylight returns.
Related Services
Related Terms
Line Voltage
Line voltage is the electrical pressure supplied by a building’s power system to operate equipment, lighting…
Disconnect Switch
A disconnect switch is a manually operated device that separates electrical equipment from its power source…
Electrical Load
Electrical load is the amount of power that connected devices and equipment draw from an electrical…
Center Electric Service
Have Questions About Photocell?
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