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What’s the Difference Between Motion Sensors and Photocells?

Difference Between Motion Sensors and Photocells

Electronic gadgets that you can use to control interior or outdoor lighting include photocells and motion sensors. Your home’s security and safety are enhanced by these sensors, which turn on lights automatically at dusk or when they sense motion. Additionally, they conserve energy by shutting off when additional light is not needed. Discover how photocells and motion sensors differ from one another and how they might improve your home’s lighting system in conjunction with dimmers and other controls.

What Is A Photocell and How Does It Work?


An LED light can be turned on or off automatically by a photocell, a device that senses ambient light levels. It is very helpful for lighting outdoor spaces.

Photocells are variable resistors that, depending on the amount of light in the area where they are installed, change the resistance in an electrical circuit. They must be positioned in exposed locations with enough light to perform correctly. Depending on the particular light fixture, photocells—also called photo controls—can be added as an accessory or integrated into the luminaire. They are available in a variety of sizes and designs.

Can a Photocell Be Bypassed?

When necessary, it is sometimes possible to avoid using a photocell. The luminaire can be turned on and off continuously or controlled by an existing switch or timer by avoiding the photocell. The type of photocell and how it is mounted in the fixture determine the bypassing technique. Using a shorting cap, a slide or DIP switch, or cutting the photocell’s wiring are common bypass techniques. It’s crucial to go to the light fixture’s user handbook to ascertain which option or options apply to you and how to utilize them safely. Before doing any wiring, always use caution and switch off the power source.

Shorting Cap

Many commercial applications use twist-lock sockets or adapters to place photocells externally, such as parking lots and area illumination. The circuit in the LED light fixture is closed by swapping out the photocell for a shorting cap, which maintains the light’s constant on state. If a central photocell or switch system is being used, this permits external control.

The Science of Photocells

Although photocells come in a variety of forms, they all regulate electric current using the same underlying semiconductor technology. Semiconductors don’t conduct electricity under normal circumstances, but when they get enough light, current begins to flow. You can select the light level that triggers the semiconductor in certain items that have adjustable photocell functions.

Photocell Functions: Dusk to Dawn

Photocells are frequently used to switch on outdoor lights at dusk and off at dawn. Photocells are insensitive to daylight-saving time because they detect ambient light levels, which allows them to automatically adapt to seasonal variations in the day/night cycle. When timers are used to switch on interior fixtures and photocells regulate outdoor lights, the illusion of occupantship is created, potentially discouraging potential intruders. Additional applications for photocells include turning on street or parking lot lights after dark, modifying indoor dimmers to account for variations in natural light, and turning on or off lit business signage.

Types of Photocells

Today, a wide range of photocells are accessible.Plug-in photocells regulate a pass-through plug by using a regular wall outlet. They provide a practical method of turning on and off a single floor or table lamp.
Almost any lamp or permanent fixture can become an automated lighting system by simply screwing in lamp or candelabra base photocells into the bulb socket. For each socket to function properly, one of these devices must be installed.
An electrical circuit can be fully controlled by connected, line-voltage photocells, which are perfect for controlling landscape or security lighting.

Motion Sensors in Action

Photocells and motion sensors are primarily distinguished by the fact that the former sense changes in light levels while the latter responds to actual motion. Two varieties of motion detectors exist. Active models have radio, light, or ultrasonic sound outputs. The sensor is activated by movement within the detection area, which modifies the reflected signals. Even some of these gadgets include motion detection around corners. Warm objects, like people or animals, release infrared energy, which is detected by passive motion sensors. The sensor and any electrical circuits that are attached are activated when these heated areas shift.

Detector Functionality

Outdoor lights are frequently activated by motion sensors, which sense movement within their detection range. In commercial buildings, they also serve as energy-saving occupancy sensors that switch off lights in vacant offices. Adjustable sensing regions on a lot of these items let you to cover certain areas, such driveways or walking routes, without picking up movement from surrounding streets or tree branches.

Motion Sensor Varieties

The majority of motion sensors made specifically for managing outdoor lighting connect straight to a 120-volt circuit and include numerous fixture controls. Alerts from security system sensors are wirelessly transmitted to a base station and are frequently powered by batteries. Since some standalone motion sensors come with built-in lights, installing and using them practically anyplace is made simple.

Bright Ideas for Lighting Applications

There are several control choices for both interior and outdoor lighting systems because to the distinctions between photocells and motion sensors.

To turn on security lights around your house, use a motion sensor and photocell combination, but only after dark.

To provide safe footing whether walking the dog or bringing out the trash at night, install motion sensor lights and outdoor lighting along a sidewalk or garden path.

Use a photocell to make sure that ornamental light fixtures are always on after dark.

A lamp, a plug-in photocell, and a conventional light switch can be combined to produce an automatic light that you can only turn on when necessary.

To provide hands-free stairwell lighting, use motion sensors that include built-in lights.

Photocells and motion sensors use light levels and sensed motion to determine when to turn on or off the electricity. They work with a variety of light fittings, and some of them are compatible with security systems. These adjustable controls will save you energy while improving the aesthetics and security of your house.

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