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how motion sensor security lights work

Shadowy garden? Dark passageways? Fitting a security light outside your home is a quick and easy route to peace of mind for when the darker evenings draw in. As a relatively affordable and straightforward piece of equipment to install, a motion sensor security light helps alleviate fears around home security and makes navigating dark outdoor spaces much safer when returning home late.

How Motion Sensor Security Lights Work

Motion sensor lights work like little electronic eyes, keeping watch over your property. The PIR (Passive Infrared) sensor detects infrared waves, which are heat waves that radiate from moving objects such as people and animals, but also from warm objects like cars. When a sensor detects these infrared waves moving across its field of view, it automatically triggers the lights to come on.

Most security lights will then stay on for a set period of time, depending on the chosen settings, and will only switch off if the sensor no longer detects any movement. A photocell is also fitted to most models to prevent the security light from operating during daylight hours by automatically deactivating the sensor. Most outdoor motion sensor lights have settings that allow you to adjust the field of view and distance of detection, so you can tailor your lights to the particular needs of your property.

Things to Consider When Fitting a Security Light

  1. Choosing the Right Type of Security Light

There are several styles to choose from when fitting a security light, with the style you choose depending on the individual needs of your property. The main types include:


These are the most common type of motion sensor lights chosen by security-conscious property owners. Floodlights are usually wall-mounted on a bracket and then adjusted until perfectly angled to cover the chosen area. The wide angle coverage and bright light makes floodlighting perfect for illuminating large areas of gardens, grounds and driveways, but the most powerful bulbs can sometimes create glare which can be disadvantageous if you rely on the security light to help you navigate the property.

You can get several different types of floodlight including LED and solar floodlights, both of which are highly energy efficient and last a long time. Halogen bulbs have also commonly been used as security floodlighting due to their power and brightness, however these are now being phased out and will no longer be available.

Decorative Security Lights

Better suited to illuminating smaller areas such as porchways and paths, are great for providing a little extra safety while looking stylish and elegant. Usually available as wall-mounted or lamp post style lanterns, decorative PIR sensor lights give you the convenience of automatic security lighting without disrupting the aesthetic of your home exterior. The only downside is that they are often less powerful and won’t illuminate particularly large areas of a property.

Bulkhead Lights

Designed more with functionality than appearance in mind, bulkhead lights are a highly practical and energy efficient way of illuminating your outdoor spaces. Traditionally made with thick, prismatic glass and protected with a wire cage, bulkhead lights are designed to be durable, weather-resistant and provide constant lighting for outdoor areas. You can, however, find bulkhead-style lights with PIR sensors to provide motion-activated lighting for security and safety purposes, with many sleek and modern designs available alongside the traditional styles.

  1. Deciding Where to Fit Your Security Light

Fitting a security light or a set of multiple security lights requires you to first decide which areas of your property need them the most. If security against intruders is your first priority, then you are best positioning motion-activated lights on the approach to all entrances and approaches to your property. This includes front and back doors, gates, pathways, driveways, patio doors and balconies, as well as some of the darker areas of your garden. Of course, good lighting cannot guarantee safety but it can be highly effective in making intruders think twice about approaching any further if they are clearly visible.

If your own safety is the higher priority, i.e. navigating outdoor spaces in the dark without falling, all of the above areas remain useful places to position your lights. Placing motion-activated lighting on driveways and in porches and front door areas ensures your lighting will be activated when you return home at night. You should also place lighting around dark pathways, steps, water features and swimming pools to prevent any dangerous falls or loss of footing in the dark.

Motion sensor lights are usually best placed at around 6 to 10 feet (1.8 to 3 meters) above the ground and facing downwards. The higher the lights are placed, the wider the radius they will cover. Placing your lights higher up will also mean that the light becomes softer as it reaches ground level, which will create fewer blind spots created by shadows – bad news for intruders, good news for you. That being said, don’t place your lights too high or the light won’t be powerful enough to reach the areas you need it to, and the PIR sensor may also not be able to detect the movement of any would-be intruders.

  1. Considering Your Neighbours

While fitting security lights means peace of mind for you, it can mean irritation for your neighbours if you’re not mindful of where you place them. If your security lights are activated every time your neighbour opens a door or walks through their garden, it’s going to get annoying. Your lights also need to be sensitively placed so as not to shine into your neighbours’ windows and dazzle them, as this will only ever lead to complaints. Once you’ve installed your lights, it’s a good idea to politely inform your neighbours and ask them to let you know if the new lights cause any problems.

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