How Do Solar Powered Security Lights Work

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We take the sun for granted. Every day we wake up to it. We enjoy its warmth, and its light. But it can do so much more than just warm us up. It generates huge amounts of energy in the form of light. The sun produces more energy than all the power stations in the world combined so it seems a shame to waste it. We could use it to power toasters, fridges, TVs MP3 players, factories and much more.

Solar powered security lights need no electricity; they are powered by the suns energy. They are designed to work all year round, even in the UK where we have a lot of cloud cover. The suns energy is so great that it passes through clouds, albeit not so strong, meaning solar powered security lights will work even on cloudy days in the UK. Because they dont require any mains electricity they are green and can be used just about anywhere.

Solar powered security lights are made up of three primary items; the solar panel, the light unit and the PIR (switch).

Solar panel.
The sun produces a range of energy. We can only see the visible white light produced by the sun. Specific rays of a different wavelength to visible white light produced by the sun are collected using the solar panel also known as a photovoltaic panel (PV). The solar panel is made of lots of electrodes covered in a conductive solution. When the sunlight, or daylight, shine son these electrodes they create an electric current. This electricity is clean, environmentally friendly electricity in the form of Direct Current (DC). Solar panels are static energy producers. They have no moving parts which could break and are completely silent making them perfect for residential use.
This electricity passes down a wire to the batteries inside the light unit.

Light unit.
The light unit is made up of three things, the light, the PIR (motion) detector and the batteries.
The batteries are usually located within the light unit. These are charged daily by the DC electricity produced by the solar panel. The amount of electricity produced to charge the batteries is dependent on how strong the sun is and how many hours of daylight there is. Also, the greater the size of the solar panel, the more electricity which can be produced. The batteries then store this energy until it gets dark, when they power the light every time the unit is triggered.

Security lights often need to be very bright so that they can illuminate large areas. Mains powered security lights use halogen bulbs. These produce very strong, bright light. However, halogen bulbs use a great deal of power. These bulbs are no good for solar powered lights as they will use up the power stored in the batteries far too quickly.
Instead, solar security lights use LEDs (light emitting diodes). LEDs only use very small amounts of energy making them ideal for solar powered lighting. Used on their own these are not as bright as a halogen bulb, but use 30 or more together and you can produce the same amount of light as a halogen bulb would but with far less energy consumption. LEDs also last for extremely long periods of time meaning that dont need replacing like halogen bulbs.

PIR sensor.
Security lights work when motion is detected at night. If the movement of a person or animal occurs within a certain range of the light a switch is triggered, turning the light on and illuminating whoever or whatever caused the light to be triggered. This movement is detected by a PIR (Passive Infrared) sensor. This sensor is just like a switch that turns the light on. These sensors can usually be adjusted so that they work depending on how dark it is, known as the LUX, and they time how long the light should illuminate.

When all of these components are used together you have an extremely energy efficient security light which can be mounted almost anywhere making it perfect for illuminating alleyways, homes, gardens, driveways and just about anywhere you can think of.