Fluorescent - Not Fluorescent
A reputable company had a feature in an equally reputable digital magazine recently, promoting the festive lighting display they did for an even more reputable retailer in London back in 2015 – the article was interesting, but I stopped reading at – “With a final count of over 3,500 fluorescent LED tube lights… “
It’s simply incorrect.
Mask. deals with many engineers and architects, as well as lighting suppliers and manufacturers from around the globe. It’s astounding how often then term “LED fluorescent” is used to describe something, and I’ve even seen this in print by esteemed publications and heard it in argument by engineers to win a point. It’s difficult to take someone seriously when they don’t even get the terminology correct. We understand that those who write the copy are not always the specialists in the field – but it saves a reputation to understand the difference. Fluorescent lighting and LED lighting are two distinct technologies with different principles of operation.
Fluorescent Lighting
Fluorescent lighting is well known to most of us- the long tubes that can be fun to pretend are lightsabres, until you realise, they can break and cut you. It’s a type of lighting technology that involves the use of gas and a phosphor coating to produce visible light.
Here’s a basic explanation of how fluorescent lighting works:
A long, narrow tube or the smaller spiral tubes in CFLs; are typically made of glass. The tube is filled with a small amount of mercury vapor and a trace amount of an inert gas, usually argon.
When an electrical current passes through the gas, it causes the gas to become ionized. (the gas sends an electron away, upsetting the balance in the tube).
Electrons in the ionized gas gain energy, and when they collide with mercury atoms, they can knock electrons out of the mercury atoms in a process called electron impact ionization. This ionization of the mercury atoms results in the release of ultraviolet (UV) photons. We can’t see these UV photons, but they are only the first part of the story. Photons are created when electrons in atoms get all excited and then release that extra energy as light.
The inner surface of the fluorescent tube is coated with a phosphor material. The specific composition of the phosphor coating varies, but they usually appear white. Different phosphors produce different colours, allowing for a range of options, from warm to cool whites and various colours. In a black light, this coating is more translucent, and lets a lot of the UV out, which is when you get the fun “neon” effects where your teeth glow like Ross’.
As the UV light strikes the phosphor coating, it excites the phosphor atoms, causing them to emit visible light.
Fluorescent lights require a ballast, a device that regulates the electrical current flowing through the tube. The ballast provides the initial surge of voltage needed to start the lamp and then regulates the current to keep it stable during operation. During the regular operation of the fluorescent lamps, the electrical resistance of the gas in the fluorescent tube decreases, which causes the current to keep increasing. If this is not regulated by a ballast, the lamp will very quickly fail, possibly damaging things around it.
Fluorescent lighting has several advantages, including energy efficiency and a longer lifespan compared to traditional incandescent bulbs. However, it also has some drawbacks, such as the presence of mercury in the tubes, which can be an environmental concern if not properly disposed of.
LED Lighting
LED lighting is the foundation of 21st century illumination, and almost everyone claims they are familiar with it, and understand it. Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. Here’s a simplified explanation of how an LED works:
An LED is made of semiconductor materials; the specific semiconductor materials used determines the colour of the light emitted. (See THIS post for more info on “light colour/temperature”) “Semi”- “conductor” materials are combinations of conductive materials like copper and aluminium, and non-conductive materials like glass or rubber. Where these materials meet, a p-n junction is created. A p-n junction is the boundary between two types of semiconductor materials: one with an excess of positive charge carriers (p-type) and the other with an excess of negative charge carriers (n-type).
When a voltage is applied across this p-n junction by connecting the LED to a power source, electrons from the n-type material move toward the p-type material, and holes (positively charged spaces where electrons have left) from the p-type material move toward the n-type material.
As electrons and holes move across the p-n junction, they recombine. When an electron falls into a hole, it releases energy in the form of a photon (light particle). The energy of the photon is determined by the bandgap of the semiconductor material. Some explain this by describing what the photons do as “jumping the gap” – the type (‘size’) of gap determines the amount of energy of the photon, and its colour. Higher energy photons are closer to the blue end of the spectrum.
These wayward jumping photons in LEDs are all in the UV range, much like the photons in fluorescent lighting. The little yellow blocks that you see when looking at any LED lamp or fixture, is also phosphor. These can be made up with varying chemical combinations and determine the CCT of the LED. These little phosphor blocks get excited with UV photons, and then the phosphors release visible light. The efficiency of this process is one reason why LEDs are so energy-efficient compared to other light sources.
By choosing different semiconductor materials or by using a combination of materials, manufacturers can produce LEDs that emit light in a variety of colours, including red, green, blue, and white.
LEDs respond quickly to changes in electrical currents, allowing for instantaneous on/off switching. This rapid response is advantageous in applications such as displays, indicator lights, and automotive lighting. The quick response to electrical current also mean it’s sensitive to changes in voltage (which we take advantage of for dimming.)
Fluorescent lights need time to start and warm up to reach their full brightness, which make it tricky to use them for quick-changing lighting displays. They’re also rarely dimmable, and if so, much more expensive.
LEDs also need current regulating components, but they’re not ballasts, they’re called drivers (often called controllers, or slightly incorrectly, transformers). These make sure that either the current or the voltage going to the LED is constant, so the LED doesn’t become damaged from a power surge. (I’ve personally damaged 3V LEDs because I didn’t realise, they were 3V, and turned the power up to 5V by mistake. They failed quite spectacularly).
Both LED and fluorescent lighting have their strengths and considerations: both are energy efficient and offer a variety of applications. Both have a long lifespan and offer excellent lighting quality. Both need components to safeguard the electrical circuit and use UV photons to create light via phosphorus layer of some kind. Both need to be disposed off safely at the end of their lives. It’s important to remember that LED is likely to surpass fluorescent technology on each criterion as times goes on, but for now – they’re not the same thing.
Should you have any additional questions, please do not hesitate to reach out.
hello@mask-design.co.za
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