Light bulbs

The candela; (cd) is the unit of luminous intensity in the International System of Units (SI), that is luminous power per unit solid angle emitted by a point light source in a particular direction. Luminous intensity is analogous to radiant intensity, but instead of simply adding up the contributions of every wavelength of light in the source's spectrum, the contribution of each wavelength is weighted by the standard luminosity function (a model of the sensitivity of the human eye to different wavelengths). A common wax candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured. The word candela is Latin and Italian for candle.

The SI base units are the standard units of measurement defined by the International System of Units (SI) for the seven base quantities of what is now known as the International System of Quantities: they are notably a basic set from which all other SI units can be derived. The lighting related units and their physical quantities are the ampere for electric current, the kelvin for thermodynamic temperature, and the candela for luminous intensity. The SI base units are a fundamental part of modern metrology, and thus part of the foundation of modern science and technology. The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter. For example, the metre has the symbol m, but the kelvin has symbol K, because it is named after Lord Kelvin and the ampere with symbol A is named after André-Marie Ampère. [Read more...]

Ambient temperature is an important factor to consider when making a lighting instalment. Heat can greatly compromise the well-being of the electronic components in a light fixture, so it is important to bear the room temperature in mind. In order to ensure that a lighting fixture is appropriate for the ambient temperature, designers can consult find a laboratory at the LIA website.

An LED is a diode which emits visible or infrared light when voltage is applied. These are common in all forms of lighting. LED is short for 'Light-Emitting Diode'. The creation of the first LED was reported by Russian inventor Oleg Losev who did so in 1927, but they were not made use of for several decades after the discovery. The voltage applied to and LED is regulated by LED drivers so that the the LED does not overheat and become damaged.

Edison is the term used to describe a lamp holder or light bulb with a screw style fitting (as opposed to one with pins which is known as Bayonet Cap) There are 3 main sizes: Small edison Screw - SES - E14 Edison screw - ES - E27 Giant Edison Screw - GES - E40 The numerical values, E40, E27 and E14 relate to the measurement in millimetres across the light bulb cap. E40 = 40mm, E27 = 27mm and E14 = 14mm Thomas Edison was the Inventor of some of the early versions of the incandescent electric light bulb.

Bi-colour LED is an LED designed to allow adjustment of the light's colour temperature from one colour to another. They are manufactured with a combination of balanced tungsten and daylight bulbs, allowing the LED to switch between warm and cold lighting looks, from green to red, or other colour combinations.

The Kelvin (K) is the SI base unit of temperature, named after the Belfast-born engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). Kelvin uses absolute zero as the null point (0°K) which is equivalent to -273°C (Celsius) or -459.67°F (Fahrenheit).

One Kilowatt hour (kWh) is equal to one thousand Watts sustained for an hour. Its SI base unit symbol is kWh. In terms of human power, a healthy adult male manual labourer performs work equal to about half a kilowatt-hour over an eight-hour day.

An LED driver is a self contained power supply which regulates the power applied to an LED or set of LEDs. The temperature of an LED light fluctuates, which is why the LED driver is important. Without one, the LEDs would become too hot and may fail or become damaged.

Colour temperature refers to the warmth or coolness of light. Warmer light appears more yellow and cooler light appears more blue. The warmth of white light is ranked on the Kelvin scale, ranging from infrared up to Ultraviolet with household fluorescent white light in the middle. The quantifiable scale at its lowest is 800°K which represents the colour of embers, and spans up to 12,000°K+ which is the colour of skylight. Most LEDs are produced to be either 2700k, 2800k, 3000k, 4000k or 5000k. 2700-3000k being warm, 4000-5000k being cool.

The lumen (L) is the the unit for luminous flux, which is a measurement of how much visible light is emitted over time. "If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, the total luminous flux emitted into that angle is one lumen (1 cd·1 sr = 1 lm). Alternatively, an isotropic one-candela light-source emits a total luminous flux of exactly 4π lumens. If the source were partly covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens. The luminous intensity would still be one candela in those directions that are not obscured." - Wikipedia

A heat sink is a heat exchanger which passively transfers the heat generated by a device away from itself by using an air or a liquid coolant, thereby allowing regulation of the temperature of the device. Heat sinks are important for LEDs as the thermal energy must be dissipated into the surroundings in order for the light to function properly. The heat sink is the last component in the thermal path of an LED luminaire and is also the most important. Heat sinks are manufactured using a variety of metal forming approaches, the most commonly used methods being casting, cold forging, extrusion and stamping. Other methods are also used such as bonding, forging, die cast, extrusion, stamping, machining, and stripping.

A dichroic reflector is used for display lighting and allows heat to pass through while reflecting the light in a cool beam that does not heat the display. You can tell dichroics apart from a ordinary lamp by shining a light at the back of it, if it's dichroic it will pass through and show a pink hue.

The Colour Rendering Index (CRI) measures how accurately a lamp reproduces the colours of the object it illuminates. The colours picked up by our eyes may differ from colours under natural lighting when using a low CRI lamp, and CRIs measure how accurate the lighting is to natural lighting so that we don't see any changes in colour. The value given by a CRI is an easily quantifiable score from 1-100, 100 being the best score and 1 being the worst.

Bayonet is the term used to describe a lamp holder or light bulb that uses 2 pins to lock in place. Also known as Bayonet Cap (as opposed to one with a screw thread known as an Edison fitting). The pins on a Bayonet Cap bulb "twist and lock" into the two slots in a Bayonet Cap Lampholder. There are 2 main sizes of Bayonet light fitting: Bayonet Cap – BC - B22d Small Bayonet Cap – SBC -B15d The numerical values, B22d and B15d relate to the measurement in millimetres across the light bulb cap. B22d = 22mm and B15d = 15mm.