AC stands for Alternating Current, and is a term used to describe the nature of the voltage/current flowing in a circuit. AC is commonly used for halogen lighting, and 230V AC - 240V AC is the supply in all New Zealand households that are connected to the national grid.
The positive terminal of a diode. For a through hole LED, this is the longer leg and the smaller terminal within the LED.
The candela is the SI base unit of luminous intensity; the power emitted by a light source in a particular direction. An ordinary wax candle generates one candela.
The negative terminal of a diode. For a through hole LED, this is the flat side on the lens and the larger terminal within the LED.
Correlated Colour Temperature or CCT rating is an indication of how "warm" or "cool" the light source appears, measured in Kelvins. Warm White LEDs are typically 2800-3500K, while Cool White is 6000-7000K. A blue tint appears above 7000K. The colour temperature for an LED is usually specified as a range.
The LED Die within the package is sometimes referred to as a Chip. The power of an individual LED is commonly increased by way of adding multiple chips within a single package. For example, many 5050 SMD LEDs have 3 chips within the one package, and LED flood lights can have more than 100 chips.
Chip-on-Board or COB refers to the mounting of a bare LED chip in direct contact with a substrate (such as silicon carbide or sapphire) to produce LED arrays. It is a newer alternative to SMD LEDs (see below) and offers a range of benefits including improved lumen density, which results in higher intensity and greater uniformity of light.
CRI is the quality of light and is represented by a number from 1 (worst) to 100 (best). A CRI of 100 means the light has the same quality as sunlight, it is pleasant and all colours look natural. If the CRI is below 50, the light has an unpleasant feel and colours look unnatural (for example, skin appears less pink).
DC stands for Direct Current, and is a term used to describe the nature of the voltage/current flowing in a circuit. DC is supplied from a Power Supply as it puts out a constant voltage, and is common in low voltage applications. Many LED products require a DC voltage (such as 12V, 24V or 48V) including LED strip lighting, LED modules etc.
LEDs are actually much smaller than the package they are sold in. They consist of a small amount of semiconductor material called a Die which is mounted in a package for the ease of handling, mounting and thermal conductivity. The LED die is sometimes referred to as a Chip.
A driver is an electronic device that outputs a constant current, required for directly driving high power LED chips such as the CREE XR-E series. The term Driver should not be confused with a Power Supply or Transformer, as it has a very different function. Common output values for a driver are 350mA, 700mA and 1A, however other values can be used within an LED product.
LED stands for Light Emitting Diode and it is an electronic semiconductor component. If current flows through the diode, light is emitted with a wavelength that depends on the semiconductor material.
A lumen is a unit of standard measurement used to describe how much light is contained in a certain area. The best way to compare the total brightness for LED products is to compare their lumen outputs.
Lux is lumen per square meter. The difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. 1000 lumens, concentrated into an area of one square meter, lights up that square meter with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produces a dimmer illuminance of only 100 lux.
Developed by David MacAdam in 1940, the MacAdam Ellipse is a measure for the quality of light. When testing what colours are perceived as the same, he discovered that all colours around a reference colour in a chromaticity diagram, which are indistinguishable to the average human eye, are circumscribed by an ellipse. MacAdam calls it a 1-step ellipse. Other concentric ellipses with the same distance to the reference point as the first ellipse are called 2-step, 3-step, 4-step ellipses and so forth. A 1116 ANSI binning can be described by a 3-step MacAdam ellipse and is currently the smallest binning offered by LED manufacturers. In 1-step binning, differences are not visible, while in 2 & 3-step binning differences are not or hardly visible. 4-step binning is where differences are visible.
A power supply is often used to power low voltage LED products such as LED strip lighting, MR16 bulbs etc. A power supply outputs a DC voltage which is required by many of these LED products and should not be confused with a transformer or driver.
RGB, RGBW, RGBCW, RGBCCT
RGB lighting products have Red, Green and Blue LEDs which can be mixed to produce a range of other colours. RGBW products also have a Warm White LED in addition to the Red, Green and Blue, and RGBCW has a Cool White LED. You can mix the colours of the RGBW to get a Cool White light, however it is not as crisp as and RGBCW product and may have a tinge of colour. You can also find RGBCCT products, which have Red, Green and Blue plus a colour temperature adjustable chip. In order to adjust the colour of and RGB LED product, you will need to use compatible control gear.
SMD stands for Surface Mount Device, and is a term used throughout electronic design of circuit boards etc. Many electronic components today are soldered onto pads on the surface of the circuit board, rather than having wires that protrude through the board. Many higher performing LEDs today are SMD, and they come in many package sizes such as 3528, 5050 and larger high-power packages. The numbers relate to the dimensions in 10s of millimetres, for example 3528 is 3.5mm by 2.8mm.
A transformer outputs an AC voltage which is required by many household halogen bulbs. It differs from a Power Supply which outputs a DC voltage.