Lighting 101. Learning the basics about lighting

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Below are some key terminology used with regards to modern lighting technology.  Click on links for more detailed information.

Efficacy:   Sometimes referred to as "Luminous Efficacy", Efficacy is the ratio of luminous flux (lumens) divided by the power consumed to produce that amount of light (watts) and is measured in lumens per watt (lm/w).

Efficiency:  In lighting, generally refers to the ratio of lumens delivered from the fixture compared to the lumens produced by the light source.  It is the measure of a particular fixture's ability to use the amount of light produced by a light source.  

        example:  If a light source (light bulb or LED chip) produces 100 lumens of light, but because the light      

                              source is enclosed in a fixture, only part of the light actually escapes from the fixture, lets say                    

                              70 watts.  The fixture efficiency is:

                                      70 Watts escaping /100 watts produced = 70% efficiency

Lumens: A unit of measure of the amount of "Luminous Flux " or "visible light" or brightness emitted by a light source.  This is defined by the International System of Units (SI).   Sometimes referred to as a unit of measure of Luminous Flux

LUX:  is the SI measure of "illuminance" or the intensity of amount of light (lumens) that actually reaches a specified amount of surface area.  LUX is the amount of lumens reaching a square meter of surface area and is sometimes referred to as luminous density (lumens per square meter) .  This is the metric equivalent to foot-candles.     1 lux is equal to .092903 foot-candles.

​Foot-Candle: Is the SAE equivalent to LUX and is measured inlumens per square foot.​  1 foot-candle is equal to 10.7639 lux.

Ballast:  Generally referred to the power supply used for HID, Fluorescent and Induction Lights to convert MAINS AC electricity to a form usable by the lamp.  Ballasts generally provide a high intensity surge of power to "ignite the lamp, and then limits the current to consistent levels to assure proper lamp operation.  Magnetic Ballasts generally are not very efficient and can consume as much as 20-30% of the electricity as the lamp it is powering.  Also, magnetic ballasts will generally provide light output at the same electrical frequency as the input power (60Hz in USA) and could cause visible flicker.  Electronic Ballasts are generally more efficient but still consume significant amounts of electricity.  Electronic ballasts can provide output power at higher frequencies than magnetic ballasts, reducing visible flicker and strobing effects.

Driver, LED:  An LED driver is a power supply that converts AC power (MAINS Power) to DC power which an LED requires.  LED drivers come in many wattages and selecting the right driver will optimize your product performance and lifetime. Drivers also are available with non-dimming, or dimming options.   LED Drivers come in Constant Current and also in Constant Voltage types.  Depending on the type or product, you will need to use the correct type.  

•  Driver, LED-Constant Current:  Constant current (CC) drivers assure long life by regulating the current output to be constant,  regardless of the number of LEDs attached.  Constant current drivers automatically adjust the output voltage to match the LED modules attached, within the Driver's operating parameters. Advantages of CC is long life of LEDs and consistent light output, and the ability to underdrive or overdrive the LEDs.  The disadvantage is that you must match the driver wattage to the  LED wattage or you run the risk of overdriving the LEDs beyond the safe operating limits of the LED and potentially burning out the LEDs prematurely.
  
•   Driver, LED -Constant Voltage: Constant Voltage (CV) LED drivers are generally used with products that are designed to be cut to length and such as LED rolls and LED flexible strip lights.  The LED strips must be equipped with current limiting resistors to limit the current flow  the the LEDs and protect against overdriving and burnout.  Advantage is the ability to power various length products with the same driver.   The disadvantage is the current limiting resistors will consume some electricity and will generate heat.
  

Driver Dimming Methods:  LED drivers are available with the following common dimming types:  TRIAC dimming, PWM dimming, or 0-10Vdimming.  You must match the driver type to the controller type.