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CREE Led Light Define Lighting Requirements

LED Design Guide  

Click on the links below to follow the Cree Luminaire Design Guide.

Define Lighting Requirements

LED Lighting Design

The LED luminaire must meet or exceed the lighting requirements for the target application. Therefore, the lighting requirements must be defined before establishing the design goals. For some applications, there are existing lighting standards that will define the requirements directly. For other applications, a good approach is to characterise an existing luminaire.

Table 2 (below) lists important characteristics to consider when characterising an existing luminaire. The light output and power characteristics are always critical, while other characteristics may or may not be important, depending on the application.

 

 

Importance

Characteristic

Units

Critical

Luminous flux

lumens (lm)

Illuminance distribution

footcandle (fc)

Electrical power consumption

watts (W)

Potentially Important

Luminaire aesthetics

Price

Lifetime

hours

Operating temperatures

°C

Operating humidity

% RH

Colour temperature

K

Colour rendering index (CRI)

Manufacturability

Ease of installation

Form factor

Table 2 - Important Characteristics of Target Luminaire

All lighting companies can provide data files or documentation that detail the “critical” characteristics for each of their fixtures. The “potentially important” characteristics are more subjective or may not be listed in the manufacturer’s documentation. In this case, it is up to the designer to characterise the existing luminaire.

 

LED Lighting Design

Figure 1 illustrates the critical characteristics for the example CFL downlight.

Part

Characteristic

Unit

Value

Lamp

Technology

CFL

Light output

lm

1,500

Power

W

23

Efficacy

lm/W

65

Lifetime

hrs

10,000

Average selling price

US $3

Fixture

Coefficient of utilization (CU)

%

54

Light output

lm

810

Power (excluding ballast)

W

23

Efficacy

lm/W

35

ASP

US $20

Table 3 - Example CFL Downlight Characterisation.

 

CREE  
CLD-AP15.000
Copyright © 2007 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo, and XLamp are registered trademarks of Cree, Inc. 4600 Silicon DriveDurham, NC 27703 http://www.cree.com/xlamp
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