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Stefan Dickerson


LED Lighting for

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Public Spaces Thesis Project Carleton University



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ace features

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Welcome Thank you for taking some time to review my

LED Lighting for Public Spaces

A flexible system

thesis project.

for public lighting The context of this project is Ecoville, an alternative present-day (or near-future) civilization that

that leverages

enables its citizens to live sustainably.

LED technology, Carleton University’s class of 2009 expressed our interpretations of Ecoville through a diverse set of

enabling targeted

eco-friendly projects.

illumination and At first we had no “model” of Ecoville. However as the projects materialized they formed a clearer picture, like pieces of a puzzle. I am grateful for this unique experience: I learned about sustainability from my peers’ projects as well as my own. For a quick read, I condensed my project in this booklet. More in-depth information is available. Here’s my piece of the puzzle.


Inside this por tfolio:




Why LED?

Early Concepts

User Testing




Environmental Impacts

Preliminary Main Concept

Design Consultation




Going Forward: Applications

LCA (LifeCycle Analysis)

Finished Product

Why LED? Efficiency, Light Quality Improving

Verrazano-Narrows Bridge, New York â–ź Photo courtesy Rick Elkins

Tough and Long Lasting Durability is important when changing bulbs is difficult and expensive. LEDS are tough (no fragile filaments or glass). The typical lifespan of LEDs is 50 to 100 thousand hours (over 10 years).

â—„ Efficiency of various light technologies (Lumens per Watt) over time â–ź Applications of lighting, quality comparison

What This Means Widespread adoption of LED technology

Obsolescence, not just LED life cycles,

is coming. While others are flat, LED

could motivate servicing. A lighting

efficiency and light quality gains are

system should be easy to upgrade, by


replacing just the LED component.

This trend will likely continue.

Environmental Impacts Why Focus on Lighting? An estimated 12 to 15% of worldwide electricity generation is used for lighting (Zissis and Rouffet 2005). Thus lighting is an excellent focal point for energy conservation efforts. A technological approach is to make the same amount of light with less electricity. A design approach is to reduce the amount of light required to begin with, i.e. “task lighting“ for the outdoors.

Light Pollution Public



Awareness of light pollution and its


adverse effects on life is growing. Ideally

Revolution for public safety, and to

we would have full control over artificial

attract people downtown.

The idea

light emissions, putting light exactly

persists that more light is better, but

where and when it is needed, and

this is being increasingly challenged.

nowhere else.






Obstacle to Lowering Impact Public lighting has become a largely

A simple LED substitution will do nothing

mature industry. It evolved in the absence

to curb light pollution. Compounding

of light pollution awareness.

this issue is legislation, which often prescribes minimum levels of lighting.

As a result of its maturity, we expect public lighting to appear as it did in the

Exceptions can be found in “Dark Sky”

gaslight era: as centralized bright light

communities like Flagstaff Arizona, in

sources on poles.

the United States. Where light pollution informs policy, and maximum, rather

Unfortunately, LED technology is under

than minimum light levels are prescribed,

pressure to mimic existing lighting. This

conventional lighting may fail to satisfy

is a common rite of passage for new








▼ LEDs adapting to current light systems

Opportunity The “Dark Sky” movement creates a market for targeted, distributed and possibly switchable lighting systems. LEDs offer these possibilities with their small size, solid-state toughness and high cycle tolerance.

Going Forward: Applications Recommendations

Concepts of Application

The following recommendations are

Targeted lighting solves the problem of

based on what was found so far:

unwanted shadows and bathing large areas in light. ▼

○ Consider light pollution and Dark Sky clients. Put light exactly where it is needed. ○ Develop a distributed lighting system. As such, it should be scalable and flexible. ○ There are many LED retrofit solutions already. Make a departure from the past. It’s been done. ○ Leverage LED technology’s strengths. Be sensitive to LEDs’ requirements. ○ Make it serviceable. Also, demarcate the LED itself from the system to minimize waste from replacement & upgrades. ○ Because it is a public product, address vandalism & tampering concerns.

By exploring possible applications (below and facing page), additional requirements were uncovered, such as physical size, and the need to get power to the fixtures.

◄ The



profiles are concealed in the storefront’s features. The desired effect is light, without the visual clutter of lighting. ◄ Area, rather than point sources are easier on the eyes.






setting for a large-scale deployment. Long-wave (reddish) light attracts fewer bugs and helps preserve night vision. ►

Early Concepts Lots of Small Bulbs and Breadboards ▼ Breadboard connector, + LED

The use of many small bulbs and breadboard technology was applied to serviceable wall-mount lighting and portable lighting stands. ▼ ►

▼ Proposed breadboard-inspired LED circuit

Fewer High-Output Bulbs The use of high-output LEDs was ultimately more promising. They require heat sinking, but are more efficient. Engineering consultations revealed problems with highly parallel LED configurations, as proposed on the facing page. The project proceeded with highoutput LEDs mounted on extruded or sheet metal bases. â–ź Ideation sketches of LED connectors

â–ź Extrusion profiles and their applications

Preliminary Main Concept Top View of Lighting Assembly

▲ Strings of six LEDs in series are connected in parallel to power lines, which are driven by a regulated power supply. For long runs, multiple power supplies can be spliced into the lines.

LED Clip Two posts on the LED clip pass through circular cutouts on the LED’s integrated heat sink, and then snap-fit into holes in the heat sink plate. LED clips help manage supply lines and secure the jumpers to the LED contacts without solder. ►

Connecting to Power Lines A supply tap links a jumper to a supply line by clasping both wires and piercing their insulation with a single metal insert. ►

â–ź Exploded view of assembly, and application of this concept to a handrail (bottom)

Life Cycle Analysis (LCA) Based on Okala Impact Factors This form of analysis measures the impact of a product by considering the ecological costs of the following: ○ Acquisition of materials (ex. mining) including energy inputs

○ Eco-toxicity of materials (assumed to be eventually released to the environment)

○ Processing of materials (including supply chain transportation costs)

○ Disposal, incineration (or recycling, if possible and likely to occur)

○ Energy inputs during use phase Energy factor depends on the electricity generation profile in the region.

LCA of LED Lighting System The following LCA covers the LEDs, the clips, copper wires, portion of an LED driver, shield, and heat sink for 1 metre of strip lighting, consisting of 6 LEDs, each drawing 2 Watts and running for 100,000 hours. Total lifespan is 22.8 years, assuming the LEDs are on 50% of the time. Below are the Okala points accrued in this 22.8 year period. 20 366 . 25

18 000 ( 88 . 4 %)

2366 . 25 ( 11 . 6 %) Electricity

Material 66 . 25 ( 0 . 33 %)

1840 ( 9 . 03 %) LED Driver Circuits

Further Consideration

460 ( 2 . 26 %) LED Lamps


All other materials and processing impacts

○ Solar power would require batteries, but it reduces the electricity impact by 75%. ○ Almost all of the material impacts come from electronic components, particularly the driver circuits. Economy of scale may help, i.e. using large centralized DC sources instead of the commercially available 50~100 W units used in this analysis. ○ Replacing LEDs as they gain efficiency will reduce the electricity impact over time.

User Testing Focus on Serviceability Five





the at

Carleton University agreed to perform simulated servicing tasks and provide comments.

First, they were introduced to my project, prototypes of the parts, and the objective of making it serviceable. They were also given a briefing on how the LEDs would be wired.

They were asked to assemble four LEDs to the clips, then mount them on a heat sink. I mounted one LED first. They were also given a pop-quiz, which involved depicting the wiring on paper.

Quiz completed by participant â–ş

Positive Feedback

Negative Feedback

○ They appreciated not needing tools

○ Small size of parts, difficult to manipulate

○ Installation and servicing tasks seemed like they would be easy

○ Ambiguity of fit (backwards install

(Prototype tolerances were a bit low,


occasionally affecting the experience) ○ Tendency to forcefully pinch the clip ○ Low skill requirement

where the delicate wire clasps are

○ Straightforward circuitry ○ Safe system to work on

Other Insights With low voltages involved, electrical connections may be weak, especially outdoors. Corrosion could be a serious problem if not properly sealed or enclosed. However, the use of pierce technology was accepted, since it is used in the automotive industry. This prompted a focus on controlling the environment surrounding the electronics. Ultimately an extrusion solution was developed. It also brought the project much closer to being a complete field-ready product.

Design Consultation Almag Aluminum, Brampton ON â–ź I gave depictions and explanations of design intent for my aluminum extrusion. FOR SHAWN COMFORT | Director, New Business Development ALMAG ALUMINUM This is a housing for highpower LED arrays, providing shelter, heat-sinking, wire management and fastenability to various surfaces. A model of a Luxeon LED is shown in place. The housing snap-fits to brackets (blue) designed for wall-mounting. Other such brackets could be designed for round surfaces like railings.

Removal would be done by prying with a screwdriver. Removal should not be possible by simply pulling on the housing.

#4 machine screw taps here Wire mgmt. Lens / Shield

light block end cap fastening feature, possibly another #4 screw

heat sink area

Actual size (LED included). ▼ Wall thickness is .06” TYP.

By sharing my design intent and concerns with an extrusion expert, the profile was improved.

Concerns: ○ Weatherproof (lens to extrusion) ○ Weatherproof (extrusion to end caps) ○ Would screws inflict a wedging force, causing the outermost regions to tip away? ○ Should the profile have a hollow in it? ○ How flexible is this extrusion? (mounting on curved surfaces)

serrated groove hidden end cap boss improved interface to wall mount

Finished Product




R.010 outside edges of notch R.008 inside notch




.832 .306

.049 .125 .060


R.010 TYP outside corners




1.806 Note: CCD is 1.822 SCALE 2:1

4 notches .120 x .120



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.105 .292 .422

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.044 .058 profile and space features .060 thick TYP unless otherwise noted SCALE 4:1



R.015 DETAIL C SCALE 8 : 1

Benefits Light fixtures can be made to virtually any length. LED spacing is also fully adjustable. Fixtures can be repaired or customized on or off site. Materials are identifiable, and separable for easy recycling.

DRAWING NUMBER  Sheet  of  DRAWING 

◄ Technical drawing












SCALE : 


1 Slot for light shield 2 Wire mgmt, supply 3 Self-tap LED screws, also wire mgmt between LEDS 4 Light blocker (optional) 5 End cap screw 7 Snap fit to wall-mount extrusion

▼ Tamper-proof screws to restrict access

Matl: 6063 T6 2



0.419 in 0.495 lb/ft Number

▲ Neoprene end cap with feed-thru wiring

6 Heat sink features


▲ Profile view of assembly


CARLETON UNIVERSITY COLONELBY DRIVE OTTAWA CANADA K1S 5B6 DRAWN  DATE  CHECKED DATE CLIENT  PROJECT  DRAWING NUMBER  Sheet  of  DRAWING 

.116 R.010 outside edges of notch R.008 inside notch


.049 .125 .168




4 notches .120 x .120



.051 .269

.105 .292 .422

.277 .217

.044 .058 profile and space features .060 thick TYP unless otherwise noted SCALE 4:1





.832 .306

R.010 TYP outside corners .032 1.806 Note: CCD is 1.822 SCALE 2:1

Thank you for reviewing my work.


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R.015 DETAIL C SCALE 8 : 1

Industrial Design Major Project  

A summary of my 4th year project, LED Lighting In Public Places

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