Posts Tagged ‘Lighting’


I propose that all pursuits of a color quality metric represented in any form of numeric value based on averages of performance over any number of color samples is wholy inadequate and a wast of time. We have been using such a system for far too long, with too many questions and related surrounding quality issues unanswered to continue with such a weak approach. I suggest that we pursue a Lighting Qualities Classification system that encompass eight (8) core variables that are critical to identification and selection of lighting products. This would be represented in a similar fashion as the successful Ingress Protection (IP) rating system already in use.

My concept is that there are three core categories of concern that lighting customers and specifiers want answers to in an easy to use and apply form. These are Uniformity, Color Quality, and for some, Human Factors. A color quality standard, as we already know, is meaningless if uniformity is not known. The current and all proposed metrics for lighting quality also fail to deliver any insight into color tonal shifts caused by Duv, and do not indicate or suggest that all sources of identical result are going to be uniform in appearance. This proposed LQC classification system addresses these issues, representing lighting product performance using data already available from current test results, in a manner that can be applied to select appropriate products for application.

Here is my first raft concept of the LQC classification in a table format, similar to that used to define the IP rating system:

LQC Rating System Table

LQC Rating System Table – Proposed Draft

In this classification system one can expect:

Uniformity Performance – Products from a range of manufacturers, or individual products from any one manufacturer, with a classification of 5 will deliver uniform appearance, while the greatest variations will occur in products with a classification of 1.

Quality Performance – Products from a range of manufacturers, or individual products from any one manufacturer, with a classification of 5 will deliver uniformly high color fidelity, minimal saturation effects, and strong color rendering over the complete spectral range, while the greatest variations and lowest color rendering results will occur in products with a classification of 1.

Human Factors Performance –  Products with a classification of 5 will deliver optimal human visual performance, while those with a classification of 1 will deliver less than optimum performance. This is an optional classification (like the thrd value in the IP rating for impact protection) recognizing that in some applications, human visual performance, either for acuity or to optimize energy use, is not a priority – such as high end hospitality where warm sources and mood/appearance are the primary drivers.

Based on this, decision makers can pre-qualify products based on application needs and requirements. Just as an IP67 rating is unnecessary for 100% of applications, an LQC555 product is not a universal requirement. Here are some examples of application of this LQC classification system:

Parking Garage Lighting – LQC124 will produce a product with minimal attention to uniformity, a good color rendering quality (for identification of color), and a high human factors performance level to optimize energy use and visibility.

Classroom – LQC445 will produce good uniformity, high color rendering performance, and strong human visual system support for learning environments at a reasonable economic level.

High End Retail or Museum – LQC55, or LQC553 will produce maximum uniformity, maximum color performance, and acceptable human factors for the application using warm color sources (optional classification).

Residential – LQC442 will produce a product that suits the majority of fussy homeowners and represents the human factors likely to be available when using warm color light sources

Critical Task and Inspection Lighting – LQC555 will produce maximum performance in uniformity, color and visual performance.

Low Activity Storage (low color demand) – LQC11, or LQC111 will support the most economical light sources and indicates a minimal need for quality over cost.

High Speed, Low Color Demand Task Application on a Budget – LQC115 might be applied,  utilizing TM-24 methods to reduce energy consumption through application of enhanced visual performance, with lowest cost products as a priority

I recognize that a classification system of this type requires more refinement. However, I suggest that this is a robust approach that with minimal understanding, manufacturers can apply this to market products toward specific intended application, while decision makers and designers can select and communicate their requirements through specification of a desired or necessary classification for the intended application.

The application of this type of multiple factors classification system encompasses the core concerns of decision makers,  answers questions not now being delivered, removes the need for decision makers to attempt to hack together evaluations based on data that is not always readily available, and builds a foundation to build products and identify latent demands that are now concealed by the virtual lack of actionable metrics for us all to work from.

Specifications could also be written around identification of a range of acceptable product classes within the three categories. For example, one might  need uniformity to remain very tight, where a specification of anb absolute “5” classification is set. However, that same specification may not require perfect quality performance beyond that, so a quality value might be represented as >2, or indicated as  range of 2-5. Meanwhile that same specification may consider energy efficiency as an important requirement, demanding a Human Factors classification of >4 or a range of 4-5 as acceptable. This opens the door to a wider range of products, from LQC524 up through LQC555 to be applied and offered by manufacturers.

Manufacturers can use this classification system to expose and promote their products performance and its comparison to competition. For example, a manufacturer that is committed to the highest uniformity in their product offerings, at the most popular quality levels, can state that all of their products deliver an LQC of 53 or better, while specific offerings targeting the human factors market space can be promoted as delivering an LQC of 534 or greater, indicating the only area of variability and performance selection is choosing a color metric that fits the application.

Just as the IP rating system is more descriptive than the UL Wet and Damp labeling standards, the LQC classification reaches beyond simplistic single aspect lighting qualities of CRIe or TM30,  that are now creating more questions than answers.


In the discussion of lighting quality, there appears to be a desire to see a simplistic set of performance factors to be met, that can be universally pointed to as “quality”. This is most apparent from fixture manufacturers, who wish to have a set of 3-5 reductive bullet points to indicate their product is a “quality” product. Color rendering is one such factor frequently singled out in this effort, regardless of its relevance to an application.  A quality lighting system is more than the sum of products lumped together into a specification, each defined as quality components, without contextual inter-connectivity. Lighting quality is the result of creating a recipe of approaches, priorities and understanding/agreement that delivers a system that satisfies the end-user occupants, the facility operator, and external influences  to the highest practical level. To this end, I have attempted below to summarize, in the most reduced form possible, the systematic factors that define a quality design.

There is no magic formula for lighting quality.

  • Quality of applied lighting approaches/systems are defined by room by room, that establish approaches to:
    1. Lighted spatial appearance, image, aesthetics
    2. Glare/brightness control
    3. Color selection and performance factors
    4. Natural and artificial light integration
    5. Visual performance support and enhancement
    6. Time and space connectivity and relationship
    7. Controls operation and function
    8. Energy use and efficiency
    9. Operational commitment – short and long term
  • Prioritization of lighting qualities requires careful evaluation and consideration of the following considerations:
    1. Practical needs of those occupying spaces
    2. Type and character of visual tasks involved
    3. Human factors (demographics, condition, etc.)
    4. Desire to support/enhancement human health
    5. Sensitivity to flicker and/or color variation/distortion
    6. Comfort of occupants
    7. Available budget (energy and capital) initial and operating
  • To deliver a quality lighting system/solution within the priorities and approaches defined above requires:
    1. Recognition that energy efficiency is not a quality of light, but it is a component of a quality lighting system
    2. Understanding of both the visual and non-visual effects of light on humans
    3. Understanding that the subjective and objective measures of quality are defined by appropriate application within established priorities and goals
    4. Recognition that human occupants are not singular entities that can be lumped into averaged assumptions.
    5. Understanding that the visual environment is a blend of objective need, subjective perception, and practical limitations that cover a broad range of requirements and perspectives.
    6. Realization that “lighting” quality factors must be resolved in concert with non-lighting features within spaces that enhance or detract from quality lighting in isolation.

Within each of these reduced descriptions lies a depth of detail that can be applied depending on the level of priority established. For example, for a space focused on task accuracy, consideration of human factors would require digging deeper into age range, physical condition, etc… to establish the demands on task lighting and the need for flexibility to accommodate the range of occupants anticipated. The dynamics of design may also place all of these factors in whatever order is appropriate to establish a quality end product in context to the practical definition of the project involved.  In truth, the most important factor in realizing a quality solution is the quality of the approach taken and how completely it includes consideration of the range of factors, considerations and priorities involved. The more superficial an approach is, the less likely the result will be of high quality. This does not mean that quality designs need be overly complex, or time-consuming, it just means that a conscious effort to balance these considerations is what defines a quality end result.

While we might all agree that glare control is important, in some applications selecting the lowest glare product may be less important than selecting a higher efficiency product. Glare is also dependent on viewing angle and movement dynamics that cannot be universally represented by a set of features defined as “quality”, outside the context of application. High color quality is not a universal requirement – ranging from highest priority to nearly irrelevant in low demand transient occupancy. Enhancement of human visual performance can be critical in high demand tasks, yet be of minimal value in low demand transient spaces. Lighting for visual effect is meaningful for some applications, or generally irrelevant. Human factors, such as supporting visual performance, as well as mood and health enhancement factors, are naturally a component of all lighting systems designs, as lighting exists for human consumption, with no other purpose beyond this context. However, the degree of effort invested in enhancing the human experience varies greatly, from critical to merely supportive. For these reasons, and many more, lighting quality cannot be reduced to a simplistic set of universal factors, out of practical context. Lighting quality is achieved through prioritization and spatial end use delineation that establishes factors that, when met, define a quality solution and end result. The deeper one digs into the needs of end users and how light effects them, the greater the opportunity there is to create a quality experience, thus, defining a quality lighting system.

The recent press release announcing Philips, Cisco, et al,  joint venturing to deploy and build Power over Ethernet (PoE) networks in lighting is going to fuel this discussion and create a stir, without a doubt. In the press release, all the current hot buttons were pressed with vigor, from App controlled lighting using smart phones to ties to the Internet of Things (IoT). The picture painted by this release, presentations on this topic, and other articles floating about, indicate a future where lighting breaks its bonds of wiring to be free to serve us all in magical, never before realized new ways, using less energy through magic DC power, finally severing us from the drag of AC power. It’s certainly got folks talking.

At the recent LED Specifier Summit in Chicago, I was asked by no less than 8 people what I thought about PoE, and whether it was going to be the next big disruptive innovation to strike lighting. Concurrent to this were phone discussions with technology providers and fixture manufacturers, asking similar questions. It was hard not to think that something was going on, as everyone seems to be all quivery about it. The problem is… I am not so sure what all the fuss is about, and whether anyone is really thinking this through. I like the concept of a distributed network style, low voltage DC lighting infrastructure. It solves fixture design issue, and presents intriguing possibilities for integrating controls, lighting and the IT universes together in ways our current system of isolation-in-high-voltage simply cannot easily address.

Advantages Impossible to Ignore

As we move into more electronics integration into lighting, it is hard not to look at the IT universe, and its capacity to deliver data in both wired and wireless networks reliably and effectively throughout large areas. It would be phenomenal to have that same level of inter-connectivity between controls and controlled lighting, with each fixture set up with its own address, and simple software interfaces to allow any fixture to be controlled by any control or population of controls, in addition to responding to global data, like time of day, light conditions, even weather conditions. No more stupid controls circuits where lighting I don’t want on is left on, because its hard wired to another I need to remain lighted. The concepts of Human Centric Lighting, and even those of the far-reaching Semantic Light concept cannot be obtained without a layer of control sophistication the existing lighting market struggles to deliver. HA! I just injected two more hot-button topics the press release had not even mentioned….

The inter-connectivity of a lighting infrastructure that has close ties to the IT universe, Bluetooth utility, wireless network visibility and access also solves issues of controlling portable lighting, specifically at the task level, that are normally plug connected with no wired control connection. To be able to address these products as components of a larger lighting package and system would bring them finally into the picture as more than accessory add-ins. In this, energy code compliance could integrate all forms of light, from portable to daylight harvesting, into one unified total system, monitored, commissioned and controllable using a single controls layer.

While there is movement toward higher and higher voltages in LED packages, the fact remains, LEDs themselves are low voltage devices. Distribution of remotely controlled, current limited 24VDC, or even 48VDC makes more sense with LEDs than any other source, and resolves a great deal of the issues of packaging driver, power conversion and light source into luminaires. Portable, surface wall and ceiling mounted products could become much cleaner and slimmer, freed of housing chunks of non-luminous hardware. Dimming control within this proposed data biased infrastructure would be far more consistent, and tunable to match human visual response, with far fewer compromises to electronic interaction and proprietary hardware interference.

Further, the idea of the IoT is pretty fantastic as a concept. Having lights not only controlled locally, but to external data sources has some interesting implications. From daylight following to being able to send someone a message that includes a “lighting” message is intriguing. To have a web site not only present a video on-screen, but control the room lights in response to the presentation at various points has real potential for video conferencing, especially when tied to white light tuning – HA, HA! I just added yet another hot button topic to this discussion.

I’ll dump a couple more hot topics into this. The discussion of AC driven LEDs and the entire flicker issue (hot topic alert), is essentially eliminated with a DC infrastructure. The issue of lumen depreciated luminaire life ratings ends, as we could adopt one of my favorite concepts – Lumen Priority, where luminaires deliver steady state illuminance over their lifetime, with reactive control to modulate current to overcome lumen depreciation of sources and dirt accumulation. The IoT would create an opportunity for this type of control to be globally monitored, allowing real-time collection of light loss data for all to utilize in future product development.

Of all the advantages of a PoE foundation to lighting that intrigues and interests me most, is that it could finally end the mish-mash of proprietary controls, generic controls, 0-10V, Ecosystem, DALI, DMX, Zigbee, Enocean, Triac, MOSFET, leading edge, trailing edge, 1%, 10%, 20%, etc… etc… that makes creation of product and lighting system functionality a nightmare. One infrastructure, one controls foundation, all products connected to remote current control power, portable and building mounted, landscape to roadway…. end of story. I am IN!

Problems that Can’t be Ignored

First and foremost, distribution of low voltage power to lighting products is a bad idea. Edison lost the DC battle, because DC stinks in distributed power systems. Tesla and the AC power grid is efficient and can support long distribution distances with minimal losses. Anyone who believes any different needs to revisit the library on this topic. Voltage drop cannot be ignored, as it is a power robbing parasite. For example, a 24W luminaire connected @120VAC, 75 feet from its power source over #12 AWG wire, experiences only .09V drop (.07%), adding up to .02W load, or .08% power loss. Even if the driver losses 5%, the total is just 5.08% total per luminaire. That same 24W luminaire tied to a DC power supply, 75 Feet from its power source, over #18AWG wire, experiences 1.53V drop, (6.83%), adding up to 1.53W load, or 6.38% power loss. If the driver at the head end of that circuit is 98% efficient, the total loss to feed that luminaire is up to 8.38%… not exactly a loss anyone is going to embrace. To eliminate the cable loss, to get it back to the 120VAC level, would mean running #6AWG to that DC fixture… not exactly a savings in distributed power hardware, nor practical in any sense of the word. Oh yes, lets not forget that the existing infrastructure of commercial lighting is not 120VAC, it is 277VAC, where the voltage drop, number if circuits involved, etc… are less than half what most of the marketing materials for PoE show as examples and cost analysis. Marketers doing what marketers do I guess.

So, really, the idea of true DC is really dead before it is even born. However, all is not lost. DC LEDs are not actually DC, are they? DC power is usually attained using switching power supplies which can deliver AC at a frequency of >20KHz. Now, the issue of DC (which is not DC at all) simply evaporates. In the aforementioned 24W luminaire, at 24VDC, over 18AWG wire, operating at 20KHz, voltage drop is now only .31 (1.29%), adding up to just .06W, or 1.2% loss. That’s not hard to absorb in the grand scheme of things, so let’s just say forget the DC thing, and look to high frequency AC circuits, since LEDs really run just fine in this type of system – perhaps better that straight DC in many cases (another topic). This is also perfectly compatible with any Ethernet system concept, since the design of that entire infrastructure is around digital data frequencies at higher speeds than that. It also makes use of PWM or PAM control of current delivered to the luminaire simpler still.

Next, let’s talk hard wiring. If anyone believes that the ideal solution to wiring lighting is to had it over to the IT, low voltage cable tossers, they need to get on their coveralls and pop a few ceiling tiles. I have had many experiences with the absolute  mess these folks think is acceptable cabling practice. Look at the spider web of cables, unsupported, running this way and that over ceiling tiles and through walls. It is a disaster now. In fact, it is so bad, that when a computer drop, phone cable, or camera line fails, they just abandon it in place, throw another cable through the plenum and down the wall, and call it a day. Now, add a run for every 24W of connected lighting load, router boxes and hubs tossed around among for good measure, redundant cabling to cover failures and miss-wiring… it is going to be an absolute, without a doubt nightmare. This is also not going to be simply accepted by code authorities. About the time the PoE revolution is beginning to heat up, there are going to be meetings and codes re-written to resolve the emerging and expanding mess of unprotected, un-supported, and disorganized wires running this way and that. There are cities everywhere that demand low voltage cables be run in pipe, for a reason. This will apply to lighting run on PoE networks as much as it does fire alarms, clocks, camera, and data today, so claims that this is not an issue, are simply incorrect. The savings of running wire in pipe for a low voltage system over line voltage are only in the cost of the wire, and perhaps the pipe size – the labor and hardware remain the same.

About installer expertise. In virtually every instance I have been party to related to LED product failures in the field, it has come down to installer errors more than any other cause. Everything from wiring line to low voltage connections, cutting off connectors and miss-wiring controls (power to 0-10V control input), arcing from live wire connection, etc… While PoE appears to resolve some of these, as the connectors preclude anyone goofing up the circuits, the fact remains, almost all of the cabling that will be run will be made from raw cable, with terminations made in the field. Than means there are more than ample opportunities for bad cable connections, broken wires, broken connectors, cut cables, etc… The idea that the IT players already experienced in this type of connection will take over from union labor paid electricians is, well absurd. Take it from someone who has had more than a few run ins with the brothers, they are not going to just let go of the work and accept this new development without being heard. How they will be heard is through the local inspectors, who will be encouraged to make code adjustments to keep the peace. It has happened before… look at the example of how EMT pipe came to being, to take the pipe work away from the plumbers unions. While I am sure there are pundits who will insist that those days are over, that the contractors have less power now then they did back “in those days”, I suggest they revisit the transformation of the market from  design/contract to design build, to see that contractors have more power today than ever to influence what is and what is not acceptable in their universe.

More on the installer base. Forgetting issues of control, the real issue of moving toward PoE will come down to installers qualified to install these new systems. There is a lot of training to be done, information to be distributed, and buy-ins to be obtained between now and full implementation. I am seeing classes, certifications, and other programs to deploy this in a way we can all depend on. None of this is even on the agenda from what I am seeing, but the concept is also far from settled and in full swing… so we’ll see.

The issue of disruption and the perceived need for it

Do business owners perceive of a need to see a massive disruption to the way lighting is connected and distributed today? No they don’t. You can show them all the wonderful presentations about energy saved (most don’t care a great deal), you can espouse the wonders of flexibility (they don’t actually understand how things work now, so this has not point of reference to work from), and you can attempt to excite them with promises of great new capabilities (they are not demanding)… and the end result will be no change at all.

There will be a few example case studies of large profile projects displayed, usually enjoying their slice of the new frontier at deeply discounted prices just be used as window dressing. That is not a revolution. The revolution comes when the customer is demanding and absorbing the new thing at a rate greater than those producing it can keep up with. That requires widespread active interest, which is founded on a general consensus of perceived need. In a market that just barely accepts that there is a need (mostly to comply with the law) to change from T12 lamps to higher efficiency bulbs, who see LEDs only in the vein of Edison socket replacement lamps, who are not absorbing other much simpler, easy to apply controls products today… it is hard to believe there is any ground swell of unsatisfied demand pointing customers to the doors of those offering PoE as the next big thing in light.

For new construction, on projects that involve Net Zero (another hot button!) concepts, or LEED, or publicity related something or another, there will be opportunities for PoE to show its stuff and demonstrate its coolness. How much this inspires the rest of the market to get in line, vs. eliciting a blank stare and a yawn, will have to be seen. I can see it going either way. I personally like the concept from a design vantage point, but am skeptical it will ever really catch fire and make a big difference overall. In the end, I am afraid it will just become one more controls system in an overly messy, over-populated universe of controls approaches. Soon enough, there will be another hot button concept proposed to get excited about, putting us all further and further away from the solutions we really need… and the cycle will start once again.

I truly hope I am wrong.


The Navy utilizes red task lighting at night to preserve vision of bridge occupants during certain operational conditions. I was asked to provide a version of the Tasca work light to be used on the bridge for map lighting, to replace incandescent products with filters they had available to them through the GSA. They wanted white light for supplemental daytime use, and red for operational conditions where red light was employed. They also wanted dimming for both conditions. To accommodate this, I added (2) Ledengin 625nm Red LEDs to the standard Tasca head, which employs a Bridgelux 4000K ES COB array, with a custom diffuse optic. One driver is all that was required, with a three position toggle switch that selects white-off-red. This allows one dimmer to be used as well for either mode. In addition to these light output modifications, they also needed the arm system to be extended vertically 6″, with a swivel mount to a bolt down base. I added a swivel lock as well as an adjustment for setting swivel resistance while I was at it, for extra measure. This is now used on two ships, with more on the way.

The head includes dimmer control, and 3 position toggle switch for color selection and off.

The head includes dimmer control, and 3 position toggle switch for color selection and off.

The bolt down base swivels and can be locked and adjusted for resistance in the pivot.

The bolt down base swivels and can be locked and adjusted for resistance in the pivot.

The arrangement of the LEDs places the red sources lower in the cup, overlapped and under the main white array. The system tested perfectly, with no issues of over-heating.

The arrangement of the LEDs places the red sources lower in the cup, overlapped and under the main white array. The system tested perfectly, with no issues of over-heating.

The diffuse reflector is part of the mixing chamber, which included Luminit diffuser material to blend the light from the two sources into one controlled output with no spots or variations on the lighted surface.

The diffuse reflector is part of the mixing chamber, which included Luminit diffuser material to blend the light from the two sources into one controlled output with no spots or variations on the lighted surface.

Overall height is 19". The base is a salvage item from Goowill.

Overall height is 19″. The base is a salvage item from Goodwill.

I am a task lighting fanatic. I use them everywhere, so am always looking for something new to add to my collection. In this installment, I am addressing the need for a light that is compact, delivers intense light (1,200+ Fc) with no glare or brightness, and high color accuracy. The application is pretty straightforward, from soldering station use where a magnifying glass is used, to fine detail work inside or on the outside of models.  For good measure, I also wanted it to aim at the wall as a photo fill light, or straight up as am ambient fill light, and have a dimmer to allow me to set whatever level I want for the application in hand at the moment.

The wiring and components are left skeletal.

The wiring and components are left skeletal.

With all the practical specifications set out, I decided to let this design be expressive of the gadgetry involved. Let it all hang out. I also decided to incorporate the new Bridgelux Vero LED with its integrated Molex connector, and a Nuventix cooler, just to amp up the tech factor.  This is where things got interesting. The Bridgelux array operates at 33.7V (500mA). The Nuventix cooler at 12V. I am powering the whole thing with a 24VDC wall wart power supply. That meant I needed to employ a boost driver for the LED and a buck (24VDC to 12VDC) power converter for the Nuventix cooler. I used Recom components to attain this, and used a cut up experimenters printed circuit board to connect these two to the power supply, the cooler, the LED and the dimmer control. That’s a lot of wires to find a path for, so I decided to leave them to roam free, let everyone see the components as well.

The lever on the left of the head is the on-off slide switch.

The lever on the left of the head is the on-off slide switch.

This is a style of design I personally enjoy, and have been doing since the 1980’s, where we made little 12V lamps with fiber optics, MR16s, halogen burners, or automotive headlamps, often suspended from structures made of building wire. In this case, the stand I found at a Goodwill. It was a table lamp, whose shade was gone, and socket was cracked. I liked the cast iron base and single post stand, so nabbed it for a dollar and tossed it in the pile with my other finds, waiting this moment to be put to service.

The wiring at the driver and power supply are exposed as well as the mess of wires leading into and out.

The wiring at the driver and power supply are exposed as well as the mess of wires leading into and out.

If you look at the head, the switch is a sliding action, on the left side of the head. Pull it forward to turn it on, push it back to shut it off. A hole in the side of the housing allows you to see the action inside. No, there is no reason for this, other than it seemed more appropriate than an off-shelf toggle or twist switch.

The light on the task surface is at 1,425 Fc, the LED is 3000K, 97CRI.

The head can pivot 180 degrees from down to straight up.

The head can pivot 180 degrees from down to straight up.

The Purple Light ‘UV’ Cure Cube

The Cure Cube is used for curing SLA 3D Prints created on the Form Labs 1+ printer. Exposing SLA prints to 405nm "UV" light increases strength and creates a harder surface for final finishing.

The Cure Cube is used for curing SLA 3D Prints created on the Form Labs 1+ printer. Exposing SLA prints to 405nm “UV” light increases strength and creates a harder surface for final finishing.

While not particularly visible to everyone in the SSL universe, over the past few years one area of interest in LED product development for me has been in use of 405nm LED light sources to cure various plastics materials. The advantages are lower power requirements and reduced overall heat in the cure zone over conventional fluorescent or HID light sources. This has been of particular interest in curing fiberglass resins manufactured by Sunrez. The typical demand is for between 200 and 1,000 µW/CM² at 400-405nm wavelength. The use of LEDs allows us to generate exactly that without the waste of visible light, and longer wavelength power the resins are not reacting to. In one project, we were able to replace a 1,500W HID light source with a 120W LED light system that produced faster cure times with less than 10% of the total power, and virtually no heat added to the heat generated by the resin’s exothermic reaction to the curing initiator. Since then, we’ve built 405nm light cure fixtures ranging from 1,200W to 25W.

In this case, I needed to cure 3D prints we generate on a Form Labs 1+ 3D SLA printer, and do so in an office environment without exposing other materials and occupants to UVA light output. The material used in the print process is acrylic based, with chemistry that is photo-reactive to 405nm. The actual prints are made using a UV laser source. When the part is removed from the printer it is washed in alcohol (91% IPA), rested for a few hours to dry the alcohol off, then placed in this cure cube for an hour or more, depending on the thickness of the final component. The end result is a hard first surface for finish sanding or painting, if necessary, and a more rigid part as a whole (less flexible).

The cube is simple, with vent reliefs top and bottom to encourage ariflow. The flush switch on the top cover was created using 3D printing processes for the slider and body, as well as top and bottom cover.

The cube is simple, with vent reliefs top and bottom to encourage ariflow. The flush switch on the top cover was created using 3D printing processes for the slider and body, as well as top and bottom cover.

The cube utilizes a simple aluminum housing, with FDM 3D printed top and bottom covers. The top cover houses a single Recom 500mA driver, slide switch and wiring terminal block on a Tasca LED driver circuit board.

5mm 450nm LEDs with a FWHM distribution of 60º, 25 per side and top (125 total), operating at 20mA each, mounted to custom circuit boards sourced at Express PCB. Each board connects the LEDs in parallel, while the boards are connected in series, resulting in a 500mA, 15.4V circuit, totaling 7.7W. The boards and internal exposed surfaces inside the box were then covered with White Optics 98 matte material to increase total light energy and diffuse The light energy at 405nm is roughly 600 µW/CM².

The bottom surface includes a glass plate where the product sits in order to make any possible stickiness of a part from adhering to the White Optic material below.

The interior of the cube is covered with White Optics 98 material for optimizing light energy re-cycling.

The interior of the cube is covered with White Optics 98 material for optimizing light energy re-cycling.

The housing was powder coated matte black polyester to make clean up easy and the box look nice. The overall interior dimensions of the box are 1″ larger than the total build volume capacity of the printer itself (5 x 5 x 6.5), as any over-sizing is unnecessary. This produces an optimal match between the location of the LED sources and any part the printer can produce.

The Cube is powered by a remote plug mounted 24VDC power converter.

The operation of the box is simple enough. The box is lifted up, the part is set on the base, the box is set over the part, and the light is turned on by sliding the switch to the on position.

Simple and compact is the order of desktop manufacturing, and this fits that model perfectly.

A look into the box lighted up and ready to accept parts.

A look into the box lighted up and ready to accept parts.

Testing so far has shown the cube can cure raw resin from liquid to fully hardened in less than an hour, and strengthens prints in that time or less. The heat generated from this arrangement is so small, there is no chance of any part being warped or affected by the process, other than the desired results of becoming stronger.

For parts to be left unfinished, that are desired to be used over extended periods, we coat the finished parts in either acrylic or polyurethane UV inhibiting clear coat, gloss or matte. This stops ambient room light or daylight exposure from making the parts brittle over time. I am building a second copy of this cube for completing extended testing of samples of the materials we are using to verify clear coat effectiveness, behavior of the print material over long exposure periods, and the behavior of these low cost LEDs over time. A commercial version of this cube could be made using more robust LEDs, but the costs would be significantly higher as well. In the current configuration, the LEDs only cost $0.60 each, so should they last a couple of years in use, replacement of the populated boards is a simple task, while the cost of higher power LEDs would have increased the cost of the entire end-product by as much as three times.

There is also an additional version of this same approach in using Red/Blue light sources for use in plant seedling starts. We’ve found tests with common rye and barley grasses, the time from germination to hearty growth ready for planting is accelerated significantly. Using an enclosure like this allows the plants to be exposed to intense light for extended periods of time (18 hours or more) without polluting the surrounding environment with the ugly light, just as the enclosed cube protects room occupants from exposure the the UVA light. In either case, the cube can be used in any room environment comfortably and safely.

So this gets us off the ground and is D1 of 52 in the series. As I’ve noted at the start, this is an exercise in making progress, and putting SSL to work. This is not a particularly exciting product in and of itself, but it is one that will be used regularly, which more than makes up for its lack of marketing sizzle for the masses – at least in my book.


My first LED fixture - 2004-2006

My first LED fixture – 2004-2006

This is my last bit of housecleaning from blogs being shut down, for the archives. KLW

This fixture is my very first LED light. It started life to be a halogen fixture in 2004, that sat on a workbench waiting completion. The first head got so hot from the 50W 12V light source, it was dangerous, so it sat as I decided what to do with it.

In 2005, as LEDs became viable for lighting, I pondered using them to replace the halogen source, but they delivered so little light, the end product was useless as a desk lamp, so it sat some more. One idea was to insert a Lamina BL3000 LED into the head, but the driver was huge, the light output too little, and the heat still an issue.

Then, in early 2006, while at Visa Lighting, Don Brandt (an engineer working with me at Visa, formerly from Emteq, now working at Cree I believe) were talking through ways of applying the latest mid-power LEDs using a simple PCB. We decided to give it a shot and built a board populated by a vendor with 8 Nichia LEDs. The inspiration struck to power these LEDs with two Xitanium drivers, which at the time were un-potted prototypes, so cutting them out of their housing to be installed in clear tubes to show their interiors off was easy enough. Two push-button switches activated the drivers for a high-low effect, and a heat sink was made up of a machined aluminum block installed in the head where the original halogen lamp and reflector once lived. More details and images of this can be found on the Lumenique archives for the Ratchet fixture.

The fixture itself is made of welded steel structure with a brass head and fiberglass tension springs. The head can be raised an lowered with a ratcheting action, staying level at any height. In the end, I left this fixture with the owner of the Oldenburg Group (owner of Visa Lighting) as a parting gift as I moved on to focus on Lumenique and SSL exclusively.