Posts Tagged ‘SSL’

 

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.

 

Zero Flicker Task Light

Posted: January 21, 2016 in Light Meters, Tasca
Tags: ,
The Tasca task lighting head. My pet project for more than 6 years now.

The Tasca task lighting head. My pet project for over 6 years.

 

When I created Tasca, I had several goals in mind:

  • Strong light output  – Check – 800 lumens is top of its class
  • Smooth wide light pattern – Check – 78 degree beam pattern with no hot spots, no streaks, no rings, >200Fc at 18″
  • High color performance – Check >80CRIe standard @4000K, moving to >90CRIe @4000 or 5000K in latest models
  • No sparkly LED arrays – Check – single high quality COB array source
  • High efficiency – Check – >70lm/W total fixture efficacy
  • Tough and Ready – Check –  examples have been in operation 24/7/365 in shop environments with zero failures
  • ZERO FLICKER – Check – see below

During the development of Tasca, finding a flicker meter was a little tough, so I improvised an oscilloscope and photocell rig that allowed me to see light output modulation. Using this we experimented and tested combinations of LEDs, drivers, and power supplies. I felt the end result was pretty much spot on, as near to the zero flicker from battery operated sources or even daylight as one could get. Yet, until recently, I had not been able to verify this was the case. Enter the UPRtek MF250N flicker meter (review to follow soon). With this, I have finally been able to see how well the Tasca head was performing. I was thrilled with what we found.

The Target

Daylight and the DC LED ideal models to set a high bar.

Daylight and a DC powered LED were set up as our performance target. They simply don't flicker, so using the meter, I tested these bench marks.

Daylight (left) and a DC powered LED (right) were set up as our performance target. They simply don’t flicker, so using the meter, I tested these bench marks. Note that small aberrations in readings (like the frequency of 5 for daylight along with a frequency magnitude of 2.6, or the frequency magnitude of 0.6 with no frequency for DC connected LED), are just that. This happens in all metering to some degree, and are within a margin of error for this meter system.

The Tasca Head Result

The results speak for themselves.

This is Tasca

The results for the Tasca head are exactly what I’d expected. Their simply is no flicker. While the meter indicates a Flicker percent of 000.6, and a magnitude of 0.2,  there is no frequency component, so these are irrelevant.

I was thrilled with the results. It meant several things. First, these metered results were essentially identical to what we got with our shop made flicker measuring rig. Second, the product itself is simply doing exactly what I intended it to do, which is truly satisfying.

Comparisons for Fun and Perspective

As long as we had the meter out, I figured why not get a few more readings for comparison. The results:

This is a T12 on magnetic ballasts. The beast that started the flicker discussion.

This is a T12 on magnetic ballasts. The beast that started the flicker discussion. The wave form shows obvious modulation, supported by poor results in both flicker % and index. The height of the wave shape is evident in the VFMA (Flicker Amplitude) and FMag (Magnitude) readings as well.

 

AC LED

LEDs connected to AC circuits are not a good thing, even this one using additional bits to supposedly reduce flicker. The results are the highest flicker % and Flicker index of any source in this comparison, in every measure.

 

Capacitor AC LED

This is an AC connected LED with big capacitors added in an attempt to fill the gaps. While it reduces the flicker index to some degree, it has no effect on the flicker %, while the odd wave form creates strange results in other areas.

 

This is a retrofit LED

This is a retrofit LED. In general, it does not do a bad job reducing flicker, but is obviously playing a trade off game between cost of driver/power supply and output modulation.

 

T8

This T8 fluorescent with electronic ballast is doing a nice job of controlling modulation, with a very small, impossible to see modulation at the native 120Hz.

P.S. Notes on the Flicker Argument

I recognize that there is a grand debate about flicker and whether or not it is an issue at all. Most of the argument against setting strict flicker standards are put forth by those who seek to market low cost LED products that exhibit flicker of 120Hz, whether that be AC LED product based or just low end power supply components.

There is no case to be made that flicker is a positive component of lighting, and extensive past industry experience with T12 fluorescent lamps on magnetic ballasts, and HID sources used in commercial application, is what started and fueled the discussion of 120Hz flicker as an issue. Complaints of visible modulation, headache, migraine, etc.. have been studied and found to be corollary to  the existence of flicker. Further, studies have proven a connection between flicker below 200Hz having a negative effect on visual performance in schools. While it is true that organizations like NEMA, IES, CIE, and IEEE have yet to come to an agreement as to what defines bad flicker vs. acceptable flicker, this lack of agreement does not indicate there is no issue. In fact, that these organizations have and continue to discuss this issue, against the steady pressure of manufacturers to set it aside, is an indication that there is a very real issue with flicker, that will eventually be resolved – albeit with some compromise included to placate manufacturers involved in standards proceedings. As a member of the IEEE 1789 committee on the topic of the risks of flicker, I can attest to the depth in which this topic has been investigated and discussed, and bear witness to the hundreds of papers written on it and its effects on vision and human physiology.

In my own opinion and recommendations to others, I ask one question – If there are sources and products available that exhibit no flicker, or flicker of such character as to not be an issue (such as T8 and T5 fluorescent on electronic ballasts, and quality LED driven products), what is the reasoning for continuing to accept any products that flicker in the zone of 100Hz to 200Hz, with a flicker amplitude >0.3 (minimal modulation depth) at all? Any level that exceeds, approaches or shares flicker characteristics with the T12 fluorescent lamp on magnetic ballasts, in my opinion, should be considered unacceptable for any use, regardless of arguments over cost saving. This includes any continued use of magnetic ballasted HID sources for interior illumination and AC connected LEDs (with no flicker mitigation) – as these are all far worse than the T12 lamp.

While in ambient lighting, a weak case might be made that flicker may be of small consequence – I propose that in task illumination, where visual acuity is critical, focus is the goal, and high illuminance and task demands increase the risk of stress, there is no rational case to be made to accept flicker of any level. For this reason, I have focused my attention and effort on creating lighting systems (and sources for components) that present either no flicker at all, or characteristics, such as high frequency operation (>2,000Hz), very low modulation depth (amplitude of <0.3%), low flicker index (<0.05), at all light level settings or dim states. I believe these to be reasonable and attainable standards, and have found no reason to accept poorer performance.

The original idea for the lighted magnifier was for inspection and reading small print on tools, which are generally done in a fixed location. The intended use was for continuous periods of work that made battery operation an issue. Mainly, the initial thinking was to turn it on and leave it on for the duration of a project. So, with it in hand and in use, I found in a short time it was being used for much more than its original intent. The magnifier lens in its unlit state is excellent in capturing ambient light, so I had it in mind that one lighted unit for the very tight and difficult work was great, with an unlit version for all other tasks. Problem is, the lighted unit provides over 1,780 FC on the target, transmitting over 700 FC to the eye at 4″. The unlit version produces no more than ambient levels, and if your head shades the ambient light, that is cut considerably. So, when comparing the two in actual use, the lighted version simply knocks the stuffing out of the unlit one. This meant I needed to cut the umbilical and create a battery powered version.

Adding a battery power pack to the Magnifier was found to be a desirable addition after finding the lighted unit so useful.

Adding a battery power pack to the Magnifier was found to be a desirable addition after finding the lighted unit so useful.

This is not a low power light unit, it is a 2W light source, running at 24V / 80mA, so is a bit of a power hog compared to the typical cheap-o LED junk  running off two AA batteries that fills the shelves of Wal Marts and other outlets hawking the greatest technology to enter lighting at low-low prices (and performance to match). That means selecting a battery strategy is not simple, especially since I wanted the product to perform the same on the battery as it does plugged into the wall.

Having the capability of connecting to a wall power supply or battery pack extends the run time and utility of the end product. Long run times on batteries is a pain with anything but low power devices. This is not a low power light source.

Having the capability of connecting to a wall power supply or battery pack extends the run time and utility of the end product. Long run times on batteries is a pain with anything but low power devices. This is not a low power light source.

The following are two approaches I considered – with a warning:  I have oversimplified the calculation of battery service life here to avoid going on and on about Puekert’s law/constant, discharge curve characteristics, and other such fiddly science. I do this to keep us from napping. The results of the more scientific method of estimating will vary to some degree, which is accepted. However, the relationship between the two battery approaches remains essentially the same, thus the conclusion as to which would best be applied would likely remain unchanged.

The AA Approach:

The ever popular AA battery is viable, at 1.5V it would require a rack of 16 to get the voltage up to 24V necessary.  If a different LED circuit were employed, (3) AA batteries in series with a current limiting resistor could be used to get the job done, operating the LEDs in parallel rather than series. However, with a 4Wh capacity (50mA load), assuming that at about 50% of that the voltage drop will not support the LED threshold Vf demand, these will run for about 1 hour before needing a recharge or replacement. If we were to use rechargeable LiIon batteries, the Wh drops to 2.7, producing a run time of about 45 minutes before needing recharge. Even if the battery pack were stored on a charger, the run time is a bit on the short side.

The 9V Approach:

The review of the AA approach led to looking at (3) 9V Lithium batteries in series to get the 27V that is necessary for the existing circuit. Since that circuit is current regulated, with a minimum required Vf of roughly 15 before failing to remain lighted, we can run the (v pack a little deeper into their discharge cycle. 9V Lithium batteries also have a 10.8Wh capacity (50mAh load). Assuming we can get 65% of that before running afoul of any voltage drop, the result is around 3.5 hours of run time. Seemed like the way to go for now. If I used Li-Ion 9V batteries, the Wh drops to 4.5, so the run time between charges drops to 1.5 hours. Not great, but, if left on the charger when not in use, this could be workable in most situations.

The battery pack simply plugs into the power connector exactly as the wall power supply does, with the existing switch still accessible.

The battery pack simply plugs into the power connector exactly as the wall power supply does, with the existing switch still accessible.

Other Ideas

In a commercialized version of this product, a rechargeable pack could be made up, tuned to an LED circuit optimized to work from that configuration, that would result in improving operating time to some degree. Further, the cost of the (3) 9V Lithium batteries at $24 (total) is troubling, leading to the conclusion that a rechargeable pack is most definitely a desirable approach. While that can also be accommodated using standard rechargeable 9V batteries and a 27V charger to keep them alive, an integrated battery pack with integral charge state regulation, etc… would be a far neater end product. Further to this, this charger could be easily connected to a small solar panel stuck in a window somewhere, using free energy to keep them fresh and ready for use.

To make battery replacement super easy, an elastic strap holds the cover in place. No tools necessary.

To make battery replacement super easy, an elastic strap holds the cover in place. No tools necessary.

 

A little industrial chique tribute to 2015 Year of Light.

A little industrial chique tribute to 2015 Year of Light.

Actually, this started as a rough lab test experiment applying thermal transfer pipes (copper pipes filled with water) to move heat from an LED platform to a simple back plane surface. The experiment included bending the pipes, soldering them using silver bearing solder, and operating the system at various angles to see the effect these had on performance. Somewhere along the line, an idea formed of making this into a wall piece, creating an industrial-chic, which led to adding a cut down reflector, and using the SLA printer to create an industrial tech representation of a flame rising from the reflector. The square cut in the diffuser aligns with the connected graphic on the back plane, and the stenciled number 15 simply represents the year.

The graphic alignment with the diffuser negative space connects the back-plane to the foremost diffuser component.

The graphic alignment with the diffuser negative space connects the back-plane to the foremost diffuser component.

The driver is housed in the FDM printed housing below the light source on the back plane, with a dimmer. Total power to the source is 19W, while the LED is 95CRI 3000K. Note that the overly red hue to the background, and slight magenta appearance of the white graphics are all issues with the camera dealing with the red-enhanced LED source, which creates high CRI, with a 90 R9 value, but in reality is a distortion of spectral power that the human eye does not readily see – but mid-range camera image sensor algorithms cannot accommodate.

The diffuser is intended to interpret a flame, or gas light sock.

The diffuser is intended to interpret a flame, or gas light sock.

 

The thermal pipes move 19W of energy from the LED platform to the back-plane - which is where the whole project started.

The thermal pipes move 19W of energy from the LED platform to the back-plane – which is where the whole project started. Cutting the back half of the reflector out provides light to the wall and plate surface.

The retro black egg - origins unknown.

The retro black egg

I found this little light on ebay at a lunch money price, so couldn’t resist. It started life as a Hamilton Industries (Chicago) lamp model 60, made in Japan in the early 1960’s.   It used a 12V magnetic transformer and a resister to provide a dual level light control of its 20W signal lamp. The amount of light it put out was barely visible in the presence of any ambient light. Meanwhile, I had a cute little key-chain wireless remote controller for less than $14 from LED Supply that delivers PWM dimming and on-off control of 12VDC LED loads. I stripped the guts out of their kit and put them inside the base of the fixture. The little lighting head was about the right size for a 12V MR16 lamp, so rather than re-invent that wheel, I just retrofitted the head to take a bi-pin socket and planned to use a retrofit MR16 lamp to deliver the light I wanted. That ended up more of an issue than I expected. First, after testing of all the LED MR’s I had around, only one brand would operate and dim effectively when run on DC power. The rest were poor dimming on AC power, but on DC they were miserable. On the LED Supply remote dimming module, they were useless. The lamp I ended up with was a Philips Enduraled product, and it will dim down to around 10%.

The remote control acts as a panel control when nested in the base, and as a remote control with cute antenna when separated.

The remote control acts as a panel control when nested in the base, and as a remote control with cute antenna when separated.

The remote control is a bit of fun, as it has an antenna that works well with the antenna arm on the fixture, so they seemed a great match. I printed a holder for the face of the power supply (now control) enclosure at the base of the fixture to hold the remote, which makes it a simple panel controller when the remote feature is not needed. When the light is used to wash a wall or light art or some other function besides a desk lamp, the remote can be removed and control the fixture from across the room. The power supply is a simple 12VDC wall wart, while the base houses only the remote control electronics now.

The base now incorporates the remote in a recessed compartment.

The base now incorporates the remote in a recessed compartment.

The base looked in need of a bit of dressing up, so I printed a retro-turbo trim ring to surround the remote control mount on the SLA printer and painted it with VHT fake chrome to give it a sand-cast aluminum look. I also printed the same part on the FDM printer for comparison. I’m throwing in two images of the raw prints to show the difference in surface quality one gets between these machines. Obviously, for parts that include details that will be hard to sand and fill, the SLA process is superior. For parts that need to be strong and can be easily finished, the FDM is the go-to tool.

The lighting head uses an LED MR16 lamp for its optic and driver components

The lighting head uses an LED MR16 lamp for its optic and driver components

So, this little weak black egg ebay find has been transformed from a barely functional desk lamp novelty, to a bright, useful, remote controllable, dimmable, black egg turbo trimmed LED light novelty. I’m a fan of the 50’s and 60’s design aesthetic, so this one felt right and was fun to put together.

The turbo fins look very rocket-man when the egg is closed up

The turbo fins look very rocket-man when the egg is closed up

 

 

 

 

 

 

 

The remote facilitates using the light as a wall accent, or ambient uplight, controlled from elsewhere in the room

The remote facilitates using the light as a wall accent, or ambient uplight, controlled from elsewhere in the room

With the remote out, the light can remain on, lighting the turbo louver as a night light

With the remote out, the light can remain on, lighting the turbo louver as a night light

The ebay purchase

The ebay purchase

The cord was ugly and the closed appearance rather out of alignment and boring

The cord was ugly and the closed appearance rather out of alignment and boring

While FDM 3D printed parts (top_ are strong and easily finished, in fineer detail work, they lack fidelity and smoothness. The SLA (bottom) part is much smoother, requiring less finish work, but are less durable. In this case, the FDM is printed at its finest setting, the SLA at its coursest, so the contrast here is greater when the SLA is pressed to maximize reolution. Both took 2.5 hours to print.

While FDM 3D printed parts (top_ are strong and easily finished, in fineer detail work, they lack fidelity and smoothness. The SLA (bottom) part is much smoother, requiring less finish work, but are less durable. In this case, the FDM is printed at its finest setting, the SLA at its coursest, so the contrast here is greater when the SLA is pressed to maximize reolution. Both took 2.5 hours to print.

 

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.

 

There remains an issue of flicker and its issues that has been drawn out by a lack of action on the part of our standards and professional organizations. The topic of flicker has been turned into years of discussion, consternation, regurgitation of old information, tests to prove what has already been known for years, and avoidance of conflict. One of my best selling products from the Lumenique Product Center is the Flicker Machine, as simple device for visually detecting and confirming that visible flicker exists within a space or from a source, indicating there is a desire of individuals to know more. I presented a bit on this device and its use here some time ago.

This little spinning wheel tells the story. If you see banding and colorful rainbows, the lights are a flickerin'

This little spinning wheel tells the story. If you see banding and colorful rainbows, the lights are a flickerin’

I have invested my personal time exploring this topic, including membership in the IEEE 1789 committee addressing the risks of flicker, presentations at DOE and other conferences, working with various manufacturers on their line voltage, non-driver products, and personal testing, experimentation and actively living with and under AC LED products.  After more than 6 years of this, one simple question surfaced for me.

If DC and high frequency (>2,000Hz) PWM driven constant current LED solutions produce no visible flicker, why consider a source with greater flicker presence? (more…)