Posts Tagged ‘Solid-state’

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.

Edit May1

As demonstrated in D1 of this series, LEDs and solid-state technology are changing more than general illumination. Other instances of applying near UV  LEDs with emission to cure light-cure resin composites. We have applied this to replace Metal Halide light sources that require 20 minutes to start-up, and are skin frying monsters. LED cure lights are also more predictable and focus-able than natural light, and can be applied indoors, and less bulky and more powerful than fragile fluorescent cure systems. LED sourced cure lights are now used in printing, dentistry, and commercial production of resin-based composites. We are also applying this on small and large scale applications from the very small (like D1 SLA curing) to larger scale units for curing large objects, like fiberglass repair of boat hulls, custom automotive body panels, and low odor repair of fiberglass bathtubs and shower floors. The use of LEDs produces instant-on high intense light, with much less power,  significantly less heat in the lighted pattern, less exposure to hot surfaces, and contain none of the damaging ultraviolet light that does nothing to enhance curing, but is harmful for operators. The use of UV initiated resins offer the advantage of extended shelf life as there is no catalyzed resin to harden in the container and less odor for use indoors. An update with  new images and details will be posted here when available.

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.

 

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.

D2-img-4

D2 Front View

This weeks project is a concept model exploring an organic form of twisted and tapering ellipses. The height is 24″, and it measures roughly 3 1/2″ x 2 3/4″ at its base. The design is intentionally simple, utilizing a single LED strip concealed behind a valence to one edge. Total power at full brightness is 5 watts, and output is roughly 400 lumens total. The interior is covered with White Optic material to create a diffuse soft edged luminance from within. There is a simple stem dimmer control at the base circuited in series to the light strip, and a two position switch to the side providing full-on / off / dim settings. This model is powered by a wall-wart 24VDC power supply.

This was printed on a 3D printer, sanded smooth and painted matte white. In a production version casting the body in ceramic with a matte glaze would render a more finished end product. Low power LEDs don’t require much thermal management, can be circuited with on-board micro IC current control driver, creating a very simple to assemble and economic end product. Even in this plastic concept model form, the costs of the entire assembly were under $200, with the power supply.

D2-Img1

D2 3/4 View

D2 View 2

D2 View 2

D2 Back

D2 Back

D2 Top

D2 Top

D2 Base

D2 Base

 

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.

 

2015 is the International Year of Light and Light-based Technologies – a United Nations observance to raise awareness of the achievements of light science and its applications, and its importance to humankind. 

Edited 12/10/2015:

The concept of pursuing another round of 52 designs in 52 weeks was the original intent for this series. However, the time involved was not available, nor were we able to rationalize the costs involved. The work of the 52/52 2010 was a significant effort, that never truly delivered an ROI, either directly or indirectly. It was a lot of fun and reflected my exploration of SSL technology on a fast track. I’d hoped to attract others in playing along this time around. This never materialized. Faced with going it solo again, I came to the realization I just couldn’t get it done, so abandoned the project. It is a serious disapointment, but did free me the time to refocus on our business and move us into a larger and more productive state and facility, so not all was lost. The original 52/52 designation for the projects has been re-titled YOL, for the Year of Light. Yes, it is a bit of revisionist history, but its my blog and I have that right.. literally and figuratively.

With that in mind, I am still sharing projects being worked on within Lumenique that are exploratory, experimental, or customer project related (when we are allowed).

In 2010, we explored everything from steam punk to toys and practical tools. 2015 will be more of the same with a 3D twist.

In 2010, we explored everything from steam punk to toys and practical tools. 2015 will be more of the same with a 3D twist.

I combine work with solid-state light sources with another emerging and revolutionary technology we started working with in 2010 – 3D printing technologies. I now have (3) such printers on hand, including a commercial FDM printer, a desktop FFM printer, and a desktop SLA printer. With these, we can now make translucent and transparent prints, including simple optics, flexible parts, and smaller, highly detailed components and mold patterns for casting in metal and urethane. I’m anxious to put these to work in creating interesting final forms. I’ll also be firing up the glass kiln a few times, and hammering out a few pieces in the blacksmith shop to keep things interesting.

In the next few days, I will be posting my first entry to start the ball rolling with something for my shop, that others in the 3D print business may find useful.

That all said, I hope that 2015 has been a great year for everyone!