Long Live the Incandescent!

To (hopefully) clarify, LEDs are in fact intrinsically "dimmable". Their light output is conventionally dimmed by holding voltage more-or-less constant and reducing current.

But incandescent lamps are typically dimmed by reducing average voltage, not current. So in practice, standard, conventional TRIAC-based dimmers are not well suited for dimming LEDs because they dim by reducing average voltage and current is held more-or-less constant (varies with filament temperature) during conduction.

Another issue is the 'dimmer curve' of particular wall-mounted dimmer. One description of a dimmer curve is the relationship between the rotation (in degrees) of a physical dimmer knob to the phase angle (in degrees)of the TRIAC conduction (output). A typical household dimmer curve that is appropriate for incandescent lamps may not be appropriate for an LED-based lamp. This issue is well addressed by emerging electronic solutions as well as by some existing conventional 'professional' dimmer consoles and panels such as those used in entertainment venues using DMX (DMX512)

There is at least one IC on the market that addresses both the current-control and dimmer-curve issues by interpreting the complex "chopped" waveform created by a TRIAC-based dimmer into the information needed by an LED for continuous dimming with a useful dimmer curve and then providing the appropriate current to the LEDs.

National's LM3445 detects the 0-180 degree phase angle of a conventional TRIAC dimmer output and translates that information into a current output with a 1:100 dimming range (about 6-1/2 f-stops of light).

Incorporation of this sort of smarter electronics into LED lamps will reduce or eliminate the problem that Bill describes. I have a pair of dimmable LEDs intended for ceiling cans in the kitchen which I can place on the same circuit as halogen incandescents and CFLs in which they perform admirably. Like CFLs, and unlike incandescents, they are not 'infinitely' dimmable, i.e, they have an abrupt shut-off at about four to five f-stops below full brightness.

HTH ... Marc Marc_F_Hult

Here Dave succinctly repeats his own logical fallacies.

There may indeed be "bigger targets". But even a 100% reduction total (elimination) of any one or two or five of the "bigger targets" will not achieve the total energy and CO2 reduction needed. The solution will lie in making reductions wherever and whenever possible.

Sober business owners and leaders, scientists, politicians, administrators, journalists, and others that Dave maligns with regularity recognize that there is often no single, simple fix to complex problems whether they be in business, science, law or other human endeavors.

Dave Houston also demonstrates once again that his approach to a serious problem is to create straw men with which to mount an self-serving, illogical and specious attack on those who actually understand the issues and are trying to implement actual solutions.

... Marc Marc_F_Hult

Vendor, manufacturer, model numbers?

Thanks!

Steve

Mine are Cree LED Recessed Lighting Luminaire LR6C 6" Downlight Module and are "Neutral Color 3500K" which provides daylight, i.e., cooler than incandescent light.. As I recall, Cree also sells a warmer, 3200K version.

GooBing " Cree LR6C " for FAQ, vendors and manufacturer site.

They are expensive -- ~ U$87

Among the claims on the LR6C box are:

1) "Designed to last 50,000 hours" 2) ' uses 85% less energy than conventional bulbs and 50% less than CFLs"

Note that CFLs and LEDs do not intrinsically put out warmer light when dimmed as do incandescent lamps. I suspect that some bright manufacturer will realize that part of the attraction of dimming incandescents is the resulting reduction in color temperature. One can, of course create most any color with a RGB or RGBY LED lamp using multi-channel DMX-512 (DMX512a) control.

I note that one web site cites specs of "dimming to 25%". I'll remeasure.

HTH ... Marc Marc_F_Hult

Back on Sun, 18 Feb 2007 16:44:26 -0500 in message in comp.home.automation, Marc_F_Hult wrote (in part):

" The study I cited

that Dave was apparently using to disparage folks that actually measure things and understand what they measure ("bureaucrats and ivory tower academics") was a study of actual measurements of actual older refrigerators in actual use in the service area of the metro Cincinnati utility that provided electricity for the fridge in Dave's house."

See

"Low-Income Refrigerator Replacement -- Selecting the Worst of the Worst" . )

HTH ... Marc Marc_F_Hult

Thanks for the reference. I'm looking a the can compatibility, and it looks like they want most 6" cans, and the trims snap onto the lights, not the cans. Also need to see if they're compatible with UPB dimmers.

Steve

Yes, The LR6/LR6C trim replaces the existing trim in a retrofit. My existing ceiling cans were not among those listed by Cree as compatible, and as I recall, it took a minor tweak to coax them to fit. Something I'd want to avoid if building a house from scratch but near-trivial compared to many other retrofit tasks.

My only complaint is the high price. I do also note that the LR6C "Neutral Color 3500K" seems much cooler than the 3400K photofloods of yesteryear. This is consistent with Cree's indicating that their LR6 "warm" lamp is 2700K, not

3200K as I mis-remembered/wrote in my previous post.

Cree readily agreed to exchange my LR6C's for LR6's at no cost, but once I got used to actually seeing and using mixed-temperature lighting, I 'warmed' to the notion and decided to keep them. They are directly in front of a north-facing window and complement and extend and simulate daylight from the window very well.

HTH ... Marc Marc_F_Hult

This is so much poodle gas it is hysterical.

I can see a relatively quick payback for these Cree LR6C lamps in a commercial/industrial application, but for a home where they may not be used more than an hour or two per day the payback would be many years, unless they get the price down.

On my visit to the Cree website I didn't see any mention of dimming capabilities.

And lastly, I hope they do a better job of living up to the claimed life expectancy than CFL's did.

One place I would really like to incorporate LED lamps is under our kitchen cabinets. I presently use inc. rope lights above the cabinets and halogen under the cabinets. These new LED strips are interesting, but they all have bulky power supplies to deal with. Have you used any undercabinet LED's Marc?

Our kitchen lights are not only the longest of any main interior light, they had the highest power use before I switched to a mixture of incandescents and LEDs ( 9 x 120watts = 1080 watts)

Note that the company has both

and sites with limited linking between the two. Residential products are primarily at creelighting.com not cree.com

Dimming is variously listed at 20% and 25% ; Also power factor > 0.9

I use DMX/analog-controlled dimmers with large inductors (chokes) mounted in a panel in the basement for the kitchen lights, but Cree lists compatible conventional dimmers: Lutron also has tested and recommends many of their dimmers with Cree lamps:

Time will tell but the signs are propitious. The vulnerability of LEDs is similar to that of CFLs in that it appears that a common failure mode of CFLs is for the electronic circuitry to be cooked and then die and LEDs also require at least some electronic components when used directly with AC sources. Many of the failures of CFLs have been in base-up or enclosed environments. (Remember the X-10 "socket rocket" and its short life when used in base-up orientation ?) But Cree has designed their units for specific orientation, geometry, and environment, namely 4", 5" and 6" ceiling cans and so has theoretical and empirical knowledge of the heat production and temperature distribution in normal, code-compliant use.

Funny you should ask. ABIR, in decades of putting up with my HA experiments, my better half has never actually made a specific request until recently -- namely to illuminate the dark space under the black steel shelf I installed for the black microwave and touch screen where the black coffee-making gadgets are stored next to the black soapstone back splash. (OK. So I created this black hole and now have to deal with it ;-) No progress or decisions yet. I am (unduly?) fascinated by the potential for RGB and RGBY LEDs.

... Marc Marc_F_Hult

However, the bulk of the effort (and cost) should be to those things that give more reward and are feasible.

Another way of saying it is EFFECT / COST -> PRIORITY

I do what is feasible for me. I can't directly control what government agencies and power companies do. However, I can affect what happens in my house. I can afford the extra cost of CFLs over incandescent bulbs so I use them. I like to keep the temperature in the house about 72F during the summer but that consumes lots of power so I leave it at 78F. Heating isn't much of an issue for me since the temperature rarely gets cold enough to bother me, even during Florida's frigid winter nights. I use solar energy to heat the pool and the Jacuzzi. Weather permitting, I usually ride my bike rather than drive the car. I used to ride a bicycle a lot but health issues make that no longer an option.

These are all small things but if more people do them and lots of other small things there can be a significant benefit. I agree that it's important to work on the big polluters and energy consumers, but IMO that doesn't relieve us all of the obligation to reduce our individual footprints.