Fully Dimmable LED?

Led as an entity is TOTALLY dimmable. But the "crude" power supply inside integrated led bulbs that involve rectifier and capacitor, is not, and never will be dimmable. the way we dim incandescent lamps, just chopping out a portion of the AC waveform. Technically it can be done with different, a bit more expensive circuitry and I hear there are already "dimmable" versions of led lamps around. But that's not a priority of lighting industry for the moment. I believe they are now trying to solve a more serious problem, the TOO long time it takes (100000 hours to drop light emission to 50%) for leds to fail. Too long I tell you. And they mean business. Eastern manufacturers have already solved the problem just using their -usual- bad circuit design, but west MUST find a more sophisticated method to get same result. A secret ingredient in the wafer? Who knows. Before you know it, led bulb life will hit 1000 hours, and will be probably... dimmable. (LOL) S.M.

It's not the LED's problem, it's the dimmer's problem.

The problem with dimming LED's is their strong point. They make light with very little current. None of the current dimmers (pun maybe?), are able to make voltages (and hence currents) small enough to truly dim the LED down to near dark levels. The trouble is that the typical el-cheapo two-wire dimmer is designed for tungsten filaments where you need a sizable current before you even start producing visible light. These are typically thyristor controlled devices that just crudely delay the firing of the thyristor to reduce the average voltage/power to the device. It's a form of pulse width modulation using visible light feedback to get the mood just right.

Even the IR sensing switches don't work very well with LED's because the parasitic current used to power the electronics in the switch is enough to make normal LED's illuminate enough to be a quite effective night light. With incandescent bulbs, the few milliamps of parasitic current to work the electronics is not enough to cause much heating and hence no visible light.

Most LED's don't work well with the older line powered electronic timer switches that are just wired in series with the 'bulb' like a regular SPST switch. To get those to work properly, I have had to have at least a 4W incandescent in parallel with the LED's to get it to work properly. My LED's flash like disco lights if I don't have that low impedance tungsten load in the circuit. The timers that use mechanical contacts and a timing clock seem to work just fine but they are not 'two-wire' and don't fit in the space of a normal wall switch.

Sorry to say, but we need dimmers designed for LED's now, if that's the bulb we want to use. Personally, I have not tried any of the new dimmers out there but here is a link to Leviton's website. They claim they will dim, but of course how well is in the eye of the beholder.

http://www.leviton.com/OA_HTML/SectionDisplay.jsp?section=37698&minisite=10251

Here is a quote from their website: (underline is my emphasis)

Pairing dimmers and bulbs which are incompatible can result in lights flickering and fluttering, limited dimming range, slow start-up, and inconsistent illumination. To avoid these types of issues it is important to know the features of the types of dimmers available and compare them to your needs and the type of bulb you wish to use.

Good luck with your quest.

Have a look for a company called LED Hut or learn where you left the toilet.

I just use nightlights to move around at night...

http://www.amazon.com/Maxxima-MLN-10-Night-Light-Sensor/dp/B002SVANCY

...or you might try the color changing bulbs, just changing to blue is like dimming the bulb...even better...

https://www.superbrightleds.com/cat/smart-bulbs/filter/Bulb_Type,PAR20,30,480:Bulb_Type,PAR30,30,484:Dimmable,Yes,38,1198:?utm_source=cat-sidebar-led-household-bulbs&utm_medium=banner&utm_content=sidebar-wl-prod&utm_campaign=featured-products

Yes, you were.

Which LED bulbs are best for built-in dimmers? - CNET

Is Cree Offering the Dimmable LED Bulb We've Been ...

If you want a light for the loo that is dimmable and will let you keep your night vision, you don't need an LED. A low-wattage red or amber incandescent lamp will work just fine.

A little-known fact about incandescent lamps is that they last a very long time if they are kept on a dimmer. It's the inrush current that usually kills an incandescent lamp, so the low-voltage start that a dimmer provides minimizes this killer inrush current. And in general, the life of an incandescent lamp goes as the 12th power of the voltage -- so if you run an incandescent lamp at half its rated voltage it will last 2¹² times longer than its rated life. Do the math; that's a very long time.

Will anybody live long enough to validate that theory observationally?

It's well documented. The power law works for any reasonable range of applied voltage. So a light bulb with a rated life of 10000 hours run at twice the rated voltage will only last 0.5¹² x 10000 hrs = 2.44 hours. If run at 75% of its rated voltage, it will last 316.8 hours. Etc. This is average life span of course, for tests done on thousands of light bulbs over many years.

Hey guy's thanks for the response to my rant. All of your replies while delivered with good intention has fallen on deaf ears. As for the 'loo' comment it was more of a proverbial use. My heartfelt response to each and all of you is the tired phrase "It must be true? I read it on the internet!"

If I'm coming across as a little harsh? Pardon me and please accept my apologies. Let me back up my claims just a little bit and give a additional background. and Yes Lyn, before you even think it... I did google the subject a bit. What I found left a little steamy about the situation. I had already read the articles you pointed to, but I did not look into the old lighting forums I used to be a part of. I'm here because I thought it was the type of curious subject enjoyed and disputed on this forum.

In my previous life I did both the design work and installation of lighting systems such as this. (pictured)

And I was fortunate enough to be doing them in homes like this.

In these situations I wasn't uncommon to have 8 to 16 lighting loads in the kitchen alone. All of the digital dimming and scene control at the touch of a button can be truly awesome, but it's only possible when coupled with the right bulbs and the ability to dim them to well below reading levels. All of the fancy equipment aside it was refreshing to know that the same type of dramatic lighting could be accomplished with they use of a bunch of $5 dimmers and inexpensive light bulbs.

Enter LED lighting. Even though the packages say (Dimmable LED on the bulbs and LED Compatible Dimmer) it's a hoax. Some of the "better" dimmers designed foe use with dimmable LED's have the dimming range of an almost imperceptible brownout. Recently I had taken a few of the devices I've accumulated and tested different bulbs with different dimmers in a light bar over the proverbial bathroom sink.

When dealing with dimmers you will sometimes notice a hum that I've always associated with sine~wave induced filament bucking. True or not I found that a replacement of the lamp/s from one brand to another or conversion to halogen style bulbs etc. would reduce or completely eliminate the buzzing / humming at dim levels.

As LED's became more mainstream I reasoned that the LED's absence of a filament would eliminate the humming. As it turns out there is a similar but far more annoying whine emitted from various configurations that made the dimming function all but useless to creatures with ears. The first time i heard it I thought a motor was running in the distance.

My background in electronics makes me familiar with PWM [pulse width modulation] and other forms of dimming. After my side by side comparison I felt as though I'd be quicker to find a solution in dusting off the breadboard and having a go at it myself.

At the end if the (test) day The cheapest dimmer available as well as these peculiar LED bulbs that I got for $2 each are doing the job better than any of the other configurations.

Here's the rub. The light bar used to have six bulbs. I've reduce it to three to avoid skin cancer when the lights are up all the way and guaranteed blindness when fully dimmed. (40W equivalent) Fewer bulbs also means fewer bulbs quietly screeching in the night. In addition to the noise and the low dim range there is the cheap and gaudy style of the cheap dimmer and the bulbs that look like they were made as paddles for table tennis.

Look at this video of supposedly "fully dimmable" LED lights and see for yourself.

...all of my griping aside.. I have not given up hope that there are some units in the market that work. If not, it's only a matter of time before units that will come to market that will work.

Why does it all matter? Well, it would be nice to have fully dimmable LED bulbs since the internet says they exist.

If the bulb above could shut off some LED's while dimming others it might have the desired effect, but I guess I'll have to wait.

Here's an unrelated video to lighten things up in another way.

I have recently purchased some LED lamps and were told they could be dimmable. The instructions of the lights said the dimmer had to be a trailing adge dimmer. Investigations showed that there are leading edge and trailing edge dimmers and also the standard type dimmer. Another one of these topics of more than meets the eyes!

Trying to dim a bulb is making me feel like a dim bulb.

Three comments:

1. I've a dimmer and a 6 light chandelier with LED bulbs in my dining room, and they dim just fine for there.

2. I have to sleep partial nights in a chair in a downstairs room and the rest in a bed in my bedroom upstairs. In the bedroom I've got a red LED light I leave on until I go to the bedroom. No night vision problems with that, as once I move, I have to be ready to go back down stairs if I awakened one of my cats and it is fussing. Don't want to wake the wife up, and they only listen to me. The armed services have used red light for decades to preserve night vision.

3. In the "loo", I've got a small artificial candle with what us old timers call a "Christmas tree light" sized LED bulb (similar to a C7 - I'm not fluent in base types) and that is sufficient to do the necessary deeds, but doesn't hurt my night vision perceptibly, as I have the "cat problem" any time I move about at night.

I think the problem here is that we're asking the wrong question:

"How do we make an LED bulb truly dimmable while using the 110VAC, chopped waveform dimmers for incandescent lamps?"

What we NEED to be asking is:

"How do we convince the lighting industry and the general public to switch to a standardized 24VDC⁽¹⁾ power scheme for LED lighting, where Dimmers will be simple voltage dividers to reduce the 24VDC to reduce the light output?"

Once we start asking THAT question, we'll probably start finding answers. Who needs the Edison Screw Socket anyway?

Notes:

1. Voltage chosen due to it already being an 'industrial standard' for many PLC-based controls.
   

Except it's not that simple. A good number of the LED bulbs have active circuitry that allows them to be used at voltages from 9-30 VDC. You will get constant brightness over that range. The current of course rises as the voltage drops because these are (approximately) constant power devices. There are little switching power supplies on these bulbs. On the disc bulbs, the regulator components are placed on the backside.

Another problem with that is that the color rendition of many LED's used for luminaires changes with current. The way that you usually dim an LED is to reduce the duty cycle on a sufficiently high PWM frequency.

However, that being said, an awful lot of things we power in our houses actually WANT dc power. We have to use wall-warts or bricks to make DC from the AC. I'd be happy to have 24 VDC or even 48 VDC power distribution in our houses and expect that all electronics manufacturers get the hell on board.

And while we're at it, it's about uckingfaye time we have a useful, reliable DC power plug in our vehicles instead of that stupid hold-over from the cigarette lighter days. Those things piss me off to no end. End of rant.

So we may need to look at a slightly more complex solution. little more instalation cost, but much more flexible in the long run:

We build the 'LED bulbs' from the 3-4-wire 'LED strip lights,' and the dimmers are replaced with a microcontroller that 'talks' to the LEDs through the data line(s). Now we end up with a control that has multiple 'dimmer' levers on it, and some preset buttons. With this configuration you can not only change the light level, but adjust the color of the light, and even set up 'special effects' like 'party mode,' where the bulb 'twinkles' like a mirrorball, cyles through different colors, or even pulses in time with the backbeat of the music.

With the innovations that LED lighting can bring to the table, we may end up having to completely rethink how we look at lighting in the home or at work, as we won't even need 'bulbs' and 'fixtures,' the lights could be incorporated right into the walls and ceiling, providing whatever 'ambient light' is needed, with the only fixtures that remain being used for 'task lighting,' or highlighting an object d'art, assuming said object does not incorporate its own lighting within its frame.

I would definitely get on board with the idea that the dimmer 'talks' to the electronics in the 'bulb' about how to best accomplish dimming. That's how an engineer approaches the problem when not encumbered by legacy requirements.

I think we will get to the point where our houses are wired with DC except to those few appliances that actually need AC power. (And more and more motor driven appliances are VFD's so we might be getting there faster than I imagined.)

Good thinking. You drilled down deeper than I have been doing. I like it!!!

Actually the DC idea has been kicked around before somewhere here lately. I can't remember where right now. They sited your point of not needing AC quite as much. Then on to how the products are ruling the lack of changes allowing good engineering.

Yeah, but we'll still need AC for the transmission lines. when it comes to schlepping kilowatts, megawatts, and gigawatts⁽¹⁾ long distance, AC wins, hands down. It's also easier/cheaper to design and build generators, especially at the scales required to produce those Jumpin' gigawatts.

Notes:

1. "Great Scott!" "Yeah, Doc, this is heavy."
2. (I need some laughs today, just heard the news about David Bowie.)
   

Well . . . . that all depends. If you Wiki HVDC, you will find that there are applications for DC transmission over VERY long distances (and some short ones too). Short hauls and regional, yes by all means AC is easier to handle for step-up/step down purposes. The LA basin gets a good bit of power from the Columbia River via DC lines. Interesting technology. DC doesn't have reactive losses of AC transmission lines. This can be also helpful for submarine cables because of their close proximity to each other and 'earth'.

Cheers!

Ah, looks like HVDC excels in undersea applications (where AC would have to deal with the dielectric effects of the surrounding seawater), long untapped runs (such as the Columbia Power Plant to the LA basin), and combining power from asynchronous AC generators.

And at the High Voltage level, the electrocution risks even out, so it's not like you've got EXTRA safety issues to deal with.

The big expense is the AC-DC/DC-AC/DC-DC converters. That's where AC really wins out for distribution; transformers are relatively cheap compared to inverters or DC-DC step down systems, and at a couple hundred volts, it's safer to use AC around morons (DC makes muscles 'lock up,' you gram a 200VDC line, your hand CANNOT let go, as much as you want it to)

I'm with you on this. How much trouble when building a house would it be to run a low voltage line. I have designed a motion detect, LED lights for my kitchen under the cabinets. I use a hidden 12 power supply to drive it all. A microprocessor works the motion detect and I can program any percent of "dimming" I want. This is child's play for microprocessor people. It ramps up to 100% when I come in, stays on, and slowly goes down when I leave.

This has become a very off topic post while remaining remarkable on topic.

So is there a general consensus that the dimmable LED bulbs in the marketplace are not actually a direct replacement for the type of dimming quality that we've enjoyed for over 100 years and despite all of our technological advancements we've achieved we will need to revive the dreams of Thomas Edison to embrace the future as we did in the past?

Since the subject has become wiring DC into homes I thought I'd share this insightful article about (the thought of) converting data centers to DC.

I like the Idea of running a secondary DC system that would be run off solar/wind. Adding to the system a little at a time.. a light and a room there.. AC/DC freezer chest and so fourth. One day down the road you've hooked up enough to get by without the grid. Then get to work collecting all downspout rain. And don't forget to solar heat the water, air, and food with a built in geothermal buffer! How's that for off topic!? Now all over again while imitating Sam Kinison.