LED Dimmers

All,
I have installed 8 Sylvania LED12BR30/DIM/HO/827/HVP LED dimmable lights in my house. I purchased a Lutron LED dimmer switch. At about 1/4 dim the lights start to pulse. I have been talking to Sylvania and Lutron on their preferred lamps/switch list and neither has come up with a solution. I have also contacted Leviton to find their preferred bulb list and this model is not on their list. Now I am not in the mood for trial and error on switched. HOWEVER, I am willing to try trial and error in order to save myself $230 and buying new bulbs. Does anyone have any suggestions for a good universal dimmer to match my bulbs. I only tried Leviton and Lutron because it is what is available to me.

Thanks,
Taylor
 

A/A Fuel GTX

Senior Member
Location
WI & AZ
This subject is a mystery to me. I have a conventional incandescent dimmer in my house controlling 3 pendants with typical A 19 style LED's ( can't remember the brand ) and they work just fine.
 
If a good LED Lutron dimmer does not work then you are out of luck., IMO. The dimmer should be rated for LED---
The dimmer is rated for CFL and LED lights. I know that price doesn't necessarily reflect quality but the Lutron dimmer I bought was not cheap and was their top model. I have a few other options with Leviton but for some reason the drivers are not compatible with the dimmer.
 

edlee

Senior Member
I've had this problem. It IS a matter of trial and error.

Most recently I had installed a couple of the Lutron LED-rated dimmers for two sets of pendants, 8 fixtures each with Phillips A19-style LED bulbs. The dimmer caused unacceptable flickering at moderate levels. So I tried a dimmer I found at Home Depot, Leviton, LED/CFL-rated, with a small rotary knob and decora frame. It solved the problem.

The problem seems to be exacerbated when you are trying to dim a set of lamps rather than just one or two. I'm no electronics guy but I figure it must be something to do with all those strange wave forms adding up when there are multiple fixtures.
 

kbsparky

Senior Member
Location
Delmarva, USA
Sometimes you can put just ONE incandescent or halogen bulb in the line, and the dimmer smooths out nicely.

I wonder if there is a resistor available that could be put into one of the fixtures that could do the same thing?
 

gar

Senior Member
131103-1124 EDT

taywoo:

You list yourself as an electrical engineer. So do some basic study.

An incandescent bulb is basicly a resistive element. However, its resistance does change with voltage or current and therefore can not be described as a constant resistance over its range of operation. The thermal time constant of the filament is sufficiently long relative to 1/120 second that there is not much change in resistance within a half cycle of 60 Hz power. At any one input voltage level it is reasonable to call the resistance constant. Also with 60 Hz power there is not much modulation of light intensity, but there is some. Any sort of voltage or current adjustment from 0 to maximum will provide light adjustment from 0 to maximum. Power factor is 1.00 .

A flourescent lamp is not a constant resistance load, but approximately a constant voltage load. Needs to be driven by an approximately constant current source. Its time constant for light output is dependent upon the characteristics of the phosophers used to convert UV to visible light. There is substantial intensity modulation with 60 Hz power. A typical current source for older fluorescent fixtures was a current limiting inductor. Electron emission from the electrodes is required for current flow, to get high current flow this means heated electrodes. Typically heating is from the current flow. Thus, a dimming problem. Dimmable fixtures supply external current to the filaments in the bulbs to get good dimming range, and dimming is controlled by current adjustment. Power factor is not 1.

Fluorescent electronic ballasts use high frequency current, 20 to 100 kHz, to drive the bulb. To get this excitation the 60 Hz power is converted to DC, and an oscillator and current limiting mechanism drive the bulb. Numerous problems exist relative to adjusting the output current from some change in the input 60 Hz power.

CFLs use high frequency current, and AC to DC to oscillator. To get much dimming range something has to be done to interpret the input 60 Hz signal. Package size limitations prevent good dimming control. On one type of standard CFL I got better dimming range with adjustable sine wave voltage (a Variac) than a phase shift dimmer with a so called dimmable CFL. On the other hand the dimmable CFL had moderately constant light output with variable sine wave input from about 100 to 130 V.

A Cree LED I have tested has fairly good dimming range with either Variac or phase shift average voltage adjustment, but not comparable to incandescent. The phase shift dimmer was a three wire device. I believe most screw-in LED replacements for incandescents convert AC to DC.

Two wire phase shift dimmers require a suitable load to supply power to the internal electronics to perform control of the Triac switching element. A three wire dimmer can provide electronic control of the Triac with or without a load. Power for the electronic circuit is provided from hot to neutral. Thus, the firing angle of the Triac is unaffected by the load. There may be some problems with reactive loads because the Triac turns off at a current zero crossing.

Start with a three wire dimmer and one of your LED bulbs and see how it performs. If it is poor, then get a $10 to $13 Cree from Home Depot and try it. Use a scope to look at your waveforms.

.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Sometimes you can put just ONE incandescent or halogen bulb in the line, and the dimmer smooths out nicely.

I wonder if there is a resistor available that could be put into one of the fixtures that could do the same thing?
I believe Lutron makes a line and/or load side filter, which of course is bulky and needs to be in a junction box.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Sometimes you can put just ONE incandescent or halogen bulb in the line, and the dimmer smooths out nicely.

I wonder if there is a resistor available that could be put into one of the fixtures that could do the same thing?
I believe Lutron makes a line and/or load side filter, which of course is bulky and needs to be in a junction box. Try a ELV dimmer, which I think they all come with a neutral wire connection.
 

ceknight

Senior Member
If a good LED Lutron dimmer does not work then you are out of luck., IMO. The dimmer should be rated for LED---
"Should", yes. But.........

I'm playing LED Dimmer Roulette this week, seems to be going around. Put in a kitchen full of 6" Nicor LED downlights, 3-W switching. Supply house sold me the Lutron Diva incandescent-rated dimmer, said it seemed to work better with those lamps. And it did work, unless the dimmer preset was lower than half, at which point the other 3W switch wouldn't turn on the lamps. And there was a tiny bit of flicker at lowest dim.

Today I swapped it out with the Diva CL dimmer, trimmed it, no flicker and both switches turned on at any dim level. Except...when you turn on from the other switch with the dim preset low, there's a brief burst of full-bore light before the dimming takes over. Freaked the customer out just a bit.

Am waiting for Lutron to get back to me on that one.
 

phawk

New member
Location
Ocean City, MD.
LED Dimmers

Were having the same problem at our American Legion. A basic lutron LED dimmer still flickered. We were told to use a Lutron MACL-153M Maestro Dimmer. Haven't tried one yet.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
I have been told by a CREE rep. that they have been recommended trying ferrite beads at each LED fixture especially the retro fit type. You can pick them up from RADIO SHACK for under $4.00, the package comes with two beads and they recommended putting them on the neutral and hot fixture wires at each fixture. Have not tried this yet.
 
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