UPB dimmer and LED lighting

[globramma]

Question about the ILR-10K resistor from PulseWorx --
 
In my setups, which use SAI 11-40 and 2-40 UPB dimmer switches, with 2 or 3 CREE A19-style soft-white LED bulbs per overhead fixture, I have no problems with flicker or with the bulbs shutting off completely. But the dimming bottoms out around, I would estimate, probably 100 lumens per bulb. (Corresponding to the 1-watt minimum dim capability of the SAI dimmers.)
 
These same bulbs, when attached to a Lutron Skylark LED-compatible manual slide dimmer will go way *way* down, I would estimate to around 10-15 lumens per bulb, staying completely stable (no flicker) all the way to the bottom. Each bulb looks like a dim, small candle, which is what I would like for the low end.
 
Will installing an ILR-10K with the SAI UPB dimmer switches result in a lower bottom-end dimming threshold?  If so, how much light output will I lose off the top end / 100% brightness setting?

 

[ano]

Question about the ILR-10K resistor from PulseWorx --
 
In my setups, which use SAI 11-40 and 2-40 UPB dimmer switches, with 2 or 3 CREE A19-style soft-white LED bulbs per overhead fixture, I have no problems with flicker or with the bulbs shutting off completely. But the dimming bottoms out around, I would estimate, probably 100 lumens per bulb. (Corresponding to the 1-watt minimum dim capability of the SAI dimmers.)
 
These same bulbs, when attached to a Lutron Skylark LED-compatible manual slide dimmer will go way *way* down, I would estimate to around 10-15 lumens per bulb, staying completely stable (no flicker) all the way to the bottom. Each bulb looks like a dim, small candle, which is what I would like for the low end.
 
Will installing an ILR-10K with the SAI UPB dimmer switches result in a lower bottom-end dimming threshold?  If so, how much light output will I lose off the top end / 100% brightness setting?

I don't think so, but you could try it.  It says for the resistor it only prevents flicker. It is doubtful it will allow you to dim more.
 
AC dimmers are not a variable resistor. They use a triac which chops the ac sine wave and that dims an incandescent bulb.  Notice I said incandescent, because LED bulbs work completely different. They have a power supply that changes the 120VAC into a current source for the LED. LEDs are current driven, not voltage driven devices.  So a very simply designed LED really would not dim at all. But since the bulb manufacturers know people like to dim bulbs, they add circuits  that watch for the chopping of the AC sin wave, then dim the bulb accordingly.  The problem is these dimmer circuits aren't perfect, so the bulb and dimmer don't always perfectly understand each other.  If they don't the bulb won't dim to zero, or it will dim too soon and you'll have dead space.
 
Maybe someday, they will create a standard so bulbs and dimmers can speak to each other, so if the dimmer wants 15% it tells the bulb go to 15% instead of this game of chopping the AC power. 
 
I know this doesn't help your problem, but until then its just a bit of trial and error finding a good dimmer/bulb match.

 

[globramma]

I understand what you mean. The LEDs run at a very low voltage, so you're saying it doesn't really matter if you shave off X% of 120 volts using a resistor. Even if the bulb only got 50 volts it would (if the driver circuitry accepted 50 volts) work fine because the driver is going to drop that to ~2 to 3 volts anyway.  Chopping the sinewave is what controls dimming, not the *height* of the sinewave. The resistor has no effect on sinewave chopping frequency or time-domain shape, it only affects the height / voltage of the sine wave.
 
 

AC dimmers are not a variable resistor. They use a triac which chops the ac sine wave and that dims an incandescent bulb.  Notice I said incandescent, because LED bulbs work completely different. They have a power supply that changes the 120VAC into a current source for the LED. LEDs are current driven, not voltage driven devices.  So a very simply designed LED really would not dim at all.

 

[ano]

The resistor just provides a small load to the dimmer, because small LED bulbs draw so little current. It won't change the voltage of the sine wave at all.  Dimmers need to "see" a small load to function correctly, if they don't they can flicker.
 
Most dimmers can control 600W or more so the extra 1.5W that the resistor draws really won't change much except it adds a small load when the bulb doesn't have much. Most bulbs and dimmers don't need this resistor, but PulseWorx sells it if you have flicker from certain bulbs.