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Topic:
do any of you who do LED lighting run low voltage to the LEDs themselves?
This thread has 19 replies. Displaying posts 1 through 15.
Post 1 made on Saturday November 8, 2014 at 00:03
Ernie Gilman
Yes, That Ernie!
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I'm working on a couple of projects where we've had a very hard time obtaining LED lighting and dimming that will smoothly dim to zero. We've gotten some that dim to about 20, then slam off; slam back on again when raising the dimming.

Only one approach has worked: A lutron dimming module intended for a magnetic load; near the LEDs a 230V to 12V transformer (AC is 230V here), a full wave rectifier, and a capacitor. And even then, the transformer and capacitor have to be chosen carefully because have too much current available messes up the dimming, and there's a sweet spot of capacitance which filters well enough but doesn't store so much energy that it slows the dimming.

If you've got 12V or other low voltage lighting, how are you dimming it?

I've come to believe that smooth dimming is beyond the state of the art, at least for high voltage LED bulbs, like 120V or 230V. They do not seem to be capable of being dimmed as we'd like because the internal drivers require a certain minimum voltage to operate.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 2 made on Saturday November 8, 2014 at 00:53
fcwilt
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I installed some LED accent lighting that worked well BUT it used a constant 12 VDC power supply feeding a separate PWM dimmer.


Here are some of dimmable LED drivers:

[Link: trcelectronics.com]
Regards, Frederick C. Wilt
OP | Post 3 made on Saturday November 8, 2014 at 05:22
Ernie Gilman
Yes, That Ernie!
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fcwilt, do you mean to say that those drivers can be used with 12V LEDs? The first few say they use TRIACs, which die when you have a transformer load, so an LED system that's a transformer and rectifier will kill that kind of dimmer, leading me to wonder what the rest of the system is.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 4 made on Saturday November 8, 2014 at 08:40
fcwilt
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Hi Ernie,

There are a number of different kinds of drivers in that selection.

There are various output voltage ratings, including ones suitable for 12V LEDs.

There are various output current ratings.

There are various ways they can be "dimmed".

Some are designed to be powered via/controlled by a "standard" AC dimmer.

Others are designed to be powered via a fixed AC source and to be controlled by a variable DC voltage, by a PWM modulated signal, by a variable resistance (built-in or external), etc.


Of the ones listed I've only used these BUT they used in an application where the dimming range was 25% to 100%.

[Link: alliedelec.com]
Regards, Frederick C. Wilt
Post 5 made on Saturday November 8, 2014 at 09:54
Dave in Balto
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Just did one from Whitegoods. Electrician put them in, transformer off the lutron dimmer, low voltage to the lights. Worked great.
Hey, careful man, there's a beverage here!

The Dude
Post 6 made on Saturday November 8, 2014 at 17:28
KRAZYK
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I am just completing a job for a major bank in Toronto. It's an auditorium which includes a couple of washrooms, meeting rooms, lounge, reception etc. The entire job uses LED's.

The entire Auditorium is controlled using a Quantum Hub which is part of the building infrastructure and uses Lutrons eco-loop system with addressable LED drivers. The main auditorium and lounge use Lutron`s 0-10V dimming panels which dim Pot lights and Pendant lighting. Control is done with Lutron`s QS system.

Each lighting fixture contains it`s own driver and is programmed from the main Hub. All low voltage wiring to the LED`s exist in the light fixture; although control wiring is daisy chained between each fixture in the eco-loop back to the Quantum Hub or 0-10V feedback wiring back to the panel.

Although there have been some challenges with this project, the LED lighting isn`t one of them.
Lutron`s Eco-Loop system and 0-10V panels have been able to dim LED`s down to 1% with no signs of pop on.

I would try using some of Lutrons drivers and their dimmers.

[Link: lutron.com]
KRAZYK

Things you own end up owning you!
Post 7 made on Tuesday November 11, 2014 at 18:05
BizarroTerl
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I recently did a remodel and used 12V DC & 24V DC strip LEDs. Bought some that were marked as dimmable and used Diodeled dimmers ([Link: diodeled.com]). Used the correct Lutron switches and dimming is very good. I will occasionally get minor pulsing on one of the 24V strings when I'm at very low light levels (<10%). Otherwise it turned out very well.
Post 8 made on Wednesday November 12, 2014 at 16:27
Late Night Bill
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Friends of ours:
http://lumencache.com/

The system distributes low voltage to the LEDs via CAT5, and can smoothly dim constant current and constant voltage type LEDs.
Post 9 made on Thursday November 13, 2014 at 09:21
thecynic315
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Both Crestron and Lutron have fixture compatibility charts and reports to let you know which equipment to use.

I have used a 10 Ohm resistor in parallel with some LEDs to create a dummy load to get smooth dimming.

I just saw that Lutron has a dummy load item that can be used as well, though my way costs WAY less.

The trick to LED dimming is taking a few hours and going through ALL the cut sheets for each fixture then checking with your chosen 'tron to see what they say.
OP | Post 10 made on Thursday November 13, 2014 at 15:42
Ernie Gilman
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On November 13, 2014 at 09:21, thecynic315 said...
Both Crestron and Lutron have fixture compatibility charts and reports to let you know which equipment to use.

For low voltage, or only 120V? This thread is about low voltage, 12 or 24 volts.

I have used a 10 Ohm resistor in parallel with some LEDs to create a dummy load to get smooth dimming.

That resistor value makes me think you're talking about voltage in the 12 volt range. You wouldn't put 10 ohms across 120V!

I just saw that Lutron has a dummy load item that can be used as well, though my way costs WAY less.

Lutron has a dummy load for 120V and for 230V LEDs. And for 12 volts, too?

The trick to LED dimming is taking a few hours and going through ALL the cut sheets for each fixture then checking with your chosen 'tron to see what they say.

Oddly, if you're running LEDs with resistors, then varying the DC voltage to them, the literature is found to be lacking or lying, depending on your point of view. You have to test everything.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 11 made on Thursday November 13, 2014 at 16:16
thecynic315
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On November 13, 2014 at 15:42, Ernie Gilman said...
For low voltage, or only 120V? This thread is about low voltage, 12 or 24 volts.

Both

That resistor value makes me think you're talking about voltage in the 12 volt range. You wouldn't put 10 ohms across 120V!

And yet I did and worked with techs at Crestron, Mouser and the Electrician to figure out the values.

Lutron has a dummy load for 120V and for 230V LEDs. And for 12 volts, too?

Don't know, saw that an item exists once. Go check/call them.

Oddly, if you're running LEDs with resistors, then varying the DC voltage to them, the literature is found to be lacking or lying, depending on your point of view. You have to test everything.

So test everything. When I get a lighting job day 1 is spent just reading cuts and specs. Looking up the actual driver info, usually buried on Phillips site. And making calls to get more info.
Post 12 made on Thursday November 13, 2014 at 16:22
thecynic315
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Oh here is the link to the resistor I used.

I was off, its a 1.4K Ohm resistor. I was confusing the Wattage I was trying to simulate, 10w, with the resistor value.

[Link: mouser.com]
Post 13 made on Thursday November 13, 2014 at 17:00
fcwilt
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On November 13, 2014 at 16:22, thecynic315 said...
Oh here is the link to the resistor I used.

I was off, its a 1.4K Ohm resistor. I was confusing the Wattage I was trying to simulate, 10w, with the resistor value.

[Link: mouser.com]

Are you putting this resistor on the output of a 120 VAC dimmer - because the LED alone does not present enough load for the dimmer to work correctly?
Regards, Frederick C. Wilt
Post 14 made on Thursday November 13, 2014 at 20:02
juliejacobson
CE Pro Magazine
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POE lighting - expensive
[Link: kickstarter.com]
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www.cepro.com
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OP | Post 15 made on Thursday November 13, 2014 at 23:31
Ernie Gilman
Yes, That Ernie!
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On November 13, 2014 at 20:02, juliejacobson said...
POE lighting - expensive
[Link: kickstarter.com]

One year at CES I saw a totally new thing. They called it a plasma display, and it had gone from theory to reality. It was about a dozen inches in size. There was a note saying that that unit at that time would sell for about $100,000. "Expensive" should not be a deterrent for the first units!
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
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