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Author Topic: LED Dimmer pack?
Dave Macaulay
Film God

Posts: 2133
From: Toronto, Canada
Registered: Apr 2001


 - posted 09-14-2013 02:24 PM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
A cinema has decided to save electrical cost by installing LED replacement lamps in all house lighting fixtures. After that they discovered the existing dimmers won't dim them, they are "dimmable" lamps but the dimmer is not compatible. The dimmer manufacturer agrees and says the unit can not be made compatible.
Has anyone found a dimmer pack that works with these lamps? We need dry contact, serial, or ethernet control with 3 presets (feature off, trailer/credits dim, exit full). Load power is about 300W with the LED lamps but having a higher load rating won't hurt.
Thanks in advance!

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Steve Moore
Expert Film Handler

Posts: 198
From: Leeds, West Yorks, UK
Registered: Apr 2008


 - posted 09-14-2013 02:46 PM      Profile for Steve Moore   Email Steve Moore   Send New Private Message       Edit/Delete Post 
If anyone has I'd love to know too, been looking for this for ages. Currently I use 20 x 100w lamps over my screen curtains and am struggling to find LEDs with a long enough throw too. I have looked into getting a DMX controller for them then buying a analog 0-10v interface and borrowing a couple of the channel feeds that come from the dimmer controls to the dimmer pack as a method, thus still the same controls in the projection room. (something like one of these http://northlightdmx.com/dmx512decoder.htm )

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16221
From: Bountiful, Utah
Registered: Jun 99


 - posted 09-14-2013 06:14 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
LED fixtures are quickly taking over in the live theater world and many of those dimmer racks are compatible with LED so it's probably just a short time till theater light dimmers make the required changes to bring compatability around.

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Harold Hallikainen
Jedi Master Film Handler

Posts: 763
From: Denver, CO, USA
Registered: Aug 2009


 - posted 09-14-2013 11:56 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
I wonder if these would work if one of the lamps remained incandescent. Triac and SCR dimmers have trouble with nonlinear loads.

Harold
Used to design dimmers for http://www.dovesystems.com .

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12206
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-15-2013 01:41 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Harold...at the AFI/Silver, they have Lutron dimmers. And yes, by leaving one incandescent in the load of each bank...LED dimming seems to work perfectly.

-Steve

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Mark Hajducki
Jedi Master Film Handler

Posts: 500
From: Edinburgh, UK
Registered: May 2003


 - posted 09-15-2013 03:33 PM      Profile for Mark Hajducki   Email Mark Hajducki   Send New Private Message       Edit/Delete Post 
I have seen theatre lighting dimmers dislike low loads (such as filament Christmas lights) once a traditional lantern was connected in parallel there was no problem.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16221
From: Bountiful, Utah
Registered: Jun 99


 - posted 09-15-2013 04:32 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
I believe you will find that most any dimmer that utilizes a solid state relay instead of a triac or dual scr will work. So checking which dimmers utilize this sort of load transfer device should be easy to find out.

This link may also help you out...
Phillips LED Lamp Dimmer Reccomendations
This article may also be helpful Understanding Dimmer Compatability & Wiring Issues

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Brad Miller
Administrator

Posts: 17687
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 09-15-2013 08:29 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Steve, what happens when that incandescent bulb dies? Does it cause any damage to the dimmer? I would assume the LEDs no longer dim properly.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12206
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-16-2013 06:09 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
The load seems like it doesn't dim....and then just goes out. It is like having a delayed switch rather than a dimmer.

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Gordon McLeod
Film God

Posts: 9460
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 09-16-2013 12:06 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
A triac SCR or SSR block all exhibit one issue in that the current and voltage must be in phase with each other or it will not be stable
Inductive loads or capacitance loads often cause them to either not have a suitable dimming range or that they flicker
Some transformer loads the transformer will fail to saturate on turn on at low levels and damage the thyristor
We usually put a large power resistor in serries with transformer LV lamps to minamize inrush and put a snubbing cap across the load to correct power factor
Some LED lights use a solidstate powersupply and they will dislike any chopped wave form

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