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Author Topic: Flourescent dimmer Tom Sauter Expert Film Handler Posts: 163 From: Buffalo, NY, USA Registered: Sep 2000 posted 07-20-2009 07:25 AM                        The Advance Mark 10 have the advantage of dimming on line voltage. In a retrofit application it is not necessary to add a control wire for the ballast and they will work with existing incandescent dimmers. The Lutron FDB ballasts are very nice, but are quite expensive in comparison and also require specialized dimmers and new wiring. In either case the dimmers have to be "profiled" to set a minimum turn-on voltage and a minimum bottom end to prevent flickering at startup and at the low end of the dimming range.  |  IP: Logged Paul Mayer Oh get out of it Melvin, before it pulls you under! Posts: 3836 From: Albuquerque, NM Registered: Feb 2000 posted 07-20-2009 12:54 PM                        LEDs are indeed coming along. Expensive to install yes, but long-term power and bulb replacement costs favor the LED. EarthLED LumiSelect line of fully dimmable LEDs  |  IP: Logged Jack Theakston Master Film Handler Posts: 411 From: New York, USA Registered: Sep 2007 posted 07-25-2009 02:40 PM                     For those who have seen actual dimmed LED lights, how does the color temperature compare to incandescent?  |  IP: Logged Paul Mayer Oh get out of it Melvin, before it pulls you under! Posts: 3836 From: Albuquerque, NM Registered: Feb 2000 posted 07-25-2009 05:45 PM                        For the PAR38 ones I want to use in my portable screening rig, the spec says they're available in warm white (2800K) and cool white (6000K). Since they're LED, I assume the color temp stays constant throughout the dimming range. But I haven't seen them in person yet.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-25-2009 06:16 PM                     LEDs generally have the same problem that florescents have in that they will just turn off below a certain voltage. That at least has always been my experience with LEDs over the years. Mark  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 07-25-2009 06:35 PM                     I can see the power LED on my laptop fading up and down just fine right now while on standby.  |  IP: Logged Oscar Neundorfer Master Film Handler Posts: 275 From: Senoia, GA Registered: May 2000 posted 07-25-2009 10:51 PM                        I have some LED lighting (Cooper Lighting Halo Series LED can lights)in my office for testing purposes with the dimmers I design. The color temp of LED lighting stays reasonably constant over the dimming range. It takes some getting used to since we are used to the shift in color temp that occurs with dimming of incandescent lamps. In fact this is one thing I do not like about LED or fluorescent dimming. I am so used to dimmed incandescents that to have no shift in color temp seems somehow weird and unnatural.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 07-26-2009 12:15 AM                     Adam, LEDs can give the appearance of dimming all the way down by pulse-modulated flashing. If you pulse an LED at above 30 Hz or so, it looks like it is on continuously. If you then vary the duty cycle, you vary the apparent brightness (e.g. at 30Hz, one cycle is 33 milliseconds. So on for 16 ms, off for 16 ms looks like full brightness. And on for 8ms, off for 24ms looks a lot dimmer. etc. etc.). --jhawk  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 07-26-2009 12:26 AM                     Then why bother trying to dim them any other way?  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 07-26-2009 01:19 AM                     Presumably because other dimmers are on-hand. Also, with commercial LED lighting, presumably there is a controller of some sort between the line voltage and the LED, to manage current limiting and who-knows-what. Who knows what that does with lower voltage, etc. --jhawk  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-26-2009 08:58 AM                     I generally don't like the look of pulsed LEDs. BTW..Oscar...we use a rack light by Mid Atlantic...it uses a mix of yellow and white LEDs...as one dims it...the white LEDs are the ones that dim at first so that as it dims, it does indeed yellow! Steve  |  IP: Logged Oscar Neundorfer Master Film Handler Posts: 275 From: Senoia, GA Registered: May 2000 posted 07-27-2009 11:31 PM                        The idea of adding some yellow LEDs is a good one as you described it Steve. In the residential lighting market in which I work, I have only played with the Cooper Lighting LED lamps so far. These do not have any kind of color shift compensation. Regarding pulse width modulation of LEDs, in a couple of our products, we have a series of indicator LEDs that need to be dimmed down pretty far for some situations. We use PWM for this process, but we are switching at about a 1kHz rate. It is really hard to see any kind of flickering or other artifacts that would be objectionable.  |  IP: Logged Jonathan Bodge Film Handler Posts: 83 From: East Dorset, VT Registered: Nov 2006 posted 08-03-2009 07:03 PM                     In video we use Kinoflo's which have an onboard dimmer or an outboard dimmer depending on model.  |  IP: Logged

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