my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Dimming Tivoli lights (Page 1)

This topic comprises 2 pages: 1  2

Author Topic: Dimming Tivoli lights Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 08-20-2007 12:04 PM                       QUESTION: What's the commonly-accepted method of dimming Tivoli lights? I received a call from a location where the transformers in 2 auditoriums burned up within a couple days of the other. The electrician replaced them only to have them go out again in a day. I suggested it was something shorted in the floor, the electrician thinks it's the dimmer. Now he says he's replaced all the lights in one auditorium and it's still overheating. I had him feed it directly (with the dimmer not even in the circuit) and it's still heating (although, since the xnsfmr may have already been damaged I can't be sure the lights are pulling it down at this point). I figured it would be a good idea to find out how they should be hooked up, so I'm thinking right. Right now, it sounds like the dimmer is in the secondary of the Tivoli xnsfmr (but if so, even if the dimmer was shorted it wouldn't take out the transformer - the lights just wouldn't dim). FWIW, the new transformers are exact replacements. The dimmer is an older Lehigh unit with Triacs. Everything has been working fine for years until now.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 08-20-2007 02:31 PM                     Tim, What are 'Tivoli lights'?  |  IP: Logged Jeremy Weigel Phenomenal Film Handler Posts: 1062 From: Edmond, OK, USA Registered: Mar 2007 posted 08-20-2007 02:58 PM                     Hey Stephen, Tivoli makes track(aisle) lighting for auditoriums along with other special use application. http://www.tivolilighting.com/  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 08-20-2007 03:12 PM                     The electrician needs to measure the current to determine if it is within limits for the circuit. He should have a clip on ammeter in his toobox. FWIW, are all the lights lit? If not, maybe one or more is shorted. For all you know someone may have plugged a socket with a chewing gum wrapper.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 08-20-2007 06:10 PM                       Rick, that's what I was thinking. Especially since both auditoriums went out at essentially the same time. But he says they laid down all new lights. I asked the electrician how much current it was drawing and all he would say is it's overheating the transformer. I never got a straight answer to that question. But at least I got him to disconnect it from the dimmer and it gave the same symptom, so he can't blame me, the "camera" guy (unless that transformer had already shorted from before, that is). So, where should the dimmer in this circuit be?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-20-2007 06:42 PM                     Tim, I'm assumming that you are using a buck boost transformer to power these. Tivoli can supply the correct type of dimmer to use on the primary of a buck boost if you need. If you use the wrong type of dimmer... soimething like a standard wall dimmer you will probably cause the Buck Boost transformer to explode. In the past I used a 3 amp or larger variac to keep the circuit as "quiet" as possible. Dimmers are inherently noisy beasts. Mark  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-20-2007 06:53 PM                     A transformer per se should not be bothered by the chopped wave form of a dimmer but some dimmers may be bothered by the inductive load and requireing a change to the snubbing resistor/cap part of the optocoupled output to the triac or SCR Often I find that the transformer is too small for the load and the electrician need to remember that the load must be no more than 80%of the VA rating of the transformer.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 08-23-2007 04:48 PM                       Thanks, Gordon. I thought it was that way (the dimmer cares but not the transformer). Also, the dimmer should be feeding the primary of the Tivoli transformer, right? The electrician says it's in series with the two secondarys right now (if I understood him correctly), at the point that would normally be shorted to get 24 volts on the output. Mark, it is a Lehigh dimmer, with triacs.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-23-2007 07:38 PM                     The dimmer should be connected to the primary of the transformer and the secondary be tapped according to the need voltage  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-23-2007 08:56 PM                     quote: Tim Reed Mark, it is a Lehigh dimmer, with triacs. LeHigh made a dimmer module specifically for dimming Buck Boost trannys. So if this is that module you should be ok. I would follow Rick's suggestions here... should lead you to the trouble. All it takes is a gooey coke spill at a splice in the lights to kill em.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-25-2007 08:16 AM                     Leigh dimmers use a pulse transformer drive for the triac so they would probably require an external snubber to make the triac fire properly  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-25-2007 10:36 AM                     I can't remember how they did it exactly but the Buck Boost dimmer module didn't resemble the standard dimmer module in the least. Mark  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 08-25-2007 01:30 PM                     Shouldn't there be a fuse or breaker wired in series with the transformer secondary if this kind of failure is common? --jhawk  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-25-2007 11:27 PM                     A buck-boost doesn't have a secondary...it is merely an autoformer that typically comes in 24 or 36V of buck or boost.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 08-26-2007 02:25 AM                     Picky picky...and not the point. A buck/boost transformer is actually an insulating transformer, it is just normally wired as an autotransformer, but it doesn't have to be; it's got separate H1-H4 taps and X1-X4 taps, you just generally interconnect them. That said, I can't quite tell from the thread if we're discussing buck/boosts or some other arrangement, and I suppose it doesn't really matter if you fuse the primary or the secondary...the point is, shouldn't it be fused so you don't blow your transformer when something goes wonky with the load? --jhawk  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 2 pages: 1  2

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.