Help needed with LED House light dimming.

We are equiping a new theatre at our school in Nairobi Kenya.
I am trying to get my head around using LED lamps for the house lights but need them to smoothly dim from 100% to 0%. (As the old tungsten ones did) We have DMX lighting control board coupled to demux and onto to a traditional dimmer pack. I have experimented with 'dimmable' 230v lamps, but they either flicker or go out at about 20%. We have a limited budget (of course!!). Any help would be much appreciated.
 
I relocated this thread to the Lighting Forum so it is posted in the proper place.

Smooth dimming is a difficult thing to get with budget LED's. We might be able to help you better if we had more information about your situation. What size area you are trying to light, from what distance, how many fixtures you are looking for, what your wiring infastructure is at these locations, what your budget is.

~Dave
 
Dear Dave,
That was quick - thank you for the re-location of the thread - I'm new to these things!!
The theatre is about 400 seat and we have got to the stage in construction where we are about to install the suspended ceiling under the roof. The celing will house the house lights. I will attach a plan view of the theatre. In our existing thetre (at another school) this house light function is acheived by 70 No 60 watt incandescent lamps inset in the ceiling. (4.2 KW). I suppose I am trying to duplicate the function which in fact works very well with LED.
In terms of wireing infrastructure provision has been left to wire from lamps to the 'Dimmer room' where the DMX signals will end up. The lighting board itself is the main seating area. All the wiring will be done by ourselves. The house lights will be part of the stage lighting set up. Budget for this house light part of lighting set up difficult to say but would like to keep it to say $1500 on top of the equipment we already have.
Terry
 

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I just laid out house lighting for a 400 seat hs auditorium - about 30 units - I'm using a Gotham Incito with a 5000 lumen engine and the DMX drivers - which I know from experience will dim smoothly. There around $600-700 each, and at 72 watts, two constant circuits. I don't believe you will approach the same level of control with mains dimming LEDs. You can only make the budget case for these if you also account for less pipe and wire, no dimmers, no need for a dimmer room, lower initial HVAC costs, etc. There are mains dimming products but none that work as well and none that cost less in new construction. They might in retrofit. I don't know if your $1500 is per house light, for all of them, just the control, or what. It sounds like it could be too late to do this sensibly.
 
With mains dimming, your last 5 to 10% is a lost cause, unless you still retain a few incandescent lamps on a separate dimmer. That way you can dim out the LEDs, and then make the final dim on the incandescent lamps.
DMX driven house fixtures will give you a very good dim down to about 1%, but the cost is much higher.
 
With mains dimming, your last 5 to 10% is a lost cause, unless you still retain a few incandescent lamps on a separate dimmer. That way you can dim out the LEDs, and then make the final dim on the incandescent lamps.
DMX driven house fixtures will give you a very good dim down to about 1%, but the cost is much higher.
With all due respect, I disagree that the total project cost of LED is "much" higher. Fewer circuits, less wire, no dimmers, less cooling load - near a wash in new construction with how the price of LED has continued to drop.
 
I recently had a demo of the R-LED retrofit unit. http://rledlighting.com/ It's not a lamp but screws into a socket for most of it's power and physical connection.

It has the best low end performance I've ever seen in a retrofit. There is a significant delay when lowering the light level. The unit glowed for up to 5 seconds after a snap off, I believe due to the large power supply unit that makes the dimming so smooth. So it's far from perfect, especially as the costs are in line with the whole fixtures of similar brightness. It is unique in the market, as far as I know.
 
With all due respect, I disagree that the total project cost of LED is "much" higher. Fewer circuits, less wire, no dimmers, less cooling load - near a wash in new construction with how the price of LED has continued to drop.
Bill, a good quality mains dimmed LED lamp, such as the TCP, is under $20. I don't know of any DMX controlled LED that is even close to that low in price.
 
Bill, a good quality mains dimmed LED lamp, such as the TCP, is under $20. I don't know of any DMX controlled LED that is even close to that low in price.

That's a lamp - and not a very powerful one. This is new build - so they have to buy fixtures, wiring, dimmers, hvac, a room to house dimmers, labor, etc. I don't think comparing lamps that top out at 1200 lumens to a complete fixture that can get up to 8000+ lumens (the one I am using is 3500 and around $500) makes sense. Plus, the dimming performance is noticeably different. All this an not to mention emergency transfer.
I recently had a demo of the R-LED retrofit unit. http://rledlighting.com/ It's not a lamp but screws into a socket for most of it's power and physical connection.

It has the best low end performance I've ever seen in a retrofit. There is a significant delay when lowering the light level. The unit glowed for up to 5 seconds after a snap off, I believe due to the large power supply unit that makes the dimming so smooth. So it's far from perfect, especially as the costs are in line with the whole fixtures of similar brightness. It is unique in the market, as far as I know.


It is good but does snap on a little - not sure if a profile and pre-warming will charge the cap or not. But this makes no sense for new install to me.
 
It is good but does snap on a little - not sure if a profile and pre-warming will charge the cap or not. But this makes no sense for new install to me.

Best Available and Good Enough are rarely the same. I'm sure you know the feeling :wall:

My understanding is that they have significant equipment installed. More details on what can be changed without major cost would help.
 
Thank you all for your comments and help - Clearly this is not as simple as I had hoped! Further information: There is no equipment or wiring actually installed. However over the years with our older theatre we have accumulated a lot of traditionl equipment - DMX Desk (Zero 88), De-Mux units and mains dimmers.) . These will form the basis of the stage lighting with traditional tungsten Stage lights (of which we have many). However I was hoping to at least get the house lights up to date with LED lamps and integrate them with the system. I bought a few cheap 'dimmable' LED mains lamps to test and have experienced the the symptoms expressed above. The 'budget' I quoted was just for the LED lamps/drivers? themselves. All the wiring and instalation costs would be in addition. I suppose I want good enough (if possible with the constraints) best available is clearly not within our means. Sorry for appearing so thick!!! Old dog new tricks syndrome!!
 
And remember that as always when dealing with international installations, the products available to the US market are not necessarily available or suitable for the overseas market.
We're talking 230V for a start here remember...

I doubt emergency transfer is a code requirement in Kenya...
 
Chris 15, you are of course right. Very limited availability of hardware here. We normally source such items from UK where voltage is similar and we are able to import.
I am not sure what emergency transfer - if our mains fails a stanby generator takes over the whole site in about 14 seconds. Some emergency lighting is pwoered by batteries during the 14 seconds.
 
Ultimately I don't think you will find using retro fit LED lamps in fixtures designed for incandescent in a new installation will be very satisfactory based on your comments.

As far as a specific design recommendation it's hard without knowing more about height, existing work vompleted, existing gear, and relative costs of labor and materials.
 
Sadly, I think I am going to have to abandon the idea of dimmable LED production house lights. Considering the cost and the equipment on hand, easier to use traditional incandescent lamps (Cheap, Cheerful and they work).
However for everyday lighting where dimming is not necessary (and used far more often than production lighting) I may install non dimmable mains LEDs, again quiite inexpensive.
Thank you all for you help.
 
Keep in mind most experts expect mains dimming lamps to get a lot better in the next few years. My best guess is 2-5 years, though I can't claim any special knowledge. You may have an opportunity to recircuit the house lights and free up dimmers for other uses.
 
Keep in mind most experts expect mains dimming lamps to get a lot better in the next few years. My best guess is 2-5 years, though I can't claim any special knowledge. You may have an opportunity to recircuit the house lights and free up dimmers for other uses.

Thank you RickR for those encouraging thoughts. We'll bear it in mind while installing the cabling.
 
This seems a good place for me to confirm a feeling I have on this topic:

The dimming quality of mains-dimmed LED houselights depends as much on the dimmers as on the lamps, does it not?
 
This seems a good place for me to confirm a feeling I have on this topic:

The dimming quality of mains-dimmed LED houselights depends as much on the dimmers as on the lamps, does it not?
Yes, in a way.
What it really depends on is the design of the dimmer firing circuit and how zero-voltage cross is detected. Almost all dimmer designs depend on a series load to supply current to fire the device (SSR). In the process, voltage is leaked forward. This is why an unloaded dimmer may meter at full or partial line voltage even if the dimmer is set to zero. So, depending on the design of a dimmer, the results for a given LED lamp may vary greatly depending on the brand and age of the dimmer. Age becomes a factor not due to any degradation of equipment but more because very new equipment has been designed in the age of LEDs, whereas older dimmers never expected or anticipated this type of unique load.
The other factor is that there is actually a logic circuit in dimmable LED lamps. For example, the Cree actually tries to read the edge of the sawtooth to determine what brightness it should be at. In order for this circuit to work it has to have some power and that is why there is a dead zone at the bottom of the curve on mains dimmed LEDs.

So yes, both the dimmer and the lamp have to be able to play nice with each other. Either can cause problems.
 
Yes, that's about what I meant: newer dimmer packs -- <2 years, probably -- have a higher chance of dimming LED lamps more smoothly, and to deeper levels, regardless of the lamp, though smarter lamps will help a lot as well.

Dumber dimmers will probably hurt you much worse than dumber lamps, I should think.

I'm waiting for someone to put wireless DMX right inside a PAR36 LED.
 

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