Modification of Smart Theatre Light Dimmer

[Marcel Birgelen]

You can only try. We went through two dozen LED bulbs until we found a type that would finally work with our specific dimmer. Since then, we are quite satisfied, the cost for buying them was very low, the saving is dramatic, and we did lose only one of 42 bulbs since 2016. Which means something by itself, because changing them is quite a bit of work.- Carsten

Since we're in the same European 220-240V boat, care to share make and model?

We're using a whole bunch of the "Philips Classic LEDspotMV D 5.5-50W 830 GU10". We like the color temperature and on-paper they're dimmable, but only because I've written the specific procedure in our PLC controlling them. On a classic dimmer, they do not behave anything close to incandescent lamps. Yes, our spots are all on GU10 fittings, but even if you're using different fittings, I'm still interested in the make/model.

[Carsten Kurz]

Would be useless. We use our traditional Rheostat Dimmers (variable voltage) - that's a freakshow for nearly all LED bulbs. We found out that some filament bulbs use a rather simple AC power supply circuit and a rather high internal voltage. As a matter of fact, they are marked 'non-dimmable' - because they do not work with triac-style dimmers. We found one that would work on variable AC voltage without flickering, and give us a nice, albeit slightly faster dimming curve. Means, they go down slightly faster, and come up quite a bit later (but still slow). But they do not flicker or jump. If I wouldn't know these were LEDs I would only notice by the missing red-shift during dimming.
There are some dimmable LED bulbs that will simulate the red-shift with dimming, but they have their own troubles, you simply don't get everything you want in one package. I guess our next solution will be some PWM dimmable solution, and DMX. Our interior is protected, so we need to find something that fits into our old fixtures (E27).

I think, if enough of these bulbs we now use have died (I do have some spares), we need to find a completely different solution. Because we need to stick with E27, I also evaluated the use of wireless control (Philips HUE). That system does support a large number of bulbs (we use 42 in our auditorium). However, even while these use PWM internally, they will not dim down to/up from zero.
There is a nice electronic dimmer from a german company 'Seebacher' that has two load circuits (both configurable independently), and allows to set your own dimming curve. https://www.seebacher.de/produkte/ko...ller%5D=Detail
It is targeted at Retrofit-LEDs and highly configurable (there's a windows software for it). 16Bit resolution, and a graphical U/I monitor for tweaking. Quite sophisticated.

That way, you could tame the unusual LED curve to your needs and even use two different types of bulbs (as far as cabling allows). That would have been our fall back solution if we hadn't found a suitable bulb for our dimmer. I think it costs around 400€.

- Carsten

[Steve Guttag]

As mentioned before, we're going towards a purpose-built solution by EPRAD. They've developed their own dimmer and lamps that use traditional medium base sockets and standard 120V wiring. It can be retrofitted to existing dimmers (take the chopper dimmer output and converts to their lamps) or used with a new install with their dimmer (or with other dimmers with the retrofit module). EPRAD LED Light Dimming System-sm.pdf

They dim to zero without issue. At the moment, they just have A19 and PAR38 style lamps.

I've found that it is just too unreliable to find suitable dimmable lamps that will still be suitable on the next batch...purpose built is the way to go, in my opinion and this is a cheaper solution than doing theatrical type DMX systems (another viable way).

[Carsten Kurz]

Yup. Even identical type numbers of brand manufacturers may contain different electronics. You would have to buy an insane amount of spares to be on the safe side. There is a company in germany offering 'free style' LED wall lights to cinemas. Basically, they sculpt any combination of materials, and then use powerful LED strips (white and/or RGB) in or behind the 'fixture'. These are then controlled with PWM/DMX modules (which have become dead-cheap nowadays). They are not even expensive compared to typical other offerings. INTEG also offers an LED Strip Dimmer module as an extension to their JNIOR.

- Carsten

[Marcel Birgelen]

Dedicated solutions for driving LEDs is certainly the future. The only problem I see though, is with distributing the power for those solutions, as 12V distribution is much less efficient than 230V or 110V. The only advantage is that with PWM modulation, the voltage is constant.

While it would make sense to centralize LED drivers in one or a select few locations, in order to facilitate access and efficiently deal with heat, the problem is, that long low-Voltage leads will also incur quite a loss. So, I'm not really certain what the best strategy is, to place those LED drivers. Centralized in one location or as close to the light source as possible? I guess it is highly dependent on the local situation what fits best.

[Gordon McLeod]

The real solution is to got to trailing edge switching for the dimmer output so instead of the triac turning on at a given point in the wave form a FET would turn off at a given point so the lamp driver gets its normal cycle start

[Steve Guttag]

Marcel, the Eprad system uses 36VDC and uses standard 120V wiring so typically 12awg wires between fixtures. With each lamp only at 6.9 - 12.6 watts, and a 320 watt capacity, you can get quite a few lamps on a load. Now it it would be wise not to wire them all daisy chained and think about the layout to minimize how many lamps are on one chain as well as how long the run is. Until I see something better, this is the direction we are going.

We recently did a theatre using Tivoli (I'm pretty sure they are Tivoli...we didn't supply them but they mount to the T-Bars of a drop ceiling) lamps and Kelmar 0-10V dimmers. Those worked well and dim to zero without fuss. Note, Kelmar does have an optional load disconnect so once you dim to zero, it will also disconnect power to loads. The Tivoli light bars have a nifty feature in that they have two circuits so you can have your cleaning lights on them as well (and they're bright and at a higher color temp than the house lights) and those are run independently of the dimmer. The only thing that I'm not a fan of are the appearance and the light shadows they cast.

[Harold Hallikainen]

Before starting at USL, I worked for Dove Systems designing light dimmers and controllers (DMX). We used phase control (triacs for low power SSRs for high power). These worked great with incandescents and poorly with LEDs. Sometimes the LED lamps could be made to work by adding a small "ghost load," a low power incandescent lamp. The triacs and SSRs had snubbers across them, so even if the lamp was supposed to be off, there was a small current through the snubber. This could charge the power supply in the LED or fluorescent lamp and make it flash. Lots of fun! We did make DMX to 0-10V decoders on an OEM basis for some LED and fluorescent lamp manufacturers. These included an SSR that removed power from the system when the DMX level got real low. Left there and went to USL in 2007, so haven't given light dimmers a lot of thought since then...

Harold

[Mark Gulbrandsen]

I've found that it is just too unreliable to find suitable dimmable lamps that will still be suitable on the next batch...purpose built is the way to go, in my opinion and this is a cheaper solution than doing theatrical type DMX systems (another viable way).

Completely agree on new equipment, but there are millions of installed dimmers in the world that are marginal or lamp fussy. I will add that it's not difficult to find lamps that work with existing dimmers if you contact the manufacturer, Almost all my installed base is Kelmar with a few Strong dimmers here and there. BY the time I retired about half my customers were running Cree LED lamps.

[Steve Guttag]

We talk to Tom all of the time...he'll tell you there is no list of safe lamps...lamps that work fine now likely will not the next time you buy. The EPRAD dimming system is offering their output module to work with other dimmers. Just insert it between your existing dimmer and their lamps (so move the load wires to the Eprad module and connect your dimmer's load terminals to the input of the module and replace all of your lamps...done.

I believe the external load module also works with 0-10 dimmers (separate input, naturally). They really have tried to make this as compatible with as many existing systems. Heck one may have a particular reason for preferring a particular dimmer brand due to how it works with their lighting strategy/control system so you could do a new system with someone else's dimmer (e.g. Kelmar) and put the Eprad module on its output and new lamps...whatever works with your company's preference.

[Carsten Kurz]

Centralized in one location or as close to the light source as possible?

As these DMX-LED supplies are typically small, I guess the best approach is to source them from the pre-existing 110/230V light supply lines, and install them locally. You need to add the DMX wiring, but that is usually not such a big problem. You may disconnect the high voltage where the DMX dimmer goes, and use the remaining cable run towards the fixture with 24V.
At least stripes can be bought in both 12V and 24V versions, so, install some local dimmers, plus 24V, that should solve the issue.

That EPRAD system sounds interesting. A very pragmatic approach. The cost for these bulbs are probably comparably high, but driven that way, they should last longer.

- Carsten

[Steve Guttag]

They aren't outrageously priced. Sure, they are much more than conventional LED lamps but they are less than DMX or other lamps that have the "smarts" in the lamp/fixture itself. And, they't don't need additional control wires...just the same traditional wiring for incandescents.

[Mark Gulbrandsen]

We talk to Tom all of the time...he'll tell you there is no list of safe lamps...

I did for years too, and considering I only sold his dimmers he obliged me about three yeas ago and told me the list of a half dozen over the phone that would work, and that they had tested at the Factory. Cree wwas at the top of his list and I always stuck with them. hey were also developing the load box but had not released it yet.