Dimmer + LED lights question

[Mike Blakesley]

We have low voltage spotlights that shine across our screen in place of a stage curtain. They use the now-obsolete 4515 bulb. They are controlled by a Xetrol dimmer (1980 vintage).

A friend of mine showed me some LED lights that can be controlled via an app. Could I use these with our dimmer? Assuming the LED lights might not play nice with the standard fade-out and fade-in on a dimmer, is there a way to set the stage-lights dimmer channel to go "instant off" so as not to damage them, or is there some other solution I should consider?

[Frank Cox]

Why not do what I did with my auditorium lights. I don't know if my Kelmar dimmer would work with led lights or not so I avoided the issue and bought a couple of dozen incandescent floodlight bulbs that I know work with it. Since those lights burn out on such an infrequent basis I figure I'll be good for the next fifty years or so.

Buy a couple of cases of those bulbs you need, stick 'em in a closet, problem solved.

[Marcel Birgelen]

We have low voltage spotlights that shine across our screen in place of a stage curtain. They use the now-obsolete 4515 bulb. They are controlled by a Xetrol dimmer (1980 vintage).

A friend of mine showed me some LED lights that can be controlled via an app. Could I use these with our dimmer? Assuming the LED lights might not play nice with the standard fade-out and fade-in on a dimmer, is there a way to set the stage-lights dimmer channel to go "instant off" so as not to damage them, or is there some other solution I should consider?

Keep in mind that this home-domotics stuff with shiny apps is a hell to integrate into professional installations, also, you want something that "just works". Your current dimmer will not work with LED strips, those need a special dimmer. LEDs are semiconductors, they react completely differently towards modulated voltage than your average light bulb. LEDs are dimmed by flashing them on an ever decreasing duty cycle.

Availability of solutions is dependent on the region, I'm pretty sure someone on this forum can provide some options for dimmable LED strips that are available in your region. What automation are you currently using?

[Phil Ranucci]

Why not do what I did with my auditorium lights. I don't know if my Kelmar dimmer would work with led lights or not so I avoided the issue and bought a couple of dozen incandescent floodlight bulbs that I know work with it. Since those lights burn out on such an infrequent basis I figure I'll be good for the next fifty years or so.

Buy a couple of cases of those bulbs you need, stick 'em in a closet, problem solved.

I see you're in Canada. In California, incandescent floodlights are very hard to find.

[Frank Cox]

They're almost impossible to find in Canada now too, which is why I got my floodlights a couple of years ago and stashed 'em away.

I see that there are at least a few websites that still sell those 4515 bulbs that Mike needs (or so sez the mighty google), so he should probably jump on that right away before they do disappear altogether.

[Mark Gulbrandsen]

With something as old as a Xetrol you'll just have to get a few lamps and try them or perhaps ask Jason. Be sure to unscrew all incandescent lamps when testing LED. Kelmar's dimmer will work on quite a few different LED lamps. They also have a list of compatible amps that work with it. So if you don't get anywhere with the Xetrol, a Kelmar will work and directly replace your existing unit. You will also gain a mid light function with a Kelmar, and that will also work with your automation.

[Mike Blakesley]

You will also gain a mid light function with a Kelmar, and that will also work with your automation.

We have that mid-light function so maybe it is a Kelmar. I'm not in front of it right now to look. But I coulda sworn it was a Xetrol. It's tan and brown on the front, does that help?

What automation are you currently using?

I'll have to circle back on that question, I never even look at that panel since the projector/server pushes all the buttons automatically, so I haven't really seen it in about 13 years.

I see that there are at least a few websites that still sell those 4515 bulbs that Mike needs (or so sez the mighty google), so he should probably jump on that right away

I did that a few years ago...found a website that sold those bulbs. The boxes AND the bulbs both said 4515 on them and they looked great in operation but they would burn out after just a couple weeks. (They were some no-name brand I'd never heard of.) I'm in a bit of luck though -- I used a whole bunch of these light fixtures when I was a mobile DJ back in the '80s, so I robbed all the bulbs out of those units. So I do have a boxful of these "used" bulbs. I'm just looking to change things up a bit.

[Tony Bandiera Jr]

A few thoughts:

If you have reasonable access from the booth to the fixture locations (Attic, crawl, or spare conduit) it wouldn't be too difficult to use theatrical type (and many DJ types of) fixtures that use DMX control signals. That only requires a single "mic" cable (IIRC Belden 8451/9451 is suitable) to control ALL of them. You would then take those fixture's power off of the dimmer and send it through a simple light switch (or, if you power down nightly via a breaker, just bypass it at the dimmer.)

I agree that any fixture using an app/Bluetooth/wifi is asking for trouble in a commercial setting.

There are simple and inexpensive controllers available to operate them, and it is possible to use an Arduino or Raspberry Pi to talk directly from the server to DMX.

Advantages?

• Fixtures can now be upgraded to LED, no more relamping;
• Your power usage will drop;
• You can now choose colors and effects;
• Better control ability so you can do many cool effects, adding a wow factor.

There are many brands and styles of fixtures to choose from, from simple light bars all the way up to movable head fixtures (Be aware the movable heads are heavy, and expensive.) But a standard spot fixture weighs about the same (or often less) than the old style fixture.

Actually Mike, can you get a picture put up on here to show what you're using now?

Tan and brown on the dimmer sounds like an LP Associates dimmer, which was similar to the Kelmar IIRC.

[Stefan Scholz]

It is possible to use "dimmable" home style LED with classic theatre control dimming equipment. With the right type even with a great dimming curve, both ways.
It is very important, if phase cutting is use to have a basic, resistive load to ensure a minimum current flow. Which can be a resistor, or to make it simple, a tungsten light bulb of 25 or 40 watt.
The benefits are long life, around 1/10 th of the power consumption.
There are even ones, which change from whiter to more orange color when dimmed. I found those from Philips.
For the spotlights, some Toshiba brand ones worked out great.
The dimming in that case is indistinguishable from halogen light bulbs.
It's probably a little try and error with different types until the best match is found, but it is worth trying. Lesser efforts than a DMX/ KNX bus installation with new fixtures and additional wiring rquired.
The bus driven ones I used had a 256 step dimming (8bit), which produces obvious jumps in brightness at lower levels when dimmed, well suited for general lighting in lecture rooms,
but inappropriate in theatres.
Not to forget keeping your dimming equipment, the interfacing remains.
With nearly all my conversions, the trick used to be my mentioned resitive base load.

[John Eickhof]

actually, kelmar has a retrofit for older dimmers, it is an inductor or choke you wire in on the output of the dimmer, it basically smooths out the spikes and flashes that may occur with leds, they work fine i had installed dozens of them years ago when the push for non-incandescent lamps was started...

[Mike Blakesley]

Well my memory must be slipping, our dimmer IS a Kelmar. Actually I think we used to have a Xetrol dimmer, and it was replaced with this Kelmar, for reasons I definitely do not remember.

So here's a couple of pics of what we're doing now. (Ignore the Christmas lights at stage front, those are going away tomorrow.) There's nothing wrong with this setup, except it's hard to get the lights aimed exactly right and it'd be fun to be able to change the colors easily, those are really the only reasons I was even thinking about the LEDs. The bottom line is it might be easiest to just leave the status quo since I have a boxful of the 4515 lamps still.

I don't know why the auditorium picture is so low-rez, I took it with the same phonecam at the same time as the dimmer picture. But it gets the point across.


screen2.jpg
thumb_3327.jpg

[John Eickhof]

Mike, I would suggest you change over to led that is the standard kelmar dimmer, if it does cause erratic operation, let me know and i can get the led retrofit for you to install, the retrofit will work with conventional lamps also. Happy Holidays!

[Mark Gulbrandsen]

If you call Tom at Kelmar, he can supply you with a list of bulbs that will work with the unmodified dimmer. But I also reccomend you do what John reccomended. Then even lamps from Dollar General will work.

[Peter Foyster]

I am currently seeking quotes for various repairs to my outdoor cinema that was hit by a sudden storm in January, which has forced me to close until further notice.

Apart from the screen, which suffered extensive damage, I am required to have electrical repairs performed to current specs. This means the aerial wiring and lamps attached to trees will need to be upgraded.

The lamps are all halogen floods, most of which received a hit from flying debris so may no longer function. With the scarcity of halogen lights in Australia I may also need to look at replacing the current lamps with LED.

The dimmer I am using is a Dynalite DIMTEK 110 which works very well but I believe will not perform properly with LEDs.

Does anyone know of an Australian Distributor for the Kelmar dimmers or, alternatively, if a retrofit exists that would allow my old dimmer to function properly with LEDs.

Any suggestions as to any other suitable replacement for my Dynalite which is not too expensive and is available in Australia (or can be imported at reasonable cost), and can be controlled by the automation, would be greatly appreciated.

The dimmer was given to me a few years ago and is now obsolete, although I did see one advertised online recently for under A$200. Being an insurance claim, the cost is not a major issue however not an excuse for being unnecessarily reckless with my claim.

[Steve Guttag]

Just in case you all are unaware, Eprad has their own LED lamps and dimmer/dimmer adapter. They run on low-voltage DC but use conventional AC wiring and medium base fixtures. They have lamps in A19 and PAR38 style. If you have an Eprad dimmer, you change the power modules from incandescent to LED. If you have another brand of phase-cut dimmer, then you splice their adapter between the output of your dimmer and your existing wiring to the lamps. The adapter will translate your phase cut dimmer to their LED driver and it will drive their DC lamps. One just has to perform a calibration to set max/min. Then, your existing dimmer/wiring/control remain and the lamp hassle is done. Their lamps dim to zero and never flicker (they are running on DC, after all).

The problem I've found with using "dimmable" lamps is that you find a good make/model...it works...or works for a period of time and then they go spastic. Or, you think you are buying the same make/model on the next batch only to find that it is labeled the same but it is a different lamp that doesn't work like the other batch did. We've jumped in with both feet with the Eprad system...it just works. And, if you have one of the eCNA automations, you can set the lighting levels there down to 1% precision. Thus, once you decide what your light levels are for each portion of the show, replicating it on every screen is painless without having to use a volt meter or "eyeballing" it.