Film-Tech Forum ARCHIVE: Dimmer Help

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Posted by Michael Voiland (Member # 5386) on 11-22-2009, 04:18 AM:

One of our theaters has a kelmar universal dimmer.
http://www.kelmarsystems.com/LightControl/LightConCat/lightconcat05.html

The problem is the automation system is older and only has a pulse that comes out of it when the lights cue goes by.
The way the thing works or used to work is a currently sensing relay would detect current and based on where the relay was set would either pulse lights up or down when the pulse came from the automation system.
This system works very very very badly and seams to always fail the current difference between high and low is just not enough in this one theater and adjusting the lighting loads is not an option. Does anyone have any good ideas on how to make this work so that it can trigger up and down or detect whether the lights are up or down and then trigger the opposite.

Posted by Demetris Thoupis (Member # 833) on 11-22-2009, 06:01 AM:

What kind of projectors do you have and what automation do you have? Is your dimmer configured simply for HIGH when film ends and low when film starts? when do you wish your lights to be at which levels? Do you have a cue detection for dowser open or close? if you do you could simply parallel the connection for when dowser open cue to pass to trigger the low level and when the light cue passes to trigger the high level.
Demetris

Posted by Kenneth Wuepper (Member # 1174) on 11-22-2009, 06:15 AM:

Michael,

The relay contacts you describe are used to "steer" the pulse from the automation to either the up or down terminal of your dimmer.

Since you say that it is this one theater that has the problem, are there others that do operate properly?

Have you determined that the relay operates for both bright and dim conditions? If the armature moves but the contacts are dirty the system will fail. If the armature stays in the energized position, the relay is at fault.

Can you determine the type of relay and manufacturer's model number? (AC 110 Volt P&B ####)

Although you say that this is a "current sensing relay", how is the coil connected to the dimming system? I might guess that it is connected across the dimmer's output terminals for the lights in the theater.

I would also guess that the relay should operate when the lights are ALMOST fully bright and then drop out when they reach a LOWER level of brightness. If your relay is simply an AC coil device, connected across the output of the dimmer, the drop out voltage across the load is too high for the relay to open. If that is the case, the spring tension of the relay armature could be increased and that would make the relay less sensitive and cause it to open sooner. Over doing this however can cause it not to close when the lights are fully bright.

I hope this is of some help.

KEN

Posted by Brad Miller (Member # 2) on 11-22-2009, 12:23 PM:

I think everyone is misunderstanding what Michael needs.

Michael, on the front of that dimmer are two knobs. Turn the top one fully clockwise (about 5:00) and the bottom one fully counter-clockwise (about 7:00). Now press the buttons (one at a time, then give it several seconds to do the job) on the front of the dimmer for up and down. Does that now give you the difference in light level you wanted...or perhaps too much difference?

Posted by Michael Voiland (Member # 5386) on 11-22-2009, 01:40 PM:

Ok. The automation has been bipased partially. I believe in an emg the lights will go up. The cue readers are the inboard / outboard foil readers. The outboard cue is our end show cue. The inboard cue is our lights pulse cue.

The problem is that we cannot adjust the lights as they are set to how the owner likes them so adjusting them is moot.
The current sensing relay is actually a current sensing device that does a comparison of current though the sensing coil and a set pot. Then steers the pulse to up or down.

The problem is that it is very unreliable. I have been toying with the idea of using 2 transistors tied to the leds on buttons to take care of the steering of the pulse but have not gotten that far. We have houses set like this and they all drift over time.

The theater I work at has 3 types of automation systems so these 3 were changed slightly so that they would function like the other 4 when they added onto the building.

We leave lights up for trailers, then lights go down at the start of the movie and come back up at the end right when the credits say "directed by"

Posted by Gordon McLeod (Member # 33) on 11-22-2009, 02:19 PM:

It would be helpfull to know what automation is involved

Posted by Michael Voiland (Member # 5386) on 11-23-2009, 01:29 AM:

The automation is a xetron maxi 11 i think. But it doesn't matter because the automation is not interfaced with the lights just the cue reader output on the inboard side.

Posted by Gordon McLeod (Member # 33) on 11-24-2009, 10:07 AM:

a simple fix is use the light cue sensor only to bring the light up on a foil
to bring the lights down wire a second relay in parralel with the changeover open one to pulse them down when the dowser opens