Film-Tech Forum ARCHIVE: interlock

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Posted by Mike Fitzgerald (Member # 1304) on 01-11-2003, 09:11 PM:

We are looking for a way to interlock 2 ch-10 consoles with century projectors. My question is will the following work. To simplify, if I use a loop accumulatir between the 2 for control purposes. Then I wire a 2 pole double throw switch to each console for starting the machines. I use the extra outboard automation to trigger the automation to light the lamp and open the dowser. Any thoughts on this other than don't do it or buy a expensive automation.
Thanks

Posted by Jon Bartow (Member # 241) on 01-11-2003, 10:26 PM:

We need more info. What automation system do you have? Many of them have the ability to interlock built-in. And many of those that do not, can be re-wired so that they can.
I assume you are referring to Christie CH-10 lamphouses? Do they have an automation installed in them such as a Kelmar AM-x ?
Jonathan

Posted by Mark Gulbrandsen (Member # 72) on 01-11-2003, 11:30 PM:

Mike,
You don't even need automation to interlock. The main thing is that both machines run at the same speed very closley, or exact speed is even better. To run sync you do need a loop accumulator, a big one is preferable if you don't have exact speed sync motors. Yes, thread the film through both machines using extra guidance hardware between both machines at least every 6 feet or so, and when threading bring the accumulator to its half way point. Feed from one sides platter, and take up on the other sides. Start both machines together and keep an eye on the accumulator as if you do not have sync motors it will slowly creep one way or the other. If you are brave you can slow one projector down by holding a thick towel against the flywheel. I have a number of customers that run this way and they only have to make this speed adjustment two or three times doring a 2 hour film. If ya have simple automation wire a dpst relay across both start buttons, or start terminals if there are any. A momentary push button to activate the relay will start both together. Needless to say, if you are without any failsafe, don't leave the booth during the show!
Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 01-12-2003, 12:26 AM:

Best to use sync motor and then a small acumuilator will work. Alpt of century's used the polyV belts and they slip and speed fluctuations can be a problem

Posted by Brad Miller (Member # 2) on 01-12-2003, 12:54 AM:

What is the layout of your booth? Are the projectors side by side, around a corner, or back to back? You may have other easier options here, but this matters.

Posted by Mark Gulbrandsen (Member # 72) on 01-12-2003, 10:13 AM:

Gord, I have one customer in Wyoming that runs interlock with his Poly V Centurys and there is no problem. I do agree that sync motors are the best route, however running a Century with a sync motor occasionally brings in another whole set of problems too......some Centurys just don't like sync motors on them and they will eat up gears occasionally.
Mark @ CLACO

Posted by Ken McFall (Member # 845) on 01-12-2003, 12:48 PM:

If you use sync motors with an inverter they won't cause any problems for any projector. The slow start and slow down will extend their life if anything...

For interlocking without automation inverters are the easiest way to go as you are only switching the low voltage control line and no current to speak of. The wiring is also very simple as you are only switching a pair of normally open contacts.

Posted by Jack Ondracek (Member # 1466) on 01-12-2003, 02:37 PM:

quote:
...from Ken McFall:
If you use sync motors with an inverter they won't cause any problems for any projector. The slow start and slow down...

...For interlocking without automation inverters are the easiest way to go

I see this mention of inverters occasionally. What are they used for in a theatre context?

Posted by Richard Fowler (Member # 893) on 01-12-2003, 03:21 PM:

Invertors are variable frequency controllers in which you can ramp up or down the speed of the motor. Kinoton projectors and other European make use of this technic. On our recent rebuilt Century projector projects we have used invertor motors and controllers to give a three to four second ramp up which really prolongs the gear train. We have also use these controllers to alter masking motor speeds on a four motor system for a special venue screen system.

Posted by Ken McFall (Member # 845) on 01-12-2003, 03:50 PM:

As Richard says they are for controlling the speed of sync motors. They allow much simpler install as they run off single phase and have a very simple controll interface. You can set up the inverter to give any frame rate you require and depending on the model these can be selected by rotary switch... ie 16, 20 24 25 fps.

They really do make a big difference to the stress on start up and run down of heavy gear trains and prolong their life considerably as the run up speed is set for whatever you require and is very smooth. It's normally set for about four second run up and maybe two run down.

In an interlock setup they are very easy to use and in my experience they are very very relaible. I've used them on a Vic 8 and FP20 setup with no problems at all.

When you take into account the cost of a conventional control setup , relays resitors timers etc etc the cost of an inverter is still quite attractive given the simplicity of the wiring required and the lack of three phase supply.

I wouldn't even consider doing another interlock setup unless it used inverters!

Hope this is of interest.

Regards Ken.

Posted by Mark Gulbrandsen (Member # 72) on 01-12-2003, 03:57 PM:

I've also used those motors but they are VERY expensive to buy. Many theatres cannot afford that sort of expense but still need to be able to interlock.
Mark

Posted by Ken McFall (Member # 845) on 01-12-2003, 04:13 PM:

From what I'm aware of, the motors are the same so expense is not an issue, we're not talking os selsyn motors. If you are already using sync motors then there will be an inverter that will match. After that the install in quite simple.

Connect the motor to the inverter.
Connect single phase supply.
Connect whatever control options you require, via any alarm switching you may already have.

Normally it's a simple normally open contact (relay or switch) and any additional switching to select different frames per second.

Richard is the guy who knows the systems you have over there.... I'm sure he's happy to help.

Posted by Ken McFall (Member # 845) on 01-12-2003, 04:20 PM:

I should add that you can use inverters on any three phase motor to give controlled start up and run down. All of the other advantages that have been mentioned still apply.

I have one Vic 8 that is running on an inverter that is a normal three phase motor. The other three Vic 8's are used for interlocking so have sync motors. They all have beautifully smooth starts and stops.

Inverters have lots of other features built in... overload protection, variable torqe settings, variable speed whilst running etc etc. On a rebuild the difference in cost is not that much and is well worth consideration.

Posted by Gordon McLeod (Member # 33) on 01-12-2003, 06:51 PM:

Inverters are geting a bit common up here as a single phase input can drive a 3phase moter.

Posted by Richard Fowler (Member # 893) on 01-12-2003, 07:06 PM:

Cinemeccanica likes to use the Gazzavi slow start controller which gives a "pop" up to speed on their newer projectors. This is not an invertor and unfortunately costs as much with less features. I have a tech friend who works for a European group who normally retires these when they fail with invertor motor controllers. Invertor drives put stress on the windings due to the high HZ the motor is receiving from the controller so it must be a judgement call if the existing motor can handle or should be swapped out.....but the advantages are worth the extra cost if required.

Posted by Darren Briggs (Member # 1071) on 01-13-2003, 02:19 PM:

Yo can get a good inverter for about £150, which is a .75kw model for any large mech, i.e. Vic 8.
No hassle's of start caps etc.
I agree with Ken, they will save alot of stress on the Proj Mech, on the film you are showing and the platter as it doesnt need to suddenly go to full speed feed/take-up. Everythingis alot happyier.

Darren