This is topic MDI Masking-Curtain Control in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Ned Fairbairn (Member # 759) on 03-22-2001, 09:15 PM:
This is from the Projectionist at the Famous/Fabulous Grauman's Egyptian Theatre in Hollywood CA. Our MDI Masking System tends to lose pre-set conditions, especially maximum opening and closing.Comments/advice appreciated
Posted by Gordon McLeod (Member # 33) on 03-22-2001, 09:31 PM:
The unit should not be powered down or needs a spike suppressor on it
We have some up here that do it all the time and others that don't
Posted by John Pytlak (Member # 331) on 03-22-2001, 09:36 PM:
Ned: Welcome to Film-Tech. Hope you continue to participate in the discussions. Are you the fellow who gave me the tour of the Chinese booth during the 70mm run of "Titanic" in January 1998? If so, the experience was memorable:
http://www.kodak.com/US/en/motion/newsletters/reel/december98/pppp.shtml Hope the construction of the Hollywood & Highland Kodak Theatre for the Motion Picture Academy isn't shaking the ground next to the Chinese too much. 
http://www.kodak.com/US/images/en/motion/news/complex.jpg
http://www.kodak.com/country/US/en/motion/news/kodakTheatre.shtml
------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
Posted by John Walsh (Member # 168) on 03-22-2001, 11:16 PM:
I'm not familiar with that particular control system, but we had to add a uninterruptible power supply to several electronic masking systems. We suspect it keeps voltage spikes from disrupting the microprocessor in there.In one place, the electronic masking system had no battery-backup to remember settings. What a poor design! Anyway, a UPS helps out with that, also.
Posted by Martin Tremblay (Member # 817) on 04-09-2001, 08:07 AM:
Hi,I am working for MDI and I will try to help you with your motor.
1- It would be interesting maybe for you to call MDI when you have a problem with a motor. (450)755-3795 ask for me.
2- When you say your motor loses its positions, what exactly happens?
3- Is there any remote plugged to your motor?
Normally we do not encounter such problems but it is always possible that your motor may be defective or that the power is not so clean so be sure to have a clean AC.
Remember that the MDI motors use a non volatile memory so even with no power it would take about 40 years for the memory to fail.
Posted by Gordon McLeod (Member # 33) on 04-09-2001, 08:10 PM:
Funny there are several units in theatre we service that we had to put in a UPS to keep them from loosing there settings. Even if it is dirty AC that was causing the problem (which I doubt sice they only had a problem on powerup) A motor device should not be installed in a theatre enviroment that is that sensitive
Posted by Martin Tremblay (Member # 817) on 04-10-2001, 08:26 AM:
Mr McLeod,MDI uses in its drives the Microchip memory IC #24C01 wich is guaranteed br Microchip to hold its data for over 40 years.(Non volatile memory databook 1995 page 3-105).
You can encounter some problems if your AC is bad; I have seen some theaters that returned me several units have 120 Vac on the motor at rest but as soon as it was activated the AC fell to 70V.(Saw that only when I had to go there).
You may loose your settings, if the motor is activated while there is a drop or a significant amount of noise in your AC; only then you may lose your settings.
I will add, we are working on our motors to have a detection of lower AC, a checksum on the positions, a self check on power loss so the motor will resume to the position it had been asked to go and EMI filtering (optionnal). All that in our new series of masking motors that will be out soon.
We have several thousand units all over the world that are working fine; yes there are some improvements to be done but we're on it!
Posted by System Notices (Member # 2357) on 05-13-2016, 01:33 PM:
It has been 5512 days since the last post.
Posted by Leo Enticknap (Member # 534) on 05-13-2016, 01:33 PM:
Just over fifteen years and a complete new software system for the AMX touch panel system that drives it later, I'm still having the same issue with this masking system at the Egyptian. The presets still wander, and #7 on the bottom doesn't work at all (it just goes to the extreme end if you call it, even after saving a position).
I think Mr. Tremblay could be onto something with the a/c. When the air handling unit kicks in, the worklights in the booth do dim momentarily. Presumably the motor start capacitors are sucking enough power to knock down the voltage somewhat, and if the masking control boards are that sensitive to a drop in line voltage, this could be behind it.
The positions wander enough such that for the more commonly used presets (1.37, 1.78, 1.85 and 'scope are the ones we use very frequently), I have to re-do them roughly every month. For the lesser used ones (e.g. Movietone, 1.66 and 70mm 2.20), it's before every show.
Posted by Carsten Kurz (Member # 5396) on 05-13-2016, 08:28 PM:
When was your last contact with MDI about this?
- Carsten
Posted by Leo Enticknap (Member # 534) on 05-13-2016, 08:57 PM:
Long before my time.
Posted by Carsten Kurz (Member # 5396) on 05-14-2016, 08:23 AM:
I guess it would be advisable to contact them with serial number/manufacturing date, etc. and ask them wether they have a solution.
I can only assume they use some sort of non-absolute position encoder. Knowledge may help to uderstand what happens, but doesn't necessarily mean a solution. But I guess there have been other MDI clients who had been more persistent in getting this issue solved.
- Carsten
Posted by Mark Gulbrandsen (Member # 72) on 05-14-2016, 11:28 AM:
Try placing it on a UPS and see if it holds the settings. The UPS will also correct for any power fluctuations. If it does hold them then the MDI unit has a crappy regulated power supply running it.
Mark
Posted by Leo Enticknap (Member # 534) on 05-17-2016, 12:11 AM:
There are three systems in total (one for the sides, one for the top and one for the bottom), and so we'd need three UPS boxes. Added to the mix is the possibility of a very major refurb project soon that might involve that system being replaced, so I'm reluctant to do that if it ends up happening. But if it doesn't, I'll try the UPS route.
The contractor who rewrote our AMX software just over a year ago told me that preset positions wandering is an occupational hazard with these masking systems, and that there's not much that you can do about it apart from reprogramming them regularly, which we do.
Posted by Martin McCaffery (Member # 37) on 05-19-2016, 10:59 AM:
Having what may be a similar problem. One of our MIDI motors stopped remembering the presets. Worked fine for and then stopped. We were still able to set the masking using the manual buttons.
Contacted Strong and they had us send in the motor controller. I've now been informed that the problem is probably the encoder in the motor and the only cure is to replace the motor (about $800). Motor is only 2-3 years old. Not happy.
They did suggest swapping motor controllers just to be sure the problem persists, but the building is being rewired right now, so not electricity when the workmen aren't here.
They did say 98% of the time it is the motor controller, if that makes you feel better.
Posted by Steve Guttag (Member # 268) on 05-20-2016, 07:10 AM:
I've dealt with numerous MDI masking systems and it is NOT unusual for their controller to get "stupid" or develop quirks...like can only move for a few seconds then try again and it moves some more for a few seconds. As for repeatability...some of that is your masking system design. Pulleys and the cord can shift/develop slack. Any slack in the system will alter its repeatability. Using drum instead of sprocket drive will also affect it...with sprocket drive it will move the system the same amount (no slippage with sprockets) though the cord and pulley system can stretch/slack.
Another big flaw in the MDI system is that they don't guide the chain/cord onto the sprocket/drum. They should have a set of tensioned idlers trying to keep the slack out of the system as well as guide the chain/cord onto the sprocket/drum (like ADC does).
Now, what I like about MDI is that you can set the speed at which it can move the system as well as it ramps up/down. ADC tends to be on or off. MDI's 4-wire preset system is less cumbersome than ADC's 1-wire per stop in their logistop system (though they may have improved that).