Controlling a Motorized Projection Screen

[Nelson]

Okay, so I have a motorized projection screen installed in our auditorium controlled by a rocker switch backstage. I would like to be able to control it from the booth, or ideally, be able to control the screen from either the booth or backstage. What is the best way to do this?

Initially, I was going to hire an electrician to move the existing switch to the control room. This may still be the best way, but I want to explore all of my options.

What about some kind of low voltage control? I thought about some kind of DMX-controlled relay so I could operate the screen from the light console, but others have mentioned that its never a good idea to control any kind of automation from the console. We currently don't have any kind of automation system. Thoughts?

 

[derekleffew]

The existing backstage control, is it really a rocker switch or a two position momentary switch? If you release while the screen is in motion, does the screen stop? How difficult would it be to run three wires from the existing control to the booth? Any licensed electrician should be able to provide you with control from either location with the addition of a couple of relay s. The hardest part is going to be the wire path, which probably needs to be in conduit.

 

[Les]

You might check in to installing an IR sensor in addition to the switch back stage. I believe these are available through DaLite.

 

[Nelson]

The switch is exactly like the one on the right in Derek's post. The wire path to the control room would be difficult and lengthy, but not impossible. However, we seem to have Cat 6 installed almost everywhere since this space was just built a few years ago. That's why I started thinking about low voltage. We also have DMX nearby.

I never thought about IR, but I will explore that as well.

 

[Chris15]

You might check in to installing an IR sensor in addition to the switch back stage. I believe these are available through DaLite.

DaLite are not the only manufacturer of motorised screens and like all good things, there won't be a cross manufacturer standard for control.

I think all of the screens I have come across (which does not mean they all are) have used LV for the control circuits...

 

[Les]

DaLite are not the only manufacturer of motorised screens and like all good things, there won't be a cross manufacturer standard for control.

I think all of the screens I have come across (which does not mean they all are) have used LV for the control circuits...

Yea, I was on my phone, which was a little cumbersome for research, so I just threw out the most commonly-found manufacturer of institutional screens .

 

[museav]

There are four general methods of controlling a motorized projection screen. The simplest is directly switching the AC to the screen motor, this is usually either up or down operation although there may also be a middle position that is effectively a stop. Next would be a low voltage interface that allows contact closure or low level logic switching for up, down and often also stop. With these a momentary contact typically initiates up or down until the screen reaches the limit stops or you hit the stop button (which itself often simply contacts up and down simultaneously). The third method is a low voltage control with IR control. Finally, there are more advanced serial and/or network low voltage controls which may add functionality such as preset positions or setting drops of defined distances. Low voltage controls of some type, which may be integrated into the screen or provided as a separate external device, are very common but are generally approached as an option when ordering the screen.

The controls that Derek linked are typical of direct AC controls where one position switches the incoming hot to the up power on the screen motor and the other one position to the down power with a middle position with no connection.

One of the advantages of low voltage controls is that it is easier to address multiple control point, for example a switch on the wall in parallel with control from an AMX, Crestron or Extron type control system. And some of the more advanced low voltage controllers can let you do things like have 16:9 and 4:3 image presets with a 4:3 projector.

If you want to just move the screen switch then if it is like the controls Derek posted you will probably need an Electrician to move it and it may have to be in conduit. The alternative would be to contact the screen manufacturer and see what low voltage control options may be available and have an Electrician wire one of those in for you, after which multiple low voltage wall switch and other control options would be possible.