How to Motorize a Projector Screen

I have always wanted to set up a home theater, although I don't have a room I can dedicate to it. I do have a large space that can be used for movies, just not all the time. With this in mind I got a used pull down projector screen from a local surplus sale. I always thought it would be nice if the screen was motorized. Screens are not cheap and motorized screens are even more expensive, but I felt I could probably motorize the screen I already had. I did a little research and found that others had done this by various means. The cleanest and best approach seemed to be to use a motor intended for window blinds. I looked on eBay and found a motor that looked like it would fit the bill for $35 shipped. The motor is basically a long cylinder with adjustable stop switches to set the upper and lower limits of movement. It is simple to control and consists of 4 wires: one is a ground, one is common, one is for up, and the other for down. The window blind motor I used (M50S 1234A) runs on 120V AC but they sell 220V versions as well. At the moment this is controlled by a light switch, but with the use of some relays another project will be to make it work by remote.

The Modification

I took apart the end cap of the projector screen and found the spring mechanism. After removing the tension from the spring I found that the spring assembly simply slides out from inside of the screen tube. The blind motor would fit easily inside but had a lot of space and would need some adapters to connect to the screen mechanism. I set about making some adapters out of plastic, I used an old ½ inch thick cutting board for my source of plastic. I cut out squares and then turned them on my lathe to get a size that would fit snugly inside the tube. I needed to mate the adapters to protrusions inside the tube. To do this I used a chisel to carefully cut out notches, allowing the mechanism to rotate the tube.

The lathe's precision was probably not required for this project but I have one so I used it. I think this could have been done with either an adjustable hole saw or by drawing the circles and carefully cutting them out with a jig saw. I also think wood could have worked instead of plastic, but I felt the plastic was a better choice.

The Results

The end product worked perfectly, and the adjustment screws of the motor were easy to use to set the top and bottom limit of the screen. One thing to pay attention to is where the motor adjustment screws will end up. I made the adapters so I could adjust the motor when the screen is down. The only permanent modification I needed to make was to drill a small hole for the cord. If I ever want to revert this back to a manual pull down screen it is just a matter of taking off the end cap and sliding the motor out and spring mechanism back in.

You can check out a video of the modified screen in action here http://youtu.be/u2MdDVpt55A