Projector Screen

Automatic projector screen for under $50

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Build an automatic projector screen that works as well as commercial units, for under $50.
This is version 4.

  • It's quiet and fast.
  • It will take 10-40 hours of your life.
  • Your toddler or his friends drawing on it won't ruin your day.

This revision has worked flawlessly, with no further adjustment and with daily use, for almost 2 years now.

EDIT: 3 houses and almost 10 years after this one was first created... still going strong.  I bent the threaded rod a bit in one of the moves, but it doesn't affect the operation so I left it.  I guess I should probably upload that schematic sometime in the next 10 years to stay on schedule.

Theory of Operation

The wiper motor is a worm gear drive and a pretty low ratio. You can direct drive the fence post at a slow even pace, no problem.

The motor turns threaded rod attached to the chain link fence post onto which the light block fabric is spooled. Support at both ends with roller blade bearings (which happen to perfectly fit 5/16in threaded rod)

The 1/2 in conduit provides a tiny bit of horizontal tension and weight across the bottom edge. The screen is tensioned vertically with this weight. You can adjust how the tension behaves by adding additional weight (filling it).

As the screen moves up, a coupler nut with an attached post moves slowly one direction. The post slides along the corner brace which stops the coupler nut from spinning around the threaded rod.

A relay, triggered from the projector 'remote power', is wired as a reversing switch. Power applied to the relay triggers the screen to descend. The motor is powered from a supply independent from the projector.

The roller switches are positioned at either end of the desired range of motion of the coupler nut/post. The post impacting either switch, simultaneously removes the motor power, and shorts the motor windings providing simple, effective electronic braking.

Mounting the roller switches by the rear screw only allows for easy adjustment in very fine increments of either stopping point. I can tune mine to within 1/8th in of travel at either stop.

The screen itself was made as three sections of 'light block' fabric, which were seamed horizontally with a clothes iron and some iron-on webbing (that was pretty hard to get perfect actually as you can't stretch or push the material or you'll get ripples in your finished screen).  The outer two sections provided the top/bottom border and were painted with black camo paint. (test if your target paint tends to rub off first!)  This lets you use the 'normal' width light block and still be able to make up to a 9ft - 16x9 aspect ratio screen with no seams.

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  • 1
    Getting started

    Get and keep everything clean, including the back of your fabric. When you roll up the screen, the back touches the front, and any dirt will transfer right into the middle of your new screen.

    Take the actuator arm off the wiper motor. See what the threads are. (take that nut to the hardware store)

    The threads on mine were metric something or other, and I had everything for the 5/16 threaded rod setup, so I very carefully welded the rod directly to the motor output. This is very hard to get right and I wouldn't recommend it.

    If you could find metric coupler nuts, that would be a better route as later you could then attach to the motor with just that and tighten the threaded rod into the coupler, jamming against the end of the motor shaft. Make sure that whatever direction you pick for your screen to roll up, the motor is on the appropriate end to tighten this joint when you pull down on the screen fabric, or you will regret it. Just dry fit the parts for now. You'll need the rod separate to make the roller for the screen.

  • 2
    The weight

    Keeping the screen tensioned is what keeps it flat. I provided the needed tension almost all in the vertical axis with weight.

    Take a scrap of your screen fabric, and test how hot you can get an iron on it, before it melts. Three layers, and two are plastic remember. Back off from that temp a little. Hot as you can go without melting or distorting, is what you want.

    Wrap the fabric around your conduit. Mark where it comes to. Add the width of your fusing tape and like 1/4 in. Mark this line across. Remove the conduit.

    Apply your self-adhesive fusing tape along this line. Fold the edge over to meet it. Now tear it all apart and flip it over so your seam is on the back. :)

    Iron the ends, then the middle, then between that at even intervals, until you run out of intervals.  Then iron all the way across. 

    Do not slide or move the iron at all while pressing down as it will cause the tape to 'migrate' while it is hot. Press, lift, move, press...

  • 3
    Painting the fabric

    The light block fabric is actually three layers. White on both sides, with black plastic in between, but you are still painting fabric so you may have to experiment to get it right.

    Lay your light block fabric out on some hard clean surface. Don't step on it, don't press on it, don't fold at all except to mark off your projector's aspect ratio in pencil, centered, leaving room for one wrap extra at the top to stay on the chain link fence post in the down position. The extra wrap does wonders. Trust me.

    Taping your fabric to the floor outside the view-able area helps greatly. Don't tension it.

    Tape off your viewing area. Completely cover the center with newspaper, tape that down at all joints too. Any over-spray is very noticeable. Paint the border with the black camo (better) or flat black paint. Take your time, light coats. Let it dry. Wipe the finished paint lightly with a towel to remove any residual over-spray.

    Too much paint thickness on the edges, will actually make your finished screen wrinkle in the middle. The edges 'roll up faster' than the middle does from the thickness of the paint! If that happens, reverse your taping and paint the middle flat white in equal amounts. (this has the added benefit that you can touch up any stains, kid's markers, etc with the same flat white paint, and the opposite is not true. Painting too thickly in the middle will not wrinkle your edges. The latest version actually got re-painted with exterior house latex (to cover some marker drawings) as I was out of enamel, and actually exhibits the best behavior I've had to date.

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