I've wanted to do this project for some time, but a long winter break during quarantine gave me a good excuse to do it.  Using parts and hardware I had on hand, mostly scavenged, I was able to finish in a couple days.  Most of the effort was making the mounting brackets, support and adjustments.

There is a lot of great information about pattern projection systems in the Projectors For Sewing Facebook group. (please keep in mind this group is for people who sew while deciding if it's appropriate for you)  The pinned post has several very helpful documents and tips, including the calibration files and tools for assembling multi page patterns into one.

Projector

I had a couple Epson PowerLite 830p (EMP-830) projectors stored that I salvaged from the trash.  They'd been discarded as they were quite old, the bulb was no longer available(at that time) and the rooms had new projectors installed.  The ones I have have 2000 and 2500 hours, out of a 3000hr lifetime, though these hours are all at low intensity, so they should last longer.  Regardless, these bulbs are now available online.

You need a projector with square pixels(or adjustments that can force it), reasonable resolution and cabling to connect to a computer.   Brighter is better so you don't have to work in the dark, and wider angle permits a larger image.  This one is 3000 lumen 1024x768 resolution, which is sufficient.  This has higher end configuration options, including corner mode keystone(more flexible than simple H/V keystone).  This brightness and throw means it is plenty bright enough to use on light colored material even with the full room lights on.  On darker material, some of the room lights need to be turned off.

See Projector and Mount project log for more details.

Mirror

Unless you have a very wide angle projector, you will need a mirror, ideally first surface.  You can use a bathroom mirror, though the image will be blurred in one direction.  I'm repurposing a mylar mirror out of an old rear projection TV.  You can purchase these for much less money than a first surface glass mirror, and they are much lighter and safer that hanging a large glass mirror overhead.

My mirror has a very slight bow in the frame along the long edge, which I adjusted out with a clamping screw.  This is another advantage and disadvantage of a mylar mirror, the frame can bend more easily, which permits perfecting the image, though a glass mirror may get away without this.  Mine is trapezoidal due to it's original purpose.  The actually used surface of the mirror is a trapezoid, though this mirror is much wider as it was from a 3 tube rear projection tv instead of a DLP.  You can easily use a rectangular one.

See Mirror and Mount project log for more details.

Projector Mount

I already had a slim projector mount, though it's hole pattern was not the same as this projector.  I used some scrap metal to make an adapter.  As this is an offset image type projector, I needed the projector as close to the ceiling as possible, making this style better than most of the ones easily available.  This style allows it to be mounted to the ceiling, and the projector side can simply be hooked on and tightened down.  This allows me to take it off if I want.  I repainted the ceiling side of the mount white to match the ceiling.

See Projector and Mount project log for more details.

Mirror Mount

They mylar  mirror I had only has mounts on one side as the other originally fit in a channel in the tv.  I made up a couple brackets which spanned the back side and clamped on.  This was based on some 1 by 1/2 inch aluminum box tube I had around.  I mounted further hardware onto this, connecting everything with tapped holes for easy adjustment.

Eyebolts stuck out the end to hang on hook on the ceiling.  At the other end, I created "spring" loaded latches which can latch onto hooks on the ceiling to keep it in the raised position, or lower it for use.

See Mirror and Mount project log for more details.

Calibration

I intentionally installed the projector,  and mirror orthogonal to each other and the table.  While not required, this substantially simplifies the calibration.  The system was made to have various adjustments to make calibration easier.

I used the calibration file from the Projectors For Sewing group.  Very little adjustment needed to be done.  The major things I needed to do:

See Calibration and Finish project log for more details.

Resulting Details

This system has resulting throw of 72" from the lens to the work table.

At maximum wide zoom of the projector, I use a 19.08% zoom factor in acrobat to get an image on the table that is just over 48 by 36 inches.  This is great for large sewing pattern pieces.

At minimum zoom of the projector, I use 30.65% (30.44%) zoom factor in acrobat to get an image on the table that is 22-7/8 by 30-1/2 inches.  This is great for tracing patterns onto 20x30 foam board, with more precise lines.

See Calibration and Finish project log for more details.