#Started thinking more about dimensions and stuff

##All I did was checking the measurements so I will attach a photo of the same acrylic panel

Devlog #1: From “just project it” to building my own projector

I wanted a Raspberry Pi display that doesn’t look like a normal monitor: an image that floats on an acrylic board. My first plan was the obvious one: point a projector down at an 880 x 300 mm acrylic board and call it a day.

That fell apart fast. Clear acrylic doesn’t show a projected image because the light goes straight through, so I’d need frosted or white acrylic. The board’s shape was also a problem. 880 x 300 is about 2.9:1, while projectors output 16:9, so around 40% of the pixels would land off the board. And a normal projector needs to sit about a meter above it.

Pivot: Pepper’s ghost

So I switched to a Pepper’s ghost setup: a hidden screen above, and clear acrylic at 45° that reflects it toward you, so the image looks like it’s floating. Much cooler. The catch is that the floating image is exactly the size of the screen, so filling the board meant a huge, heavy, expensive monitor hanging overhead. Not happening on a Hack Club budget.

Building my own projector

What I actually wanted was to take a small screen and magnify it. I looked at a Fresnel lens over a screen, but the physics doesn’t work: a magnifier only makes the screen look bigger from one spot. It can’t put a sharp image onto a surface. The only thing that does that is a projector. So instead of buying one, I’m building one from parts:

• 5.5” 2K LCD panel + HDMI driver board
• 100W LED
• A pair of Fresnel lenses
• A multi-element projection lens

The Pi just sees it as an HDMI monitor.

The rest of the system

• OS: Arch Linux ARM. Hard mode, but I’ll actually understand the whole system.
• Input: a global-shutter camera running MediaPipe hand tracking, so the display works like a touchscreen without a touch sensor. I skipped YOLO; it’s object detection and overkill for tracking fingertips.
• Two Pis: Pi A runs the display and UI, and Pi B only does camera and hand tracking, then sends fingertip positions to Pi A. Splitting by workload means neither one stutters.
• Failover: planned for later. If Pi A dies, Pi B takes over the whole system.

The budget fight

The hardest part so far was the budget. Hack Club grants are capped at $600 and you only get one submission, so everything had to fit now. My first parts list came to $661, before shipping. I trimmed it line by line:

• Storage: microSD instead of NVMe for now.
• Keyboard projector: I’ll fund the second projector myself.
• Lens: kept the good multi-element one. That’s the one place I refused to cut, because it decides whether the image looks sharp or muddy.
• Frame: 3D-printed brackets instead of an aluminum extrusion frame.

Then I checked every link and price, and found the Pi 5 had gotten a lot more expensive this year because of the RAM shortage. More rebalancing, but the final list fits.

Next: CAD for the ghost box.