The Pi Projector

In a week, I return to teaching classes, and my course is going to meet face to face. The pandemic has kept me indoors more or less since the week before Thanksgiving, so I am itching to see students. That said, I’m aware that the virus is not at all contained, and there’s little chance for me to get the vaccine in the near future. [Yes, as a faculty member, I’m allowed to get the vaccine, and I can get it … sometime in April … when classes will be essentially over.

Thanks, government.

Enough of my soap box. I wanted a way to interact with students during office hours, but was worried if we were trying to show work on a computer screen or piece of paper (and thus breaking social-distancing guidelines). I decided solve this problem as I normally do lately – with the help of a Raspberry Pi.

Enter – the Pi Projector.

The Pi Projector, complete with CNC case and a cooling fan!

The Pi is a model 3B+ and the projector part is a cool development board from TI. It’s a tiny, relatively cheap DLP display that is designed to fit onto a BeagleBone Black. I’m not the first one to use this unit with a Raspberry Pi, and in fact I found some pretty straightforward instructions for setting it up.

In earlier iterations of my design, I tried to make a small box with the projector stacked on the RPi. It turned out that I ran into some heating problems and had to rethink the design. I also added a heatsink to the RPi and the mini cooling fan to the box.

Projecting at a distance of about 20 inches results in an image that displays rather clearly on a sheet of paper.

The projector isn’t terribly bright, but it does a decent job with projecting an image about the size of a sheet of paper in a room with normal daylight. You’ll note that I added a wireless keyboard and mouse so I can use the RPi right from the box. But that’s not the way I typically plan to use it.

How many commercial projectors come with VNC?

Once the projector is connected to the internet, I can use VNC to connect from my desktop. That way, I can work at a normal screen and project the RPi screen at a place where students can see my work without leaning over my shoulder to look at my screen. Adding sound to the projector is a breeze, especially with a Bluetooth speaker.

Feel the beat!

All of that is cool (I think) but the main reason why I wanted to build the Pi Projector was to serve as a display for my iPad. I find that I spend a lot of time opening up an application there and doodling or typing away something I’d like my students to see. It’s simply not possible to share an iPad screen and stay socially distant.

Enter RPiPlay.

It turns out that a Raspberry Pi can masquerade as an airplay receiver. Once the software is set up on the RPi and the server is started, my iPad sees the projector and is ready to display.

Not the best image, but you get the point, I hope.

I’m pretty happy with the results of this project: a box about the size of a 4×6 index card that can project a pretty decent image (in the dark it can do 50 inch diagonal) that has all the features of a Raspberry Pi plus can connect to Bluetooth speakers and mirror an iPad display.

I think I’m ready to hold office hours.

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