Backyard Planetarium with Magnets

If you are a Hackaday reader, you probably like space in real life, fiction, or both. A trip to a planetarium is a great treat, but what if you could have a planetarium in your backyard? [Ecasill] thought so and used a Zip Tie domes kit to create just such a thing. It takes some sewing and a projector, but there’s a problem. The dome needs to come down if there is going to be bad weather. The answer? Magnetic dowel rods.

Because the magnets are brittle, plastic dip covers them after epoxy sticks them in place. The cloth has steel bolts to adhere, too. All in, the setup cost about $2,000. That includes a projector, a mirror ball, a sound system, and all the construction.

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Raspberry Pi Projection Mapping Crash Course

Projection mapping might not be a term you’re familiar with, but you’ve certainly seen the effect before. It’s when images are projected onto an object, usually one that has an interesting or unusual shape, to create an augmented reality display. Software is used to map the image or video to the physical shape it’s being projected on, often to surreal effect. Imagine an office building suddenly being “painted” another color for the Holidays, and you’ll get the idea.

This might seem like one of those things that’s difficult to pull off at the hobbyist level, but as it turns out, there’s a number of options to do your own projection mapping with the lowly Raspberry Pi. [Cornelius], an avid VJ with a penchant for projection mapping, has done the legwork and put together a thorough list of different packages available for the Pi in case you want to try your hand at the futuristic art form. Many of them are even open source software, which of course we love around these parts.

[Cornelius] starts by saying he’s had Pis running projection installations for as long as three years, and while he doesn’t promise the reader it’s always the best solution, he says its worth getting started on at least. Why not? If the software’s free and you’ve already got a Raspberry Pi laying around (we know you do), you just need a projector to get into the game.

There’s a lot of detail given in the write-up, including handy pro and con lists for each option, so you should take a close look at the linked page if you’re thinking of trying your hand at it. But the short version is that [Cornelius] found the paid package, miniMAD, to be the easiest to get up and running. The open source options, ofxPiMapper and PocketVJ, have a steeper learning curve but certainly nothing beyond the readers of Hackaday.

To make things easier, [Cornelius] even goes on to give the reader a brief guide on setting up ofxPiMapper, which he says shouldn’t take more than 30 minutes or so using its mouse and keyboard interface. It would be interesting to see somebody combine this with the Raspberry Pi integrated projector we saw a couple years back to make a highly portable mapping setup.

Bringing Augmented Reality to the Workbench

[Ted Yapo] has big ideas for using Augmented Reality as a tool to enhance an electronics workbench. His concept uses a camera and projector system working together to detect objects on a workbench, and project information onto and around them. [Ted] envisions virtual displays from DMMs, oscilloscopes, logic analyzers, and other instruments projected onto a convenient place on the actual work area, removing the need to glance back and forth between tools and the instrument display. That’s only the beginning, however. A good camera and projector system could read barcodes on component bags to track inventory, guide manual PCB assembly by projecting which components go where, display reference data, and more.

An open-sourced, accessible machine vision system working in tandem with a projector would open a lot of doors. Fortunately [Ted] has prior experience in this area, having previously written the computer vision code for room-scale dynamic projection environments. That’s solid experience that he can apply to designing a workbench-scale system as his entry for The Hackaday Prize.

A Telepresence System That’s Starting To Feel Like A Holodeck

[Dr. Roel Vertegaal] has led a team of collaborators from [Queen’s University] to build TeleHuman 2 — a telepresence setup that aims to project your actual-size likeness in 3D.

Developed primarily for business videoconferencing, the setup requires a bit of space on both ends of the call. A ring of stereoscopic z-cameras capture the subject from all angles which the corresponding projector on the other end displays. Those projectors are arranged in similar halo above a human-sized, retro-reflective cylindrical screen which can be walked around — viewing the image from any angle without a VR headset or glasses — in real-time!

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Roll Up Your Sleeve, Watch a Video with This Smart Watch Forearm Projector

We’re all slowly getting used to the idea of wearable technology, fabulous flops like the creepy Google Glass notwithstanding. But the big problem with tiny tech is in finding the real estate for user interfaces. Sure, we can make it tiny, but human fingers aren’t getting any smaller, and eyeballs can only resolve so much fine detail.

So how do we make wearables more usable? According to Carnegie-Mellon researcher [Chris Harrison], one way is to turn the wearer into the display and the input device (PDF link). More specifically, his LumiWatch projects a touch-responsive display onto the forearm of the wearer. The video below is pretty slick with some obvious CGI “artist’s rendition” displays up front. But even the somewhat limited displays shown later in the video are pretty impressive. The watch can claim up to 40-cm² of the user’s forearm for display, even at the shallow projection angle offered by a watch bezel only slightly above the arm — quite a feat given the irregular surface of the skin. It accomplishes this with a “pico-projector” consisting of red, blue, and green lasers and a pair of MEMS mirrors. The projector can adjust the linearity and brightness of the display to provide a consistent image across the uneven surface. An array of 10 time-of-flight sensors takes care of watching the display area for touch input gestures. It’s a fascinating project with a lot of potential, but we wonder how the variability of the human body might confound the display. Not to mention the need for short sleeves year round.

Need some basics on the micro-electrical mechanic systems (MEMS) behind the pico-projector in this watch? We’ve got a great primer on these microscopic machines.

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Laser projector ditches galvanometer for spinning drum

Laser projectors like those popular in clubs or laser shows often use mirror galvanometers to reflect the laser and draw in 2D. Without galvos, and on a tight budget, [Vitaliy Mosesov] decided that instead of downgrading the quality, he would seek an entirely different solution: a spinning mirror drum.

He fires a laser at a rotating drum with twelve mirror faces, each at a different adjustable vertical angle. The laser will hit a higher or lower point on the projection surface depending on which mirror it’s reflecting off – this creates resolution in the Y direction.

Timing the pulsing of the laser so that it reflects off the mirror at a certain horizontal angle provides the X resolution.

As you can already tell, speed and timing is critical for this to work. So much so that [Vitaliy] decided he wanted to overclock his Arduino – from 16 MHz to 24.576 MHz. Since this changes the baud rate, an AVR ISP II was used for programming after the modification, and the ‘duino’s hardware serial initialization had to be hacked too.

For the laser itself, [Vitaliy] designed some nifty driver circuitry, which can respond quickly to the required >50 kHz modulation, supply high current, and filter out voltage transients on the power supply (semiconductor lasers have no protection from current spikes).

On the motor side of things, closed loop control is essential. A photo-interrupter was added to the drum for exact speed detection, as well as a differentiator to clean up the signal. Oh, and did we mention the motor is from a floppy disk drive?

We’ve actually seen builds like this before, including a dot-matrix version with multiple lasers and one made apparently out of Meccano and hot-glue that can project a Jolly Wrencher. But this build, with its multiple, adjustable mirrors, is a beauty.  Check it out in action below.

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DIY Planetarium Built From PVC Pipes and Cardboard

When you think about DIY projects, you probably don’t consider building your own planetarium. Why would you? Building the thing is surely outside the capabilities of the individual, and even if you could figure it out, the materials would be far too expensive. There’s a limit to DIY projects, and obviously building a planetarium is on the wrong side of the line. Right?

Well, apparently not. [Gabby LeBeau] has documented the planetarium she built as her senior project, and if you’ll forgive the pun, it’s absolutely out of this world. Using readily available parts and the help of family and friends, she built a fully functional planetarium big enough to seat the Physics Department. No word on what grade she got, but it’s a safe bet she screwed the curve up for the rest of the class.

After two months of research and a couple of smaller proof of concept builds, she was able to find a business who graciously allowed her to construct the full scale planetarium in their warehouse. The frame is made of PVC pipes held together with zip ties. The big advantage to using the PVC pipes (beyond being cheap and easy to works with) is that they will automatically find a hemispherical shape when bent; saving the time and trouble it would take to create the shape with more rigid building materials.

Once the PVC frame was up, white cardboard panels were cut to shape and attached to the inside. The panels were lined up as closely as possible, but gaps were covered with white tape so the fit didn’t need to be perfect. When the dome was finished, it was lifted and placed on metal trusses to get some room underneath, and finally covered with a black tarp and stage curtain to block out all light.

Of course, she didn’t go through all this trouble to just stick some glow in the dark stars on the inside of this thing. The image from a standard projector is directed at a flat mirror, which then bounces off of a convex mirror. Driving the projector is a laptop running Stellarium. While there were some imperfections she couldn’t get polished or cleaned off of the mirrors, the end result was still very impressive.

Unfortunately, you can’t really do a planetarium justice with a camera, so we aren’t able to see what the final image looked like. But judging by the slack-jawed faces of those who are pictured inside of it, we’re going to go out on a limb and say it was awesome.

We might suggest trying to quiet down the projector or adding some lasers to the mix, but overall this is a truly exceptional project, and we’re jealous of everyone who got to experience it first hand.