Multiple Monitors With Multiple Pis

One of the most popular uses for the Raspberry Pi in a commercial setting is video walls, digital signage, and media players. Chances are, you’ve probably seen a display or other glowing rectangle displaying an advertisement or tweets, powered by a Raspberry Pi. [Florian] has been working on a project called info-beamer for just this use case, and now he has something spectacular. He can display a video on multiple monitors using multiple Pis, and the configuration is as simple as taking a picture with your phone.

[Florian] created the info-beamer package for the Pi for video playback (including multiple videos at the same time), displaying public transit information, a twitter wall, or a conference information system. A while back, [Florian] was showing off his work on reddit when he got a suggestion for auto-configuration of multiple screens. A few days later, everything worked.

Right now, the process of configuring screens involves displaying fiducials on each display, taking a picture from with your phone and the web interface, and letting the server do a little number crunching. Less than a minute after [Florian] took a picture of all the screens, a movie was playing across three weirdly oriented displays.

Below, you can check out the video of [Florian] configuring three Pis and displays to show a single video, followed by a German language presentation going over the highlights of info-beamer.

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Superconference Interview: Ben Krasnow

Ben Krasnow is a consummate prototyper. He’s built a machine that makes the perfect chocolate chip cookie, he has a ruby laser, and he produces his own liquid nitrogen in-house because simply filling up a dewar is too easy. If you need a prototype, Ben is the guy to talk to.

Ben gave a talk at last year’s Hackaday Superconference on prototyping quickly and verifying technical hypotheses. The philosophy can be summed up simply as, ‘Build First, and Ask Questions Later’. This philosophy served him well when he wanted to see if backscatter x-ray machines were actually more effective than metal detectors at TSA checkpoints. The usual bean-counter protocol for answering this question would be to find an x-ray expert, wait weeks, pay tens of thousands of dollars, and eventually get an answer. Ben simply built his own backscatter x-ray machine from parts sourced on eBay.

After the talk, we asked Ben about the limits of this philosophy of building first and asking questions later. With the physical and mental toolset Ben has, it’s actually easy to build something that can get in the ballpark of answering a question. The problem comes when Ben needs to prove something won’t work.

Answering this question is all a matter of mindset. In Ben’s view, if a prototype works, a hypothesis is verified. Even if it’s a complete accident, he’s totally okay with the results. Some of his other colleagues have an opposite mindset — if a quick and dirty prototype doesn’t work, a research hypothesis is verified.

This rapid-proof-of-concept mindset is something we see a lot in the Hackaday audience, and we know there are some of you out there who have a mind and garage that is at least as impressive as Ben’s. We’ve extended the Call for Proposals for the 2017 Hackaday Superconference. If you have a story about rapid prototyping or just making the perfect chocolate chip cookie with robots, we want to hear about it. Tickets are still available for the Superconference in Pasadena, California on November 11th and 12th.

Friday Hack Chat: Graphical Programming Languages with Boian Mitov

There is a long history of Visual or Graphical Programming Languages, and most of them make more sense than the name of Microsoft’s Visual Basic, C#, and Visual Studio IDE. Some people don’t like to code, and for them, graphical programming languages replace semicolons and brackets with easy-to-understand boxes and wires.

This Friday, we’re going to be talking about graphical programming languages with [Boian Mitov]. He’s a software developer, founder of Mitov Software, and the creator of Visuino, a graphical programming language for the embedded domain. Everything from the Arduino to Teensy, ESP8266, ESP32, the chipKIT, and Maple Mini are supported with this IDE. It’s a simple drag-and-drop way of programming microcontrollers that Scratches an itch (see what I did there?) for an easy way to introduce non-programmers to the embedded world and also provides a faster way to build custom applications.

When it comes to graphical programming languages, we can’t find a better Hack Chat guest than [Boian]. He’s the author of the OpenWire dataflow processing technology — another graphical programming language –, the IGDI+ library, VideoLab, SignalLab, AudioLab, PlotLab, InstrumentLab, and author of VCL for Visual C++. He’s a regular contributor to Blaise Pascal Magazine, too.

During this Hack Chat, we’ll be discussing what makes Visual Programming worth it, how and why it works, when it doesn’t and how to develop a graphical programming language. Visuino will be of special interest, And I’m sure someone will work in a, ‘what’s happening with Max/MSP under Ableton’ question. If you have a question for [Boian], here’s a question sheet to guide the discussion.

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hack Chat group messaging. This Hack Chat will take place at noon Pacific time on Friday, August 11th. Here’s a time and date converter!

Log into, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talk

Swedish Rocket Knives

There are trends in YouTube videos among various video producers. A few weeks ago, it was all about fidget spinners until some niche tech blog ran that meme into the ground. Before that, the theme was red-hot knives cutting through stuff. The setup was simple; just heat a knife up with a blowtorch, cut through a tomato or golf ball, hit stop on the high-speed camera, and collect that sweet, sweet YouTube money.

[David] from isn’t like most YouTube stars. He actually knows what he’s doing. When the latest trend of rocket-propelled knives hit the tubes, he knew he could blow this out of the water. He succeeded with a fantastic rocket-propelled machete able to slice through watermelons and fling itself into the woods behind [David]’s house.

Unlike most of the other YouTube stars trying their hand at rocket-powered slicers, [David] is doing this one right. He’s using hobby rocket motors, yes, but they’re reloadable. [David] crafted an engine casing complete with a proper nozzle machined out of stainless for this build. The rocket sled itself is an aluminum bracket bolted to a piece of carbon fiber plate that travels down a rail with the help of four skateboard wheels. A machete is then bolted to the plate, which is propelled down the track a bit faster than 200 km/h.

When it comes to rocket-propelled knives, the word ‘professional’ really doesn’t come into play. This, however, is an amazing piece of craftsmanship that you can check out in the videos below.

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Building An Ultralight Out Of Foam In A Basement

[Peter Sripol] is something of a legend in the DIY RC aircraft crowd. He’s friends with Flite Test, and there he built an enormous RC cargo plane that could easily carry a small child aloft. Now, [Peter] is aiming a bit higher. He’s building an ultralight — a manned ultralight — in his basement. It’s made out of insulation foam.

Yes, this ultralight is constructed out of insulation foam, but you can think of that as just a skin. The real structure here comes from a wooden frame that will be fiberglassed. The design of this aircraft is an electric, twin-engine biplane. The relevant calculations have already been done, and [Peter] is already flying an RC scale model of this craft. So far, everything is not as sketchy as it could be.

As with any, ‘guy builds an airplane in his basement’ story, there must be a significant amount of time dedicated to the legality, practicality, and engineering of said plane. First off, the legality. [Peter] is actually building an ultralight under Part 103. The certifications for a Part 103 ultralight are much more lenient than the next step up in FAA-certified aircraft, a light sport or experimental aircraft. An ultralight is not required to have an airworthiness certification, and pilots of ultralights are not required to pass any tests of aeronautical knowledge or hold a medical certificate. Yes, legally, any moron can jump in an ultralight and fly. Think about that the next time someone brings up the Part 107 ‘drone’ certification.

Next, the practicality and engineering. [Peter]’s plane can weigh a maximum of 254 pounds, and should not be capable of more than 55 knots in full power level flight, while having a stall speed that does not exceed 24 knots. This is slow for a Cessna, but just about right for the gigantic remote-controlled planes [Peter] has already built.  A few years ago, [Peter] built a gigantic remote-controlled cargo plane out of what is basically foam board and a few aluminum tubes. The construction of [Peter]’s ultralight will be a highly refined version of this. He’s using foam insulation sheets for the body of the fuselage, reinforced with plywood and poplar struts. This foam and wood build will be wrapped with carbon fiber and fiberglass sheet, epoxied, and hopefully painted with flames on the side.

The use of poplar is a bit curious for an ultralight aircraft. For the last hundred years, the default wood for aircraft has been either spruce or douglas fir. The reason for this choice is the strength to weight ratio; spruce and douglas fir have the highest strength to weight ratio of any other wood. Poplar, however, is ultimately stronger and available at his local home improvement store, even though it does weigh a bit more. If [Peter] can keep the weight down in other areas, poplar is an excellent choice due to cost and availability. The video (below) is unclear, but we can only hope [Peter] has read up on the strength of aircraft frames and the orientation of the grain of each structural member.

This is the first video in what will be an amazing build series, and [Peter] hopes to get this thing up in the air by September. If you’re concerned about [Peter]’s safety, he’s also put up a GoFundMe page for a parachute. [Peter]’s going to fly this thing if you complain or concern troll or not, so donate a dollar for the parachute if you’re that concerned.

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Bibles You Should Read: PoC || GTFO


For the last few years, Pastor Manul Laphroaig and friends have been publishing the International Journal of PoC || GTFO. This is a collection of papers and exploits, submitted to the Tract Association of PoC || GTFO, each of which demonstrates an interesting exploit, technique, or software toy in the field of electronics. Imagine, if 2600 or Dr. Dobb’s Journal were a professional academic publication. Add some whiskey and you have PoC || GTFO.

This is something we’ve been waiting a while for. The International Journal of PoC || GTFO is now a real book bible published by No Starch Press. What’s the buy-in for this indulgence? $30 USD, or a bit less if you just want the Ebook version. The draw of the dead tree version of PoC includes a leatherette cover, gilt edges, and the ability to fit inside bible covers available through other fine retailers. There are no rumors of a children’s version with vegetable-based characters.

PoC || GTFO, in reality, is an almost tri-annual journal of reverse engineering, computer science, and other random electronic computational wizardry, with papers (the Proof of Concept) by Dan Kaminsky, Colin O’Flynn, Joe FitzPatrick, Micah Elisabeth Scott, Joe Grand, and other heroes of the hacker world. What does PoC || GTFO present itself as? Applied electrons in a religious tract publication. The tongue is planted firmly in the cheek here, and it’s awesome.

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Hackaday Links: August 13, 2017

We found the most boring man on the Internet! HTTP Status Code 418 — “I’m a teapot” — was introduced as an April Fools Joke in 1998. Everyone had a good laugh, and some frameworks even implemented it. Now, the most boring man on the Internet and chairman of the IETF HTTP working group is trying to get 418 removed from Node and Go. There is an argument to removing code 418 from pieces of software — it gums up the works, and given only 100 code points for a client error, with 30 of them already used, we don’t really have space for a joke. There’s a solution, though: someone has submitted a request to register 418 as ‘I’m a teapot’.

The Travelling Hacker box is a migratory box of random electronic junk. The box has traveled across the United States several times, and earlier this year it started across Canada — from Vancouver to St. Johns — to begin an International journey. The box is now missing, and I’m out. I’m turning this one over to the community. There are now several rogue boxes traveling the world, the first of which was sent from [Sophi] to [jlbrian7] and is now in Latvia with [Arsenijs]. The idea of the Travelling Hacker Box is now up to you — organize your own, and share random electronic crap.

Bluetooth 5 is here, or at least the spec is. It has longer range, more bandwidth, and advertising extensions.

Guess what’s on the review desk? The Monoprice Mini Delta! If you have any questions you’d like answered about this tiny, very inexpensive printer, put them in the comments. I only have some first impressions, but so far, it looks like extending the rails (to make a taller printer) is more difficult than it’s worth. That’s not to say it’s impossible, but with the effort required, I could just print another printer.

Interested in PCB art? [Drew] found someone doing halftone art with PCBs. This is a step up from nickels.

Indiana University is getting rid of some very, very cool stuff in a government auction. This device is listed as a ‘gantry’, but that’s certainly not what it is. There have been suggestions that these devices are a flight sim, but that doesn’t sit quite right either. It’s several thousand pounds of metal, with the minimum bid of $2.00 at the time of this writing. Any guesses on what this actually is?