Weatherproof Pi Looks Up So You Don’t Have To

November 9, 2017 by Tom Nardi 27 Comments

Skywatching is a fascinating hobby, but does have the rather large drawback of needing to be outside staring at the sky for extended periods of time. Then there’s the weather to contend with, even if you’ve got yourself a nice blanket and it isn’t miserably cold, there might be nothing to see if cloud cover or light pollution is blocking your view.

To address these issues, [Jason Bowling] decided to put a Raspberry Pi in a weatherproof enclosure and use it as a low-cost sky monitoring device. His setup uses the No-IR camera coupled with a cheap wide-angle lens designed for use with smartphone camera. The whole setup is protected from the elements by a clear acrylic dome intended for a security camera, and a generous helping of gasket material. Some experiments convinced [Jason] to add a light pollution filter to the mix, which helped improve image contrast in his less than ideal viewing area.

The software side is fairly straightforward: 10 second exposures are taken all night long, which can then be stitched together with ffmpeg into a timelapse video. [Jason] was concerned that the constant writing of images to the Pi’s SD card would cause a premature failure, so he set it up to write to a server in the house over SSHFS. Adding a USB flash drive would have accomplished the same thing, but as he wanted to do the image processing on a more powerful machine anyway this saved the trouble of having to retrieve the storage device every morning.

This isn’t the first time [Jason] has used a Pi to peer up into the heavens, and while his previous attempts might not be up to par with commercial offerings, they definitely are very impressive considering the cost of the hardware.

Continue reading “Weatherproof Pi Looks Up So You Don’t Have To” →

Twin Pis For Remote Computer Management

November 5, 2017 by Lewin Day 32 Comments

Sometimes you have a whole bunch of computers that you need to work with, and having a keyboard, monitor, and mouse for each one becomes too much to deal with. There are a multitude of solutions to this problem, but [Fmstrat] went the hacker route, and built their own.

The build is a rather unique way of controlling PCs remotely, but it does the job. A Raspberry Pi 3 is pressed into service as the core of the operation. It’s accessible over IP for remote control. Video is captured from the controlled machines through the combination of an HDMI-to-S-Video adapter and an analog video capture card plugged into the Pi. Keystrokes are sent in a roundabout way, first sent to a Pi Zero over a USB-to-Serial adapter. From there, the Pi acts as an emulated mouse and keyboard to the PC under control.

One caveat of remotely controlling computers over a network is that if things go pearshaped, it can become necessary to power cycle the machine. [Fmstrat] deals with this by fitting a relay board to the Pi 3, which is connected to the reset buttons of the machines under control.

It may not be the quickest, easiest, or industry standard way of controlling remote computers, but it works. [Fmstrat] tells us this build was primarily designed to get around the fact that there aren’t any decent cheap IP-KVM systems, and consumer motherboards don’t support the IPMI standard that would otherwise be useful here.

We particularly like the hard-wired relays for rebooting a machine – great for when a network dropout is stopping Wake-on-LAN packets from achieving their goal. While the conversion of HDMI outputs into analog video for capture is unusual and somewhat costly on a per-machine basis, it’s functional and gives the system the ability to work with any machine capable of outputting a basic analog video signal. With the Pi Zero keyboard emulation and analog video capture, we could see this being used with everything from modern computers to vintage 80s hardware. If you’ve ever needed to control an Amiga 2000 remotely for whatever reason, this could be the way to do it.

We’ve seen plenty of other KVM builds over the years, too – like this low-cost HDMI switcher.

DIY Multi-Touch All The Surfaces

November 4, 2017 by Kristina Panos 11 Comments

Ever wanted to build a touch table or other touch-input project, but got stuck figuring out the ‘touch’ part? [Jean Perardel] has your back with his multi-touch frame over on IO that makes any surface touch-reactive. In [Jean]’s case, that surface is ultimately a TV inside of a table.

Of course, it’s a bit of a misnomer to say the surface itself becomes touch-reactive. What’s really happening here is that [Jean] is using light triangulation to detect shadows and determine the coordinates of the shadow-casting object. Many barcode scanners and consumer-level document scanners use a contact image sensor (CIS) to detect objects in the path of IR LEDs. These are a low-power, lower-resolution alternative to the CCDs found in high-grade scanners.

As [Jean] explains in the video below, an object placed in the path of a single IR LED facing a sensor array of either type will block the light from reaching the sensors. Keep adding LEDs and their emission angles will begin to overlap, increasing the detection precision. [Jean] reverse engineered a couple of different types of scanners until he found a suitable one. He ended up with CIS that has 2700 light sensors lined up in the space of 20cm (7.87″).

[Jean] designed a 3D-printable frame to hold 96 IR LEDs in stacks of three. A Teensy turns on the LEDs, detects the touch event, calculates the position, and sends those coordinates to a Pi to be displayed on the screen. He eventually went wireless and then built a nice looking touch table to house a 32″ TV.

This is not the only way to build a multi-touch table, nor is it the simplest. Here’s one that uses finger presses to scatter light and an industrial strength projection-based table that was open-sourced a few years ago.

Continue reading “DIY Multi-Touch All The Surfaces” →

What Is Entropy And How Do I Get More Of It?

November 2, 2017 by Elliot Williams 55 Comments

Let’s start off with one of my favorite quotes from John von Neumann: “Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin. For, as has been pointed out several times, there is no such thing as a random number — there are only methods to produce random numbers, and a strict arithmetic procedure of course is not such a method.”

What von Neumann is getting at is that the “pseudo” in pseudorandom number generator (PRNG) is really a synonym for “not at all”. Granted, if you come in the middle of a good PRNG sequence, guessing the next number is nearly impossible. But if you know, or can guess, the seed that started the PRNG off, you know all past and future values nearly instantly; it’s a purely deterministic mathematical function. This shouldn’t be taken as a rant against PRNGs, but merely as a reminder that when you use one, the un-guessability of the numbers that it spits out is only as un-guessable as the seed. And while “un-guessability” isn’t a well-defined mathematical concept, or even a real word, entropy is.

That’s why entropy matters to you. Almost anything that your computer wants to keep secret will require the generation of a secret random number at some point, and any series of “random” numbers that a computer generates will have only as much entropy, and thus un-guessability, as the seed used. So how does a computer, a deterministic machine, harvest entropy for that seed in the first place? And how can you make sure you’ve got enough? And did you know that your Raspberry Pi can be turned into a heavy-duty source of entropy? Read on!

Continue reading “What Is Entropy And How Do I Get More Of It?” →

Pi Handheld With A Mindblowing Enclosure

November 2, 2017 by Lewin Day 14 Comments

The Raspberry Pi is possibly the world’s most popular emulation platform these days. While it was never intended to serve this purpose, the fact remains that a small, compact computer with flexible I/O is ideally suited to it. We’ve featured a multitude of builds over the years using a Pi in a mobile form factor to take games on the go. [Michael]’s build, however, offers a lot more than a few Nintendo ROMs and some buttons from eBay. It’s a tour de force in enclosure design.

The build starts with the electronics. In 2017 it’s no longer necessary to cobble together five different accessory boards to handle the controls, battery charging, and display. Boards like Kite’s Super All In One exist, handling everything necessary for a handheld game console. With this as a starting point, he then set out to recreate Nintendo’s classic Game Boy, with a few tweaks to form and function.

It’s a textbook example of smart planning, design, and execution. We are taken through the process of creating the initial CAD drawings, then combining 3D printed parts with wood and carbon fibre for a look that is more akin to a high-end piece of hi-fi gear than anything related to gaming. The attention to detail is superb and the write-up makes it look easy, while [Michael] shares tips on how to safely cut carbon fibre to make your own buttons.

The final results are stunning, and it’s a great example of why a fine piece of wood is always a classy way to go for an enclosure. For another great example, try this walnut keyboard, or check out the roots of the Raspberry Pi Game Boy movement.

Pumpkin Piano Promises A Gourd Time

October 31, 2017 by Lewin Day 9 Comments

Fall – it’s that time of year that brings falling leaves, Hallowe’en, and a pumpkin version of everything that you hold dear. In this case, it’s not a latte – it’s [Robert Vorthman]’s Pumpkin Piano.

[Robert] took a straightforward approach to the build, pressing a Raspberry Pi into service as the backbone of the operation. This is combined with an Adafruit breakout board for the MPR121, which is a chip that provides 12 capacitive touch-sensitive inputs. These are connected to the bountiful produce which make up the piano keys in this fun holiday hack. [Robert] uses some Python code that talks to fluidsynth, a software synthesizer that uses Soundfont files to create different sounds. It’s all wrapped up with some Neopixels that flash when each vegetable is triggered.

The build would make a great party piece for just about any fall gathering, and [Robert] has done a great job of rolling up all the hardware and software required in the write-up. For another take on a vegetable-based orchestra, check out last year’s Harpsi-gourd.

Raspberry Pi Media Streamer Is Combat Ready

October 26, 2017 by Tom Nardi 21 Comments

We are truly living in the golden age of media streaming. From the Roku to the Chromecast, there is no shortage of cheap devices to fling your audio and video anywhere you please. Some services and devices may try to get you locked in a bit more than we’d like (Amazon, we’re looking at you), but on the whole if you’ve got media files on your network that you want to enjoy throughout the whole house, there’s a product out there to get it done.

But why buy an easy to use and polished commercial product when you can hack together your own for twice the price and labor over it for hours? While you’re at it, why not build the whole thing into a surplus ammo can? This the line of logic that brought [Zwaffel] to his latest project, and it makes perfect sense to us.

It should come as no surprise that a military ammo can has quite a bit more space inside than is strictly required for the Raspberry Pi 3 [Zwaffel] based his project on. But it does make for a very comfortable wiring arrangement, and offers plenty of breathing room for the monstrous 60 watt power supply he has pumping into his HiFiBerry AMP+ and speakers.

On the software side the Pi is running Max2Play, a Linux distro designed specifically for streaming audio and video remotely. [Zwaffel] says that with this setup he is able to listen to music on his Squeezebox server as well as watch movies via Kodi.

While none are quite as battle-hardened as this, we have seen several other Raspberry Pi Squeezebox clients over the years if you’re looking for more inspiration.