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Simulating A Speaker

Hackaday - 2 hours 25 minก่อน

Speakers are one of those components that are simple to use, but difficult to simulate. Most of us have used a simple resistor to do the job. But a speaker’s response is much more complex, and while that might be enough for a simple simulation the fidelity is nowhere near close. [Sourav Gupta] recently shared his technique for modeling speakers and it looks as though it does a credible job.

[Sourav] shows how a simple resistor and an inductor can do the job, but for better fidelity you need more components to model some mechanical effects. The final model has six components which keeps it easy enough to construct but the problem lies in finding the values of those six components. [Sourav] shows how to use the Thiele-Small parameters to solve that problem. Speaker makers provide these as a guide to low frequency performance, and they capture things such as Q, mass, displacement, and other factors that affect the model.

If you can find those parameters — often known as TSP — then you can use the formulae provided to get the component values. There’s even a real-word example for a specific speaker. We would have been interested to see how the simulation stacked up to a real speaker, but this is still an interesting post.

Of course, if you grab a surplus speaker you may or may not be able to find the TSP data. At that point, you could make some guesses or measurements, but it certainly won’t be as easy.

The techniques in the post were not simulator-specific, so they ought to work with whatever tool you use. Our favorite browser simulator, Falsted, doesn’t have a speaker (but it does have an audio output port). The same tricks should work in LT Spice, too.

Little Emulators Do 8 Bits At A Time

Hackaday - 5 hours 25 minก่อน

Have you ever wondered how many, for example, Commodore 64s it would take to equal the processing power in your current PC? This site might not really answer that, but it does show that your machine can easily duplicate all the old 8-bit computers from Commodore, Sinclair, Acorn, and others. By our count, there are 86 emulators on the page, although many of those are a host machine running a particular application such as Forth or Digger.

If you are in the US, you might not recognize all the references to the KC85, this was an East German computer based on a Z80 clone. Very few of these were apparently available for personal purchase, but they were very popular in schools and industry. These were made by Robotron, and there are some other Robotron models on the page, too.

If you aren’t interested in period games, there is still Forth, Basic, and even assembler for several of the machines. The emulation isn’t very snappy but probably is still faster than the real things. If you get stuck, it might pay to know that the Esc key is mapped to the break key.

Speaking of keyboards, the KC85 was notorious for having a very cheaply made “chiclet” keyboard. So using one with your full PC mechanical gaming keyboard feels like cheating. Of course, you don’t need a full PC to emulate an old computer. We’ve even seen the Commodore and the PC XT emulated on the ubiquitous ESP8266.

Retro Wall Phone Becomes A Doorbell, And So Much More

Hackaday - 8 hours 25 minก่อน

We have to admit that this retasked retro phone wins on style points alone. The fact that it’s filled with so much functionality is icing on the cake.

The way [SuperKris] describes his build sounds like a classic case of feature creep. Version 1 was to be a simple doorbell, but [SuperKris] would soon learn that one does not simply replace an existing bell with a phone and get results. He did some research and found that the ringer inside the bakelite beauty needs much more voltage than the standard doorbell transformer supplies, so he designed a little H-bridge circuit to drive the solenoids. A few rounds of “while I’m at it” later, the phone was stuffed with electronics, including an Arduino and an NFR24 radio module that lets it connect to Domoticz, a home automation system. The phone’s rotary dial can now control up to 10 events and respond to alarms and alerts with different ring patterns. And, oh yes – it’s a doorbell too.

In general, we prefer to see old equipment restored rather than gutted and filled with new electronics. But we can certainly get behind any effort to retask old phones with no real place in modern telecommunications. We’ve seen a few of these before, like this desk telephone that can make cell calls.

Scratch-Building A Supersized Laser Cutter

Hackaday - 11 hours 25 minก่อน

Now that 3D printers have more or less hit the mass market, hackers need a new “elite” tool to spend their time designing and fiddling with. Judging by the last couple of years, it looks like laser cutters will be taking over as the hacker tool du jour; as we’re starting to see more and more custom builds and modifications of entry-level commercial models. Usually these are limited to relatively small and low powered diode lasers, but as the following project shows, that’s not always the case.

This large format laser cutter designed and built by [Rob Chesney] is meticulously detailed on his blog, as well as in the in the video after the break. It’s made up of aluminium profile and a splattering of ABS 3D printed parts, and lives in an acrylic enclosure that’s uniquely isolated from the laser’s internal gantry. All told it cost about $2,000 USD to build, but considering the volume and features of this cutter that’s still a very fair price.

[Rob] carefully planned every aspect of this build, modeling the entire machine in CAD before actually purchasing any hardware. Interestingly enough his primary design constraint was the door to his shed: he wanted to build the largest possible laser cutter that could still be carried through it. That led to the final machine’s long and relatively shallow final dimensions. The design was also guided by a desire to minimize material waste, so when possible parts were designed to maximize how many could be cut from a one meter length of aluminum extrusion.

The laser features a movable Z axis that’s similar in design to what you might see in a Prusa-style 3D printer, with each corner of the gantry getting an 8 mm lead screw and smooth rod which are used in conjunction to lift and guide. All of the lead screws are connected to each other via pulleys and standard GT2 belt, but as of this version, [Rob] notes the Z axis must be manually operated. In the future he’ll be able to add in a stepper motor and automate it easily, but it wasn’t critical to get the machine running.

He used 3D printed parts for objects which had a relatively complex geometry, such as the laser tube holders and Z axis components, but more simplistic brackets were made out of cut acrylic. In some components, [Rob] used welding cement to bond two pieces of acrylic and thereby double the thickness. Large acrylic panels were also used for the laser’s outer enclosure, which was intentionally designed as a separate entity from the laser itself. He reasoned that this would make assembly easier and faster, as the enclosure would not have to be held to the same dimensional tolerances as it would have been if it was integrated into the machine.

[Rob] gives plenty of detail about all the finer points of water cooling, laser control electronics, aligning the mirrors, and really anything else you could possibly want to know about building your own serious laser cutter. If you’ve been considering building your own laser and have anything you’re curious or unsure about, there’s a good chance he addresses it in this build.

Short of having the fantastically good luck to find a laser cutter in the trash that you can refurbish, building your own machine may still be the best upgrade path if you outgrow your eBay K40.

Crowdfunded Gameband watch cancelled (no tiny screen Atari games for you)

Liliputing - 11 hours 30 minก่อน

The Gameband was supposed to be a watch with a 1.6 inch touchscreen display, the sort of hardware you’d expect to find in a smartwatch, and a focus on gaming — the developers partnered with Atari and planned to load the Gameband with games including Asteroids, breakout, Centipede and Pong. But a year and a […]

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Gorgeous Bartop Arcade Build is a Cut Above

Hackaday - 12 hours 56 minก่อน

At this point we’ve seen a good number of desktop-sized arcade cabinets, and while they’ve naturally all been impressive in their own ways, they do tend to follow a pretty familiar formula. Cut the side panels out of MDF (or just buy a frame kit), stick a Raspberry Pi and an old LCD monitor in there, and then figure out how to control the thing. Maybe a couple strategically placed stickers and blinking LEDs to add a few extra horsepower, but nothing too surprising.

[Andy Riley] had seen plenty of builds like that, and he wasn’t having any of it. With the heart of an old laptop and bones made of IKEA cutting boards, his build is proof positive that there’s always more than one way to approach a problem that most would consider “solved” already. From the start, he set out to design and build a miniature arcade cabinet that didn’t look and feel like all the other ones he’d seen floating around online, and we think you’ll agree he delivered in a big way.

Powering the arcade with an old laptop is really a brilliant idea, especially since you can pick up older models for a song now that they’re considered nearly disposable by many users. As long as it doesn’t have a cracked display, you’ll get a nice sized LCD panel and potentially a rather powerful computer to drive it. Certainly the graphical capabilities of even the crustiest of used laptops will run circles around the Raspberry Pi, and of course it opens the possibility of playing contemporary PC games. As [Andy] shows in his detailed write-up, using a laptop does take more custom work than settling for the Pi, but we think the advantages make a compelling case for putting in the effort.

Of course, that’s only half the equation. Arguably the most impressive aspect of this build is the cabinet itself, which is made out of a couple IKEA bamboo cutting boards. [Andy] used his not inconsiderable woodworking skills, in addition to some pretty serious power tools, to turn the affordable kitchen accessories into a furniture-grade piece that really stands out from the norm. Even if you aren’t normally too keen on working with dead trees, his step-by-step explanations and pictures are a fascinating look at true craftsman at work.

If you’re more concerned with playing Galaga than the finer points of varnish application, you can always just turbocharge the old iCade and be done with it. But we think there’s something to be said for an arcade cabinet that could legitimately pass as a family heirloom.

Daily Deals (11-20-2018)

Liliputing - 12 hours 58 minก่อน

The Lenovo IdeaPad 720s is a thin and light laptop that comes with a choice of Intel or AMD processors… but the AMD models are usually cheaper. And today a model with an AMD Ryzen 7 2700U processor, 8GB of RAM, and a 512GB SSD is cheaper than ever — Newegg is selling it for […]

The post Daily Deals (11-20-2018) appeared first on Liliputing.

The Linux Throwie: A Non-Spacefaring Satellite

Hackaday - 14 hours 24 minก่อน

Throwies occupy a special place in hardware culture — a coin cell battery, LED, and a magnet that can be thrown into an inaccessible place and stick there as a little beacon of colored light. Many of us will fondly remember this as a first project. Alas, time marches inevitably on, and launching cheerful lights no longer teaches me new skills. With a nod to those simpler times, I’ve been working on the unusual idea of building a fully functional server that can be left in remote places and remain functional, like a throwie (please don’t actually throw it). It’s a little kooky, yet should still deliver a few years of occasional remote access if you leave it somewhere with sunlight.

A short while ago, I described the power stages for this solar-powered, cloud accessible Linux server. It only activates on demand, so a small solar cell and modest battery are sufficient to keep the whole show running.

Where we left off, I had a solar cell that could charge a battery, and provide regulated 12v and 5v output. For it to be a functional device, there are three high level problems to solve:

  1. It must be possible to set up the device without direct physical access
  2. You must be able to remotely turn it on and off as needed.
  3. It needs to be accessible from the Internet.

The funny thing is, this hardware reminds me of a satellite. Of course it’s not meant to go into space, but I do plan to put it somewhere not easy to get to again, it runs off of solar power, and there’s a special subsystem (ESP8266) to tend the power, check for remote activation, and turn the main computer (Raspberry Pi 3) on and off as necessary. This sounds a lot like space race tech, right?

As I have a bit more code than usual to share with you today, I’ll discuss the most interesting parts, and provide links to the full firmware files at the end of the article.

Device Setup

Device setup is a good place to start, and it has two components: the operating system on the Raspberry Pi 3 (in this case Raspbian Stretch Lite), and the low-power systems that control whether the Raspberry Pi 3 is turned on or off. In both cases, we handle this by scanning for a wireless network with known SSID (say from your mobile phone).

In Raspbian, this is pretty easy – we open up /etc/network/interfaces and set the priority of our configuration network to a high number:

network={ ssid = "setup network name" psk = "setup network password" priority = 999 }

For our power control hardware, there is a module available in NodeMCU called ‘end user setup’ that allows you to connect to the ESP8266 remotely, scan for networks, and connect to one of them, saving the credentials. All we need to do is selectively run a program containing it when a certain hotspot is in range:

function listap() dofile('setup.lua') end scan_cfg = {} scan_cfg.ssid = "setup network name" scan_cfg.show_hidden = 1 wifi.sta.getap(scan_cfg, 1, listap)

Then in setup.lua, we run end user setup. This causes the ESP8266 to act as a hotspot named ‘SetupGadget’ followed by a few hex digits:

enduser_setup.start( function() print("Connected to wifi as:" .. wifi.sta.getip()) end, function(err, str) print("enduser_setup: Err #" .. err .. ": " .. str) end ) tmr.alarm(1,1000, 1, function() if wifi.sta.getip()==nil then print(" Wait for IP address!") else print("New IP address is "..wifi.sta.getip()) tmr.stop(1) node.dsleep(2000000) end end)

With this set up, we can connect the server and controlling hardware to a new wireless network without direct physical access. Solar power requires light, this is likely going to be on my roof, and I don’t relish the idea of climbing up to get it any time I need to reset my home WiFi password. If you have a really tall roof, build yourself a directional waveguide antenna — I’ve been able to get a range of over 100 meters this way, through several concrete buildings. There’s also Brian Benchoff’s 3D-printable ESP8266 dish antenna.

Remote Power Control

Next, we need to be able to remotely turn the server on or off. We’ll do this with MQTT pointed at a domain name that resolves to a cloud VPS. The only thing you’ll need on that VPS is the mosquito MQTT broker, so no sense in paying for a high-end server. Note that there are ways to implement some basic security here, but for the sake of brevity, I’ll leave that as an exercise for you to explore on your own.

Note that our hardware is only active occasionally – I’ve set it to wake up every 15 minutes or so to check the MQTT broker. To make sure it receives messages, the sender needs to set the “retain” flag when sending the activation command. This guarantees that the message will be there when the ESP8266 wakes up and checks for new messages, as long as we don’t replace it with some other retained message. A short example in Python for an MQTT broker at domain.com, and topic solarserver:

import paho.mqtt.client as mqtt #import the client broker_address="domain.com" client = mqtt.Client("P1") #create new instance client.connect(broker_address, port=1883) #connect to broker client.publish("solarserver", payload="activate", qos=0, retain=True)

On our ESP8266, we check for the command ‘activate’ and then run a program that turns on the Raspberry Pi 3:

ClientID = 'Node001' m = mqtt.Client(ClientID, 120) m:connect("domain.com", 1883, 0, function(client) print("connected") client:subscribe("/solarserver", 0, function(client) print("subscribe success") end) end) m:on("message", function(client, topic, data) print(topic .. ":" ) if data ~= nil then print(data) if data == "activate" then dofile('active.lua') m:close() end end end)

The program ‘active.lua’ raises a GPIO high to enable the 5v line to the Raspberry Pi 3, and monitors the battery voltage. If the battery voltage drops too low, or a shutdown command is received, it will cut power (shutting down first is a good idea).

Digging Deeper Into SSH Tunnels

What good does it do us though, if we can turn the device on but not access it? As I plan to move this device around for software demos, it would be great if I didn’t have to worry too much about firewalls, routers, and other drudgery that it might be behind. This is where we explore reverse SSH tunnels.

Normally, you establish an SSH connection because you want secure shell access to a remote machine, and have a certificate or username+password pair along with the address of the machine. In this situation, the address of the client and state of its network (the routers it is behind and so on) is not usually important, but the address of the server is assumed to be known and all port forwarding and firewall settings configured to accept the traffic.

In a reverse SSH connection, the server initiates a connection to the client that is used to allow the client to connect back to the server. On initiating the connection from server to client, you specify a port. When logged into the client, you use SSH to log in to localhost on that port, and the traffic will be sent to the server, allowing you to log in.

We’ll need to automate this process for it to be useful. The first step is to create a user (your_username in this example) with restricted access on your VPS. Our server will be automatically logging in to it, doing this with the root account is probably a terrible idea if you have anything there you remotely value. Note the password for this new user.

Next we power on the Raspberry Pi 3 (we’ll assume you use Raspbian Lite here), set a new root password, install autossh to manage the connection, create a new user (same name as the VPS user) with a certificate, and finally copy that certificate using SSH-copy-id to our VPS:

$apt-get install autossh $useradd -m -s /bin/bash your_username $su – your_username $ssh-keygen -t ed25519 $ssh-copy-id your_username@(VPS IP address) -p 22

Then we run raspi-config to enable the SSH server and have that user automatically logged in at boot. Now we’re set up to log in to our VPS over SSH with certificates instead of a username+password pair, which is easier to automate. Let’s establish a reverse SSH tunnel from our Raspberry Pi 3 to test it:

$autossh -M 0 your_username@(VPS IP address) -p 22 -N -R 8081:localhost:22 -vvv

If that succeeds, you ought to be able to establish an SSH connection to your Raspberry Pi from your VPS via the command:

$ssh your_username@localhost -p 8081

Assuming that works as intended, we move on to creating a service that establishes that connection a few seconds after the network interfaces go up. We’ll do this with systemctl, but first we need to create a short shell script for systemctl to call. Create a file autossh.sh, make it executable (e.g. with chmod), and populate it with:

sleep 15 autossh -M 0 your_username@(VPS IP address) -p 22 -N -R 8081:localhost:22 -vvv

The ‘sleep 15’ waits for 15 seconds after network interfaces go up during boot. Without this, I found that the script runs slightly too early, and I cannot resolve the VPS host. There are more elegant ways to fix this, but this was the easiest. Now we create the service that runs this script with:

$systemctl edit --force --full autoautossh.service

We then enter the following, then save the file:

[Unit] Description=My Script Service Wants=network-online.target After=network-online.target [Service] Type=simple User=pi WorkingDirectory=/home/your_username ExecStart=/bin/bash /home/your_username/autossh.sh [Install] WantedBy=multi-user.target

Then we enable it and test it. After the second command, the reverse SSH tunnel should be operational and you can try it – if it doesn’t work now, it won’t work on boot either:

$systemctl enable autoautossh.service $systemctl start autoautossh.service

If you have access now, then it ought to automatically establish the reverse SSH tunnel after boot, and also automatically re-establish it if it gets broken. If you’re having trouble with poor network connections, you might investigate Mosh as an alternative to SSH.

The case should probably be white, given that it’s going to be sitting in the sun a lot. Two solar panels fit nicely, so now it uses 0.6W of solar panels. Hot glue is to fill the small gap between the panels and the case, and for cosmetic effect, of course.

At this point, you’re more or less done: just plug the 5V output of your power stages into your Raspberry Pi and put it in a weatherproof box. When you send a retained message ‘activate’ to your MQTT topic, the server will turn on within 15 minutes or so. I recommend testing it and listening to the MQTT topic a while to make sure it all works as expected and so that you have an idea how long the battery lasts.

As promised, here is the full firmware source code. Dig through it an leave any questions you have in the comments section below. I’d also love to hear what you’d use a Linux throwie for?

Valve retires Steam Link in-home game streaming device

Liliputing - 14 hours 56 minก่อน

Valve’s Steam Link is a small device that lets you stream PC games to your TV. Connect the $50 device to your TV with an HDMI cable, plug in an Ethernet cable, and connect a game controller and it’s like having a gaming PC in your living room… without having to actually move your gaming […]

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The slow death of the disc drive continues (next Xbox One may not have one)

Liliputing - อังคาร, 11/20/2018 - 23:51

Readers of a certain age probably amassed a significant collection of CDs, DVDs, and maybe even Blu-ray discs in the days before digital downloads largely took over (and vinyl made a somewhat comeback). These days you don’t see a lot of CD or DVD players at electronics stores. And it’s becoming more and more rare […]

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Rapid-Fire Hail Of Chopstick Arrows Makes Short Work Of Diminutive Foes

Hackaday - อังคาร, 11/20/2018 - 23:30

Many Hackaday readers may also be familiar with the Discworld series of fantasy novels from [Terry Pratchett], and thus might recognise a weapon referred to as the Piecemaker. A siege crossbow modified to launch a hail of supersonic arrows, it was the favoured sidearm of a troll police officer, and would frequently appear disintegrating large parts of the miscreants’ Evil Lairs to comedic effect.

Just as a non-police-officer walking the streets of Ank-Morpork with a Piecemaker might find swiftly themselves in the Patrician’s scorpion pit, we’re guessing ownership of such a fearsome weapon might earn you a free ride in a police car here on Roundworld. But those of you wishing for just a taste of the arrow-hail action needn’t give up hope, because [Turnah81] has made something close to it on a smaller scale. His array of twelve mousetrap-triggered catapults fires a volley of darts made from wooden kebab skewers in an entertaining fashion, and has enough force to penetrate a sheet of cardboard.

He refers to a previous project with a single dart, and this one is in many respects twelve of that project in an array. But in building it he solves some surprisingly tricky engineering problems, such as matching the power of multiple rubber bands, or creating a linkage capable of triggering twelve mousetraps (almost) in unison. His solution, a system of bent coat-hanger wires actuated by the falling bar of each trap, triggers each successive trap in a near-simultaneous crescendo of arrow firepower.

On one hand this is a project with more than a touch of frivolity about it. But the seriousness with which he approaches it and sorts out its teething troubles makes it an interesting watch, and his testing it as a labour-saving device for common household tasks made us laugh. Take a look, we’ve put the video below the break.

Flagging Down Aliens with World’s Biggest Laser Pointer

Hackaday - อังคาร, 11/20/2018 - 22:00

As you’re no doubt aware, humans are a rather noisy species. Not just audibly, like in the case of somebody talking loudly when you’re in a movie theater, but also electromagnetically. All of our wireless transmissions since Marconi made his first spark gap broadcast in 1895 have radiated out into space, and anyone who’s got a sensitive enough ear pointed into our little corner of the Milky Way should have no trouble hearing us. Even if these extraterrestrial eavesdroppers wouldn’t be able to understand the content of our transmissions, the sheer volume of them would be enough to indicate that whatever is making all that noise on the third rock orbiting Sol can’t be a natural phenomena. In other words, one of the best ways to find intelligent life in the galaxy may just be to sit around and wait for them to hear us.

Of course, there’s some pesky physics involved that makes it a bit more complicated. Signals radiate from the Earth at the speed of light, which is like a brisk walk in interstellar terms. Depending on where these hypothetical listeners are located, the delay between when we broadcast something and when they receive it can be immense. For example, any intelligent beings that might be listening in on us from the closest known star, Proxima Centauri, are only just now being utterly disappointed by the finale for “How I Met Your Mother“. Comparatively, “Dallas” fans from Zeta Reticuli are still on the edge of their seats waiting to find out who shot J.R.

But rather than relying on our normal broadcasts to do the talking for us, a recent paper in The Astrophysical Journal makes the case that we should go one better. Written by James R. Clark and Kerri Cahoy,  “Optical Detection of Lasers with Near-term Technology at Interstellar Distances” makes the case that we could use current or near-term laser technology to broadcast a highly directional beacon to potentially life-harboring star systems. What’s more, it even theorizes it would be possible to establish direct communications with an alien intelligence simply by modulating the beam.

A Laser to Rival the Sun

At interstellar distances, it’s very difficult to discern a planet from the star it’s orbiting. This is why we’ve only been able to directly image a small number of exoplanets; the only reason we know they are there is by watching for dips in the light output of their host star. The same is of course true in reverse. An alien intelligence that has a telescope pointed towards our solar system is really just going to be looking at our sun. That means any laser we fire out into space with the intention of getting somebody’s attention would need to appear brighter than the sun, otherwise it would be like somebody on the Moon trying to get our attention with a flashlight.

This would require a laser in the megawatt range that could be fired continuously or at least in bursts of several seconds. Admittedly it’s a pretty tall order, but not beyond our current level of technology. The US Air Force explored using an aircraft mounted megawatt laser as an anti-missile weapon in the mid-1990’s, which culminated with the development of the Boeing YAL-1. In 2010 the YAL-1 demonstrated it was possible to track and destroy ballistic missiles during their boost phase using its chemical oxygen iodine laser (COIL), though ultimately the project was canceled due to the tremendous costs involved in building and maintaining an operational fleet of the aircraft.

Regardless of its failings as a practical weapon, Clark and Cahoy cite the YAL-1 as proof that a similar laser could be constructed for interstellar communication. If the military can develop a megawatt laser that can fire for long enough to destroy a missile while still being small and light enough to mount in a modified 747, there’s no technical reason it couldn’t be done in an observatory on the ground.

As an added bonus, the COIL technology pioneered by the Air Force produces an infrared beam with a frequency of 1315 nm. This is particularly advantages for signaling purposes as our sun doesn’t produce much light at this wavelength, so the laser’s beam intermixed with light from the sun would be seen from a distant observer’s perspective as a star with a wildly fluctuating spectral output; an anomaly no alien astronomer could ignore.

Bringing it into Focus

As Clark and Cahoy explain, the megawatt class laser is only half the puzzle; it would still need similarly supersized optics to deliver the beam with the optimal divergence. But even here the hardware they have in mind, namely a 30 m to 45 m telescope, isn’t beyond our reach. The paper specifically mentions that the Thirty Meter Telescope Observatory (TMT) currently in the planning phases and scheduled to be operational by 2030 could provide adequate beam characteristics if it were paired with a 2 MW laser.

Artist’s impression of TMT primary mirror

Somewhat counterintuitively, the paper argues that a tightly focused beam is not the ideal choice for flagging down our celestial neighbors. For one, such a beam would need to be aimed and tracked with exceptionally high accuracy to hit a target tens or even hundreds of light-years away. More importantly, our ability to detect distant planets is still too rough to produce models of their orbits with sufficient accuracy; we simply don’t know where to aim the laser.

The solution is a beam that has a large enough divergence to compensate for our poor aim. In fact, Clark and Cahoy suggest a beam wide enough to illuminate large swath’s of a star system could be ideal in some scenarios. Multiple planets within a star’s habitable zone would be able to see our laser at the same time, greatly reducing the amount of repositioning we’d have to do on our end.

Against the Odds

Of course, there’s still plenty of variables in play that make such an attempt a very literal shot in the dark. For instance we can fire our laser towards Gliese 667, where Kepler previously detected a planet within its habitable zone, but its possible that the organisms who reside on that planet are insectoids with no appreciable technology. So whether it’s a rerun of “I Love Lucy” or a blast of infrared light from across the cosmos, they aren’t likely to pay it much mind and we come away with no more knowledge of our place in the universe than we had before.

But paling in comparison to technological or logistical hurdles is the most obvious problem: the economics of such a system. If even the United States Air Force didn’t think it was cost effective to continue operating a megawatt laser that proved it could destroy incoming ballistic missiles, who would possibly pick up the tab for an even more powerful and elaborate long-shot that arguably has no practical function other than to placate our yearning for exploration? Missions to the Moon or Mars can be argued to have practical benefits to mankind that offset their multi-billion dollar price tags, but shining a monstrous laser into the eyes of alien creatures that may or may not even exist for nearly the same price is a much tougher sell.

In the end, James R. Clark and Kerri Cahoy make a compelling and well-reasoned argument for interstellar laser communications. That the idea could work, and that it’s within humanity’s capabilities to bring such a system online within the next few decades is difficult to refute. But like so many great ideas, it seems unlikely it will ever see the light of day without the sort of concerted global effort that to date we’ve been largely unable to muster.

ODROID-H2 Gemini Lake single-board PC launches for $111

Liliputing - อังคาร, 11/20/2018 - 21:50

About a month after unveiling plans to sell its first single-board computer powered by an Intel processor, Hardkernel is now taking orders for the ODROID-H2. It’s priced at $111 and features a 10 watt, quad-core Intel Celeron J4105 processor and a 4.3″ x 4.3″ x 1.7″ with a bunch of ports, two slots for DDR4 […]

The post ODROID-H2 Gemini Lake single-board PC launches for $111 appeared first on Liliputing.

[Ben Krasnow] Gasses MEMS Chips, for Science

Hackaday - อังคาร, 11/20/2018 - 19:00

Why in the world does helium kill iPhones and other members of the Apple ecosystem? Enquiring minds want to know, and [Ben Krasnow] has obliged with an investigation of the culprit: the MEMS oscillator. (YouTube, embedded below.)

When we first heard about this, courtesy in part via a Hackaday post on MRI-killed iPhones, we couldn’t imagine how poisoning a micro-electromechanical system (MEMS) part could kill a phone. We’d always associated MEMS with accelerometers and gyros, important sensors in the smartphone suite, but hardly essential. It turns out there’s another MEMS component in many Apple products: an SiT 1532 oscillator, a tiny replacement for quartz crystal oscillators.

[Ben] got a few from DigiKey and put them through some tests in a DIY gas chamber. He found that a partial pressure of helium as low as 2 kPa, or just 2% of atmospheric pressure, can kill the oscillator. To understand why, and because [Ben] has a scanning electron microscope, he lapped down some spare MEMS oscillators to expose their intricate innards. His SEM images are stunning but perplexing, raising questions about how such things could be made which he also addresses.

The bottom line: helium poisons MEMS oscillators in low enough concentrations that the original MRI story is plausible. As a bonus, we now understand MEMS devices a bit better, and have one more reason never to own an iPhone.

The Electric Imp Sniffs out California Wildfires

Hackaday - อังคาร, 11/20/2018 - 16:00

The wildfires in California are now officially the largest the state has ever seen. Over 50,000 people have been displaced from their homes, hundreds are missing, and the cost in property damage will surely be measured in the billions of dollars when all is said and done. With a disaster of this scale just the immediate effects are difficult to conceptualize, to say nothing of the collateral damage.

While not suggesting their situation is comparable to those who’ve lost their homes or families, Electric Imp CEO [Hugo Fiennes] has recently made a post on their blog calling attention to the air quality issues they’re seeing at their offices in Los Altos. To quantify the problem so that employees with respiratory issues would know the conditions before they came into work, they quickly hacked together a method for displaying particulate counts in their Slack server.

The key to the system is one of the laser particle sensors that we’re starting to see more of thanks to a fairly recent price drop on the technology. A small fan pulls air to be tested into the device, where a very sensitive optical sensor detects the light reflected by particles as they pass through the laser beam. The device reports not only how many particles are passing through it, but how large they are. The version of the sensor [Hugo] links to in his blog post includes an adapter board to make it easier to connect to your favorite microcontroller, but we’ve previously seen DIY builds which accomplish the same goal.

[Hugo] then goes on to provide firmware for the Electric Imp board that reads the current particulate counts from the sensor and creates a simple web page that can be viewed from anywhere in the world to see real-time conditions at the office. From there, this data can be plugged into a Slack webhook which will provide an instantaneous air quality reading anytime a user types “air” into the channel.

We’ve covered a number of air quality sensors over the years, and it doesn’t look like they’re going to become any less prevalent as time goes on. If anything, we’re seeing a trend towards networks of distributed pollution sensors so that citizens can collect their own data on their air they’re breathing.

[Thanks to DillonMCU for the tip.]

DIY Mini Helical Antennas From Salvaged Co-ax Cable

Hackaday - อังคาร, 11/20/2018 - 13:00

[Mare] has a visual guide and simple instructions for making DIY mini helical 868 MHz antennas for LoRa applications. 868 MHz is a license-free band in Europe, and this method yields a perfectly serviceable antenna that’s useful where space is constrained.

A metric 5 mm drill bit makes a convenient core.

The process is simple and well-documented, but as usual with antenna design it requires attention to detail. Wire for the antenna is silver-plated copper, salvaged from the core of RG214U coaxial cable. After straightening, the wire is wound tightly around a 5 mm core. 7 turns are each carefully spaced 2 mm apart. After that, it’s just a matter of measuring and bending the end for soldering to the wireless device in question. [Mare] has used this method for wireless LoRa sensors in space-constrained designs, and it also has the benefit of lowering part costs since it can be made and tested in-house.

Antennas have of course been made from far stranger things than salvaged wire; one of our favorites is this Yagi antenna made from segments of measuring tape.

A Candle Powered Guitar Pedal

Hackaday - อังคาร, 11/20/2018 - 10:00

When it comes to guitar effects pedals, the industry looks both back and forward in time. Back to the 50’s and 60’s when vacuum tubes and germanium transistors started to define the sound of the modern guitar, and forward as the expense and rarity of parts from decades ago becomes too expensive, to digital reproductions and effects. Rarely does an effects company look back to the turn of the 19th century for its technological innovations, but Zvex Effects’ “Mad Scientist,” [Zachary Vex], did just that when he created the Candela Vibrophase.

At the heart of the Candela is the lowly tea light. Available for next to nothing in bags of a hundred at your local Scandinavian furniture store, the tea light powers the Zvex pedal in three ways: First, the light from the candle powers the circuit by way of solar cells, second, the heat from the candle powers a Stirling engine, a heat engine which powers a rotating disk. This disc has a pattern on it which, when rotated, modifies the amount of light that reaches the third part of the engine – photoelectric cells. These modulate the input signal to create the effects that give the pedal its name, vibrato and phase.

Controls on the engine adjust the amount of the each effect. At one end, the effect is full phasor, at the other, full vibrato. In between a blend of the two. A ball magnet on a pivot is used to control the speed of the rotating disk by slowing the Stirling engine’s flywheel as it is moved closer.

While more of a work of art than a practical guitar effect, if you happen to be part of a steam punk inspired band, this might be right up your alley. For more information on Stirling engines, take a look at this post. Also take a look at this horizontal Stirling engine.

A Hacked Solution For Non-Standard Audio Modules

Hackaday - อังคาร, 11/20/2018 - 07:00

When life hands you lemons, lemonade ends up being your drink of choice. When life hands you non-standard components, however, you’ve got little choice but to create your own standard to use them. Drinking lemonade in such a situation is left to your discretion.

The little audio record and playback modules [Fran Blanche] scored from eBay for a buck a piece are a good example. These widgets are chip-on-board devices that probably came from some toy manufacturer and can record and playback 20 seconds of audio with just a little external circuitry. [Fran] wants to record different clips on a bunch of these, and pictured using the card-edge connector provided to plug them the recording circuit. But the pad spacing didn’t fit any connector she could find, so she came up with her own. The module and a standard 0.1″ (2.54 mm) pitch header are both glued into a 3D-printed case, and the board is connected to the header by bonding wires. It makes a nice module that’s easily plugged in for recording, and as [Fran] points out, it’s pretty adorable to boot. Check it out in the video below.

Sure, the same thing could have been accomplished with a custom PCB breaking out the module’s pins to a standard card-edge connector. But [Fran] knows a thing or two about ordering PCBs, and our guess is she wanted to get this done with what was on hand rather than wait for weeks. There’s something to be said for semi-instant gratification, after all. And lemonade.

Calibrate a magnetic sensor

dangerous prototype - อังคาร, 11/20/2018 - 05:40

Liudr shared a how-to on calibrating a sensor:

First of all, what is calibration? In a general sense, calibrating a sensor makes the sensor provide the most accurate readings allowed by the sensor’s own precision. As an example, let’s assume for a moment that the earth’s magnetic field and any other stray magnetic fields are shielded and you have a uniform magnetic field generated artificially for the sole purpose of calibration. Let’s say that the field strength is 400 mG (milliGauss), equivalent to 40,000 nT (nanoTesla). Now if you align one axis of your magnetic sensor parallel to the direction of the field, it should read 400mG. If you then carefully rotate your sensor so that the axis is anti-parallel with your field, it will read -400mG. If you didn’t do a good job in either alignments, you will read less values, say 390mG, if you’re off by about 13 degrees, because only a portion of the field, which is a vector, is projected along your magnetic sensor’s axis.

See the full post on Liudr’s blog.

A 3D Printed Kinematic Camera Mount

Hackaday - อังคาร, 11/20/2018 - 04:00

[Enginoor] is on a quest. He wants to get into the world of 3D printing, but isn’t content to run off little toys and trinkets. If he’s going to print something, he wants it to be something practical and ideally be something he couldn’t have made quickly and easily with more traditional methods. Accordingly, he’s come out the gate with a fairly strong showing: a magnetic Maxwell kinematic coupling camera mount.

If you only recognized some of those terms, don’t feel bad. Named for its creator James Clerk Maxwell who came up with the design in 1871, the Maxwell kinematic coupling is self-orienting connection that lends itself to applications that need a positive connection while still being quick and easy to remove. Certainly that sounds like a good way to stick a camera on a tripod to us.

But the Maxwell design, which consists of three groves and matching hemispheres, is only half of the equation. It allows [enginoor] to accurately and repeatably line the camera up, but it doesn’t have any holding power of its own. That’s where the magnets come in. By designing pockets into both parts, he was able to install strong magnets in the mating faces. This gives the mount a satisfying “snap” when attaching that he trusts it enough to hold his Canon EOS 70D and lens.

[enginoor] says he could have made the holes a bit tighter for the magnets (thereby skipping the glue he’s using currently), but otherwise his first 3D printed design was a complete success. He sent this one off to Shapeways to be printed, but in the future he’s considering taking the reins himself if he can keep coming up with ideas worth committing to plastic.

Of course we’ve seen plenty of magnetic camera mounts in the past, but we really like the self-aligning aspect of this design. It definitely seems to fit the criterion for something that would otherwise have been difficult to fabricate if not for 3D printing.

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