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Powering Your Mining Rig The Right Way

อาทิตย์, 12/17/2017 - 22:00

It happens to the best of us. We power up our project and immediately run into issues. Be it spotty communication or microcontroller reset or any number of bugs that have us mystified and picking though our code… only to find that it’s a power supply issue. Anyone who has tried doing Raspberry Pi stuff and depended on the USB power from their PC has certainly been bit by this.

It’s the same with larger, more power hungry projects as well. [Nerd Ralph] has been running a mining rig for a few years now, and has learned just how important proper power supply management can be. His strategy involves using interlocks to ensure everything powers up at the same time to avoid feedback problems, running a separate ground wire between all GPU cards and the PSU and running the supplies at 220 for the NA folks.

Be sure to check out [Nerd Ralph’s] blog for more details and tips to power your own mining rig.

Filed under: Misc Hacks

Final Project for Better Sleep

อาทิตย์, 12/17/2017 - 19:00

It’s that time of year again, and students around the world are scrambling (or have already scrambled) to finish their final projects for the semester. And, while studying for finals prevents many from sleeping an adequate amount, [Julia] and [Nick] are seeking to maximize “what little sleep the [Electrical and Computer Engineering] major allows” them by using their final project to measure sleep quality.

To produce a metric for sleep quality, [Julia] and [Nick] set out to measure various sleep-related activities, specifically heart rate, motion and breath frequency. During the night, an Arduino Nano mounted to a glove collects data from the various sensors mounted to the user, all the while beaming the data to a stationary PIC for analysis and storage. When the user awakes, they can view their sleep report on a TFT display at the PIC base station. Ideally, users would use this data to test different habits in order to get the best nights sleep possible.

Interestingly, the group chose to implement their own heart rate sensor. With an IR transmitter, IR phototransistor and an OP amp, the group illuminates user’s fingers and measure reflection to detect heartbeats. This works because the amount of IR reflected from the user’s finger changes with blood pressure and blood oxygen level, which also happen to change when the heart is beating. There were some bumps along the road when it came to the heartbeat sensor (the need to use a finger instead of the wrist forced them to use a glove instead of a wristband), but we think it’s super cool and totally worth it. In addition to heart rate, motion is measured by an accelerometer and breath is measured by a flex sensor wrapped around the user’s chest.

With all of their data beamed back by a pair of nRF24L01s, the PIC computes the sleep “chaos” which is exactly what it sounds like: it describes just how chaotic the user slept by looking for acyclic and sudden movement. Using this metric, combined with information from breathing and heart rate, the PIC computes a percentage for good sleep where 100% is a great night and 0% means you might have been just as well off pulling an all-nighter. And, to top it all off, the PIC saves your data to an SD card for easy after-the-fact review.

The commented code that powers the project can be found here along with a parts list in their project write-up.

This device assumes that sleeping is the issue, but if waking up if your problem, we’ve already got you covered, aggressive alarm clock style. For those already on top of their sleep, you might want some help with lucid dreaming.

Video of the project explained by [Julia] and [Nick] after the break.

Thanks to [Nick] for sending this in!

Filed under: hardware

Google’s AIY Vision Kit Augments Pi With Vision Processor

อาทิตย์, 12/17/2017 - 16:00

Google has announced their soon to be available Vision Kit, their next easy to assemble Artificial Intelligence Yourself (AIY) product. You’ll have to provide your own Raspberry Pi Zero W but that’s okay since what makes this special is Google’s VisionBonnet board that they do provide, basically a low power neural network accelerator board running TensorFlow.

AIY VisionBonnet with Myriad 2 (MA2450) chip

The VisionBonnet is built around the Intel® Movidius Myriad 2 (aka MA2450) vision processing unit (VPU) chip. See the video below for an overview of this chip, but what it allows is the rapid processing of compute-intensive neural networks. We don’t think you’d use it for training the neural nets, just for doing the inference, or in human terms, for making use of the trained neural nets. It may be worth getting the kit for this board alone to use in your own hacks. An alternative is to get Modivius’s Neural Compute Stick, which has the same chip on a USB stick for around $80, not quite double the Vision Kit’s $45 price tag.

The Vision Kit isn’t out yet so we can’t be certain of the details, but based on the hardware it looks like you’ll point the camera at something, press a button and it will speak. We’ve seen this before with this talking object recognizer on a Pi 3 (full disclosure, it was made by yours truly) but without the hardware acceleration, a single object recognition took around 10 seconds. In the vision kit we expect the recognition will be in real-time. So the Vision Kit may be much more dynamic than that. And in case it wasn’t clear, a key feature is that nothing is done on the cloud here, all processing is local.

The kit comes with three different applications: an object recognition one that can recognize up to 1000 different classes of objects, another that recognizes faces and their expressions, and a third that detects people, cats, and dogs. While you can get up to a lot of mischief with just that, you can run your own neural networks too. If you need a refresher on TensorFlow then check out our introduction. And be sure to check out the Myriad 2 VPU video below the break.

This is the second AIY kit that Google has released, the first being the Voice Kit, which we also covered. That inspired our own [Inderpreet Singh] to, within just a couple of weeks, come out with his own equivalent voice kit.

Here’s the Myriad 2 VPU video. For the meatier hardware overview, skip to around 2:25.



Filed under: google hacks, Raspberry Pi

Neural Network Learns SDR Ham Radio

อาทิตย์, 12/17/2017 - 13:00

Identifying ham radio signals used to be easy. Beeps were Morse code, voice was AM unless it sounded like Donald Duck in which case it was sideband. But there are dozens of modes in common use now including TV, digital data, digital voice, FM, and more coming on line every day. [Randaller] used CUDA to build a neural network that could interface with an RTL-SDR dongle and can classify the signals it hears. Since it is a neural network, it isn’t so much programmed to do it as it is trained. The proof of concept has training to distinguish FM, SECAM, and tetra. However, you can train it to recognize other modulation schemes if you want to invest the time into it.

It isn’t that big of a task to identify signals using your built-in neural network. However, this is a great example of a practical neural net and it does open the door to other possibilities. For example, automated monitoring of multiple channels would need something like this.

One interesting tidbit is that the neural network doesn’t really know what it is learning, so input samples could be IQ samples, audio, or even waterfall graphics. You just have to use the same input to train that you want to use during operation. In fact, the code apparently started out as an image classification network from a course by Stanford.

If this gives you the urge to go out and buy an RTL-SDR dongle, you might want to look at some reviews. What else could you do with an intelligent radio? We’ve already seen a different kind of neural network decode Enigma traffic.

Filed under: Wireless Hacks

If 3D Printer, Then Custom Aluminum Extrusion Brackets

อาทิตย์, 12/17/2017 - 10:00

Aluminum extrusions are a boon for mechanical assemblies, but they require a stock of brackets and other hardware to be kept on hand. [mightynozzle] has decided to make things a little easier for prototyping and low-stress assemblies by creating a collection of 3D printable brackets for aluminum extrusions. 3D printing your own bracket hardware means faster prototyping, and if the assemblies don’t need the extra strength and rigidity of metal brackets you can just stick with the 3D printed versions.

The files are on Thingiverse, and include STL files of common brackets as well as an OpenSCAD script for customizing. Not familiar with OpenSCAD? No problem, we have a quick primer with examples.

This project showcases two things well. The first is that while brackets are not particularly expensive or hard to obtain, it can still be worth 3D printing them to reduce the overall amount of hardware one needs to keep on hand to make prototyping faster. The other is that 3D printing can shine when it comes to the creation of things like brackets: a few dimes’ worth of plastic can be turned into precise yet geometrically simple objects that would be a pain to make by other means. It certainly beats sitting on one’s hands waiting for parts to be delivered.

Filed under: 3d Printer hacks, hardware

Poor Man’s Laser Scanner Probably Won’t Shoot Your Eye Out, Kid

อาทิตย์, 12/17/2017 - 07:00

Yes, laser cutters that come off the slow boat from China are more affordable than ever, and with some tweaks and hacks they can turn out some decent results. But if you just want a laser lightshow that’ll draw boxes on your living room ceiling, this simple X-Y laser scanner might be a good platform to build.

Let’s say right up front that there are more than a few safety issues with [ThingEngineer]’s 3D-printed two-axis scanner. He’s well aware of these potential retina-cooking issues and duly notes that a good pair of laser safety goggles is a must and that the cheap anti-lawsuit glasses that laser module manufacturers often include with their products don’t count.

[Editor’s Note: Glasses are really only intended for alignment operations. Pros enclose lasers beyond a certain power to prevent anyone going blind. Know where your beam terminates, kids.]

With that in mind, there’s a lot to be said for this poor man’s scanner build. Yes, it would be faster with real galvos and low-mass mirrors, but time is money, and the steppers and craft store mirror discs do the job, albeit slowly. We like that everything is so simple, even the method for turning a regular mirror into a front-surface mirror.

[ThingEngineer] proves you don’t need galvanometers to have some simple laser fun. And if steppers don’t do it for you, you can try little brushed DC hobby motors or even 3D-printed cams.

Filed under: Laser Hacks

Hangprinter Build Videos

อาทิตย์, 12/17/2017 - 04:00

We figure with the rise in 3D printing, it is time for a new Finagle’s law: Any part you want to print won’t fit on your print bed. There was a time when a 100 mm x 100 mm bed was common for entry-level printers. These days, more printers have beds around (200 mm)2. A hangprinter’s work area can be larger. Much larger. [Thomas Sanladerer] is building one, and has a series of videos about the build. You can see the first one below, but there are several posted, including about 11 hours of recordings of live sessions of the build.

If you haven’t heard of a hangprinter, it is essentially a 3D print head that — well — hangs from cables and can turn an entire room into a 3D printer. When we looked at the original, it was printing a five-foot tall model of the tower of Babel.

The hangprinter is true to its RepRap roots, with a lot of self-printed parts, and an open source design. Even if you don’t want to build one, watching the videos can show you a lot about how one works.

If you want something more conventional, several of us have been hacking on Anet A8s. Sometimes you don’t care about  having a lot of build volume for one part, but you do care about having a lot of volume to make multiple parts, but that’s a different problem.

Filed under: 3d Printer hacks

Better 3D Printing Through Holography

อาทิตย์, 12/17/2017 - 01:00

When most of us think about 3D printing, we usually think about a machine that melts plastic filament and extrudes it through a nozzle. But we all know that there are other technologies out there that range from cutting and laminating paper, to printing with molten metal or glass. Many of those are out of range for the common hacker. Probably the second most common method uses photo resin and some light source to build the layers in the resin. Researchers at Lawrence Livermore National Laboratory (LLNL) and several universities are experimenting with a new technique that exposes photo resin using three lasers, printing an entire object at one time. You can see a cube formed using the technique in the video below.

In all fairness, the process really isn’t holography but LLNL refers to it as “hologram-like.” In fact, it appears the lasers project more like an oblique projection (you know, like in drafting) which is considerably simpler. Simple enough, that we can’t help but wonder if the hacker community couldn’t develop machines based on this principle. The key would be arranging for the resin to only cure where laser light overlaps.

In addition to being fast, the researchers note that because the object forms all at once, it doesn’t have problems associated with layering or being formed in a particular direction. The technique has printed beams, planes, struts at arbitrary angles, lattices and complex curved objects.

There’s clearly work to be done to improve the process. Complex objects would require lots of lasers. There is also a fine balance between underexposing the resin and overexposing it. Better laser controls and better photo resins would help, but there are doubtlessly new techniques to develop, as well.

The hacker community contributed a lot to the growth of fused deposition 3D printing. It would be great to see hacker innovation on this technology as well.

LLNL does a lot of interesting things with 3D printing. If you want to look at what conventional laser resin printers can do, check out the Midwest RepRap Festival.

Filed under: 3d Printer hacks, News

Don’t Get Caught Up In Blockchain Hype

เสาร์, 12/16/2017 - 22:00

It’s the story of the moment, isn’t it. As the price of Bitcoin continues on its wild and crazy rollercoaster ride, everyone’s talking about cryptocurrencies, and in almost mystical terms, about blockchains. Perhaps to be a little more accurate, we should report that they are talking about The Blockchain, a single entity which it seems is now the answer to all ills.

Of course, there is no single blockchain, instead blockchain technologies form the underpinnings of the cryptocurrency boom. Since little dollar signs seem to be buzzing around in front of everyone talking about that subject, it has attracted the attention of hordes of people with little understanding of it. APNIC have a good article aimed at those people: Don’t Get Caught Up In Blockchain Hype, which is worth a read even if you do understand blockchain technologies.

It makes the point that many large enterprises are considering investments in blockchain technologies, and lists some of the potential pitfalls that they may encounter. There may be a slight element of schadenfreude for some of the technically literate in seeing this in action, but given that such things can have consequences for those among us it’s too important to ignore.

As an analogy of a relatively clueless executive jumping on a tech-driven bandwagon, a software company of our acquaintance had a boss who decided in the heady days before the dotcom crash that the organisation would fully embrace open-source. Something to be welcomed, you might think, but given that the software in question was a commercially sensitive asset upon which all company salaries depended, it was fortunate that he listened to his developers when they explained to him exactly what open source entails.

Whether you are a blockchain savant or an uninterested bystander, it’s worth a read as you may sometime need its arguments to save someone from their own folly. If you fancy a simple example to help understand something of how blockchains work, we’ve got that covered for you.

Bitcoin coins image: Mike Cauldwell [Public domain].

Filed under: Tech Hacks

Digital Kiln

เสาร์, 12/16/2017 - 19:00

A kiln or foundry is too often seen as a piece of equipment which is only available if a hackspace is lucky enough to have one or individuals are dedicated enough to drop the cash for one of their own. [The Thought Emporium] thought that way until he sourced materials to make his own kiln which can also be seen after the break. It costs half the price of a commercial model not including a failed—and exploded—paint can version.

As described in the video, these furnaces are tools capable of more than just pottery and soft metal baubles. Sure, a clay chess set would be cool but what about carbon fiber, graphene, aerogel, and glass? Some pretty hot science happens at high temperatures.

We get a nice walk-through of each part of the furnace starting with the container, an eleven-gallon metal tub which should set the bar for the level of kiln being built. Some of the hardware arrangements could be tweaked for safety and we insist that any current-carrying screw is safely mounted inside an enclosure which can’t be opened without tools. There’s good advice about grounding the container if metal is used. The explanation of PID loops can be ignored.

What else can you do with a kiln? How about jewelry, heat treating metal, or recycle your beer cans into an engine.

Filed under: Tool Hacks

The Smartest Air Freshener In The Room

เสาร์, 12/16/2017 - 16:00

Many automatic air fresheners are wasteful in that they either ceaselessly spritz the room, and manual ones need to be — well — manually operated. This will not do in an era of smart products, so Instructables user [IgorF2] has put together an air freshener that does more than check if you’re around before freshening things up.

The air freshener uses a NodeMCU LoLin and an MG 995 servomotor, with a NeoPixel ring acting as a status light. Be aware — when the servo is triggered there is a significant spike in current, so be sure you aren’t powering the air freshener from a PC USB port or another device. After modeling the air freshener’s case in Fusion 360 — files available here — [IgorF2] wired the components together and mounted them inside the 3D printed case.

Hardware work completed, [IgorF2] has detailed how to set up the Arduino IDE and ESP8266 support for a first-time-user, as well as adding a few libraries to his sketch. A combination of an Adafruit.IO feed and ITTT — once again, showing the setup steps — handles how the air freshener operates: location detection, time specific spritzing, and after tapping a software button on your phone for those particularly lazy moments.

[IgorF2] has conveniently supplied and broken down the code he used for those newcomers in the audience to wrap up his thorough Instructable. Ah, the sweet smell of a completed project.

If you didn’t already know, consumer air fresheners are also a trove of parts that can be put to use for many other uses!

Filed under: home hacks, how-to, Wireless Hacks

Give Workshop Pencils a Flush-Mounted Home

เสาร์, 12/16/2017 - 13:00

Pencils and pens are apt to go wandering in a busy workshop if they don’t have a handy storage spot. For most of us a soup can or an old coffee mug does the trick, but for a prettier and more useful holder [Stuff I Made] has a short video demonstrating a storage unit made from an elbow fitting and a scrap piece of plywood. He cuts a plywood disk that is friction-fit into one end of the elbow, then it gets screwed into a wall making an attractively flush-mounted holder in a convenient spot.

With the right joint the bottom of the holder remains accessible, as a 90 degree bend would be no good. With a shallower joint angle, a regular screwdriver can still reach the mounting screw and it’s possible to access the bottom of the holder just in case it needs cleaning or something small falls inside. You can see the process and results in the video embedded below. Not bad for one screw, a spare joint, and a scrap piece of plywood.

Storage and clutter is always on a busy worker’s mind in one way or another, even if we all enjoy different levels of success in dealing with it. Gadgets and organizers, whether simple like the one above or more complex like storage drawers from empty 3D printer filament spools, are one tool to use in the fight against clutter. But when gadgets aren’t enough, it might be time to try a whole different way of thinking and acting.

Filed under: how-to, Misc Hacks

Turning Saw Blades Into Throwing Stars

เสาร์, 12/16/2017 - 10:00

The holidays are nearly upon us, and if you haven’t found the perfect gift for the Mall Ninja in your life yet, this latest hack might be just what you’re looking for. On his YouTube channel, [The Nocturnal Alchemist] demonstrates how to make ninja throwing stars (shuriken) out of an old circular saw blade. One could probably argue that a circular saw itself is close enough to throwing star if your only goal is to wreck some stuff in your backyard, but with this method they’ll have that official samurai look.

To start the process, he hits both sides of the circular saw blade with a grinder to smooth out the surface. He then traces the desired star shapes onto the blade, and cuts the blade into pieces so it’s easier to manage. The rough shape of the stars is cut out with an angle grinder, and a belt sander lets him sharpen the edges.

At this point the stars are effectively finished, but if you want something that’s going to look good on the shelf next to the katana you bought online, you need to do some more finish work. He sands both sides of the stars by hand, starting at 80 grit and working all the way up to 1200 grit wet paper. Once sanded, paste wax is rubbed in with a cloth to give it a protective coating.

With the finish work done, all that’s left to do is throw your new shuriken at cans of soda and watermelons as a demonstration of their power. To this end, he has come prepared with a 1,000 FPS camera; so if you’ve ever wanted to see cans of off-brand soda getting exploded with a throwing star, your Mall Ninja friend isn’t the only one about to get a gift.

With circular saw blade shuriken completed, all you’ll need to do to complete your urban samurai transformation is forge yourself a sword, and perfect your run in virtual reality.

Filed under: Weapons Hacks

Coin cell powered sea turtle research

เสาร์, 12/16/2017 - 07:00

Hacking and tinkering are always fun and games, but one just has to appreciate when all efforts are additionally aimed towards doing something good. [Nikos] sets an example by combining his interest in technology with his passion for wildlife conservation by creating a low cost and ultra-low power temperature logger — and he is using a coin cell for it.

As the founder of a sea turtle conservation project in Greece, [Nikos] enjoys building scientific instruments that help him and his team on their mission. With a goal to log the temperature every 10 minutes over a period of at least 180 days, he designed a PCB just big enough to hold a CR2032 coin cell. Fifty of them will eventually be sealed in waterproof enclosures, and buried in the sand for the whole research duration.

Limiting the design to its bare necessities, the rest of the PCB is housing a digital temperature sensor, an SPI EEPROM to hold all the recorded sensor values over those 180 days, and an ATmega328PB clocked by a 32.768kHz crystal. Wondering what to do with all the extra, unused pins of the ATmega, [Nikos] simply routed them to be accessible through pin headers, thus turning the data logger alternatively into a coin cell powered development board.

Assuming your logging interval requirements are significantly lower, you might be thrilled to hear that [Nikos] estimates a theoretical 7+ years an average coin cell could power the data logger in sleep mode, which makes him confident to reach the 180 days goal.

Coin Cell Challenge   Build something cool powered
by a coin cell, win prizes!
Filed under: green hacks

A Robot Arm for Virtual Beer Pong

เสาร์, 12/16/2017 - 04:00

Leave it to engineering students to redefine partying. [Hyun], [Justin], and [Daniel] have done exactly that for their final project by building a virtually-controlled robotic arm that plays beer pong.

There are two main parts to this build: a sleeve worn by the user, and the robotic arm itself. The sleeve has IMUs at the elbow and wrist and a PIC32 that calculates their respective angles. The sleeve sends angle data to a second PIC32 where it is translated it into PWM signals and sent to the arm.

There’s a pressure sensor wired sleeve-side that’s worn between forefinger and thumb and functions as a release mechanism. You don’t actually have to fling your forearm forward to get the robot to throw, but you can if you want to. The arm itself is built from three micro servos and mounted for stability. The spoon was a compromise. They tried for a while to mimic fingers, but didn’t have enough time to implement grasping and releasing on top of everything else.

Initially, the team wanted wireless communication between the sleeve and the arm. They got it to work with a pair of XBees, but found that RF was only good for short periods of use. Communication is much smoother over UART, which you can see in the video below.

You don’t have to have a machine shop or even a 3-D printer to build a robot arm. Here’s another bot made from scrap wood whose sole purpose is to dunk tea bags.

Filed under: Beer Hacks, Microcontrollers, Robots Hacks

Brute Forcing Passwords with a 3D Printer

เสาร์, 12/16/2017 - 02:31

Many of us use a 4 digit pin code to lock our phones. [David Randolph] over at Hak5 has come up a simple way to use a 3D printer to brute force these passwords. Just about every 3D printer out there speaks the same language, G-code. The same language used in CAD and CNC machines for decades.

[David] placed a numeric keypad on the bed of his printer. He then mapped out the height and positions of each key. Once he knew the absolute positions of the keys, it was easy to tell the printer to move to a key, then press and release. He even created a G-code file which would press every one of the 10,000 4 key pin combinations.

A file this large was a bit unwieldy though, so [David] also created a python script which will do the same thing — outputting the G-code and coordinates to brute force any 4 pin keypad. While a printer is quite a bit slower than Hak5’s own USB Rubber Ducky device (which acts as an automated keyboard), it will successfully brute force a password. Although most phones these days do limit the number of password attempts a user gets.

[David] admits this is probably useless in a clandestine/hacking application, but the video is still a great introduction to G-code and using 3D printers for non-printing functions.

Interested in pushing 3D printers to print more than just plastic? You can always print chocolate.

Filed under: 3d Printer hacks

Thermistors and 3D Printing

เสาร์, 12/16/2017 - 01:01

I always find it interesting that 3D printers — at least the kind most of us have — are mostly open-loop devices. You tell the head to move four millimeters in the X direction and you assume that the stepper motors will make it so. Because of the mechanics, you can calculate that four millimeters is so many steps and direct the motor to take them. If something prevents that amount of travel you get a failed print. But there is one part of the printer that is part of a closed loop. It is very tiny, very important, but you don’t hear a whole lot about it. The thermistor.

The hot end and the heated bed will both have a temperature sensor that the firmware uses to keep temperatures at least in the ballpark. Depending on the controller it might just do on-and-off “bang-bang” control or it might do something as sophisticated as PID control. But either way, you set the desired temperature and the controller uses feedback from the thermistor to try to keep it there.

If you print with high-temperature materials you might have a thermocouple in your hot end, but most machines use a thermistor. These are usually good to about 300 °C. What got me thinking about this was the installation of an E3D V6 clone hot end into my oldest printer which had a five-year-old hot end in it. I had accumulated a variety of clone parts and had no idea what kind of thermistor was in the heat block I was using.

Does it Matter?

When you build the firmware for your printer, you get to tell it what thermistor you are using. There are a few printers that can switch the thermistor type at runtime and — of course — you could just adjust your temperature settings to account for any error if you knew what they were. You usually use a negative temperature coefficient (NTC) device where the resistance goes down as the temperature goes up. But exactly what resistance corresponds to what temperature depends on the device.

So for my upgrade, the old hot end had a thermistor in it that — I think — was made by Honeywell that the firmware knew about. The new hot end was a total unknown. Most (but not all) common thermistors you’ll use in a printer read 100 kΩ at room temperature and that was true of both of these, as well. I wanted to understand how much off my temperatures would be if I picked up the wrong conversion. Surprisingly, while there was plenty of information about how to read a thermistor, I had not seen much data about error from using an incorrect temperature curve, so I decided to take matters into my own hands.

But First

First, it might be worth to think about what really happens in a typical 3D printer’s temperature sensor. Sure, the thermistor changes value, but what then? Most controllers will have a resistor divider with a fixed resistor and the thermistor and then use an A/D to read the voltage.

You don’t want to pass too much current through the thermistor because that current causes some heating and is a source of error. A typical printer will use a 4.7 kΩ resistor at 5 V to excite the thermistor and read the resulting voltage. Suppose the thermistor is at 500 Ω. The voltage across the thermistor will be 5 * (500/(4700+500)) or about a half volt.

I mentioned that most thermistors you’ll find in a printer read 100 kΩ at room temperature. You might think 500 Ω seems kind of low. In fact, as the device gets hot, the resistance rapidly falls off. A 500 Ω resistance corresponds to around 190 °C in a typical 100 kΩ thermistor.

The microcontroller running the printer has to do the opposite math. That is, it will take the equation above and solve for the resistance. In other words: 0.5 = 5 * (R/4700+500) so solve for R. The problem is you don’t want to set your filament temperature in ohms! You want to use degrees.

The best way to compute temperature from a thermistor reading is the Steinhart-Hart model. This requires three parameters and a little number crunching. However, most 3D printer software uses a simplification that uses just the second parameter, or beta, of the thermistor.

Rather than give you the formula, I’ll point you to this spreadsheet. Column A has some resistance values and the other columns have different beta values and show temperatures in degrees C. If you really want to dig into the math and other applications, check out [Peter Vree’s] video, below.

Big Difference?

Armed with that spreadsheet, it is pretty easy to figure out how big a deal it is to be out of tune with your thermistor. Of course, you’d like to have the right value, but in the case of a generic thermistor, how big of a deal is it?

My methodology was simple. I went to Digikey and searched for thermistors. I used their filters to only look at 100 kΩ NTC devices that could read at least 300 °C and specified a beta at 100 °C. The beta values ranged from 3988 to 4280 and based on price and quantities, the real range was even less spread than that. For example, Digikey only had about 180 of the device with a beta of 4280. Not very scientific, I’ll admit, but it did give me a range of beta values you might expect to find “in the wild.”

If you note on the spreadsheet (and the graph below), there’s not a lot of temperature difference at the typical range you’ll print plastics like PLA, ABS, and PETG. Of course, you could get unlucky. If you do have that bottom-most curve, the temperature is a good bit off for that one. Or maybe you have a one of a kind thermistor that has some wacky value that will be way off. But statistically, you’d think you are going to be in the ballpark even if you can’t change the thermistor table. Now, if either thermistor has a different room-temperature resistance, all bets are off. But most of the 3D printers I’ve seen do use 100 kΩ sensors.

The Result

Although it shouldn’t make much difference, I did make an educated guess based on some heuristics and changed the thermistor type. I thought about trying to set a precise temperature on the thermistor to get a few more data points but decided it wasn’t worth breaking out the sous vide cooker.

After all, every printer is a little different and the temperature the plastic sees probably isn’t the thermistor temperature anyway, so there’s always a little “dialing in” required to determine what temperature your printer needs for a particular job. A difference of five or even ten degrees, then, will be in the noise. You’ll find out your PLA is too runny at 210 °C and drop the temperature to 190 °C. Or perhaps ABS is causing extruder skips and you’ll goose the temperature up a few degrees. You are going to have to do across different brands, or colors, of filament anyway.

At the end, though, I got great results. Who knew that what might be the tiniest part of a 3D printer could be so important? If you look carefully in the photo to the right, there are two thin Teflon-coated wires coming out of the heat block. That’s the thermistor, whatever brand and model number it is.

Thermistors, of course, have lots of other uses. They can be used to limit inrush current, provide temperature-stable bias, and — of course — sense temperature in many different situations. For example, they can be the heart of a very minimalist soldering iron controller.

Filed under: 3d Printer hacks, Hackaday Columns, Original Art

Design a Microcontroller With Security In Mind

ศุกร์, 12/15/2017 - 23:30

There are many parts to building a secure networked device, and the entire industry is still learning how to do it right. Resources are especially constrained for low-cost microcontroller devices. Would it be easier to build more secure devices if microcontrollers had security hardware built-in? That is the investigation of Project Sopris by Microsoft Research.

The researchers customized the MediaTek MT7687, a chip roughly comparable to the hacker darling ESP32. The most significant addition was a security subsystem. It performs tasks notoriously difficult to do correctly in software, such as random number generation and security key storage. It forms the core of what they called the “hardware-based secure root of trust.”

Doing these tasks in a security-specific module solves many problems. If a key is not stored in memory, a memory dump can’t compromise what isn’t there. Performing encryption/decryption in task-specific hardware makes it more difficult to execute successful side-channel attacks against them. Keeping things small keeps the cost down and also eases verifying correctness of the code.

But the security module can also be viewed from a less-favorable perspective. Its description resembles a scaled-down version of the Trusted Platform Module. As a self-contained module running its own code, it resembles the Intel Management Engine, which is currently under close scrutiny.

Will we welcome Project Sopris as a time-saving toolkit for building secure networked devices? Or will we become suspicious of hidden vulnerabilities? The researchers could open-source their work to ease these concerns, but value of their work will ultimately depend on the fast-moving field of networked device security.

Do you know of other efforts to add hardware-assisted security to microcontrollers? Comment below or let us know via the tip line!

[via Wired]

Image of Mount Sopris, namesake of the project, by [Hogs555] (CC-BY 4.0)


Filed under: Microcontrollers

Hardware Heroes: Isambard Kingdom Brunel

ศุกร์, 12/15/2017 - 22:01

There are some notable figures in history that you know of for just one single thing. They may have achieved much in their lifetimes or they may have only been famous for Andy Warhol’s fifteen minutes, but through the lens of time we only know them for that single achievement. Then on the other hand there are those historic figures for whom there is such a choice of their achievements that have stood the test of time, that it is difficult to characterize them by a single one.

Isambard Kingdom Brunel, in front of the launching chains for the Great Eastern. [Public domain]Such is the case of Isambard Kingdom Brunel, the subject of today’s Hardware Heroes piece. Do we remember him for his involvement in the first successful tunnel to pass beneath a river, as a builder of some of the most impressive bridges on the 19th century, the innovator in all aspects of rail engineering, the man behind the first screw-driven ocean-going iron ship, or do we remember him as all of those and more?

It is possible that if you are not British, or in particular you are not from the West of England, this is the first you’ve heard of Brunel. In which case he is best described as a towering figure of many aspects of engineering over the middle years of the 19th century. His influence extended from civil engineering through the then-emerging rail industry, to shipbuilding and more, and his legacy lives on today in that many of his works are still with us.

Engineering: The Family Trade

Brunel’s father, Marc Brunel, was an engineer and refugee from the French Revolution who found success in providing the British Navy with a mass-production system for wooden pulley blocks as used in the rigging of sailing ships. He enters this story for his grand project, the world’s first tunnel to be dug under a navigable river, beneath London’s River Thames from Rotherhithe to Wapping, and for his patented tunneling shield which made it possible to be dug.

It’s easy to spot that it’s the Brunel Museum.The Thames at Rotherhithe flows over soft ground, and this caused significant problems for the project including a breach, flooding, and recovery. Brunel was his father’s on-site manager after the departure of the first incumbent due to overwork, and continued in the role until the tunnel’s eventual completion, hugely over time and budget, in 1843. The tunnel remains in use today by the London Overground railway, and its two vertical construction shafts have survived. The southern shaft  and its associated engine house are now in use as the Brunel Museum, and we took a trip there on a chilly November morning.

Visiting the Brunel Museum

The museum is not a large one, and has a primary focus on Brunel himself and the tunnel in particular. Its exhibition and video presentation are informative, but not necessarily enough to detain the visitor for too long. The reason you should visit it lies a short walk from the engine house; visitors can descend into the construction shaft itself for a tantalising glimpse at a remnant of Victorian London.

It appears that the shaft leads a double life as an event venue, being we would guess comfortably large enough to place a London bus inside it. So entry is down a modern staircase and there is some modern seating, but once you ignore those you can see some of the original features. The floor is a later addition placed above the train tracks, so periodically you can hear the London Overground beneath your feet, meanwhile the walls are the grimy Victorian brick of the shaft lining. This was laid at ground level as it descended under its own weight while the shaft was dug, and still bears the clearly visible imprint of the original 1840s double staircases that carried the foot passengers who first used the tunnel.

It’s odd, this is on one hand a grimy and relatively featureless place, yet as an engineer it’s simultaneously hallowed ground. The Brunels — both father and son — made this happen alongside the hard work of many nameless Victorian labourers. From this achievement came all the other achievements of Victorian civil engineering from Brunel and those who followed him in the Great Western Railway and his other ventures. If engineering had cathedrals, this might be one of them.

This photograph (taken in low light and edited) does not do justice to the tunnel construction shaft as a space.

A visit to the museum is not complete without a quick run over the road to survey the riverscape, followed by a short walk to Rotherhithe station for a trip through the tunnel itself. To be fair, other than knowing you’re in Brunel’s tunnel it’s just like any other Tube journey, however it is rumoured that when special trains are laid on for enthusiasts they turn off the train lights and leave on the tunnel lighting, allowing passengers to see some of the surviving original brickwork.

Brunel the Railroad Builder

A modern Brunel statue at the GWR Paddington terminus.The tunnel may have been Brunel’s signature early work, but it is not the achievement he is most remembered for. If we were to ask a typical person in the street about him, particularly if they lived in the West of England, we’d be greeted with the instant answer: the Great Western Railway. This was the transport empire that spread westwards from London, initially to Bristol, but then further west to cover the entire West of England and Wales. Brunel was the chief engineer who laid out and surveyed its route, was responsible for its principal structures, and decided its engineering principles including its unique 7’0.25″ broad gauge.

The GWR became such an integral part of that region of the country that it stamped its culture and by extension Brunel’s presence across it. Today his name can be seen in pub signs, street signs, a university and a shopping centre, and the modern-day train operating company. Those passenger trains now cover the area with the renamed moniker GWR and the company is busy adopting the signature green livery of its ancestor.

A Trio of Bridges: Masterpieces All

It is difficult to conceive in an age when highway bridges are prefabricated and assembled in days, just how much of an achievement a single bridge could be. In Brunel’s case there are three of the many bridges he designed that stand out as engineering masterpieces, his brick arches over the Thames at Maidenhead, his twin-span Royal Albert Bridge over the Tamar at Saltash, and the Clifton Suspension Bridge over the Avon gorge just outside Bristol.

The Royal Albert Bridge, Saltash. [by: Geof Sheppard CC BY-SA 3.0]The Maidenhead bridge carries the GWR main line over the Thames, with two arches meeting at a central pier on one of the river’s islands. It is exceptional because both arches take the shape of an extremely low and wide ellipse, which in 1839 upon it opening were the widest and flattest brick arches in the world. Even today when standing under the arch it is a particularly graceful structure. Famously the GWR board were concerned that Brunel had pushed the technology of brick arches too far, so he left the wooden construction supports in place for its first winter until the river’s floods carried them away. 178 years later it still carries all the trains heading for the West of England.

The Saltash bridge carries the GWR main line to Cornwall, in the extreme south west of the country, at high level over the River Tamar. To maintain navigability for sailing ships, it takes the form of two 455-foot wrought iron trusses 100 feet above the water. Each of the trusses contains a pair of ellipses from which the track bed is suspended, giving the bridge its distinctive appearance.

The Clifton Suspension Bridge. [Gothick CC BY-SA 3.0]The Clifton bridge bears Brunel’s name, but as a memorial to him from the civil engineers who completed it after his death. Brunel had completed the stone towers, but the project had foundered for lack of funds in the 1830s. After Brunel’s death it was completed using chains from an earlier Brunel design that had been demolished, and finally opened in 1864. With its spectacular position over a deep gorge it remains one of the most famous views of a suspension bridge in the world, and though today it carries a fairly minor road it is well worth a visit.

Ship Building? Why Not!

The logical extension of a transport network built to serve Western British ports was to establish a shipping line, and Brunel brought his engineering expertise to the design of a series of ships for the Great Western Steamship Company. The Great Western of 1838 was a wooden-hulled paddle steamer, but the ship that followed it, the Great Britain of 1843, was the world’s first iron-hulled screw-driven steamship. As such it was the direct ancestor of all modern shipping, at a time when much of the world’s ocean-going transport still relied on sail power. Astoundingly it survived, eventually being retrieved as a hulk from the Falkland Islands in 1970 and returned to Bristol for restoration and display as a museum ship.

A contemporary picture on the Great Eastern at sea. [Public domain]Brunel’s final maritime design was the 1859 Great Eastern, featuring both screw and paddle wheels as an extreme long-distance ship for the journeys from Britain to India and Australia. The famous photograph of him standing in front of an immense reel of chain is taken at its construction, they are part of its launch chains. The Great Eastern was the largest ship ever built at the time, and would not be surpassed in either size or tonnage until the years surrounding the turn of the 20th century. Upon completion its launch was unsuccessful, and it lay for a few months while a series of hydraulic rams were assembled to force it sideways into the River Thames. Its first sea trial in early September 1859 was marred by a steam explosion, which blew a substantial hole in its deck and toppled one of its funnels into the English Channel.

The pressure of the Great Eastern project had its effect on Brunel’s health, and following the Great Eastern explosion he suffered a stroke and died a few days later on the 15th of September 1859. He is buried in a rather unassuming family plot in Kensal Green Cemetery, London.

The Fails Only Make You Stronger

The projects we’ve described so far in this piece are only the larger and better known among Brunel’s work. Perhaps one day we’ll devote an entire article to his disastrous experiment with an atmospheric railway for instance, or his success with a prefabricated military hospital for the British involvement in the Crimean War. Even our talking about bridges has omitted many interesting structures, his timber viaducts, or the intersection of a canal, road, and railway bridge in a London suburb. To be an engineer like Brunel in the 19th century was to be a polymath, and this is why he’s an obvious choice for a Heroes piece.

Brunel’s memorial on the Embankment.Going back to our journey across London, there are many different possible routes over the London Transport network from the tunnel museum at Rotherhithe to the Great Western Railway terminus at Paddington, but we took one of the less obvious ones to take in one last Brunel site. A couple of stops down the line to Whitechapel and a switch to the District line (green on the Tube map), and a trundle along the Embankment to Temple station where we find after a short walk his memorial statue. It’s a modest structure though clean and not neglected, his bronze stands on a plinth looking down at a pedestrian crossing as the taxis thunder past. Pedestrians barely give it a second glance, as the Embankment is home to a large number of statues of notable people. But then you might ask yourself, why should they? This is Brunel’s monument, but it’s not the monument that matters. Every time you board an express train, every time we use a product that has been transported by rail or ship, and every journey through a tunnel under water, those are his monuments. Stand by a piece of Brunel’s work, if you want to see his real commemoration. Most of it has survived for a century and a half, how many of today’s engineers will be able to say that!

[Source for main image: Royal Museums Greenwich]

Filed under: Featured, History, Slider

Modernizing Puerto Rico’s Grid

ศุกร์, 12/15/2017 - 19:00

After two massive hurricanes impacted Puerto Rico three months ago, the island was left with extensive damage to its electrical infrastructure. Part of the problem was that the infrastructure was woefully inadequate to withstand a hurricane impact at all. It is possible to harden buildings and infrastructure against extreme weather, and a new plan to restore Puerto Rico’s power grid will address many of these changes that, frankly, should have been made long ago.

Among the upgrades to the power distribution system are improvements to SCADA systems. SCADA allows for remote monitoring and control of substations, switchgear, and other equipment which minimizes the need for crews to investigate problems and improves reliability. SCADA can also be used for automation on a large scale, in addition to the installation of other autonomous equipment meant to isolate faults and restore power quickly. The grid will get physical upgrades as well, including equipment like poles, wire, and substations that are designed and installed to a more rigorous standard in order to make them more wind- and flood-tolerant. Additional infrastructure will be placed underground as well, and a more aggressive tree trimming program will be put in place.

The plan also calls for some 21st-century improvements as well, including the implementation of “micro grids”. These micro grids reduce the power system’s reliance on centralized power plants by placing small generation facilities (generators, rooftop solar, etc) in critical areas, like at hospitals. Micro grids can also be used in remote areas to improve reliability where it is often impractical or uneconomical to service.

While hurricanes are inevitable in certain parts of the world, the damage that they cause is often exacerbated by poor design and bad planning. Especially in the mysterious world of power generation and distribution, a robust infrastructure is extremely important for the health, safety, and well-being of the people who rely on it. Hopefully these steps will improve Puerto Rico’s situation, especially since this won’t be the last time a major storm impacts the island.

Filed under: Repair Hacks