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Functioning Technic SLJ900 Bridge Builder

พฤ, 11/23/2017 - 13:00

There is definitely a passion for detail and accuracy among LEGO builders who re-create recognizable real-world elements such as specific car models and famous buildings. However, Technic builders take it to a level the regular AFOLs cannot: Not only must their model look like the original, it has to function the same way. Case in point, [Wolf Zipp]’s version of a massive bridge-building rig. The Chinese-built SLJ900 rolls along the tops of bridges and adds ginormous concrete spans with the aplomb found only in sped-up YouTube videos. It is nevertheless a badass robot and a worthy target for Technicization.

[Wolf]’s model is 2 meters long and weighs 10.5kg, consisting of 13 LEGO motors and a pneumatic rig, all run by a handheld control box. The rig inserts LEGO connectors to a simulated bridge span, lifts it up, moves it over the next pier, then drops it down into place. The span weighs 2.5kg by itself — that ain’t no styrofoam! There are a lot of cool details in the project. For instance, the mechanism that turns the wheels for lateral movement consists of a LEGO-built pneumatic compressor that trips pneumatic actuators that lift the wheels off the ground and allows them to turn 90 degrees.

Sometimes it blows the mind what can be built with Technic. Check out this rope-braiding machine and this 7-segment display we’ve posted.

Filed under: Toy Hacks

Teardown Of A Cheap Glue Gun

พฤ, 11/23/2017 - 10:00

A hot glue gun is one of those standard tools of the hardware hacker’s bench, called upon to provide adhesion between an astonishing range of materials, and to provide a handy filler and strain relief in the form of blobs of polymer glue. We’ve all got one, but how many of us have taken a look inside it?

[Andrew Lorimer] bought a super-cheap eBay glue gun, and subjected it to a teardown. As you might expect, he found it to be a pretty simple device with only a trigger mechanism and a dumb heating element, but his write-up is of passing interest because he’s characterised its heating element. It has a positive temperature coefficient, which means that its resistance increases from around 2.5 kΩ at room temperature to about 7 kΩ at its 150 ºC operating temperature. This limits the current, and provides a very simple thermostat action.

The build quality is surprisingly good for such a cheap appliance, and he notes a surfeit of screws holding its shell together. But the quality of the insulation and strain relief leaves a lot to be desired, and he wonders whether it truly qualifies for its double-insulated logo. The LED pilot light is simply fed from the 240 V mains supply through a 250 kΩ resistor which he replaces with a 12 kΩ component for a brighter result.

We cover plenty of teardowns here at Hackaday. Often they are of extremely expensive and complex devices, but sometimes they are of much simpler subjects.

Filed under: Teardown

Digital Panel Meter Tear Down

พฤ, 11/23/2017 - 07:00

[Big Clive] had some 22mm digital AC voltmeters, made to put in a panel. There was a time when this would have been a significant pain, since it required you to make a large square hole. Of course, in a world of CNC and 3D printers that isn’t as big a deal as it used to be, but the ones [Clive] has are nice because having a round footprint you can drill a hole for them with a hole saw or a stepped bit. Of course, he wasn’t satisfied to just use these inexpensive meters. He had to tear one apart to look inside. You can see his review and teardown in the video below. The meters are available in a range of AC voltages, although [Clive] didn’t think the ones he had would safely handle their rated maximum.

Inside, the modules reminded us of cordwood construction in a way. Most of the electronics are on a small round board. But several components connect to the board and the bottom cap in a vertical orientation. The meters are available in several colors, but [Clive] likes the red ones as they appear brighter than the others. The voltage reading compared favorably to a Fluke meter.

The verdict is that for the price (under $2 from China; a little more in the US) they are handy, but you might not want to consider running significant voltage through them. You could use these instead of pilot lights and get the voltage reading for free. We were surprised that someone doesn’t make a DC version in the same form factor, at least if they do, we couldn’t find it. If you don’t mind drilling the square hole and letting a bezel cover your sins, you could use a universal meter with an Arduino instead for many applications.

Filed under: Teardown

Trinket Chills Your Drinks

พฤ, 11/23/2017 - 04:00

Who wants warm drinks? Well, coffee drinkers, we guess. Other than them, who wants warm drinks? Tea drinkers, sure. How about room temperature drinks? No one, that’s who. It’s silly to buy a refrigerator to cool down a single drink, so what option are you left with? Ice cubes? They’ll dilute your drink. Ice packs and a cooler? Sure, they’ll keep your drinks cold, but they’re hardly cool are they? No, if you want a cold drink the cool way, you build a thermoelectric cooler. And if you want to build one, you’re in luck, because [John Park] has a tutorial to do just that up on AdaFruit.

The parts list includes an AdaFruit Trinket M0, a more powerful version of AdaFruit’s Trinket line. The Trinket is used to control the main part in this build, a Peltier thermoelectric cooler, as well as the temperature display and switches. The other part controlled by the microcontroller is a peristaltic pump, which is used to do the dispensing of the liquid. The code to control everything is written in Python as the Trinket M0 comes with AdaFruit’s CircuitPython by default. Also included in the tutorial are the files for the stand, should you want to 3D print it or cut it with a CNC or laser cutter.

After the break, you can watch as [John] goes over the project and builds it, or go to the AdaFruit website and follow the instructions to build your own. As [John] says, there might be better ways to chill your drinks, but this is “definitely one of the more science-y and interesting ones.” For more projects using the Peltier Effect, try this one that uses the effect in sous-vide cooking, or this one, a Peltier cooled micro-fridge!

Filed under: hardware

A Passion for the Best is in Mechanical Keyboards

พฤ, 11/23/2017 - 02:30

There is an entire subculture of people fascinated by computer keyboards. While the majority of the population is content with whatever keyboard came with their computer or is supplied by their employer — usually the bottom basement squishy membrane keyboards — there are a small group of keyboard enthusiasts diving into custom keycaps, switch mods, diode matrices, and full-blown ground-up creations.

Ariane Nazemi is one of these mechanical keyboard enthusiasts. At the 2017 Hackaday Superconference, he quite literally lugged out a Compaq with its beautiful brominated keycaps, and brought out the IBM Model M buckling spring keyboard.

Inspired by these beautiful tools of wordcraft, [Ariane] set out to build his own mechanical keyboard and came up with something amazing. It’s the Dark Matter keyboard, a custom, split, ergonomic, staggered-columnar, RGB backlit mechanical keyboard, and at the 2017 Hackaday Superconference, he told everyone how and why he made it.

A rubber dome keyboard. The only spring pressure comes from a sheet of rubber

Ninety-nine percent of the keyboards you’ll ever see are crappy rubber dome keyboards. This is a specific type of switch, made with two contacts on a PCB, a sheet of rubber with a bunch of little bubbles in it, and a conductive foam pad mounted to the bottom of a key. The keys get their springiness from these rubber domes, and when a key is pressed it smashes into the PCB contacts, closing a circuit.

It’s certainly an inexpensive way to build a keyboard, but compared to a true mechanical switch it feels like crap. The key doesn’t activate until it hits bottom, and the lifetime of each of these switches is measured in the tens of thousands of cycles instead of the millions of cycles a mechanical keyswitch can handle.

The Cherry MX Blue keyswitch

On the other end of the spectrum is a mechanical keyswitch, best represented by the Cherry MX switch; a make and model of switch, with clones also built by Gateron and Kailh. These switches use actual springs and bits of brass to close a switch and they provide tactile feedback to the typist. There are even different varieties of MX-style switch; the ones with red stems are almost linear in their feedback, while browns, clears, and blues have a little bit of resistance in the middle of the key’s travel. The blues are clicky and are somehow even louder than the buckling springs found in the IBM Model M. They sound like a machine gun, and it’s awesome.

An entire community has grown up around putting these MX-style switches into custom designed enclosures for the perfect typing experience. There are innovations in ergonomics like columnar spacing, where the Q, A, and Z keys are in a straight line. There are split keyboards, where the left and right side of the keyboard are attached by a cable. Ariane decided he wanted the ultimate keyboard. It would be a split keyboard, and it should have a columnar layout. Because he’s part of the Hackaday crowd, this keyboard must have a ton of blinkies. This led to the creation of the Dark Matter keyboard, one of the most technologically impressive keyboards we’ve seen in a long time.

Like a lot of mechanical keyboard projects, Ariane is using a Teensy as the controller for each half of his keyboard. Unlike most mechanical keyboard projects, Ariane is using the Teensy LC, the cost-reduced version of this family of dev boards. Until very recently, the most popular firmwares for keyboards haven’t been brought over to the Teensy LC. Ariane did just that, and added support for driving WS2812 RGB LEDs. Combine this with an MX-compatible keyswitch with a clear housing and some polycarbonate keycaps, and Ariane made the blinkiest keyboard you’ve ever seen that doesn’t have individual OLED displays embedded in each keycap.

Ariane’s talk is a wealth of information on how to manufacture keyboards, from firmware and software development to how to build an enclosure. Keyboards are a surprisingly popular side topic in our little niche here on Hackaday, and we’re pleased Ariane could give this talk and extol the virtues of mechanical keyboards.

Filed under: cons, Hackaday Columns

Radio Apocalypse: The GWEN System

พฤ, 11/23/2017 - 01:01

Recent developments on the world political stage have brought the destructive potential of electromagnetic pulses (EMP) to the fore, and people seem to have internalized the threat posed by a single thermonuclear weapon. It’s common knowledge that one bomb deployed at a high enough altitude can cause a rapid and powerful pulse of electrical and magnetic fields capable of destroying everything electrical on the ground below, sending civilization back to the 1800s in the blink of an eye.

Things are rarely as simple as the media portray, of course, and this is especially true when a phenomenon with complex physics is involved. But even in the early days of the Atomic Age, the destructive potential of EMP was understood, and allowances for it were made in designing strategic systems. Nowhere else was EMP more of a threat than to the complex web of communication systems linking far-flung strategic assets with central command and control apparatus. In the United States, one of the many hardened communications networks was dubbed the Groundwave Emergency Network, or GWEN, and the story of its fairly rapid rise and fall is an interesting case study in how nations mount technical responses to threats, both real and perceived.

Reliability Through Physics

GWEN began as a patch for a perceived gap in the communications network connecting the country’s strategic nuclear assets — primarily the launch control centers (LCC) of the ballistic missile launch facilities — to the National Command Authority, which is basically the president. Like all strategic communications systems, GWEN was designed to incorporate best practices for surviving the electromagnetic effects of an EMP. But GWEN had another mission.

Ground wave propagation. Source: Electronics Notes

Groundwave propagation is the tendency of certain radio waves to hug the surface and follow the curvature of the earth and is an exception to the general rule that radio waves only travel in straight lines. The earth acts as a conductor below 5 MHz, so radio waves traveling along the surface of the earth induce currents. The induced currents slow down propagation near the surface, curving the wavefront down as it spreads out. There is considerable attenuation of the signal, of course, and careful consideration has to be given to antenna design and construction. But when properly engineered, ground wave propagation systems can be very effective at over-the-horizon communications that do not rely on the ionosphere.

Groundwave propagation requires long wavelengths to work, so GWEN operated in the low frequency (LF) band from 150 to 175 kHz, well below the commercial AM radio medium frequency (MF) band from 530 to 1700 kHz.

GWEN Nodes A GWEN relay node. Source: Wikipedia, public domain.

GWEN was envisioned as a wide area network of LF relay nodes about 150 to 200 miles apart. Each GWEN relay node communicated to input-output nodes, which were generally located at Air Force bases and other such facilities. The relay nodes were to take command and control messages from the IO nodes and propagate them over the entire network until they reached receive-only nodes, typically the LCC bases. GWEN encoded messages on the LF signals using minimum-shift keying at a data rate of 1200 bps. Messages were encrypted, of course.

Only about 58 of the planned 240 GWEN stations were built between 1982 and the early 1990s, when the program was shut down. GWEN was mostly a victim of Congress, who were unwilling to fund what they perceived to be a Cold War relic after the fall of the Soviet Union. There was also a certain amount of NIMBY-ism with regard to future GWEN sites; with the increasingly popular perception that everything from power lines to cell towers were capable of causing profound biological effects, the prospects of having a powerful radio transmitter that would also be a possible war target in the neighborhood was more than enough reason to mothball the program.

By that time, GWEN’s technology was certainly looking a little long in the tooth anyway, with the rise of the Internet and the proliferation of satellite communications. This may prove shortsighted, though; while there’s certainly a lot of redundancy built into today’s strategic communication systems, there’s something to be said for a simple and robust system that uses basic physical principle like GWEN did.

Filed under: Featured, History, Original Art, Wireless Hacks

Fail of the Week: Cheap Chips Cause Chaos

พุธ, 11/22/2017 - 23:30

We all know the old saw: if it’s too good to be true, it probably is. But nowhere does this rule seem to break down as regularly as when we order parts. Banggood, AliExpress, and eBay are flooded with parts ready to be magically transported across the globe to our doorsteps, all at prices that seem to defy the laws of economics.

Most of these transactions go off without a hitch and we get exactly what we need to complete our Next Cool Thing. But it’s not always so smooth, as [Kerry Wong] recently discovered with an eBay order that resulted in some suspicious chips. [Kerry] ordered the AD633 analog multiplier chips as a follow-up to his recent Lorenz Attractor X-Y recorder project, where he used an Arduino to generate the chaotic butterfly’s data set as a demo for the vintage instrument. Challenged in the comments to do it again in analog, [Kerry] did his homework and found a circuit to make it happen. The needed multipliers were $10 a pop on DigiKey, so he sourced cheaper chips from eBay. The $2 chips seemed legit, with the Analog Devices logo and everything, but the circuit didn’t work. [Kerry]’s diagnosis in the video below is interesting, and it’s clear that the chips are fakes. Caveat emptor.

Here’s hoping that [Kerry] sources good chips soon and regales us with a successful build. Until then, what are your experiences with cheap chips? Have you been burned by overseas or domestic suppliers before? Does any single supplier seem like a better bet to you, or is it all hit or miss? Sound off in the comments below.

Filed under: Fail of the Week

Skin (Effect) in the Game

พุธ, 11/22/2017 - 22:00

We love to pretend like our components are perfect. Resistors don’t have capacitance or inductance. Wires conduct electricity perfectly. The reality, though, is far from this. It is easy to realize that wire will have some small resistance. For the kind of wire lengths you usually encounter, ignoring it is acceptable. If you start running lots of wire or you are carrying a lot of current, you might need to worry about it. Really long wires also take some time to get a signal from one end to the other, but you have to have a very long wire to really worry about that. However, all wires behave strangely as frequency goes up.

Of course there’s the issue of the wire becoming a significant part of the signal’s wavelength and there’s always parasitic capacitance and inductance. But the odd effect I’m thinking of is the so-called skin effect, first described by [Horace Lamb] in 1883. [Lamb] was working with spherical conductors, but [Oliver Heaviside] generalized it in 1885.

Put simply, when a wire is carrying AC, the current will tend to avoid traveling in the center of the wire. At low frequencies, the effect is minimal, but as the frequency rises, the area in the center that isn’t carrying current gets larger. At 60 Hz, for example, the skin depth for copper wire — the depth where the current falls below 1/e of the value near the surface — is about 0.33 inches. Wire you are likely to use at that frequency has a diameter less than that, so the effect is minimal.

However, consider a 20 kHz signal — a little high for audio unless you are a kid with good ears. The depth becomes about 0.018 inches. So wire bigger than 0.036 inches in diameter will start losing effective wire size. For a 12-gauge wire with a diameter of 0.093 inches, that means about 25% of the current-handling capacity is lost. When you get to RF and microwave frequencies, only the thinnest skin is carrying significant current. At 6 MHz, for example, copper wire has a skin depth of about 0.001 inches. At 1 GHz, you are down to about 0.000081 inches. You can see this (not to scale) in the accompanying image. At DC, all three zones of the wire carry current. At a higher frequency, only the outer two zones carry significant current. At higher frequencies, only the outer zone is really carrying electrons.

So What?

There are a few practical issues to think about. Manufacturers that create cables for high-frequency use spend a lot of time perfecting the surface of the wire since a small imperfection on the surface that isn’t significant to the entire diameter of the wire might be a very important part of the current-handling capacity at a high frequency.

Cables that are copper clad — that is, that have a steel core and a copper surface — will conduct DC differently than AC at the design frequency. Some very high power applications save weight and cost by using hollow tubes instead of solid conductors. This is very common in transmitting coils that use what appears to be copper plumbing tubes. Electric power stations often use tube conductors, also, and benefit from the ability of a tube to stretch across a long distance without as much support as a heavier wire. Sometimes these tubes are silver plated since the plating will carry most of the current and silver is a good conductor but relatively expensive.

To mitigate skin effect, you can use litz wire for frequencies up to about 1 MHz. This is wire woven from many separate, insulated conductors. In addition to providing multiple “skins” for the current to flow, the weaving follows certain patterns to minimize the proximity effect between the wires. If you’ve ever taken apart an old AM radio with a ferrite rod antenna inside, you’ve probably seen litz wire as most of those antennas employ litz windings. Carbon nanotube threads can also work and are not as limited in frequency.

Another place this shows up is in welding rods. An iron rod will work fine for welding at DC, but not for high-frequency welding. The reduced current-handling capacity will cause the welding power to dissipate in heat throughout the rod instead of causing an arc.

The Math

The theory behind skin effect is that the change in current causes a change in magnetic field and that generates a reverse voltage (“back EMF”) in the wire. This reverse is strongest in the center of the wire and it forces the electrons away from the center. This is the same effect, by the way, that causes metals to reflect electromagnetic waves.

There is a complex formula for the skin depth that depends on the material’s resistivity, magnetic permeability, and other exotic values. However, as a rule of thumb, you can ignore the skin effect when the frequency is at or below 124 divided by the square of the wire diameter in thousandths of an inch. Beyond that point, assume resistance will increase about 3.2 times for every 10X increase in frequency.

For example, consider a two-inch piece of #18 wire. At DC, the wire would have a 1.06 mΩ resistance. The diameter in mils is 40.3. Squaring 40.3 and dividing it into 124 gives 76 kHz. Suppose you were going to use the wire at 100 MHz. Since this is just an estimate, consider that 100 kHz is three decades below 100 MHz and you can figure the resistance will be 1.06 x 3.2 x 3.2 x 3.2 = about 35 millohms. If you do the long math, the real answer comes out to just under 41 milliohms, so that’s not bad.

If you really want to look at the hairy math, you might enjoy the video below.

In Practice

Most of the time, you won’t care much about skin effect. That’s what makes it so insidious. We all know batteries, for example, don’t behave like ideal voltage sources and so we work around it. But wires are pretty good, until they aren’t. Long wires, high frequencies, and high currents can all conspire to make the pretty schematic an ugly circuit. Skin effect is just one of the reasons wires don’t behave like we wish they would.

Photo credit: Title graphic [Mariusz.stepien] CC BY-SA 3.0

Filed under: Engineering, Hackaday Columns

Hacking A K40 Laser Cutter

พุธ, 11/22/2017 - 19:00

The distinctive blue-and-white enclosure of the Chinese-made K40 laser cutter has become a common sight in workshops and hackerspaces, as they represent the cheapest route to a working cutter that can be found. It’s fair to say though that they are not a particularly good or safe machine when shipped, and [Archie Roques] has put together a blog post detailing the modifications to make something better of a stock K40 performed at Norwich Hackspace.

After checking that their K40 worked, and hooking up suitable cooling and ventilation for it, the first task facing the Norwich crew was to install a set of interlocks. (A stock K40 doesn’t shut off the laser when you open the lid!) A switch under the lid saw to that, along with an Arduino Nano clone to aggregate this, a key switch, and an emergency stop button. A new front panel was created to hold this, complete a temperature display and retro ammeter to replace the modern original.

Norwich’s laser cutter has further to go. For example, while we secretly approve of their adjustable bed formed from a pile of beer mats, we concede that their plans to make something more practical have merit. The K40 may not be the best in the world, indeed it’s probable we should be calling it an engraver rather than a cutter, but if that means that a small hackerspace can have a cutter and then make it useful without breaking the bank, it’s good to see how it’s done.

This isn’t the first K40 enhancement we’ve featured. Norwich might like to look at this improved controller, or even extend their cutter’s bed. Meanwhile if [Archie]’s name rings a bell, it might be because of his Raspberry Pi laptop.

Filed under: Laser Hacks

Roll Your Own Rotary Tool

พุธ, 11/22/2017 - 16:00

Rotary tools are great little handheld powerhouses that fill the void between manual tools and larger shop machines. They’re also kind of expensive for what they are, which is essentially a power circuit, a switch, and a high-RPM motor with a tool coupling on the shaft. If your tooling needs are few and you have the resources, why not make your own?

[DIY King 00] built himself a cordless rotary tool for less than $10 out of commonly-available parts. It doesn’t run nearly as fast as commercial rotary tools, but that’s not necessarily a bad thing. He made the body out of 2″ diameter PVC and mounted a 12 V, 400 RPM DC motor directly to one of the fiberglass end caps. Tools are chucked into a collet that screws into a coupler on the motor shaft.

For power, [DIY King 00] built a 7.4 V battery pack by wiring two 18650 cells from an old laptop battery in series. It isn’t the full 12 V, but it’s enough power for light-duty work. These 2200 mAh cells should last a while and are rechargeable through the port mounted in the other end cap.

Drill down past the break to see the build video and watch the tool power through plywood, fiberglass, and inch-thick lumber. Once you’ve made your own rotary tool, try your hand at a DIY cordless soldering iron.

Filed under: Tool Hacks

Reanimating Boney the Robot Dog

พุธ, 11/22/2017 - 13:00

[Divconstructors] cashed in after Halloween and picked up a skeleton dog prop from the Home Depot, for the simple and logical purpose of turning it into a robot.

The first step was to cut apart the various body parts, followed by adding bearings to the joints and bolting in a metal chassis fabricated from 1/8″ aluminum stock. This is all pretty standard stuff in the Dr. Frankenstein biz. For electronics he uses a Mega with a bark-emitting MP3 shield on top of it. Separately, a servo control board manages the dozenish servos — not to mention the tail-wagging stepper.

[Divconstructors] actually bought two skeletons, one to be his protoype and the other to be the nice-looking build. However, we at Hackaday feel like he might have missed an opportunity: As any necromancer can tell you, a freakish combination of two skeletons beats out two normal skeletons any night of the week. Also, two words for you to consider: cyberdog ransomeware. We imagine you don’t really feel ransomware until there’s the family robodog ready to test out its high-torque jaw servos on your flesh. Of course if he were a real dog we could either remotely control him with a hot dog, or just give him a talking collar.

Filed under: Robots Hacks

A look at Chinese Value Engineering

พุธ, 11/22/2017 - 10:00

Seventy cents doesn’t buy you a lot these days. Maybe some sweets or candies at most. How about a string of LEDs that you can use to decorate your home during the festive season? [Amaldev] was curious to know what was, or wasn’t, inside these blinky LED strings which made them so cheap. He’s done a Christmas LED Light Teardown and shows how blinky LED string lights can be built with the bare minimum of components.

The string he purchased had 28 LEDs – seven each in four colors, a controller box with one push button and a  power cord. Without even knowing what is inside the controller box, the cost of the product seems astonishing based on this BoM. The single push button cycles through eight different light patterns for each press. It even has a faux CE mark for the supply plug. Cracking open the case, he finds that the controller board is sparsely populated with just seven through hole components and a COB (chip on board) module. A simple, 8-bit, 8-pin microcontroller is possibly what controls the device.

[Amaldev] sketches out a schematic to figure out how it works. There are two arms with 14 LEDs of alternating colors, each of which is controlled by an SCR. Two GPIO output pins from the COB control the gates of each of these SCR’s. The button is connected to a GPIO input, and a second input is connected to the AC supply via a current limiting resistor. Most likely, this is used to determine the zero crossing of the waveform so that the COB can generate the appropriate trigger signals for the gate outputs.

It is unlikely that these products are manufactured using automated processes. The PCB production could be automated, but soldering all the wires, fitting it all in the enclosure and preparing the LED string itself would require manual labor. At US$ 0.7 retail on the street, it is difficult to imagine the cost breakdown even when the quantities are in large numbers. Maybe a combination of cheap components, recycled or rejected parts (mains cord/enclosure), lack of safety and protection measures (no fuses, no strain reliefs) and reducing the component BoM to an absolute, bare minimum, coupled with very high volumes lets them pull it off? What are your thoughts – chime in with comments.

Filed under: Teardown

Bolt-Together Belt Grinder for the No-Weld Shop

พุธ, 11/22/2017 - 07:00

Belt grinding offers a lot of advantages for the metalworker, and since belt grinders are pretty simple machines, shop-built tools are not an uncommon project. A bolt-together belt grinder makes this tool even more accessible to the home gamer.

With no access to a welder but with a basic milling machine and an ample scrap bin at his disposal,  [IJustLikeMakingThings] had to get creative and modify some of the welding-required belt grinder designs he found online to be bolt-up builds.  The key to a cool running belt grinder is for the belt to be as long as possible, and the 2″x72″ belt seems to be the sweet spot, at least here in the States. Machined drive and idler wheels with the crown needed for proper belt tracking were sourced online, as was the D-bracket for holding the two guide wheels. But the rest of the parts were fabricated with simple tools and bolted together. [IJustLikeMakingThings] provides a lot of detail in his write-up, and it shouldn’t be too hard to build a belt grinder just like this one.

Looking for other belt grinder plans to compare notes? Here’s a grinder with an even simpler design, but with welding required.

Filed under: Tool Hacks

Flip-Dot Display Brought Out of Retirement by New Drivers

พุธ, 11/22/2017 - 04:00

LED matrix displays and flat-screen monitors have largely supplanted old-school electromechanical models for public signage. We think that’s a shame, but it’s also a boon for the tinkerer, as old displays can be had for a song these days in the online markets.

Such was the case for [John Whittington] and his flip-dot display salvaged from an old bus. He wanted to put the old sign back to work, but without a decent driver, he did what one does in these situations — he tore it down and reverse engineered the thing. Like most such displays, his Hannover Display 7 x 56-pixel flip-dot sign is electromechanically interesting; each pixel is a card straddling the poles of a small electromagnet. Pulse the magnet and the card flips over, changing the pixel from black to fluorescent green. [John] used an existing driver for the sign and a logic analyzer to determine the protocol used by the internal electronics to drive the pixels, and came up with a much-improved method of sending characters and graphics. With a Raspberry Pi and power supply now resident inside the case, a web-based GUI lets him display messages easily. The video below has lots of details, and the code is freely available.

You may recall [John] from a recent edge-lit Nixie-like display. Looks like he’s got a thing for eye-catching displays, and we’re fine with that.

Filed under: classic hacks, Teardown

Anouk Wipprecht: Robotic Dresses and Human Interfaces

พุธ, 11/22/2017 - 02:31

Anouk Wipprecht‘s hackerly interests are hard to summarize, so bear with us. She works primarily on technological dresses, making fashion with themes inspired by nature, but making it interactive. If that sounds a little bit vague, consider that she’s made over 40 pieces of clothing, from a spider dress that attacks when someone enters your personal space too quickly to a suit with plasma balls that lets her get hit by Arc Attack’s giant musical Tesla coils in style. She gave an inspiring talk at the 2017 Hackaday Superconference, embedded below, that you should really go watch.

Anouk has some neat insights about how the world of fashion and technology interact. Technology, and her series of spider dresses in particular, tends to evolve over related versions, while fashion tends to seek the brand-new and the now. Managing these two impulses can’t be easy.

For instance, her first spider was made with servos and laser-cut acrylic, in a construction that probably seems familiar to most Hackaday readers. But hard edges, brittle plastic, and screws that work themselves slowly loose are no match for human-borne designs. Her most recent version is stunningly beautiful, made of 3D printed nylon for flexibility, and really nails the “bones of a human-spider hybrid” aesthetic that she’s going for.

The multiple iterations of her drink-dispensing “cocktail dress” (get it?!) show the same progression. We appreciate the simple, press-button-get-drink version that she designed for a fancy restaurant in Ibiza, but we really love the idea of being a human ice-breaker at parties that another version brings to the mix: to get a drink, you have to play “truth or dare” with questions randomly chosen and displayed on a screen on the wearer’s arm.

Playfulness runs through nearly everything that Anouk creates. She starts out with a “what if?” and runs with it. But she’s not just playing around. She’s also a very dedicated documenter of her projects, because she believes in paying the inspiration forward to the next generation. And her latest project does something really brilliant: merging fashion, technology, and medical diagnostics.

It’s a stripped-down EEG that kids with ADHD can wear around in their daily lives that triggers a camera when their brains get stimulated in particular ways. Instead of a full EEG that requires a child to have 30 gel electrodes installed, and which can only be run in a medical lab, stripping down the system allows the child to go about their normal life. This approach may collect limited data in comparison to the full setup, but since it’s collected under less intimidating circumstances, the little data that it does collect may be more “real”. This project is currently in progress, so we’ll just have to wait and see what comes out. We’re excited.

There’s so much more going on in Anouk’s presentation, but don’t take our word for it. Go watch Anouk’s talk right now and you’ll find she inspires you to adds a little bit more of the human element into your projects. Be playful, awkward, or experimental. But above all, be awesome!

Filed under: cons, Hackaday Columns, Wearable Hacks

Joan Feynman Found Her Place in the Sun

พุธ, 11/22/2017 - 01:01

Google ‘Joan Feynman’ and you can feel the search behemoth consider asking for clarification. Did you mean: Richard Feynman? Image search is even more biased toward Richard. After maybe seven pictures of Joan, there’s an endless scroll of Richard alone, Richard playing the bongos, Richard with Arline, the love of his life.

Yes, Joan was overshadowed by her older brother, but what physicist of the era wasn’t? Richard didn’t do it on purpose. In fact, no one supported Joan’s scientific dreams more than he did, not even their mother. Before Richard ever illuminated the world with his brilliance, he shined a light on his little sister, Joan.

Baby Joan works on the Feynman smirk. Image via r/physics A Sign From Above

Joan Feynman was born in Queens, New York City in 1927 to Lucille and Melville Feynman, nine years after Richard came along. Both children were raised to be insatiably curious. Their parents encouraged them to always ask why, and to take notice of the world around them.

Joan deeply admired her brother and was always interested in whatever he was doing. Richard capitalized on this right away, making Joan his first student. He taught her how to add simple numbers together when she was three. Whenever Joan got one right, Richard let her pull his hair and would make funny faces. Anything Richard learned about math or science, he would repeat all over the house, which had the dual effect of reinforcing his understanding and piquing Joan’s interest.

Their working relationship continued, too. When Joan was five, Richard hired her assist him in his bedroom electronics lab. For a few cents a week she would flip switches at the appropriate time. Sometimes she had to put her finger in a spark gap to amuse his friends.

One night when Joan was quite young, Richard pulled her out of bed and led her down the street to a nearby golf course. He told her to look up into the sky, which was ablaze in the brilliant colors of aurora borealis. Joan was mesmerized. In that moment, her destiny became clear to her.

No one could foil Joan’s plans. Image via Popular Science A Woman’s Place is in a College-Level Astronomy Textbook

At the time, no one knew what caused auroras. Joan became determined to unlock their mysteries. Her mother had other ideas, though. When Joan proclaimed to her at age eight that she wanted to be a scientist, her mother told her that “women can’t do science because their brains aren’t able to understand enough of it.” Joan was crushed. From that day on, she doubted her abilities.

Lucille Feynman wasn’t trying to be cold-hearted or unprogressive. She had marched for women’s suffrage in her teens. Still, she believed that women weren’t as intellectually capable as men. This was then.

For a while, Joan’s aspirations were put on hold. There weren’t many women scientists to look up to in the 1930s, anyway, except for Marie Curie. She was iconic, perhaps too much so. Joan saw her as mythological, a majestic unicorn of scientific greatness, not a human woman she could try to emulate.

Even so, Joan wasn’t discouraged enough to lose interest in science. For one thing, Richard had never stopped rooting for her. When she turned fourteen, he gave her a college-level astronomy textbook. She found the material difficult but took his advice to start over from the beginning when she got stuck.

On page 407, Joan found something that would give her the one thing she needed the most to seal her future—validation. On the page was a graph of spectral absorption lines credited to one Cecilia Payne. Joan was ecstatic. A woman scientist! Finally, concrete proof that her mother was wrong. Not only can women understand science, they can have their work referenced in a textbook. Joan’s confidence was renewed.

The science of homemaking. Image via NPR The Science of Homemaking

Of course, becoming a scientist wasn’t that simple. Joan faced adversity everywhere. During her undergraduate studies at Oberlin, she did all the lab experiments while her ill-prepared lab partner got all the credit. A professor at Syracuse University told Joan she should write her dissertation on cobwebs, because she would encounter them regularly as a housewife.

After finishing her PhD in 1958, Joan tried to find a research scientist position by posting in New York Times classifieds. The listings were split by gender, and they told her she wasn’t allowed to post among the men. But who would look for an astrophysicist in the women’s section?

By the early 1960s, Joan was working for a small company that made solid-state devices. She was also raising two young sons with her husband Rich Hirshberg, a fellow scientist she met at Oberlin. When the commute became too much, she quit to try full-time domesticity. For three years, Joan did nothing but cook, care for the boys, and clean the family’s five-bedroom house. The only semblance of science in her life involved baked goods. Joan was miserable. On the advice of a psychiatrist, she went to Lamont Observatory at Columbia University to look for a job, but worried that she’d been away too long. Immediately, she had three offers.

Solar Interference

At Lamont, Joan studied interactions between the magnetosphere and the solar wind. In those days, astrophysicists believed the magnetosphere was closed and tapered like a teardrop. Joan discovered that it’s actually open-ended, and has a long tail on the side opposite the Sun where the solar wind don’t blow. In an open model, the Sun’s magnetic field more directly influences the magnetosphere.

Several years later at NASA’s Jet Propulsion Laboratory (JPL), Joan was able to demonstrate that aurora happen when solar particles penetrate the magnetosphere. As these particles mix with those in the magnetosphere, the collisions manifest as brilliant colors.

Solar Wind vs. Magnetosphere. Image via NASA

She also studied sunspot cycles and coronal mass ejections (CME). These are solar storms that can greatly affect the magnetosphere and are capable of disabling satellites and interrupting terrestrial communications. At the time, CMEs were difficult to pinpoint. Joan’s research showed that wherever there are CMEs, there is also a significant increase of helium in the solar wind.

Joan also proved that CMEs occur in groups. From this research, she devised a statistical calculation to predict the number of high-energy particles that could bounce off the average spaceship during its lifetime. This important development resulted in better designs with greater longevity. In 1999, NASA honored her with an Exceptional Scientific Achievement Award.

Joan retired from JPL in 2002. Since then, she has turned her focus to the effect of solar cycle variations on climate change  and historical climate anomalies. At the age of 90, she’s still fascinated by all the crazy things the Sun does and is still determined to find explanations.

Joan thinks the Sun is excellent. Image via BBC


Filed under: Hackaday Columns, History, Original Art, Solar Hacks

Python keeps a gecko happy: terrarium automation with Raspberry Pi

อังคาร, 11/21/2017 - 23:30

For better or worse, pets often serve as inspiration and test subjects for hardware hacks: smarten up that hamster wheel, tweet the squirrel hunting adventures from a dog’s point of view, or automate and remote control a reptile enclosure. [TheYOSH], a gecko breeder from the Netherlands, chose the latter and wrote TerrariumPi for the Raspberry Pi to control and monitor his exotic companion’s home through a convenient web interface.

The right ecosystem is crucial to the health and happiness of any animal that isn’t native to its involuntarily chosen surroundings. Simulating temperature, humidity and lighting of its natural habitat should therefore be the number one priority for any pet owner. The more that simulation process is reliably automated, the less anyone needs to worry.

TerrariumPi supports all the common temperature/humidity sensors and relay boards you will find for the Raspberry Pi out of the box, and can utilize heating and cooling, watering and spraying, as well as lighting based on fixed time intervals or sensor feedback. It even supports location based sunrise and sunset simulation — your critter might just think it never left Madagascar, New Caledonia or Brazil. All the configuration and monitoring happens in the browser, as demonstrated in [TheYOSH]’s live system with public read access (in Dutch).

It only seems natural that Python was the language of choice for a reptile-related system. On the other hand, it doesn’t have to be strictly used for reptiles or even terrariums; TerrariumPi will take care of aquariums and any other type of vivarium equally well. After all, we have seen the Raspberry Pi handling greenhouses and automating mushroom cultivation before.

Filed under: green hacks, Raspberry Pi

Hackers vs. Mold: Building a Humidistat Fan

อังคาร, 11/21/2017 - 22:01

Having a mold problem in your home is terrible, especially if you have an allergy to it. It can be toxic, aggravate asthma, and damage your possessions. But let’s be honest, before you even get to those listed issues, having mold where you live feels disgusting.

You can clean it with the regular use of unpleasant chemicals like bleach, although only with limited effectiveness. So I was not particularly happy to discover mold growing on the kitchen wall, and decided to do science at it. Happily, I managed to fix my mold problems with a little bit of hacker ingenuity.

What Level of Humidity Leads to Mold?

I did some research into the underlying causes of the issue. We know mold loves moisture, but the specific root of the problem seems to be a high relative humidity in the surrounding air.

There is a limit to how much water vapor the air can contain at a given temperature. Relative humidity is the percentage of that water vapor limit at the current air temperature. High relative humidity also makes condensation worse, another source of moisture for mold growth. The thing to know is that moisture is our enemy here and the unit of measure that gives us the most reliable information about that is relative humidity.

A study done in Tokyo (PDF warning) seemed to show that the magic number is a bit below 70% relative humidity. Below that, the types of mold being studied grew much less. A previous study (PDF warning) described that the relative humidity required for mold growth was highly dependent on the surface in question; staying below 76% relative humidity prevented mold growth on most surfaces they studied. However, the Japanese study specifically dealt with walls in homes. The United States Environmental Protection Agency recommends below 60%.

Measuring My Home’s (Really High) Relative Humidity

Here in Southeast Asia, humidity below 60% is not really a thing for most of the year. Ever see packaging that says ‘store in a cool, dry place’? Better not to bring those things here.

Anyway, I had taken some quick measurements with a DHT11 combined temperature/humidity sensor while investigating IoT data logging platforms. They showed a range of 52% to 70% outdoors (we’re at the end of rainy season presently), drier in the mornings and more humid at night. In any case, with proper ventilation alone, it looks like 70% relative humidity or lower is achievable.

I repeated the measurement in the problem area of the house, and recorded a consistent 86% relative humidity! That was clearly problematic so I considered solutions. Running an air conditioner all the time was not practical. We’ve seen a couple of projects out there addressing mold problem with dehumidifiers, and those are sold here at around USD $150 for a small one, but it’s yet another appliance in the house. One effect of population density is that houses here are small.

Building a Smart Fan

My solution is a simple one: up the ventilation. The numbers so far suggest moving the humid air out would be sufficient. I was short a fan in the house anyway, and fans are cheap so there was little penalty if I was wrong.

I didn’t really want to leave a fan on all the time though. It may only use 40 watts, but it’s irritating to hear it, and I had a bunch of parts left over from learning to use gracefully silent solid-state relays. So why not add a humidistat to the fan? Humidistats are like thermostats, but they switch based on humidity rather than temperature.

You know those days when everything just comes together? This was one of those days. The fan had no electronics inside, only switches that connected mains power directly to ‘something’ further in the fan.

As much as possible, I avoid using solder for anything that uses mains power. In this case though, the wiring was just soldered to brass conductors already, and moreover, there were perforations in it that exactly fit the wire I had. As a result, all I had to do was put the solid-state relay across the switch for the fastest fan speed, and I had an OK test system:

I used a DHT11 combined temperature/humidity sensor to track humidity, interfaced with a Wemos Mini D1 board running NodeMCU to control the relay. A small mains to 5 volt module powered the control system. I wrote up a quick Lua program to control when the fan should be on:

gpio.mode(2, gpio.OUTPUT) gpio.mode(1, gpio.OUTPUT) gpio.write(2, gpio.LOW) gpio.write(1, gpio.LOW) pin = 4 x = 'off' function currentlyon(level) status, temp, humi, temp_dec, humi_dec = dht.read(pin) print(string.format("DHT Temperature:%d.%03d;Humidity:%d.%03d\r\n", math.floor(temp), temp_dec, math.floor(humi), humi_dec )) print('Currently ON. Temp:'..temp..' ,Humidity:'..humi) if humi < 66 then gpio.write(2, gpio.LOW) x = 'off' end end function currentlyoff(level) status, temp, humi, temp_dec, humi_dec = dht.read(pin) print('Currently OFF. Temp:'..temp..' ,Humidity:'..humi) if humi > 68 then gpio.write(2, gpio.HIGH) x = 'on' end end function statuscheck() print('Checking Status') if x == 'on' then currentlyon() elseif x == 'off' then currentlyoff() else print('Invalid state') end end tmr.alarm(1, 20000, tmr.ALARM_AUTO, function() statuscheck() end) A Simple Hysteresis Example and the Hunting Problem

The humidity required to change the state of the fan depends on whether the fan has last switched from on to off, or from off to on. This is called hysteresis: the state of the system depends on it’s history, and it’s an inelegant but easy way to avoid a common control issue called ‘the hunting problem’.

Hunting problems can be an issue in closed-loop control systems, where the behavior of the controller depends on feedback from a sensor coupled to the process you are measuring. In our situation, if we simply set the target humidity to 70%, then the fan will get to that value and turn on or off frequently due to small fluctuations in humidity. The fan can only be completely on or off, and neither of those states result in the target humidity being reached for long.

As in our case an acceptable humidity is a rather wide range, we set the fan to turn on at anything over 68% humidity, and once on, turn off under 66% humidity. The sensor resolution is 1%, so that’s a 4% range which seemed reasonable to start.

Some quick tests were run by blowing into the sensor, and it all worked as expected. The humidity problem tentatively solved, I put on protective gear and bleached the mold as best I could. Since then, it hasn’t returned.

It Works! Now Make It Better

Some improvements were added afterwards. Initially, the control system just toggles the fan in response to humidity by taking control of the actual switch. This means it doesn’t work well as a normal fan – it can ignore your speed selection depending on humidity! It would be better to interrupt the main power line with the solid-state relay, and have the control system default to the fan being on. Only when a dehumidifier function is selected (a switch), the control system will then connect or disconnect power to the fan as needed.

In the end that was an easy update. I removed the relay from the fan switch, added it as above, and added a toggle switch that connects GPIO D5 on the Wemos Mini D1 to either +3.3 volts or ground. Then I updated the code as below, assembled everything into the fan case, and it just worked:

gpio.mode(2, gpio.OUTPUT) gpio.mode(1, gpio.OUTPUT) gpio.write(2, gpio.LOW) gpio.write(1, gpio.LOW) gpio.mode(5, gpio.INPUT) pin = 4 x = 'off' function currentlyon(level) status, temp, humi, temp_dec, humi_dec = dht.read(pin) print(string.format("DHT Temperature:%d.%03d;Humidity:%d.%03d\r\n", math.floor(temp), temp_dec, math.floor(humi), humi_dec )) gpio.write(2, gpio.HIGH) print('Currently ON. Temp:'..temp..' ,Humidity:'..humi) if humi < 66 then x = 'off' end end function currentlyoff(level) status, temp, humi, temp_dec, humi_dec = dht.read(pin) gpio.write(2, gpio.LOW) print('Currently OFF. Temp:'..temp..' ,Humidity:'..humi) if humi > 68 then x = 'on' end end function statuscheck() fanmode = gpio.read(5) print (fanmode) print('Checking Status') if x == 'on' and fanmode == 1 then currentlyon() elseif x == 'off' and fanmode == 1 then currentlyoff() else print('Humidity mode inactive. Fan always on.') gpio.write(2, gpio.HIGH) end end tmr.alarm(1, 5000, tmr.ALARM_AUTO, function() statuscheck() end)

As a final note, solid-state relays of this type should normally have heat sinks attached, but I’m using it at a very small fraction of the rated current. It does not heat up perceptibly even after running for a long time. This large relay is overkill, as there are many smaller and cheaper options more suitable for the low currents used by the fan, but I had it on hand… so in it went.

There are many ways I could have tackled my mold problem. The most eloquent turned out to the a little bit of head scratching, and a lot of fun.

Filed under: green hacks, Hackaday Columns, home hacks

Mad Eye For The WiFi

อังคาร, 11/21/2017 - 19:00

In the Harry Potter universe, Professor Moody was, perhaps unfairly, given the nickname Mad Eye for the prosthetic eye he wore. His eye remains a challenge for technically-minded cosplayers aiming to recreate the look and feel of this unique piece of headgear. [cyborgworkshop] had already mastered the basic eye, but wanted to take things further.

The original build relied on a sub-micro servo to move the eyeball. This was done at random as an attempt to simulate the eye’s behaviour in the books and films. However, wanting more, [cyborgworkshop] decided to make the eye more reactive to its surrounding environment. Using the Adafruit Huzzah, a breakout board for the ESP8266, code was whipped up to detect the number of WiFi access points in the area. The more access points, the more frequent and erratic the movement of the eye. Occasional slower periods of movement are coded in before the eye resumes its wild darting once more, depending on just how saturated the local WiFi environment is.

It’s a great twist on the project, and [cyborgworkshop] has provided more details on the initial build, too. If you think you’re having déja vu, check out this build using recycled parts.

Filed under: Wireless Hacks

Prototyping, Making A Board For, And Coding An ARM Neural Net Robot

อังคาร, 11/21/2017 - 16:00

[Sean Hodgins]’s calls his three-part video series an Arduino Neural Network Robot but we’d rather call it an enjoyable series on prototyping, designing a board with surface mount parts, assembling it, and oh yeah, putting a neural network on it, all the while offering plenty of useful tips.

In part one, prototype and design, he starts us out with a prototype using a breadboard. The final robot isn’t on an Arduino, but instead is on a custom-made board built around an ARM Cortex-M0+ processor. However, for the prototype, he uses a SparkFun SAM21 Arduino-sized board, a Pololu DRV8835 dual motor driver board, four photoresistors, two motors, a battery, and sundry other parts.

Once he’s proven the prototype works, he creates the schematic for his custom board. Rather than start from scratch, he goes to SparkFun’s and Pololu’s websites for the schematics of their boards and incorporates those into his design. From there he talks about how and why he starts out in a CAD program, then moves on to KiCad where he talks about his approach to layout.

Part two is about soldering and assembly, from how he sorts the components while still in their shipping packages, to tips on doing the reflow in a toaster oven, and fixing bridges and parts that aren’t on all their pads, including the microprocessor.

In Part three he writes the code. The robot’s objective is simple, run away from the light. He first tests the photoresistors without the motors and then writes a procedural program to make the robot afraid of the light, this time with the motors. Finally, he writes the neural network code, but not before first giving a decent explanation of how the neural network works. He admits that you don’t really need a neural network to make the robot run away from the light. But from his comparisons of the robot running using the procedural approach and then the neural network approach, we think the neural network one responds better to what would be the in-between cases for the procedural approach. Admittedly, it could be that a better procedural version could be written, but having the neural network saved him the trouble and he’s shown us a lot that can be reused from the effort.

In case you want to replicate this, [Sean]’s provided a GitHub page with BOM, code and so on. Check out all three parts below, or watch just the parts that interest you.

[Sean]’s neural network is one that learns using supervised learning, an approach where you iterate through a table of inputs and expected outputs. If you instead want your robot to learn from experimenting in its environment, called unsupervised learning, then check out [Basti]’s four-legged walking robot.

Filed under: robots hacks