Marvelous Mechanisms: The Ubiquitous Four Bar Linkage

The four bar linkage is a type of mechanical linkage that is used in many different devices. A few examples are: locking pliers, bicycles, oil well pumps, loaders, internal combustion engines, compressors, and pantographs. In biology we can also find examples of this linkage, as in the human knee joint, where the mechanism allows rotation and keeps the two legs bones attached to each other. It is also present in some fish jaws that evolved to take advantage of the force multiplication that the four bar mechanism can provide.

How It Works

Deployable mirror with scissor linkages. By [Catsquisher] via Wikimedia CommonsThe study of linkages started with Archimedes who applied geometry to the study of the lever, but a full mathematical description had to wait until the late 1800’s, however, due to the complexity of the resulting equations, the study and design of complex linkages was greatly simplified with the advent of the digital computer.

Mechanical linkages in general are a group of bodies connected to each other to manage forces and movement. The bodies, or links, that form the linkage, are connected to each other at points called joints. Perhaps the simplest example is the lever, that consists of a rigid bar that is allowed to pivot about a fulcrum, used to obtain a mechanical advantage: you can raise an object using less force than the weight of the object.

Two levers can be connected to each other to form the four bar linkage. In the figure, the levers are represented by the links a (A-D) and b (B-C).  The points A and B are the fulcrum points.  A third link f (C-D) connects the levers, and the fourth link is the ground or frame g (A-B) where the mechanism is mounted. In the animation below, the input link a (the crank) performs a rotational motion driving the rocker rod b and resulting in a reciprocating motion of the link b (the rocker).

This slider-crank arrangement is the heart of the internal combustion engine, where the expansion of gases against a sliding piston in the cylinder drives the rotation of the crank. In a compressor the opposite happens, the rotation of the crank pushes the piston to compress the gas in the cylinder. Depending on how the mechanism is arranged, it can perform the following tasks:

  • convert rotational motion to reciprocating motion, as we just discussed above.
  • convert reciprocating motion to rotational motion, as in the bicycle.
  • constrain motion, e.g. knee joint and car suspension.
  • magnify force, as in the parrotfish jaw.

Locking pliers mechanism. Image from [Engineering made easy]

Some Applications

One interesting application of the four bar linkage is found in locking pliers. The B-C and C-D links are set at an angle close to 180 degrees. When force is applied to the handle, the angle between the links is less than 180 (measured from inside the linkage), and the resulting force in the jaws tries to keep the handle open. When the pliers snap into the locked position that angle becomes less than 180, and the force in the jaws keeps the handle in the locked position.

In a bicycle, the reciprocating motion of the rider´s legs is converted to rotational motion via a four bar mechanism that is formed by the two leg segments, the bicycle frame, and the crank.

An example from nature, the Moray eel. Image from [Matthew West]As with many other inventions of humankind, we often find that nature has already come up with the same idea via evolution. The parrotfish lives on coral reefs, from which it feeds, and has to grind the coral to get to the polyps inside. For that job, they need a very powerful bite. The parrotfish obtains a mechanical advantage to the muscle force by using a four bar linkage in their jaws! Other species also use the same mechanism, one is the Moray eel, shown in the image, which has the very particular ability to launch its jaws up in the mouth to capture its prey, much like the alien from the film series.

The joints connecting the links in the linkage can be of two types. A hinged joint is called a revolute, and a sliding joint is called a prismatic. Depending on the number of revolute and prismatic joints, the four bar linkage can be of three types:

  • Planar quadrilateral linkage formed by four links and four revolute points. This is shown in the animation above.
  • Slider-crank linkage, formed by three revolute joints and a prismatic joint.
  • Double slider formed by two revolute joints and two prismatic joints. The Scotch yoke and the trammel of Archimedes are examples.

There are a great number of variations for the four bar linkage, and as you can guess, the design process to obtain the forces and movements that we need is not an easy task. An excellent resource for the interested reader is KMODDL (Kinematic Models for Design Digital Library) from Cornell University. Other interesting sites are the 507 mechanical movements, where you can find nice animations, and [thang010146]’s YouTube channel.

We hope to have piqued your curiosity in mechanical things. In these times of ultra fast developments in electronics, looking at the working of mechanisms that were developed centuries ago, but are still present and needed in our everyday lives can be a rewarding experience. We plan to work on more articles featuring interesting mechanisms so please let us know your favorites in the comments below.

Posted in classic hacks, Engineering, Featured, four bar linkage, linkage, machine, mechanical engineering, mechanism | Leave a comment

Friday Hack Chat: Audio Amplifier Design

Join [Jørgen Kragh Jakobsen], Analog/digital Design Engineer at Merus-Audio, for this week’s Hack Chat.

Every week, we find a few interesting people making the things that make the things that make all the things, sit them down in front of a computer, and get them to spill the beans on how modern manufacturing and technology actually happens. This is the Hack Chat, and it’s happening this Friday, March 31, at noon PDT (20:00 UTC).

Jørgen’s company has developed a line of multi level Class D amplifiers that focus on power reduction to save battery life in mobile application without losing audio quality.

There are a lot of tricks to bring down power consumption, some on core technologies on transistor switching, others based on input level where modulation type and frequency is dynamically changed to fit everything from background audio level to party mode.

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging.

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

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

Upcoming Hack Chats

We’ve got a lot on the table when it comes to our Hack Chats. On April 7th, our host will be [Samy Kamkar], hacker extraordinaire, to talk reverse engineering.

Posted in ASIC, digital audio hacks, Hack Chat, Hackaday Columns, Keysight, manufacturing, Matt Martin, silicon | Leave a comment

Swan: Better Linux on Windows

If you are a Linux user that has to use Windows — or even a Windows user that needs some Linux support — Cygwin has long been a great tool for getting things done. It provides a nearly complete Linux toolset. It also provides almost the entire Linux API, so that anything it doesn’t supply can probably be built from source. You can even write code on Windows, compile and test it and (usually) port it over to Linux painlessly.

However, Cygwin’s package management is a little clunky and setting up the GUI environment has always been tricky, especially for new users. A project called Swan aims to make a full-featured X11 Linux environment easy to install on Windows.

The project uses Cygwin along with Xfce for its desktop. Cygwin provides pretty good Windows integration, but Swan also includes extra features. For example, you can make your default browser the Windows browser with a single click. It also includes spm — a package manager for Cygwin that is somewhat easier to use, although it still launches the default package manager to do the work (this isn’t a new idea, by the way).

Here’s a screenshot of Windows 10 (you can see Word running native in the background) with top running in a Bash shell and Thunar (the default file manager for Swan). Notice the panel at the top with the swan icon. You can add things there and there are numerous settings you can access from the swan icon.

Swan is fairly new, so it still has some rough edges, but we like where it is going. The install process is in two parts which doesn’t make sense for something trying to be easier. Admittedly, it is already easier than doing an X11 install with normal Cygwin. However, on at least one test install, the virus scanner erroneously tripped on the wget executable and that caused the install to fail.

The project is hosted on GitHub if you want to examine the source or contribute. Of course, Windows has its own support for Linux now (sort of). Swan isn’t quite a finished product and, like Cygwin, it isn’t a total replacement for Linux. But it is still worth a look on any machine that you use that boots Windows.

Posted in cygwin, linux, linux hacks, swan, windows | Leave a comment

Don’t Fear the Filter: Cascading Sallen-Keys

In the last edition of Don’t Fear the Filter, we built up two examples of the simplest and most-used active filter of all time: the two-pole Sallen-Key lowpass. This time, we’re going to put two of these basic filter blocks in a row, and end up with a much sharper lowpass filter as well as a bandpass filter. For the bandpass, we’ll need to build up a quick highpass filter as well. Bonus!

I claimed last time that the Sallen-Key lowpass would cover something like 80% of your filtering needs. (And 72.4% of all statistics are totally made up!) These two will probably get you through another 10% or so. Honestly, I’ve never built a standalone active highpass, for reasons we’ll see below, but the active bandpass filter that we’re building it for is a great tool to have in your belt, especially for anything audio.

Cascading Sallen-Key Lowpasses for More Rolloff

If, as we said last time, a two-pole filter has two reactive elements (the two capacitors) and a rolloff of -12 dB per octave, surely we could just add another copy of the same circuit downstream and get even more filtering done, right? Yes, but it’s not optimal.

A little bit on a detail that I glossed over last time. All filters of a given order have the same asymptotic (eventual) rolloff rate of -6 db per octave per pole. The main performance difference among the various responses — Butterworth, Bessel, or Chebyshev — is in how quickly the filter gets from flat in the passband to the eventual rolloff rate. A 1969 VW Bug will drive the speed limit at the same rate as a Lamborghini, but how fast you get up to the speed limit can differ.

fifth-order-butterworth-cascadeSame idea, but with a 5th order filter, from Analog Devices’ “Basic Linear Design”

It turns out that, as long as you’re stacking filters, you can pick one to be slightly peaky (resonant at the cutoff frequency) and the other to be a little too flat, and the combination will have a nice flat transition that nonetheless gets to the rolloff rate faster than simply stacking identical filters. Which is to say, the overall filter has a Butterworth response, but the individual stages won’t. This makes the design a tiny bit more critical, but it’s nothing you can’t handle.

Picking the optimal resonance values is a matter of math, and not really informative. In the old days, you’d look them up in a table in a book and then scale up the prototypical 1 Hz filter to your needs, using pencil and paper. Today, we cheese out and head to an online calculator. Click Butterworth, 4-pole, enter 1 for the various stage gains, and enter your cutoff frequency, and you’re done. This tool is even nice enough to draw the circuit diagram and pick the nearest capacitor values out of the standard-value E6 or E12 series. Bam!

filter_designerYou’ll notice that there are no round-number resistors anymore: the values are strange, and no longer in integer ratios. Getting close to these values is a good goal, but again with a Butterworth response, nothing is too critical. So where it calls for a 21,584 Ω resistor, I’d just pull out a 22 kΩ out of the box. With the particular tool above, you can even measure the actual capacitors that you’re using, enter the real values into the spreadsheet, and it will re-calculate the resistors for you. A nice touch, but not necessary with a forgiving circuit.

Constructing a fourth-order filter is slightly more than twice as much work as a second-order filter, but the results are worth it when you need them. Here are some FFT spectrograms to show off. In both cases, the input is a square wave at 800 Hz. Square waves have harmonics of diminishing volume at all of the odd values, so there’s a substantial peak here at 2400 Hz and another at 4000 Hz.

In all of these scope shots, the input is a square wave at 800 Hz being run through a filter with a cutoff at 1000 Hz. The first pane displays a comparison of two- and four-pole filters. The remaining three scope shots also show the Fourier transform of the source and two filtered waves. You can see how the peaks fall off nearly twice as fast in the four-pole filter. Success!

The Sky is the Limit?

filter_orderBut why stop at four poles? Each additional pole-pair only costs you two resistors, two capacitors, and an op-amp stage, right? To maintain the overall non-resonance of the filter, the different stages will need carefully controlled resonance values, and this will mean exact capacitor ratios. With practical parts tolerances, this gets more and more difficult. Additionally, as more stages get added on, the resonance that the final stage requires to compensate for the early stages puts increasing demands on the op-amp’s frequency abilities, in particular requiring a higher gain-bandwidth product.

Finally, at some point the simplicity advantages of the relatively slow Butterworth response is outweighed by the extra stages, and you’re better off designing a lower-order Chebyshev filter than a higher-order Butterworth. On the other hand, the four-pole Butterworth is a beautiful and stable filter. Don’t overcomplicate things unless you really need to.

Two-Stage Bandpass Filter

fil97_bgAnd now for something completely similar: cascading highpass and lowpass filters to make a bandpass filter. If a lowpass filter knocks out the high frequencies and lets the lows pass, you won’t be surprised that a highpass knocks out the lows, and a bandpass knocks out both the highs and lows, leaving the juicy middle frequencies intact. The strategy is to take the signal first through a highpass followed by a lowpass.

Bandpass filters like this are a great frontend to any ADC scheme where you have a general idea in what range the frequencies of interest lie, but you don’t want to narrow down on one thin slice of the spectrum. If you’re lowpass sampling with an ADC, you’ll at least need the lowpass filter. If you’re not interested in the lowest of the low frequencies, why not trim them off in analog while you’re at it?

For instance, in a capacitive-sensing application, a person touching a metal plate is an event that can span frequencies from something like 10 Hz up to maybe 1 Hz — even a short tap will last 100 ms, and you probably don’t care if the person holds their finger on the button for much longer than a second. Here, bandpassing the signal has the effect of throwing away the low-frequency environmental changes (humidity, temperature) that will cause capacitive drift over the course of a day, and also throws away high-frequency noise like interference from nearby electronic devices. Doing this up front in analog makes the programming and analysis work in firmware very easy.

The Highpass

There’s not much to say about the Sallen-Key highpass filter, because it’s the same circuit as the lowpass with the capacitors and resistors swapped. In the lowpass we set the resistors equal and the capacitors in a ratio of 1:2, but now the capacitors are equal and the resistors are 1:2 for the Butterworth response. If you’re powering the op-amp off of a single-sided power supply, as opposed to matching positive and negative voltages, you will need to create a constant mid-rail voltage (GNDREF in the diagram). Doing so can be as easy as making a voltage divider out of two relatively low-value resistors. If you have an unused op-amp stage anywhere, you can buffer this “virtual ground” as well.

Active highpasses just aren’t as useful as lowpasses. Highpass filters really shine in radio-frequency applications, but most op-amps are too slow to keep up. Still, you’ll find them in audio applications like crossover and equalization circuits. As with the lowpass, the highpass version of the Sallen-Key filter can be cascaded for steeper rolloff.

The one time I’ve built a standalone highpass was in a bat-detector preamp, filtering out the audible portion of the audio range to focus on the bats’ high-frequency chirps. If you’ve used active highpass filters, I’d love to hear about it in the comments. Am I missing obvious applications?

The Bandpass

The bandpass simply cascades a highpass and a lowpass. This circuit isn’t intended for extreme selectivity of a particular frequency, and a rule of thumb is to make the highpass and lowpass cutoff frequencies differ by at least a factor of five or so. This is a good fit for the human vocal range — 75 Hz to 1000 Hz fundamentals, with important content up to 3000 Hz — or for pre-filtering slow-moving DC analog values before sampling them with an ADC.

When you’re aiming for a particularly tight frequency band, this circuit may not help that much. Narrow bandpass filters are a separate topic of their own, and I’ll cover them along with narrow band-reject (notch) filters on their own, because they’re tricky to design right, but are very useful when you need them.

As mentioned while discussing the highpass filter, there is no need for an extra DC-blocking capacitor on the input of this circuit because the highpass already takes care of that. There’s also no need for DC-blocking between the stages, because even though the second stage is a lowpass, the signal has already been centered in the middle of the op-amp’s response range by the time it gets there. So the only difference between DC- and AC-coupled bandpasses of this design is the addition of an output capacitor.

To demonstrate this circuit, I built up a highpass with a cutoff at 20 kHz and a lowpass with a cutoff at 50 kHz. Feeding white noise into this bandpass filter gives you a good feeling for the frequency response, at least as well as my ‘scope will capture it. You’ll note that the slopes of the highpass and lowpass sections don’t look the same. This is partly due to the fact that frequency rolloffs are multiplicative in nature — they would look the same on a log scale in frequency. Indeed, this would be the empirical version of a Bode plot.

Wrapup

The two-pole Sallen-Key filter that we built last time is a workhorse, but sometimes you need a racehorse and sometimes you need a show pony. Stacking two of the units that you already know together, while taking care to tweak the resonance values just right, makes the four-pole design easy to build and quite stable when you need that extra rolloff. Similarly, stacking a highpass and a lowpass together is child’s play and adds a new filter type to your toolkit.

And since all of these circuits are made with (multiples of) the same circuit topology, perhaps with the resistors and capacitors switched around, you could easily imagine making a single circuit board based on a two- or four-op-amp chip where you just plug in the right values for the passives, maybe with optional AC-decoupling stages, and you’re ready for anything. Since most op-amps share a common pinout, it would be easy to swap them out as well. Hmmm…maybe I’ll do that.  If you beat me to it, post up in the comments.

Up next are going to be the single-purpose filters: tight bandpass and notch filters. These are useful when you want to emphasize or reject a tiny sliver of the frequency spectrum while leaving the rest ideally unchanged. Want to detect a particular tone or remove that nasty AC hum? Stay tuned.

Posted in Engineering, Hackaday Columns, how-to | Leave a comment

Use a Mini PCI-e 3G Card with USB Instead

Back the late 2000s, when netbooks were the latest craze, some models would come with an inbuilt 3G modem for Internet access. At the time, proper mobile Internet was a hip cool thing too — miles ahead of the false prophet known as WAP. These modems would often slot into a Mini PCI-e slot in the netbook motherboard. [delokaver] figured out how to use these 3G cards over USB instead.

It’s actually a fairly straightforward hack. The Mini PCI-e standard has a couple of pins dedicated to USB data lines, which the modem in question uses for communicating with the host computer. Unfortunately it’s not quite as simple as just soldering on a four-wire USB cable. The modem relies on the 3.3V power from the Mini PCI-e slot instead of the 5V from USB. No problem, just get a low-dropout 3.3V regulator and run that off the USB port. Then, it’s a simple enough matter of figuring out which pins are used to talk to the SIM card, and soldering them up to a SIM adapter, or directly to the card itself if you’re so inclined. The guide covers a single model of 3G modem but it’s likely the vast majority of these use a very similar setup, so don’t be afraid to have a go yourself.

Overall Mini PCI-e is a fairly unloved interface, but we’ve seen the reverse of this hack before, a Mini PCI-e to USB adapter used to add a 12-axis sensor to a laptop.

[Thanks to Itay for the tip!]

Posted in 3g, laptops hacks, mini-PCIe, usb | Leave a comment

Retrotechtacular: Stereo Records

The 20th century saw some amazing technological developments. We went from airplanes to the moon. We went from slide rules to digital computers. Crank telephones to cell phones. But two of the most amazing feats of that era were ones that non-technical people probably hardly think about. The transformation of radio and TV from mono and black and white, to stereo and color. What was interesting about both of these is that engineers managed to find a way to push the new better result into the same form as the old version and — this is the amazing part — do it in such a way that the old technology still worked. Maybe it is the rate that new technology moves today, but we aren’t doing that today. Digital TV required all-new everything: transmitters, receivers, frequencies, and recording gear. Good luck trying to play the latest video game on your 25-year-old PC.

It is hard to remember when stores were full of all sorts of audio and video media. We’ve noticed that all forms of media are starting to vanish. Everything audio and video are all streamed or downloaded these days. Records, 8-tracks, cassettes, and even CDs and DVDs are vanishing. However, vinyl records have made a come back in the last few years for their novelty or nostalgic value.

Audio recording on wax, foil, or vinyl was more or less the same process perfected by [Thomas Edison] (or, perhaps, people who worked for him) back in 1877 although the flat records we think of didn’t appear until around 1890.

The principle is simple. Air pressure from sound cuts a groove into the recording medium. A piezoelectric stylus (or later, a stylus with a dynamic element) traced the groove and reproduced the same sound. Amplify it, and the phonograph is in business. You might enjoy the gramophone [SynthDan1] restored in the video below.

Stereo

By the 1950s, the hackers of their day were building or buying “hi-fi” equipment, gear that sounded better than the poor-quality audio spewing out of record players and AM radios of the day. Eventually, companies would roll out stereo recordings. But the records didn’t look any different, and they would still play on a standard (mono) record player. How is that possible? No, it isn’t two separate records like the vintage player at the top of this post found in the Museum of Technology in Paris.

We could explain it, but it is more fun to let [Bob Banks] from RCA explain it in this vintage advertisement.

The Real Story

Pretty impressive special effects for the time. [Bob] did oversimplify a few things, though. First, the groove can have a vertical component and a horizontal component. But the resolution on the vertical isn’t nearly as good, so that means one channel would be disadvantaged. Instead, the two tracks in the single groove are spun 45 degrees so that each channel has some horizontal and some vertical component.

[Bob] wants you to think RCA invented this, although he never actually says that flat out. In fact, [Alan Blumlein] of EMI patented the scheme back in 1931. The first commercial stereo records, which were not from RCA either, would not appear until 1957.

Because of how the groove was rotated, the movement of the stylus horizontally was the combination of the left and right tracks — the same as the mono signal. The vertical motion carried the difference: the left channel minus the right channel, or L-R.

That’s how a mono record could play back normally on a stereo player. The horizontal motion on the track will reproduce the same sound on both channels. Conversely, a mono stylus reading a stereo track would only pick up the horizontal part of the track and play both channels together. Unfortunately, many mono players didn’t move up and down very well and could wear a stereo record, so users learned not to play stereo records on mono players, even though it would work. Of course, that assumes you have the same-sized grooves. Older records had wider grooves and wider needles.

If you want to see how a stereo cutter works, check out [EpicenterBryan’s] video below.

Compatibility

In a market where Elvis Presley was still selling 78 RPM records because his fans couldn’t afford new record players, this compatibility was very important. We imagine [Alan Blumlein] would be horrified to see how we routinely tell everyone to throw away their tapes for CDs and their CDs for digital music. TV was the same. Making a signal with color that black and white sets could still receive was quite the marvel (and a topic for a future Retrotechtacular). The idea of making everyone throw out their sets for new ones or buy government-subsidized converters would have been poorly received, indeed.

We can’t help but wonder if we are doing all we can on compatibility. Do we really have to trash operating systems and CPUs every few years? Do we really need to double the memory in our phones every time our contracts run out? Or is it a clever planned obsolescence ploy? As people who create things, how are we doing on compatibility? We’ll see how history judges.

Featured image by [ParameterBond], Public Domain

Posted in gramophone, Hackaday Columns, HiFi, history, phonograph, RCA, rca victor, Retrotechtacular, stereo | Leave a comment

Next Weekend: The Vintage Computer Festival East

Next weekend is the Vintage Computer Festival East in Wall, New Jersey. We’re going, and you should be there too.

The VCF East is the largest gathering of retrocomputing aficionados on the east coast. It’s three days of talks, exhibits, a flea market, and a pow-wow of the greatest minds buried under obsolete technology. No VCF is complete without a few talks, and this year is shaping up to be great. Keynotes will include [Bjarne Stroustrup], designer / implementor / inventor of C++. Computer historian [Bill Degnan] will give a review of 40 years of ‘appliance computers’, and [Tom Perera], Ph.D. will be giving a talk on the Enigma machine.

The exhibits at VCF are always the star of the show, and this year is no different. Highlights include mechanical computers, the finest from Silicon Graphics, and a version of Unix published by Microsoft. The individual exhibits are always great; last year the world’s first digital camera made an appearance. If you’re in the area, this isn’t an event to miss. VCF is going down at InfoAge, a science center at the former Camp Evans — a military installation that is best described as, ‘DARPA before World War II’.

Hackaday is proud to once again sponsor VCF East. This has been going on for a couple of years now and our Art Director, [Joe Kim] has created some incredible art as part of the sponsorship. Click on the thumbnail of this year’s art to embiggen. The VCF West art from last year is a stunning take on the Macintosh and last year’s VCF East art reflected the retro hackathon we sponsored.

Posted in cons, Original Art, VCF East | Leave a comment

Russian Hackers Domain Fronting

FireEye just put out a report on catching the Russian hacker group “Advanced Persistent Threat 29” (APT29, for lack of a better code name) using the meek plugin for TOR to hide their traffic. If you’re using meek with meek-reflect.appspot.com, you’ll find it’s been shut down. If all of this is gibberish to you, read on for a breakdown.

meek is a clever piece of software. Imagine that you wanted to communicate with the Tor anonymizing network, but that you didn’t want anyone to know that you were. Maybe you live in a country where a firewall prevents you from accessing the full Web, and blocks Tor entry nodes as part of their Great Firewall. You’d want to send traffic somewhere innocuous first, and then bounce it over to Tor, in order to communicate freely.

That’s what meek does, but it goes one step further. The reflector server is hosted using the same content-delivery network (CDN) as a popular service, say Google’s search engine. The CDN has an IP address, like every other computer on the Internet, but it delivers content for any of the various services it hosts. Traffic to the CDN, encrypted with TLS, looks the same whether it’s going to the meek reflector or to Google, so nobody on the outside can tell whether it is a search query or packets destined for Tor. Inside the CDN, it’s unencrypted and passed along to the reflector.

Anyway, meek was invented to help bring the uncensored Internet to people who live in oppressive regimes, and now cybersecurity researchers have observed it being used by Russian state hackers to hide their tracks. Sigh. Technology doesn’t know which side it’s on — the same backdoor that the FBI wants to plant in all our communications can be used by the mafia just as easily. Plugins that are meant to bring people freedom of speech can just as easily be used to hide the actions of nation-state hackers.

What a strange world we live in.

Posted in anonymizer, cdn, meek, news, russian hackers, security hacks, state actors, tor | Leave a comment

Source Parts on TaoBao: An Insider’s Guide

For hardware aficionados and Makers, trips to Shenzhen’s Huaqiangbei have become something of a pilgrimage. While Huaqiangbei is a tremendous and still active resource, increasingly both Chinese and foreign hardware developers do their sourcing for components on TaoBao. The selection is vastly greater and with delivery times rarely over 48 hours and frequently under 24 hours for local purchases it fits in nicely with the high-speed pace of Shenzhen’s hardware ecosystem.

For overseas buyers, while the cost of Taobao is comparable to, or slightly less than AliExpress and Chinese online stores, the selection is again, many, many times the size. Learning how to effectively source parts from Taobao will be both entertaining and empowering.

XKCD: Up Goer Five

Understanding How Chinese Works is Helpful

You can find nearly anything on TaoBao, if you know the Chinese name for it. This doesn’t mean you need to speak Chinese, but you should understand how it works. While the site can be navigated using Google Translate, it can’t accept English language searches. Figuring out what an object or part is called in Chinese is therefore the first and largest challenge. Once you find that string of characters you don’t need to be able to read it any more than any other snippet of code needs to be human readable in order to be manipulated. So long as you know roughly what the code represents that’s all that you need.

In Bunnie Huang’s Essential Guide to Electronics in Shenzhen (yes, it is (absolutely essential), Bunnie compares Chinese to XKCD’s Up Goer Five. This installment of the comic uses “only the ten hundred words people use the most often” to explain all the parts of a rocket. It’s a very accurate analogy, and once non-Chinese speakers grasp this they are able to more accurately define their search terms when sourcing online. A few thousand words are used to describe a huge number of components. Often in a pretty intuitive way if you break it down.

A 电脑 (Diànnǎo), directly translates as “Electric Brain” or a computer in English. While most Chinese characters have diverged so far from their origins to be unrecognizable — 电 (Diàn) or “electric” is one you’ll see a lot. This character is a representation of a cloud with a lightning bolt going to ground. Likewise, a 手机 Shǒujī or “Hand Machine” is a mobile phone, and 手 still looks a bit like fingers on a hand.

If you keep this structure in mind — that Chinese part names are rarely one dedicated word, and more of a semi-intuitive set of keywords — it will make finding those names much easier.

Finding Your Part by Name

Some parts you can simply use Google Translate, but sometimes it’s not specific enough or returns the wrong context for that word. In that case, it’s best to use technical websites that have been localized into Chinese as a resource.

For electronic parts the .com and .cn versions of the Mouser site are interchangeable. Mostly just the category names are translated but that can get you very close and is useful for working with Chinese engineers. You can send them the URL of the type of part you want, there is a picture and no confusion. They can do the same for English speakers but in reverse.

So:

http://www.mouser.com/Sensors/Capacitive-Touch-Sensors/_/N-1b8oy/

becomes

http://www.mouser.cn/Sensors/Capacitive-Touch-Sensors/_/N-1b8oy/

For mechanical parts, Misumi offers similar functionality by replacing “us” with “cn”.

https://us.misumi-ec.com/vona2/mech/M1500000000/M1501000000/M1501030000/M1501030100/

becomes

http://cn.misumi-ec.com/vona2/mech/M1500000000/M1501000000/M1501030000/M1501030100/

Refining your search

Google Translating “switch” will get you “开关” You can paste that into the TaoBao search field and get a large and somewhat random collection of mostly AC light switches. But if we make the string “开关 DPDT” things start to get more useful. When possible add the numbers for the voltage, amperage etc. required and it will get you a lot closer.

If we see something pretty close to what we want we have two options, the first is to mouse-over the product image. An orange bar will come up, it may give you the option to “找相似” or “Find Similar”. Clicking on this will bring up things that are close, but not identical to that product.

If there is no option to “Find Similar” you can copy the Chinese description into Google Translate for more useful keywords.

6只脚DPDT蓝色MINI小型SMTS-202双刀双通钮子开关 YW2-102

and Google Translate tells us the string “双刀双通钮子开关” is “Double pole double button switch”. A search using that string gets us a large number of similar switches to choose from.

Finding Your Part by Image

Taobao has a very clever search-by-image function. If you have an image of the part you want you can use that to search. It’s the little camera icon on the right hand side of the search bar.

This has a number of uses: finding the upstream distributors of products, finding unauthorized copies of products, and seeing if new Crowdfunding campaigns are based on pre-existing Chinese products.

Making Your Order

Unlike Amazon, the “Buy” button on Taobao is more an invitation to chat about buying with the store owner. There’s usually a certain amount of required conversation. Some non-Chinese speakers copy and paste a “sorry I don’t speak Chinese” boilerplate but many stores won’t fulfill an order based on this because they are concerned that miscommunication will lead to a bad review which will cost them more than the profit on the item.

This process of chatting for more than half of all orders and lack of a straightforward shopping-cart-and-buy-it process means it can be difficult for those who can’t read Chinese to make TaoBao purchases. They also don’t accept PayPal and while supposedly there is a process to accept Western credit cards I don’t know anyone who’s set it up successfully.

Fortunately, there are services that will simply take care of this on you behalf. You send them links to the products you want and for a modest fee they take care of the rest. These brokers buy the items, charge it to your PayPal or credit card, accept the packages on your behalf, consolidate them and then forward them to you. Usually, the cost of the item plus this service fee is still less than purchasing the same items through AliExpress and gives you access to a far larger selection.

Some TaoBao brokers (in no order):

When in Shenzhen, Ringy provides translation services for free over WeChat and can have the packages sent to your hotel.

  • WeChat: ringyringy

Things to Avoid

“Will it be ready by Monday”

Never ask if it will be ready by a specific date, the answer will almost always be “yes”. There’s nothing much you can do if it’s not, so they have no reason to lose the sale. So when dealing with your TaoBao broker don’t ask “Can they have it ready by Monday?”, instead ask “What day do they say it will be ready?” and you get a much more accurate answer.

In general, this pattern should be followed when sourcing in China. Ask “What colors does it come in?” before the much more problematic “can they make it in pink?”. It’s far easier to be successful when working within the supplier’s established timeline and product range then starting out with something new.

“What do you want it for?”

Never answer this question from a store owner. This means they want to know if they can substitute something else based on what imagine will suffice for your requirements. Why would a 3D printer heated bed need an expensive sheet of PEI? Acrylic should be fine. You’ll get a very nice sheet of PEI colored acrylic for a bit less than the cost of PEI but a lot more than what acrylic costs. Stick with the item as listed on the BOM, if they don’t know what it’s for there is more risk of a substitution failing immediately and a poor review.

Avoid buying anything that has not been reviewed by other buyers.

Are their fake reviews? Sure, tons of them (although it’s getting better). But they cost money for the store owners to purchase and usually there are authentic ones as well — that’s cost sunk into that listing. If a listing has no feedback, a store owner loses nothing by simply taking it down in the event that you (or the agent on your behalf) gives it a bad review.

Don’t Bargain Hunt

The “get it cheaper” part is already done with when you made your choice to use TaoBao instead of a distributor back in the West. Further attempts to save money will result in problems. Everyone on Taobao sources from the same factories, if an identical or very similar product is much cheaper there’s a reason for it. Look at the top five most popular listings for a part, the average price of those or higher is what you can expect to pay.

While there are certainly challenges to sourcing on TaoBao, for any hardware enthusiast the vast, and frequently customizable selection available make it a very useful resource and skill set to have should the need arise.


Naomi Wu is a hardware enthusiast and Shenzhen native. The above guide was compiled with the generous assistance of the Shenzhen hardware community.

Posted in broker, Business, china, Featured, how-to, parts, shenzhen, taobao | Leave a comment

Arch Your Eyebrow at Impression Products V. Lexmark International

When it comes to recycled printer consumables, the world seems to divide sharply into those who think they’re great, and those who have had their printer or their work ruined by a badly filled cartridge containing cheaper photocopy toner, or God knows what black stuff masquerading as inkjet ink. It doesn’t matter though whether you’re a fan or a hater, a used printer cartridge is just a plastic shell with its printer-specific ancilliaries that you can do with what you want. It has performed its task the manufacturer sold it to you for and passed its point of usefulness, if you want to fill it up with aftermarket ink, well, it’s yours, so go ahead.

There is a case approaching the US Supreme Court though which promises to change all that, as well as to have ramifications well beyond the narrow world of printer cartridges. Impression Products, Inc. v. Lexmark International, Inc. pits the printer manufacturer against a small cartridge recycling company that refused to follow the rest of its industry and reach a settlement.

At issue is a clause in the shrink-wrap legal agreement small print that comes with a new Lexmark cartridge that ties a discounted price to an agreement to never offer the cartridge for resale or reuse. They have been using it for decades, and the licence is deemed to have been agreed to simply by opening the cartridge packaging. By pursuing the matter, Lexmark are trying to set a legal precedent allowing such licencing terms to accompany a physical products even when they pass out of the hands of the original purchaser who accepted the licence.

There is a whole slew of concerns to be addressed about shrink-wrap licence agreements, after all, how many Lexmark owners even realise that they’re agreeing to some legal small print when they open the box? But the concern for us lies in the consequences this case could have for the rest of the hardware world. If a precedent is set such that a piece of printer consumable hardware can have conditions still attached to it when it has passed through more than one owner, then the same could be applied to any piece of hardware. The prospect of everything you own routinely having restrictions on the right to repair or modify it raises its ugly head, further redefining “ownership” as  “They really own it”. Most of the projects we feature here at Hackaday for example would probably be prohibited were their creators to be subject to these restrictions.

We’ve covered a similar story recently, the latest twist in a long running saga over John Deere tractors. In that case though there is a written contract that the farmer buying the machine has to sign. What makes the Lexmark case so much more serious is that the contract is being applied without the purchaser being aware of its existence.

We can’t hold out much hope that the Supreme Court understand the ramifications of the case for our community, but there are other arguments within industry that might sway them against it. Let’s hope Impression Products v. Lexmark doesn’t become a case steeped in infamy.

Thanks to [Greg Kennedy] for the tip.

Lexmark sign by CCC2012 [CC0].

Posted in court case, Current Events, drm, hardware, impressum, legal, Lexmark, news, supreme court | Leave a comment