Andrew Huang's Blog, page 24

Name that Ware, May 2018

The Ware for May 2018 is shown below.

This month’s contest isn’t about naming a ware. Instead, the challenge is to guess the total amount of vias + holes on the NeTV2 PCB. The closest (or first correct) guess will get a DVT-revision of the board (same as the one shown above) as a prize! Please note: depending on your country of residence you may have to cover import duties or VAT.

At the end of this month, once the contest is over, I’ll upload the PCB source files to a public repo. The contest would be just too easy otherwise :)

Winner, Name that Ware April 2018

The ware for April 2018 is an SAE 316L stainless steel cerclage currently embedded in my right kneecap. There’s also a pair of 2.5mm holes drilled lengthwise through the patella, and a set of sutures woven into my quadriceps, neither of which show up in an X-ray. The hardware is to repair a double-break of my knee; I simultaneously suffered a patellar avulsion fracture and a tear of the quadriceps tendon. It’s rare to get both injuries at once, but hey why do anything half-assed. As for how it happened – well, you’ll have to believe me that it’s just from falling while walking on flat ground. There was a puddle of greasy/soapy water outside a hawker stall and boom, I’m unable to walk for months. I wish I had some cooler story, so that’s why I had this month’s competition – to try and find a better bar story. To that end, gratz to perlfriend for the most imaginative story; email me for your prize!

This was my first time going through major surgery. I’ve previously had some minor patches and cuts, where I only used local anesthesia and watched the surgeon perform. As a hardware guy, I think your body is the most fascinating piece of hardware you’ll ever own so I don’t miss an opportunity to take a peek inside when maintenance is required (to clarify, I find it totally gross to watch other people’s surgeries, but somehow when it’s my own body its different – my sense of wonder overtakes my aversion to blood).

So I’ve never been put full under before. When the anesthesiologist came to interview me, I asked what my options were for local anesthesia. She then tried to convince me that general anesthesia is very safe because they have this computer running some complicated algorithm that considers my weight and height to dose me correctly. Besides the fact that they had to estimate my weight because I couldn’t stand on a scale, my inner monologue was screaming “As a hardware engineer, putting my life in the hands of a computer sounds terrifying” but instead I manage to ask politely, “and what happens if the computer has a problem?” At which point she smiles and re-assures me that she’s constantly monitoring my vital signs and trimming the dosage.

Side note, a friend of mine later on pointed me to an article where apparently some infusion pumps have Wifi that’s on during surgery and the protocol is pathetically hackable. OK, medical equipment makers: there’s some equipment that simply should not be IoT, and an infusion pump is absolutely one of them. There is simply no valid reason for the computer attending to the dosage level of a potentially fatal chemical to be spending any cycles answering TCP packets. Death by DDoS is not an acceptable scenario. If you need to push an update, do it by a USB disk or a plug-in Ethernet jack, so they can at least air gap the damn thing during an operation.

Had I known about the wifi vulnerability of anesthesia infusion pumps, I probably would not have consented to general anesthesia, or at least asked to check that the model they were using had no IoT capability. But the anesthesiologist finally convinced me under the argument that the local procedure would require sticking a needle into my spinal cord and withdrawing cerebrospinal fluid, and I’m like, I don’t know what that is but it sounds important for my brain to work and I kind of like my spinal cord intact, so maybe it’s not worth the risk.

So, I finally consent to being put under. Propofol, the drug she used to initiate anesthesia, is pretty incredible. It acts within seconds, and despite taking over an hour to metabolise in the liver, it clears from the brain in minutes so you can come out of anesthesia quickly. I have to wonder how they discovered it, or developed it. Anyways, the anesthesiologist inserted an IV into my right hand – I appreciated her attentiveness to the detail that I’m left-handed – and proceeded to administer the propofol. I could definitely feel the propofol as it entered my system. I had the same feeling of pins and needles that one gets when a limb falls asleep, a sort of searing, prickling pain. The pain quickly shot up my arm, then a warm wave of prickling across my face, and then…

I’m in the recovery room, and my surgeon is there giving me the post-op interview. About 2.5 hours of my life went by and I had no memory of it. Sure enough, no nausea or dizziness – the anesthesiologist did a good job. I was lucid and talking to the surgeon about the operation. Then, maybe about five or maybe fifteen minutes later, my body goes into shock – I’m shivering uncontrollably, and I’m starting to become acutely aware of the pain in my knee.

Apparently, during the surgery, I was given Fentanyl and Ultiva, both potent opioid painkillers. They give it to you because even though you’re out, your body has autonomous responses to pain that can complicate surgery with excess bleeding and so forth. From what I read, both clear pretty quickly, so I’m guessing the onset of shock corresponded with the painkilling effect of the injected opioids wearing off.

I know exactly what drugs and equipment they used because at the conclusion of the surgery I was given a detailed itemized bill of everything involved; above is a tiny sample of it. It was fascinating to reverse engineer the surgery from the BOM. That’s how I knew they used a 2.5mm drill bit, how I knew they put a breathing tube in me, and that I also got injected with Aloxi to help suppress nausea. I actually sort of wish I knew about the drill bit ahead of time, because I would have asked to keep it. I figured they’re throwing it away so getting the surgical-grade 2.5mm bit that was used to drill holes in my body to use later on to drill mounting bosses would be pretty neat.

Just for the record, the overall hospital bill including surgeon’s fees, surgical materials, OT rental, recovery ward, drugs, X-rays and my first round of physiotherapy was about S$20.7k, or US$15.5k at the prevailing exchange rate. This is considered expensive by Singapore standards, as I went to one of the nicer private hospitals for the operation, but as I understand it is quite cheap by US standards. Fortunately my insurance covered all but about $350 of it.

This was also my first time using opioid painkillers in a serious way. I’m deeply concerned about the addictive nature of opioids, so I don’t take them lightly. I had taken Vicodin once before when I had a wisdom tooth removed, and I remember it having the effect of “moving the pain sideways” – it felt like the pain was just outside arms length, so I could ignore it if I wanted to, but I definitely knew it was still there. Knee surgery was about a hundred times more traumatic than getting a wisdom tooth removed, and for the first day there’s a terrific amount of pain. So they gave me Targin, which is a mix of oxycodone and naloxone.

Targin is a clever way to manage opioid addictiveness. Oxycodone is the opioid; naloxone is the stuff they use to treat opioid overdoses, and it blocks the painkilling effects. Nalaxone is mixed in with the oxycodone to prevent mis-use (crushing & snorting or injecting), and naloxone is poorly absorbed through the digestive system, so when taken orally the oxycodone can still work. For a short time. When the surgical painkillers wore out, basically all the pain receptors in my knee were screaming at me and informing me rather viscerally about what I already knew intellectually – that my knee was cut up, had holes drilled in it, wired up with stainless steel, fibers woven into the muscles, and stitched back together. So I got one dose of Targin, which kicked in in about 20-30 minutes. The oxycodone effect was pretty strong – the acute pain just went away, everything felt okay and I drifted into sleep…only to be woken up about 2-3 hours later by the pain in my knee, presumably due to the nalaxone component finally kicking in and suppressing the opioid effect. However, I was only allowed one Targin pill every 12 hours, and thus had only acetaminophen to manage the pain until the next scheduled dose. It was definitely manageable with some distraction, but there was no way I was going back to sleep again. I could see how oxycodone could be addictive; everything just seemed so okay despite everything being incredibly wrong, so I’m grateful they mixed it with nalaxone and administered it such that my final memory of the trip was being clobbered with my knee pain rather than a lingering desire for more.

Of course, the pain doen’t end in 24 hours, but they “graduated” me to a weaker painkiller, Ultracet. The Ultracet is a mix of Tramadol and acetaminophen. Tramadol itself really kicks in only after it’s processed by the liver into desmetramadol by the enzyme CYP2D6, and I’m heterozygous for a copy with reduced activity. I guess that might explain why when I took the prescribed dosage of two pills it was reasonably effective, but when I halved it to one pill I felt almost nothing at all. Overall, Tramadol was less effective at painkilling and more effective in just making me feel a little dizzy and sleepy. In addition to binding to opioid receptors, it’s also a seratonin releasing agent, a bit like MDMA. So during the daytime I would just deal with the pain by distracting myself with work, and at night time when trying to fall asleep, I’d take the Ultracet and sleep like a baby – I was sleeping almost 12 hours a night for the couple weeks after surgery, which I think was extremely helpful in my recovery. Significantly, Tramadol doesn’t quite suppress pain; like my one experience with Vicoden, it turns it into a fact I’m aware of but can deal with. When I would sleep, my dreams would be deep and lucid, but my brain would often reference the pain in my knee and ascribe it to some random weird dream explanation, like trying to go in for a big penalty kick in a soccer game over and over again. Fortunately, Tramadol didn’t feel like it had too much of an addiction risk for me – the awake-state “high” was a bit unpleasant, as I don’t particularly enjoy the dizziness or drowsiness. It was more of a sleeping aid, as it allowed my mind to let go of the pain in my knee while falling asleep. I was finally able to wean myself off painkillers entirely and fall asleep drug-free about two weeks after the operation, but in a weird way I ever so slightly missed that really sound sleep I’d have while on them. Opioid painkillers are no joke. They’re absolutely essential for dealing with pain, but take them with discipline and caution.

While the story behind the accident itself wasn’t very interesting, I did find going through the surgery, healthcare system, and drugs to be an interesting learning experience.

Paper As a Substrate for Circuits

I’ve spent a considerable portion of my time in the past couple of years helping to develop products for Chibitronics, a startup that blends two unlikely bedfellows together, papercraft and electronics, to create paper circuits. The primary emphasis of Chibitronics is creating a more friendly way to learn, design and create electronics. Because of this, much of the material relating to paper circuitry on the Internet looks more like art than electronics.

This belies the capabilities of paper as an engineering material. Google’s Cardboard and Nintendo’s Labo are mainstream examples of paper’s extraordinary capability as an engineering material. Prof. Nadya Peek at the University of Washington has written several academic papers on building multi-axis CNC machines using paper products.

A couple points to clarify up top: for the sake of brevity, I will use the term “paper” instead of “paper and/or cardboard”, analogous to how one would refer to a PCB made of Kapton or FR-4 both as printed circuits. Furthermore, while Chibitronics focuses on providing solderless solutions for younger learners, the techniques shared in this post targets engineers who have the skill to routinely assemble modern SMT designs. I assume you’ve got a good soldering iron and a microscope, and you know how to use both (or perhaps are up to the challenge of learning how to use them better).

The Argument for Paper

For prototyping and learning the principles of electronics, paper has several distinct advantages over breadboards.

The primary advantage of a breadboard is that it’s solderless, and as a result you can re-use the components. This made a lot more sense back when a 6502 used to cost $25 in 1975 ($115 in 2018 money), but today the wire jumper kit for a solderless breadboard can cost more than the microcontroller. Considering also the relatively high cost of a solderless breadboard and the relatively low value of the parts, you’re probably better off buying extra parts and soldering them to disposable paper substrates than purchasing a re-usable solderless breadboard for all but the simplest of circuits.

Electronic components used to be really expensive, so you wanted to re-use them as much as possible. The 8-bit 6502 at $115 (adjusted for inflation) was considerably cheaper than its competition in 1975 (from Wikipedia).

On the other hand, paper has a number of important advantages. The first is that it’s compatible with surface mount ICs. This is increasingly important as chip vendors have largely abandoned DIP packages in favor of SMT packages: mobile computing represents the highest demand for chips, and SMT packages beat DIP packages in both thermal and parasitic electrical characteristics. So if you want a part that wasn’t designed by someone wearing a jean jacket and highwaters, you’re probably going to find it only available in SMT.

The evolution of packaging (from left to right): DIP, SOIC, TSSOP, and WLCSP. The WLCSP is shown upside-down so you can see how solder balls are applied directly to a naked silicon chip. It’s the asymptotic size limit of packaging, and is quite popular in mobile phones today.

The second and perhaps more important advantage is that it’s electrically similar to a printed circuit substrate. Breadboards feature long, loose wires with no sense of impedance control at all. Printed circuits are 2.5-D (e.g. planar multi-layer) constructions that feature short, flat wires and often times ground planes that enable impedance control. Paper circuit construction is much closer to that of a printed circuit, in that flat copper tape forms traces that can be layered on top of each other (using non-conductive tape to isolate the layers). Furthermore, when laid on top of a controlled-thickness substrate such as cardboard, the reverse side can be covered with a plane of copper tape, thus allowing for impedance control. The exact same equations govern impedance control in a paper circuit constructed with a ground plane as a printed circuit constructed with a ground plane – just the constants are different.

This equation works for both FR-4 and cardboard. Just plug in the corresponding ε, w, t, and h. From rfcafe.com.

This means you can construct RF circuits using paper electronic techniques — from directional couplers to antennae to amplifiers. The low parasitics of copper tape also means you can construct demanding circuits that would be virtually impossible to breadboard, such as high-power switching regulators, where ripple performance is heavily impacted by parasitic resistance and inductance in the ground connections.

A 10W, 5V buck regulator laid out with paper electronics. The final layout closely resembles the datasheet layout example and performs smoothly at 2A load; this circuit probably wouldn’t regulate properly at high loads if built with a SMT-to-DIP breakout and a breadboard.

In addition to impedance control and lower parasitics, the use of copper tape to form planes means paper electronics can push the power envelope by leveraging copper plans as heatsinks. This is an important technique in FR-4 based PCBs; in fact, for many chips, the dominant path for heat to escape a chip is not through the package surface, but instead through the pins and package traces.

Copper conducts heat about 1000x better than plastic, so even the tiny metal pins on a chip can conduct heat more efficiently from an IC than the surface of the plastic package. Flip-chip on lead frame graphic adapted from Electronic Design.

The copper which forms the pins and lead frames of a chip package is a vastly superior (about 1000x better) heat conductor compared to air or plastic, so a cheap and effective method of heatsinking is to lay out a large plane of copper connected to the chip. Below is an example of a 60-watt power driver that I built using paper electronics, leveraging a copper tape plane plus extra foil as heat sinks.

That’s a 12A power transistor, and this heater control circuit can use much of that ampacity. Additional copper foil was soldered on for extra heat sinking. The equivalent in DIP/TO packages might melt a breadboard during normal operation.

Paper electronics has one additional advantage that is unique to itself: the ability to fold and bend into 3-dimensional shapes. This is something that neither breadboards nor FR-4 circuit boards can readily do. Normally, circuit boards that can bend require more exotic processes like rigi-flex or flex PCB manufacture; but paper supports this natively. Artists take advantage of this property to create stunning electronic origami, but engineers can also use this property to great effect.

Trox Circuit Study 05 by Jonathan Bobrow, from the Paper Curiosities gallery

The ability to fold a sheet of cardboard or paper means that paper circuits can be slotted around tight corners and conformed to irregular or flexible surfaces, eliminating connectors and creating a thinner, sleeker packages. Need a test point? Cut a hanging tab out of your substrate, and you’ve got a fold-up point where you can attach an alligator clip!

Using Paper to Facilitate Prototyping with SMT

Here’s a detailed example of the construction techniques I use when working with paper electronics. I built a breakout board to solve a common problem: matching voltages between chips. Older chips are powered by 5V, newer ones by 1.8V or lower, and none of these are a match for your typical 3.3V-tolerante microcontroller. There are small circuits called “level shifters” that can safely take digital signals of one signal swing to another range. The problem is that most of the “good” ICs today come only in SMT packages, so if you’re prototyping on a breadboard or using alligator clips to cobble something together, you’ve got very limited options. In fact, one of my “go-to” ICs for this purpose is the 74LVC1T45; it’s capable of 420Mbps data rates, and can convert anywhere from 1.65V to 5.5V in a direction that can be selected using an input pin. The packaging options for this chip range from a DSBGA to a SOT-23 – clearly a chip targeted at the mobile phone generation, and not meant for breadboarding.

However, I’m often confronted with the problem of driving a WS281B LED strip from the I/O of a modern microprocessor. WS2812B LEDs operate off of 5V, and expect 5V CMOS levels; and no modern microprocessor can produce that. You can usually get away with driving a single WS2812B with a 3.3V-compatible I/O, but if you’re driving a long chain of them you’ll start to see glitches down the chain because of degraded timing margins due to improper voltage levels at the head of the chain. So, I’d love to have a little breakout board that adapts a SOT-23-sized 74LVC1T45 to an alligator-clip friendly format.

Instead of laying out a PCB, fabbing a one-off, and soldering it together, I took a piece of cardboard and built a breakout board in under an hour. Furthermore, because I can bend cardboard, I can make my breakout board dual-purpose: I can add pins to it that make it breadboard-compatible, while having fold-up “wings” for alligator clips. Without the ability to fold up, the alligator clip extensions would block access to the breadboard connections. Below are some shots of the finished project.

Native comments plus on-board decoupling caps makes this simple to use, even with long alligator clips

DIP pins coming out the bottom side allow this to be used in a breadboard, too

SMT, DIP, and alligator clips all coexisting in a single breakout — easy to do with paper!

The first step in making a paper circuit is to grab a suitable piece of cardboard. I’ve come to really enjoy the cardboard used to make high-quality mats for picture framing. It’s about 1.3-1.4mm thick, which is fairly similar to FR-4 thickness, and its laminate structure means you can score one side and make accurate folds into the third dimension. The material is also robust to soldering temperatures, and its dense fiber construction and surface coating keeps the paper surface intact when pulling off mild adhesives, like the ones found on copper tape.

I’ll then cut out a square about the size I think it needs to be. I’ll usually cut a little larger, because it’s trivial to trim it back later on, but janky to tape on an extension if it’s too small.

Then, I lay the components on top and sketch a layout – this one’s pretty simple, I just note where I want the SOT-23 to go, and where the breakouts should run to.

Once I’m happy with the sketch, I’ll lay down copper tape, solder on the components, and then fold/bend the breakout into the final shape.

The trickiest and most important technique to master is how to mate the copper tape to the tiny pins of the SOT-23 (or other SMT) package. I use a trick that Dr. Jie Qi taught me, which is to cut a set of triangular notches into the tip of a wider piece of copper tape of roughly the right pitch. The triangular shape lets you adjust the size of the landing pad by simply changing the gap between the two ends of the tape, alleviating the need for precise alignment. Then, once the component is soldered to the wide piece of copper tape, you take a knife and cut the tape into individual traces – voilà, an SMT breakout is born!

A lot of this is better shown not told, so I’ve created a little video, below, that walks you through the entire process of building the breakout.

Try Something Different, and You Might be Rewarded!

Paper as an electrical engineering material is something I would never have thought of on my own – I grew up prototyping with breadboards and wire-wrap, and I was prejudiced against paper as a cheap, throwaway material that I incorrectly thought was too flammable to solder. Instead, I spent hundreds of dollars on breadboards and wire wrap sockets, when I could have made do with much cheaper materials. Indeed, there is an irrational psychology that regards expensive things as inherently better than cheap things, which means cheap options are often overlooked in the search for solutions to hard problems.

But this is why it’s important to collaborate with experts outside your normal field of expertise – the further outside, the better. In addition to being a great engineer, Jie Qi is a prodigious artist. Through our Chibitronics collaboration, she’s added so much more depth and dimension to my world on so many fronts. She’s imparted upon me invaluable gifts of skills and perspectives that I would never have developed otherwise.

It’s my hope that by sharing a little more about paper electronics, I can bring a fresh perspective on old problems while broadening awareness and getting more users to improve upon the basics. After all, this is a new area, and we’re just starting to explore the possibilities.

Interested in hacking paper electronics? Check out the Chibitronics Creative Coding Kit, and the Love to Code product line. It’s a gentle introduction to paper electronics targeted at newcomers, but it’s also open source, so you can take it as far as your imagination can go — hook up a JTAG box, build the OS, and get hacking! Get 30% off the Creative Coding Kit with the TRY-LTC-18 coupon code until June 30, 2018!

Quick edit: some basic techniques on using copper tape are documented at Chibitronics’ Copper Tape Chronicles. It’s a small compilation of videos like the one below:

Also, here’s a handy tip on how to keep copper tape from falling off the roll:

Name that Ware, April 2018

The Ware for April 2018 is shown below:

It’s a simple ware, but you could say I’m rather personally attached to it. Prize to the funniest/most creative story about this ware :)

Winner, Name that Ware March 2018

The Ware for March 2018 is a Fuso 150 Fish Finder. Mangel hit the nail on the head with this guess — excellent work, as always! email me for your prize :)

Name that Ware, March 2018

The Ware for March 2018 is shown below.

Thanks to Charl for contributing this ware!

Winner, Name that Ware February 2018

The ware for February 2018 is an Ethernet card by Digitel, a Brazilian manufacturer, circa 1992. Brazil is an interesting market because protectionist trade measures made import electronics very expensive. The nominal theory, as it was explained to me, was to protect and encourage local industries, thus creating and maintaining high-paying local jobs. I had never seen a piece of electronics from Brazil, but indeed, many of the circuit board’s components bear company logos I had never seen before and a Brazilian country of origin. While at least facially it seems the trade policies created local jobs, a comparison of this card to its contemporaries outside Brasil — such as this 1992-vintage SMC “Elite 16” Ethernet card featured at vintagecomputer.net — gives a hint at how these policies might have also impeded the progress of technology.

While 0x3d named the ware almost immediately, I really appreciated the cultural insight that Paulo Peres shared about the ware. For example, the fact that the ROM labeled MAQUEST is probably “MAQuina de ESTado” (state machine) and could have been a hack at the time to use locally-produced components to substitute for imported components. Even though in a free market a ceramic EEPROM + 74-series registers would be much more expensive than a PAL, the fact that the EEPROM and registers were produced in Brazil would have made the combo cheaper than an imported PAL once the trade tariffs were factored in. So congrats Paulo, email me for your prize! Although, my understanding is the trade barriers are still in place to this day, so maybe sending you something from overseas would cost you much more duty than it’s worth if you’re located in Brazil… :-O

An Intuitive Motor: IQ Control’s Serial-to-Position Module

Back when I was a graduate student, my advisor Tom Knight bestowed upon me many excellent aphorisms. One of them was, “just wrap a computer around it!” – meaning, rather than expending effort to build more perfect systems, wrap imperfection-correcting computers around imperfect systems.

An everyday example of this is the noise-cancelling headphone. Headphones offer imperfect noise cancellation, but by “wrapping a computer around it” – adding one or more microphones and a computer in the from of a digital signal processor (DSP) – the headphones are able to measure the ambient noise and drive the headphones with the exact inverse of the noise, thus cancelling out the surrounding noise and creating a more perfect listening experience.

Although the principle has found its way rapidly into consumer goods, it’s been very slow to find its way onto the engineer’s workbench. It’s the case of the cobbler’s children having no shoes.

In particular, it’s long bothered me that motors are so dumb. Motors are typically large, heavy, costly, power-hungry, and riddled with small mechanical imperfections. In comparison, microcontrollers are tiny, cheap, power-efficient, and could run software that trims imperfections while improving efficiency to the point where the motor + microcontroller combo is a win over a dumb motor on almost every metric. So why aren’t we wrapping a computer around every motor and just calling it a day?

Then one day a startup called IQ Motion Control showed me a demo of their smart motor, the IQ Position Module, at HAX in Shenzhen. My eyes instantly lit up – these guys have done it, and done it in a tasteful manner. This is the motor I’ve been waiting years for!

Meet the IQ Position Module

Simply put, the IQ Position Module is a brushless DC motor that talks serial and “thinks” at a higher level. I don’t have to design any complicated drive circuitry or buy a proprietary controller that talks some arcane or closed standard. I just plug an FTDI cable into my laptop, hook up power, clone a small git repo and I’m good to go.

Because of the microcontroller on the inside, the IQ Position Module can emulate a range of behaviors, from a simple stepper to a range of BLDC drive standards, but the real magic happens when you tell it where you want it to go and how fast, and it figures out the best way to get there.

“But wait”, you say, “my servos and brushed DC motors can do that just fine, I just control the pulse width!” This is true for crude and slow motion control applications, but if you really want to run at high speeds – like the ones achievable by a BLDC – you have to consider things like acceleration and deceleration profiles.

The video below shows what I mean. Here is a pre-production IQ Position Module that’s being commanded to turn once in two seconds; then twice, three times, and finally ten times in two seconds. The motor can go even faster, but the figurine I attached on top isn’t balanced well enough to do that safely. Notice how the speed “ramps up” and back down again, so that the motor stops with the figurine in precisely the same position at the end of every cycle, regardless of how fast I commanded the motor to turn.

https://bunniefoo.com/bunnie/iq_turn_demo.mp4

That is magic.

And here’s a snippet of the core code used in the above demo, to give you an idea of how simple the API can be:

Just tell it where you want it, and by when — and the motor figures out an acceleration profile. Of course other parameters can be tweaked but the default behavior is reasonable enough!

A Motor That’s Also an Input Device

But wait! There’s more. Because this is a “direct drive” system, there’s no gears to shear. Anyone who has busted a geared servo motor by stalling or back-driving it knows what I mean. IQ Position Modules don’t have this problem. When you stop driving the IQ module – put it in a “coast” mode – it turns freely and without resistance.

This means the IQ motor doesn’t just “write” motion – it can “read” motion as well. Below is a video of a simple motion copy demo I cooked up in about an hour (including time spent refactoring the original API), where I implement bidirectional read/write of motion between two IQ Position Modules.

https://bunniefoo.com/bunnie/iq_motion_copy_demo_lbr.mp4

The ability to tolerate back-drive and also “go limp” is advantageous in robotics applications. Impact-oriented tasks — such as hammering a nail or kicking a ball — would rapidly degrade the teeth in a geared drive train. Furthermore, natural human motion incorporates the ability to go limp, such as the forward swing of a leg during walking. Finally, biological muscles are capable of applying a static force without changing position, such as when holding a cup on its sides without crushing it. Roboticists have developed a wide range of specialty actuators and techniques, including series elastic and variable stiffness actuators to address these scenarios. However, these mechanisms are often complicated and pricey.

The IQ Position Module’s lack of gearing means it’s back-drive tolerant, and it can apply an open-loop force without any risk of damage. This means you could, for example, use it to build a robot arm that can hammer a nail or pick up a cup. Robotic elements built using these would have far greater resilience to motion interference and impact forces than ones built using geared servos.

Having Fun with the IQ Position Module

While attending 34C3 back in December 2017, I managed to sit down for about an hour with my good friends Prof. Nadya Peek and Ole Steinhauer, and we built a 2-axis robot arm that could do kinesthetic learning through keyframing, using nothing more than two IQ Position Modules, a Dunkin’ Donuts box, a bunch of schwag stickers we stole from the FOSSASIA assembly, and the base plate of an old PS4 … because fail0verflow.

This was improvisational making at its best; we didn’t really plan the encounter so much as it emerged out of the chaos that is the Computer Congress. While Nadya was busy cutting, folding, and binding the cardboard into a 2-axis robot arm, Ole “joined” (#lötwat?!) together the power & serial connectors, and I furiously wrote the code that would do the learning and playback — while also doing my best to polish off a couple beers. Nadya methodically built one motion axis first, and we tested it; satisfied with the result, she built and stacked a second axis on top. With just a bit of tweaking and prodding we managed to pull off the demo below:

https://bunniefoo.com/bunnie/iq_2axis_robot.mp4

It’s a little janky, but given the limited materials and time frame for execution, it hints at the incredible promise that IQ Position Modules hold.

So, if you’ve ever wanted to dabble in robotics or motion control, but have been daunted by control theory and arcane driver protocols (like I’ve been), check out the IQ Position Module. They are crowdfunding now at CrowdSupply. I backed their campaign to reserve a few more Position Modules for my lab – by wrapping a smart computer around a dumb motor, they’ve created a widget that lets me go from code to physical position and back with a minimal amount of wiring and an accessible API.

Their current funding campaign heavily emphasizes the capabilities of their motor as a “better BLDC” for the lucrative drone market, and I respect their wisdom in focusing their campaign message around a single, economically significant vertical. A cardinal sin of marketing revolutionary tech is to sell it as a floor wax and a dessert topping — as painful as it may be, you have to pick just one message and push hard around it. However, I’m happy they are offering the IQ Position Module as part of the campaign, and enabling me to express my enthusiasm to the maker and robotics communities. I’ve waited too long to have a motor with this capability in my toolbox — finally, the cobbler’s children has shoes!

Name that Ware, February 2018

The Ware for February 2018 is shown below.

Ware courtesy of Hernandi Krammes!

Every board designer leaves a thumbprint on their ware — and this one is from a region I had never previously seen a ware from before. So while probably easy to guess the function, I still appreciated it for the small, unique details.

Winner, Name that Ware January 2018

The Ware for January 2018 is a front panel VFD/switch controller board for an HP Laserjet 4+. Archels nailed it — I checked u19pb1996 in Google for hits and nothing came up, but maybe I was too hasty and typo’d the number when cross-checking the image. Anyways, this post is now the top hit for that part number :) Congrats, email me for your prize.

+1 to zebonaut’s comment about the firmware code from the early 90’s never needing an update, ever…they just don’t write software like they used to anymore! It’s funny to see the panic in the eyes of a modern software developer when you tell them a subsystem has no firmware update path, ever, and their code just has to work reliably from day one. And then you tell a hardware developer the same thing and they go “yah, so?”…there’s no such thing as a downloadable hardware update, of course the product ships complete, working & tested. And not only does the hardware have to work, it carries a warranty, unlike most software…