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Longform articles, the best of what the Hackaday writing crew has to offer.

Esoteric Actuators

December 10, 2015 by 35 Comments

Motors are everywhere; DC motors, AC motors, steppers, and a host of others. In this article, I’m going to look beyond these common devices and search out more esoteric and unusual electronic actuators that might just find a place in one of your projects. In any case, their mechanisms are interesting in their own right! Join me after the break for a survey of piezo, magnetostrictive, magnetorheological, voice coils, galvonometers, and other devices. I’d love to hear about your favorite actuators and motors too, so please comment below!

Piezo actuators and motors

Piezo_bending_principle
The flexing of a piezo buzzer from arcbotics

Piezoelectric materials sometimes seem magic. Apply a voltage to a piezoelectric material and it will move, as simple as that. The catch of course is that it doesn’t move very much. The piezoelectric device you’re probably most familiar with is the humble buzzer. You’d usually drive these with less than 10 volts. While a buzzer will produce a clearly audible sound you can’t really see it flexing (as it does shown above).

To gauge the motion of a buzzer I recently attempted to drive one with a 150 volt piezo driver, this resulted in a total deflection of around 0.1mm. Not very much by normal standards!

legs
The PiezoMotor LEGS actuator “walks” along a rod, pushing it as it goes.

For some applications however resolution is of primary interest rather than range of travel. It is here that piezo actuators really shine. The poster-boy application of piezo actuators is perhaps the scanning probe microscope. These often require sub-nanometer accuracy (less than 1000th of 1000th of 1 millimeter) in order to visualize individual atoms. Piezo stacks are ideal here (though hackers have also used cheap buzzers!).

Sometimes though you need high precision over a larger range of travel. There are a number of piezo configurations that allow this. Notably Inchworm, “LEGS”, and slip-stick actuators.

The PiezoMotor LEGS actuator is shown to the above. As noted, Piezos only produce small (generally sub-millimeter) motion. Rather than using this motion directly, LEGS uses this motion to “walk” along a rod, pushing it back and forth. The rod is therefore moved, in tiny nanometer steps. However, piezos can move quickly (flexing thousands of times a second). And the LEGS (and similar Inchworm actuator) allows relatively quick, high force, and high resolution motion.

slowfast

The tablecloth trick (yes this one’s fake, the kid is ok don’t worry. :))

Another type of long travel piezo actuator uses the “stick-slip phenomenon”. This is much like the tablecloth magic trick shown above. If you pull the cloth slowly there will be significant friction between the cloth and this crockery and they will be dragged along with the cloth. Pull it quickly and there will be less friction and the crockery will remain in place.

This difference between static and dynamic friction is exploited in stick-slip actuators. The basic mechanism is shown in the figure below.

picomotor1
Motion caused by a stick-slip motor

When extending slowing a jaw rotates a screw, but if the piezo stack is compressed quickly the screw will not return. The screw can therefore be made to rotate. By inverting the process (extending quickly, then compressing slowly) the process is reversed and the screw is turned in the opposite direction. The neat thing about this configuration is that it retains much of the piezo’s original precision. Picomotors have resolutions of around 30 nanometer over a huge range of travel, typically 25mm, they’re typically used for optical focusing and alignment and can be picked up on eBay for 100 dollars or so. Oh and they can also be used to make music. Favorites include Stairway to Heaven, and not 1 but 2 versions of Still Alive (from Portal). Obligatory Imperial March demonstration is embedded here:

There are numerous other piezo configurations, but typically they are used to provide high force, high precision motion. I document a few more over on my blog.

Magnetostrictive actuators

Magnetostriction is the tendency of a material to change shape under a magnetic field. We’ve been talking about magnetostriction quite a lot lately. However much like piezos it can also be used for high precision motion. Unlike piezos they require relatively low voltages for operation and have found niche applications.

Magnetorheological motion

Magnetorheological (MR) fluids are pretty awesome! Much like ferrofluids, MR fluids respond to changes in magnetic field strength. However, unlike ferrofluids it’s their viscosity that changes.

MRfluidThis novel characteristic has found applications in a number of areas. In particularly the finishing of precise mirrors and lens used in semiconductor and astronomical applications. This method uses an electromagnet to change the viscosity of the slurry used to polish mirrors, removing imperfections. The Hubble telescope’s highly accurate mirrors were apparently finished using this technique (though hopefully not that mirror). You can purchase MR fluid in small quantities for a few hundred dollars.

Electrostatic motors

While magnetic motors operate through the attraction and repulsion of magnetic fields, electrostatic motors exploit the attraction and repulsion of electric change to produce motion. Electrostatic forces are orders or magnitude smaller that magnetic ones. However they do have niche applications. One such application is MEMS motors, tiny (often less than 0.01mm) sized nanofabricated motors. At these scales electromagnetic coils would be too large and specific power (power per unit volume) is more important than the magnitude of the overall force.

Voice coils and Galvanometers

The voice coil is your basic electromagnet. They’re commonly used in speakers, where an electromagnet in the cone reacts against a fixed magnet to produce motion. However voice coil like configurations are used for precise motion control elsewhere (for example to focus the lens of an optical drive, or position the read head of a hard disc drive). One of the cooler applications however is the mirror galvanometer. As the name implies the device was originally used to measure small currents. A current through a coil moved a rod to which a mirror was attached. A beam of light reflect off the mirror and on to a wall effectively created a very long pointer, amplifying the signal.

These days ammeters are far more sensitive of course, but the mirror galvanometer has found more entertaining applications:

High speed laser “galvos” are used to position a laser beam producing awesome light shows. Modern systems can position a laser beam at kilohertz speeds, rendering startling images. These systems are effectively high speed vector graphic like line drawing systems, resulting in a number of interesting algorithmic challenges. Marcan’s OpenLase framework provides a host of tools for solving these challenges effectively, and is well worth checking out.

In this article I’ve tried to highlight some interesting and lesser known techniques for creating motion in electronic systems. Most of these have niche scientific, industrial or artistic applications. But I hope they also also offer inspiration as you work on your own hacks! If you have a favorite, lesser known actuator or motor please comment below!

Echo Of The Bunnymen: How AMD Won, Then Lost

December 9, 2015 by 177 Comments

In 2003, nothing could stop AMD. This was a company that moved from a semiconductor company based around second-sourcing Intel designs in the 1980s to a Fortune 500 company a mere fifteen years later. AMD was on fire, and with almost a 50% market share of desktop CPUs, it was a true challenger to Intel’s throne.

An AMD 8080A. source
An AMD 8080A. source.

AMD began its corporate history like dozens of other semiconductor companies: second sourcing dozens of other designs from dozens of other companies. The first AMD chip, sold in 1970, was just a four-bit shift register. From there, AMD began producing 1024-bit static RAMs, ever more complex integrated circuits, and in 1974 released the Am9080, a reverse-engineered version of the Intel 8080.

AMD had the beginnings of something great. The company was founded by [Jerry Sanders], electrical engineer at Fairchild Semiconductor. At the time [Sanders] left Fairchild in 1969,  [Gordon Moore] and [Robert Noyce], also former Fairchild employees, had formed Intel a year before.

While AMD and Intel shared a common heritage, history bears that only one company would become the king of semiconductors. Twenty years after these companies were founded they would find themselves in a bitter rivalry, and thirty years after their beginnings, they would each see their fortunes change. For a short time, AMD would overtake Intel as the king of CPUs, only to stumble again and again to a market share of ten to twenty percent. It only takes excellent engineering to succeed, but how did AMD fail? The answer is Intel. Through illegal practices and ethically questionable engineering decisions, Intel would succeed to be the current leader of the semiconductor world.

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Theremin’s Bug: How The Soviet Union Spied On The US Embassy For 7 Years

December 8, 2015 by 175 Comments

The man leaned over his creation, carefully assembling the tiny pieces. This was the hardest part, placing a thin silver plated diaphragm over the internal chamber. The diaphragm had to be strong enough to support itself, yet flexible enough to be affected by the slightest sound. One false move, and the device would be ruined. To fail meant a return to the road work detail, quite possibly a death sentence. Finally, the job was done. The man leaned back to admire his work.

The man in this semi-fictional vignette was Lev Sergeyevich Termen, better known in the western world as Léon Theremin. You know Theremin for the musical instrument which bears his name. In the spy business though, he is known as the creator of one of the most successful clandestine listening devices ever used against the American government.

Continue reading “Theremin’s Bug: How The Soviet Union Spied On The US Embassy For 7 Years” →

How To Be The Hardware Engineer At A Startup

December 7, 2015 by 32 Comments

For those who prefer the smell of solder smoke to lines of code then you may be a hardware engineer. What you should consider is how to land a job at a startup, how to work fast, be a team player, keep an open mind, and be organized. Joining a startup will be the greatest challenge of your career. You can do it! Be a hardware engineer at a startup and change the world.

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The Death Of Surplus

December 7, 2015 by 148 Comments

I thought the surplus electronics market in Dallas was a byproduct of local manufacturing, after all we have some heavy hitters in our back yard: Texas Instruments, Maxim (Dallas Semiconductor), ST Micro (at one time), Diodes Incorporated. If we widen our radius to include Austin (3 hours down the road) we can make a much more impressive list by including: National Instruments, Freescale Semiconductor, better yet I’ll just insert the graphic I’m pulling data from right here:

texas_companies_map
Texas Electronics Map Source: Texas.gov

Granted, not all of these are companies that manufacture silicon, or even have manufacturing facilities here in Texas. That doesn’t necessarily matter for surplus to exist. Back to my point of where surplus originated. While I wasn’t completely wrong (these companies certainly have helped contribute to the surplus electronics market) the beginnings of surplus storefronts date back to World War II. Did anyone see that coming? Neither did I. However it does make sense, the US government would have had a large stock of “stuff” to get rid of at the end of the war.

Enter the sale of government surplus all over the nation, usually near air force bases. So this is how the more generalized concept of a surplus shop came to be in existence; mix in the domestic manufacturing of electronics in the 1970’s and we have electronics surplus shops aplenty.

My First Hand Experience

I didn’t really appreciate how valuable my local electronics shop was until watching Beers in Bunnie’s Workshop – Workshop Video #36. If you haven’t seen the video you only need to know that [Ian] of Dangerous Prototypes and [bunnie] of Andrew [bunnie] Huang are standing in [bunnie]s work-space in Singapore drinking beer and talking about the lab that is [bunnie]s life. You with me now? Okay, there is a point in the video where the two discuss the ability to run down the street and buy a connector as something only available in Singapore or Shenzhen. Let me briefly pause here to clarify that I’m not comparing my local electronics shop to the Shenzhen market or Sim Lim Tower in Singapore, only stating that I too can hold parts in-hand before purchasing them. I’m also not [brandon] of Dangerous Prototypes or Andrew [brandon] Huang, clearly.

I do however have an electronics selection at my disposal that is unmatched until you get to the west coast shops. I went on a bit of an adventure with the owner [Jim Tanner] of my local shop [Tanner Electronics] to take some pictures of the retail floor and a few behind the scenes (warehouse) shots that you can check out after the break.

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Toward The Optionally Piloted Aircraft

December 4, 2015 by 25 Comments

Aviation Week and Space Technology, the industry’s leading magazine, has been publishing “pilot reports,” on new aircraft for decades. Its pilot report on an aircraft called Centaur ⁠was the first in which the pilot doing the test never touched the controls. Centaur is an optionally-piloted aircraft, or OPA.

The reporter conducted the test while sitting in the back seat of the small, twin engine aircraft. Up front sat a person acting as the safety pilot, his arms calmly resting on his lap. Sitting beside him, in what is ordinarily the co-pilot’s seat, was an engineered series of linkages, actuators, and servos. The safety pilot pulled a lever to engage the mechanisms, and they began moving the pilot’s control stick and pressing the rudder pedals. The actuators are double and redundant; if one set fails another will immediately take over. The safety pilot can disengage the mechanism with a single pull of the lever if something goes wrong; unless something goes wrong he does not touch the controls.

In the back seat, the “operator,” commanded the plane through a laptop, using an interface identical to that of the ground control station for an unmanned vehicle. Through the screen, he could change altitude, fly to waypoints, takeoff or land. Pushing the “launch” button began an autonomous takeoff. The computer held the brakes, pushed the throttles forward, checked the engines and instruments, and released the brakes for the takeoff roll. The plane accelerated, took to the air, and began to climb out on a semi-autonomous flight.

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Is Via Rail On Time?

December 4, 2015 by 25 Comments

Personally, I’m a fan of trains. They’re a nice, albeit slow, way to get around the country. Canada isn’t the best candidate for rail transit, given the rather large space between coasts, but Via Rail does operate regular train service in their corridor between Windsor and Quebec City.

Unfortunately, passenger rail has to yield to commercial rail in Canada which often causes delays. After noticing that some trains have very frequent delays, it seemed like it would be useful to know the average performance of each Via train. Via does not provide this data publicly.

However, they do provide some data about arrival and departure times. Digging into the data available through any browser viewing the Via Rail site, it was possible to query for past scheduled/actual arrival data. The result is TrainStats.ca, a display of Via’s on time performance. Join me after the break as I discuss how this all works, and how to pick a winner when buying your next train ticket.

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