Archive for the ‘General’ Category

I P, U P, everybody (DHC)Ps…

My page that tells you your IP address is up and running again, after a PHP configuration change by my web host knocked it out. Anyway, enjoy the glory of finding out your external IP address without getting socked by porn popups!

Image segmentation for PnP optical placement





Quick ‘n dirty (but working!) image segmenter for randomly-strewn part identification. About 1 page worth of scripting takes an image of objects on background, determines which part is the background, determines the outside contour of each object and numbers each as a separate object. Now that it’s known where to look for one specific object, the task of identifying that object (or just matching it to another just like it) becomes a whole lot simpler. Combined with the auto-aligner, this reduces a “naive” (bruteforce cross-correlation between needle and haystack images) image matcher to only having to scan against 4 orientations (90-degree rotations) to find which has Pin 1 in the right place (and whether it’s the same part, etc.) Hopefully as I dig deeper into opencv, there is a less-naive algorithm builtin for this that does not rely on contrast/color historgrams: most electronic parts basically consist of a flat black body and shiny reflective metal leads (i.e. appearing the same color as your light source and/or the background, and/or whatever happens to be nearby at the moment). Edge-based stuff still seems like a better approach, though I would welcome being proven wrong if it means not having to write the identifier from scratch myself :-)

Steps in brief:
The first image was taken using the actual webcam that will be attached to the pick n place head, looking at a handful of representative parts on a piece of white paper. This image was dumbly processed using a Sobel edge-detector (it’s builtin to Gimp and I was feeling lazy), Gaussian blur to expand the soon-to-be-resulting mask around the part a little and close any gaps in the edge-detection result, and finally threshold the result to produce the second image. The goal in these steps is to produce a closed-form contour blob for each part that’s at least as wide as the part, while minimizing stray blobs from random noise / dirt specs / etc. (internal, fully-enclosed blobs/noise due to part features/markings is OK). Finally, opencv’s FindContours function is run (mode=CV_RETR_EXTERNAL) on the resulting image, returning a vector that contains a polygonal approximation of each external contour found. Each discrete (non-touching) contour blob is returned separately, that is, every part in the frame is now effectively tagged and numbered!

There are a couple noise points identified in the image above. Better-chosen constants for the initial image operations (threshold, blur radius, …) may help, but I’ll probably end up having it measure the area of the blobs and throw away any that’s too small to possibly contain a valid part. Switching to a more advanced edge-detector, e.g. Canny, may help too. In any case, the full image matcher should figure it out eventually :-)

Code Demo – basically ripped straight from the pyopencv examples
Segmentation example – requires Python (2.6) and opencv 2.1.0 / pyopencv.

Pick ‘n Place Head

This weekend I got some parts in and put together a preliminary placement head for my open-source pick ‘n place project. My requirements are that it be buildable with off-the-shelf parts (ideally same-source, to save on shipping) and no special equipment, allow +/-180 degree rotation while maintaining an undisturbed vacuum, and support interchanging of the “tools” (vacuum needles). All that’s really needed to build this are the discrete parts shown, a bit of drillable plastic (e.g. Delrin) for the base material, and a drill. A drill press would be handy (a CNC mill *really* handy, and not such an out-there thing to have considering you are probably retrofitting this onto one).

This head consists of a hollow rotary shaft with a Luer lock fitting on one end, right-angle flexible tubing barb on the other end, and a large toothbelt (notched belt, timing belt) gear in between. The shaft is held in place but allowed to rotate by a pair of bearings, and the rotation is provided by a small stepper motor at the other end of the toothbelt. The gear ratio is approximately 5.2:1, providing a rotational resolution of about 0.35 degrees/step with a common 200 step/rev stepper motor (if no microstepping is used). Finally, just to the left of it is a 1024×768 Webcam with manually adjustable focus and a ring of built-in LEDs for lighting. The webcam mounting is definitely not ideal, given the camera’s weird eyeball-like shape. Tentative plan is to lash it down with some string, align it nicely with respect to the CNC table, then backfill the opening the camera’s butt sits in with epoxy.

The hardest part was finding a combination of parts that would all fit together nicely. Currently, the fits are mostly exact to “pretty damn good”, but a bit of adhesive is needed to join them permanently.

Parts List
Unless otherwise noted, all of these parts were sourced from Small Parts Inc. in the US due to the large selection and an actually competent parametric search engine, which was a great help in finding combinations of mutually-fittable parts. Accordingly, measures are in Imperial unless noted otherwise (that’s just how they come here).

Partnumber Desc.
3002DSTNTG18 Nice Ball Bearing 3002DS, .250″ bore x .6875″ OD x .250″ width
BFM-250-P Mounted sleeve bearing, .250″ ID, 1 17/32 center-to-center bolt spacing
B00137SITY Steel tubing, 1/4″ OD .152 ID, 12″ long
40DP-14/S-01 Timing Belt Pulley Delrin, 0.0816 Pitch, 40DP, .350″ Diameter, 1/8″ Bore, For up to 1/4″ Wide Belt, 14 teeth
40DP-70/S-01 Timing Belt Pulley Delrin, 0.0816 Pitch, 40DP, 1.806″ Diameter, 1/4″ Bore, For up to 1/4″ Wide Belt, 70 teeth
TB188-090-01 Timing Belt Urethane/Polyester, Single-Sided, 0.0816″ Pitch, 0.1875″ Wide x 7.3440″ Long, 90 Teeth
LCX-LC005 Male Luer Lock to tubing adapter, .145″ OD hose barb (mates well enough with .152″ ID steel tubing)
F1-EL001 Elbow Connector , Classic Barbs for 3/32″ ID Tubing, .145″ OD
HSTA-08-24-10 1.5″ aluminum standoffs, 8-32 thread
B00137UP68 (Optional) 11ga Steel Tubing, .120″OD, .094″ID (for mating 2mm shaft stepper motors, if used, to the 1/8″ pulley

Misc. Parts
2x 2″ x 4.5″, 1/4″ thick pieces of Delrin or similar
4x 1/2″, #4-40 bolts and nuts (assuming 2 bolts for stepper motor)
4x 1/2″, #8-32 bolts for standoffs
1x Webcam, manual focus, hi-res and builtin lighting strongly recommended
1x 3mm shaft stepper motor*
1x Method of attaching to your mill – a bit of aluminum angle bracket, or a dovetail, etc., depending on your mill.
1x 3-way air solenoid valve
1x Vacuum source (see here for a cheap one)
Air tubing and appropriate couplings to your solenoid valve. The head’s air path terminates in a 3/32″ hose barb, so you’ll want a 3/32″ to (whatever) barb adapter, or a 3/32 that screws directly into your solenoid. Those using metric are on your own :-) but will probably have an easier time of it anyway.

* The timing pulleys and stepper motors only come in a handful of diameters (imperial for the pulleys and usually metric for the small motors), so a 3mm (.118″) motor onto a .125″ ID pulley was the closest I could come up with in a reasonable amount of effort. Any small, el-cheapo permanent magnet (“tin can”) stepper motor should work here, but sourcing it may be annoying. Off-the-shelf 3mm-shaft motors I found are Jameco’s ValuePro 42BY48H08, Anaheim Automation’s TSM42 series, and Portescap’s 42/44 series e.g. 42×048 and 42S100. This surplus stepper is also worth a look, but you’ll have to remove a pre-attached plastic(?) gearhead. Beware, many of these smaller motors are 7.5deg/step, so even with the gear reduction, you will probably want to look at microstepping them to ensure adequate rotational resolution. Also, most of the companies selling them have no online click-and-buy ordering; you’ll have to phone up a salesdouche at the least, hope that you are worth their time to buy One Lousy Motor, and possibly haggle (“Request a Quote”). How companies that don’t know what their product costs stay in business is beyond me, but that’s a rant for another day.

If you want to skip that hassle, I’ve taken an alternative approach and simply bodged a surplus 2mm-shaft motor up to a 3mm shaft by gluing a short piece of thicker steel tubing onto the existing shaft (see partlist).

Design Files
CamBam drawings with machining operations for the top and bottom plates. The machining ops assume 1/4″ thick plastic, 1/8″ endmill for most cuts, and .166″ (#19) drill for the #8-32 bolt holes into the standoffs. It’s designed for the Cubeternet webcam (or equivalent eyeball-cam) and a stepper motor with 42mm center-to-center mounting holes. You can get the free CamBam at http://www.cambam.co.uk/.

Note, I made some small improvements to these files after the above prototype was carved, so what you see in the file will not match it exactly. In particular, the standoffs were moved to more optimal places and a feature has been added allowing the motor to be slid to remove any slack in the belt.

Assembly
The assembly should be pretty self-explanatory. One bearing on each of the Delrin plates (inset the ball bearing if you can; otherwise gluing it down should be fine). The hollow shaft goes thru the bearings, Luer adapter and hose barb go on either end (use adhesive, just don’t clog the air path with it). The motor shaft center should sit just a hair (50-100 mils?) over 1.75″ from the hollow shaft. On mine, an online calculator produced the 1.75 figure, but the belt turned out to be a bit loose once built this way. If possible, make an elongated hole for one of the motor screws so the motor position can be adjusted to tension the belt. You could probably also insert a peg somewhere in the belt path to push it inward and take up the slack. With the camera focus set such that the largest part you will ever populate can fit in-frame, find the resulting camera height (distance from part) and set the depth of the shaft so that the camera is “in focus” maybe an inch or two above the placement position (i.e. with the needle touching the board). This will allow the head to focus on parts without touching the needle down.

For my build, I used instant glue to attach the Luer adapter to the needle shaft, and hot-melt glue to tack down the large pulley and hose barb. None of these parts should be seeing significant force; if they are, you’re Doing It Wrong and the hot glue should hopefully break loose before something more important does. Using a non-permanent adhesive for the hose barb and pulley also allows this assembly to be disassembled later if needed. The shaft itself is free-floating and the large pulley rests against the ball bearing due to gravity. This will prevent damage due to crashing the needle into the table or too-tall part, but if you experience problems with the shaft riding up on its own, try adding a bit of extra weight or put a dab of adhesive where the shaft passes through the lower bearing.

Suggested “v2” improvements
–Move air valve (if/when one is specified) onto head to minimize air volume between valve and head. Needed? (may be beneficial for reversed aquarium pumps or other weak vacuum sources)
–Bump detect: rather than firmly adhere the shaft into the bearing, allow it to float up and down, normally resting by gravity with the large pulley against the ball bearing. Place a contact switch just above the pulley: if the head/part contacts the surface with more than minimal force (enough to lift the shaft), contact switch is triggered. This could be used to halt the machine if a bump was not expected. If the switch’s trigger position is reliable enough, it could be used intentionally to automatically determine component heights.
–Probe function: There is a conductive metal path from the needlepoint all the way up to and including the bearing outer race, so it would be easy to touch a contact here and use the needle to probe for any conductive objects (e.g. find the tabletop if it is metal, or some capacitive shenanigans for PCBs/etc.). Useful?

Toward an open-source Pick and Place machine

So, there’s some really cool, empowering stuff going down these days with regard to manufacturing. Cartesian machines (i.e. CNC mills) are relatively simple to build from off-the-shelf parts; there are a bajillion people doing this and plenty of ready-made open-source designs available. More recently, hobbyists have gotten in on designing open-source rapid prototypers (3D printers); as a result, designs have now crossed the sub-$1000 threshold off-the-shelf, and you can even build a GPL’ed 3D printer that can almost replicate itself!

One thing that I haven’t seen cross the blood-brain barrier of proprietary commercial systems is pick-and-place machines that can assemble electronics. These things are badass; full of automated win and articulating robotic arms, but they’re also damned expensive: the crap ones start at >$10k and use literally a fishing-lure-and-weight type arrangement to peel back the tape covering tape-and-reel parts, so you have to keep resetting the weights. Those with more advanced / less manual feeders scale skyward from there. And of course, the software end of these things, especially machine vision algorithms to place parts more accurately, is some serious $ecret $auce. So… let’s change this!

Most of the “big stuff” is straightforward: The PCB layout software generates a list of coordinates for each part. A small vacuum needle mounted on a Cartesian head picks up each part from a known location, rotates it 90/180/etc. degrees as needed, and sets it down at its coordinates. It does not even need to be 100% accurate: surface tension of the solder during reflow will pull most minorly misaligned parts back into place.

The big barriers are:

1) Low cost / self-manufacturable feed mechanisms:
Electronic parts are packaged in several different ways, most commonly tape-and-reel, plastic tubes, or in trays. Each has a different, maybe cumbersome, way of knowing the location of the next part in the package and freeing the part from the package. Picking up stuff and putting it down is easy compared to dealing with the wide variety of tape and tube sizes reliably. Oh, and if your board uses 50 unique parts, you need 50 feeders. Hence the emphasis on making them cheap and mass-self-produceable, e.g. by CNC or casting or 3D printing.

and/or…

2) Machine Vision
For larger parts, once the first part is successfully picked (e.g. by human intervention), it is enough to know how many parts per inch of tape, advance the tape a known amount per pick, then just grab blindly for the part and plant it at its destination coordinates. But for smaller and finer parts, this is not accurate enough: the parts can be slightly off-center or crooked in their tape wells, and this becomes significant as the part size decreases. Professional machines use a set of cameras and image processing algorithms to recognize the part, find its dead center and correct any rotational error. In theory, a suitably good vision system would allow you to peel back the tape and just sprinkle the parts on the table, forgoing feed mechanisms entirely at the expense of some small manual labor. Actually programming this algorithm on the other hand…

Another nice thing to have would be:

3) Automatic needle swapping. Many more advanced CNC mills are able to spit out their current tool, e.g. a specific size drill bit (in a known location in a tool rack) and pick up a different tool. It would be nice for the pick and place machine to be able to change to smaller and larger needles/suction cups to handle large and small parts seamlessly. If not, placements can be sorted, e.g. smallest to largest, so that the needle only has to be manually changed a couple times.

I’ve made some very initial feasibility-study stabs at building such a machine, and begun building a bit of hardware. I created a separate page for this project with more detailed specs/documentation and progress so far:
Pick and Place Project

I quit, I win, final, no talkbalks

It’s like third grade all over again, except that I could theoretically have ice cream for breakfast if I wanted to.

Windows 2000/XP Driver for (some) Veo Stingray and IBM PC Camera V5000 webcams

UPDATE: For Veo Stingray drivers, try these first. In case they disappear… Stingray 300V (Win98/ME/2000/XP) and Stingray 323V (Win2k/XP only). The one sold by AllElectronics uses the 323V driver.

I picked up an old “Veo Stingray” camera from surplus dealer AllElectronics. These things are pretty junk by modern standards (320×240 resolution, unsightly rounded “looking through a tube” image), but it does have the variable (manual) focus I needed for an imaging project, and the price was right. As for drivers… the company that makes this thing seems to have evaporated, and the particular variant (USB product ID 808B) seems to have never been heard of by anyone, even though there are some identical cameras with slightly different internal hardware (and different Product ID) floating around. They all are (were?) manufactured by Xirlink.

This particular variant can be identifed by USB VID 0545 (Xirlink), Product ID 808B.

Here is a solution that might work (but see update above first): This camera and several IBM PC Cameras use the same or similar chipsets (Sunplus SPCA5xx)…with a small tweak, the IBM camera driver can also be tricked into supporting the ‘808B’ Stingray (maybe others?) by adding its VID/PID to the driver .INF file. Kinda like slipping your cuckoo egg into another nest.

This file includes the IBM driver and tweaked .INF. The following devices are supported:

%XIRLINK.DeviceDesc%=Xirlink.Device,USB\VID_0545&PID_8002
%XIRLINK.DeviceDesc%=Xirlink.Device,USB\VID_0545&PID_8080
%XIRLINK.DeviceDesc%=Xirlink.Device,USB\VID_0545&PID_8009
%XIRLINK.DeviceDesc%=Xirlink.Device,USB\VID_0545&PID_808B

To install, follow the README.TXT included.

Win2K/XP Driver for Veo Stingray (808B) and IBM V5000

Linux?
It looks like several open-source driver projects may support the Veo Stingray, IBM PC Cameras and similar SPCA50xx variants (not to mention the classic Dakota Digitals). Note, if your exact ID is not listed as supported, you may be able to get it working with a tweak similar to the above. Have a look at:

http://xirlinkwebcam.sourceforge.net/
http://www.linux-usb.org/ibmcam/ (older project)
In addition, the package ‘gspca’ may work for these and many other SPCAxxx-based (and other!) webcams. See here for the gspca/spca5xx project and a list of supported cameras.

Tubthumping (or, Sears/Kenmore washers are shit, do not buy them)

So there we are, minding our own business, when an angry demon springs to life in the basement. He is on a rampage, pounding against the walls with all his might, THUMP THUMP THUMP THUMP BANG BANG BANG. We race downstairs. Turns out it is only the Sears Kenmore front-loading washing machine’s internals beating themselves to death during the final spin.

After ruling out an unbalanced load (even fully empty, BOOM BOOM BOOM), I lookup the symptoms online. After a few thousand pages of angry ex-customers’ rants, without even lifting a wrench, there is no doubt what the failure is.

All available evidence confirms that this machine is DESIGNED TO FAIL EVERY FIVE YEARS*. The fuse is an innocent-looking metal bracket on the back of the spinning clothes basket known as a spider; its purpose is to support the basket on the drive shaft leading back to the motor. This spider, an uncoated pot-metal part made of a brittle Al+Fe alloy, is fully exposed to and tumbles its way through all the detergent, bleach, dirty laundry water, etc. After a few short years of this, it corrodes through and shatters during the spin cycle! Of course, you can’t buy just this part; you have to plunk down for the entire basket/etc. assembly at $200 a pop**. Guess who now has a nice spare stainless steel basket laying around to turn compost in, heh.

My brief description does not do this problem justice, but there is an excellent video from a former Kenmore owner detailing this spider issue and several other, likely intentional, design flaws.

So, you probably guessed what I did next – took it apart. The insides of the plastic wash tub are a bitch to get at (nondestructively); the whole thing has to be carefully unhooked from a pair of shocks and large springs, liberated from half a dozen hard-to-reach hoses and tubes with fiddly retaining clips, and the glued-on rubber seal cut away from the front of the machine. There are also cinderblock weights (yes, really!) on the tub which ought to be removed unless Hulk Hogan is helping you lift it out. On mine, the bearing surfaces were also so rusted, it took beating the living hell out of the shaft with a big hammer to separate the assembly from the tub.

Here is what I found inside:



One rotted, broken-ass spider. Surprised? Also note all the "used to be spider" white crud packed in beneath the bearing.


One rusted-out shaft for a rotted, broken ass-spider.


One reaction vessel washtub for a rotted, broken-ass spider. Yuck, my clothes were in there? The white crap looking like crushed concrete at the bottom is corroded bits of spider that haven’t yet ground away at the pump impeller while making their way to the city’s sewer. You can also see where the grease has begun leaking out from the cheap rubber lip seal that’s supposed to be keeping water out of the bearings.


One rusted-out hole for a rusted-out driveshaft to grind slide into. "That’s not my mating surface, baby!"

All this because Sears/Kenmore*** could have easily solved this with $1 worth of engine paint (etc.) to coat this fiddly metal bracket, but chose not to. Also, like in the video above, my outer tub has a nice deep gouge line where the screws in the wildly-flailing basket tore it up. Luckily we were home when it went, and our catlike reflexes caught it before they could carve all the way through.

*says everyone on the Internets. Don’t McLibel me.

** and if you want to save the hassle of retaining clips patwanging across your basement and the Hulk sneaking looks up your skirt, and have the new part installed by an authorized repairman… there’s a reason they have those commercials with the repairman playing Solitaire all day because no support calls come in… it really is cheaper to buy a new machine. ($75 diagnostic visit + $450-$700 repair quotes vs. $500-600 for current units.)

***technically, Sears/Kenmore just buy the appliances from other OEMs and put their names on them. This particular model (417.42142100) is made by Electrolux; others are rebadged Frigidaire or Whirlpool units. Unfortunately, all seem to share a similar design, right down to the fail timer.

No, she cannot has cheezburger. Laser pointer, yes!

We got a kitty last weekend. Like many new additions of the human kind, we hadn’t really planned on it*, but now we are in love with her. Her name is Spirit (she comes pre-named).

She had no trouble settling into the new house, except for spooking out at the noise from the radiators at first. She’s such a little attention whore – follows the hyoominz all around, and if we are on the couch, sits down next to someone and headbutts them ’til she gets belleh rubs.

So far she has also discovered that Christmas tree ornaments swing and make a tinkling noise when swatted at, knitting needles move and click while in use, and must therefore be attacked, and – OMG WIIMOTE CURSOR!

http://www.youtube.com/watch?v=pr2UmofoYAE

http://www.youtube.com/watch?v=dFuf_wMFs1E

*Somewhere between “rescue mission” and “interstate feline trafficking” does the truth lie.

Banned from Google (or, How I Became A Dirty Rotten Spammer)

An update, 1/28/2011: It turns out there was a legitimate problem on the site after all! Specifically, hacked by spammers at some point and filled with invisible links & keywords. Skip down to the comments for the details, and be aware that the rant that follows is based on a fairly complete lack of information! (Said information being over a year in coming, but I have to say that hearing it from the man in charge himself pretty solidly exceeds my expectations….and makes me hang my head in shame a little for even thinking of defecting to Bing.)

So, as of sometime within the last few weeks or so, I am a convicted Google Spammer! As you may guess from this tone, I have not actually done or considered any such thing. But as tends to happen when you take all humans out of the loop and put all faith in the smartness of an infallible Algorithm, you throw your fair share of babies out with the bathwater, and today, one of those babies is me. I discovered this (not like I would have gotten an email or anything) when I happened to Google the name of my product to get to its mainpage (much faster than typing the full URL, which is longish), and it wasn’t there. With some further digging, I found my entire domain and all subdomains have been blacklisted from Google’s index.

That particular level of digging leads to a tool called Google Webmaster Tools, which, after proving myself the owner of the site, returns this:

This site may be in violation of Google’s quality guidelines. More Details
Pages on your site may not appear in Google search results pages due to violations of the Google webmaster guidelines. Please review our webmaster guidelines and modify your site so that it meets those guidelines. Once your site meets our guidelines, you can request reconsideration and we’ll evaluate your site.
Submit a reconsideration request

Full stop.

These webmaster guidelines cover “quality” (i.e. don’t spam the index)–including such helpful first-grade spam no-nos as not stuffing pages with invisible keywords, bogus META tags, providing special fake pages to known search bots, and other stuff that might have worked on Lycos in 1996–as well as various style-guide suggestions, admonishing webmasters to be on their best grammar, and even going as far as discussing size and placement of images on the page. Is a webmaster really expected to perform feng shui to stay in Google’s good graces?

Anyway, I’m at quite a loss to explain why I would be banned from Google, as getting an entire high-ranking site removed from a search index seems like something that would require some pretty big-ticket shenanigans. Of course, this is The Algorithm we’re talking about; there seems to be no indication that a live human was involved in this decision*.

Of course, any of the usual SEO tricks would fit the bill. But I don’t engage in any of that (for here, the boards or the main site), and the only “optimization” I do to this blog’s traffic is to post something interesting once in a while. (Really, since everything on this server is ad-less and free anyway, the only thing More Traffic can get me is a bigger bandwidth bill.) I do know that Google will display warnings / block content if it detects a site has been compromised, but a thorough dig through the server-side files indicates this is not the case, either.

So what’s left are some straws to grasp at:

  • Legitimate incoming links from adult-ish sites and adult-ish search queries for my side project
  • “Bad Words” or links appearing in message board posts (forget this piddly blog, what the rest of the free world knows cexx.org for is one of the oldest continuously running spyware help forums in existence. Posts here–especially diagnostic logfiles posted by affected users– contain references to bad programs/sites, links to same, and repetitive content (e.g. Windows registry trees) that occasionally generate false positives. A human would easily see that we are helping people rather than spamming the world; The Algorithm may not do as well.)
  • Occasional comment spams slipping through in UGC (“User-generated content”, the current buzzword for “stuff the site owners didn’t write themselves”, such as blog comments, message board posts, every video on Youtube, etc.) As you can see from the numbers showing at the bottom of this page, comment spam is as fundamental to the Internet as the threat of rickroll, and the filter’s doing pretty well at blocking them. If transient v1@gra comment spams were grounds for being delisted, half the internet wouldn’t show up. Then again, for those of us who have not used Lycos et al lately, how would we google-addicts know if half the internet wasn’t showing up in our searches…?)
  • My content being scraped and appearing on third-party spamblogs (yes, it happens. I–of all people!– have fired off a couple DMCA takedown demands in the last couple years, but really, for splogs on splog-friendly Korean ISPs this has about as much effect as firing off complaints for every email spam your receive. These automated scrapers usually end up scraping from someone with deeper pockets and much better arm-twisting power at some point, and the problem (for lil old me) solves itself.)
  • Old pages/posts, dead links, occasional bad grammer or speling mistakes?
  • Maybe Google are still mad at me for exposing a huge bug in their search some years ago? (In theory, this would make it trivial for someone to determine whether they ranked higher than a competitor, or see how a specific tweak to their keywords/etc. affected their ranking. But since I’m pretty sure no humans were actually involved in this, I kinda have to rule this hypothesis out…)
  • Statistically anomalous distribution in keyword content of sites that link to mine?
  • Statistically anomalous distribution of topics I discuss, tag clouds, etc. (or as mentioned earlier, help forum posts)
  • Someone I’ve pissed off in the past robo-submitting my URL to the automated “report a spammer” page?**
  • Googlebombs or other shenanigans performed (maliciously or not) by third-party sites?
  • Wild Conspiracy Theories (paid off by a malware company? Malware authors have been trying to block their victims from being able to reach help forums such as cexx.org’s for years; maybe the’ve found a way to up the ante. Or maybe Sergey bought my Trance Vibrator and didn’t like it.)

The possibility that any site could be delisted by the actions of third-party sites (e.g. competitors) is simply disturbing. As unlikely as I’d hope it to be, Google’s complete secrecy regarding its delisting criteria (even I, after proving myself the legal owner, can’t get boo about what’s going on with my own site) makes such a scenario impossible to rule out. For what it’s worth, Google does explicitly mention links to “bad neighborhoods” in this Guidelines page, and some sites by and for the SEO people (who presumably know their stuff, this being their entire business model) seem to think this does apply to incoming links as well.
That is unacceptable.

If I haven’t gotten to the bottom of it soon, my only choice might just be to block Google from the site outright (why pay for the bandwidth their crawler uses if we are being excluded from the results?) and personally wean myself from Google search, for whatever that is worth as a personal stance. Is my best alternative really “Bing, and it’s done“?? Google, you really put me between a rock and a hard place.

* nor, based on analysis of the server logs, the “Reconsideration request” you can submit via the Webmaster tools thingy. Unless there are human reviewers lurking in an underground bunker somewhere disguised as residential cable customers from Peoria, or a vast distributed network of speed-readers who are each assigned one line to read, the speed of the hit-streams identifiable as coming from Google during the time of said review easily beat my personal best, and, much like the MTV Music Awards, show no evidence of human intelligence.

** From said page: “If you believe that another site is abusing Google’s quality guidelines, please report that site at https://www.google.com/webmasters/tools/spamreport. Google prefers developing scalable and automated solutions to problems, so we attempt to minimize hand-to-hand spam fighting. The spam reports we receive are used to create scalable algorithms that recognize and block future spam attempts.” Great, The Algorithm is now in charge of deciding who the humans on the Web are.

My quickie guide for setting up mspgcc for ez430-cc2500

Mostly for my own reference for the next time I have to set it up on a new machine, but may help others on their first time install. Valid as of Feb. or so this year.

Software ‘shopping’ list (all free/OSS tools)
Set up the toolchain (mspgcc). There seem to be several important tools
missing from the mspgcc distro as of this writing, including ‘make’ and
msp430-insight (graphical debugger) that the docs claim are included
with the package. So the complete shopping list is:

mspgcc-win32:
http://downloads.sourceforge.net/mspgcc/mspgcc-20081230.exe?use_mirror=voxel
NOTE: This binary IIRC was not linked on Sourceforge’s downloads page at the time; there was only an older build and this link had to be fished from semi-private newsgroup postings. If there is a newer binary available, download that one.

MinGW/msys (provides ‘make’ and some utilities) :
http://downloads.sourceforge.net/mingw/MinGW-5.1.4.exe?use_mirror=voxel
If it gives you the options of installing minGW and msys, say YES to both.

CoreUtils (provides unix-like ‘rm’ tool required by make) :
http://gnuwin32.sourceforge.net/packages/coreutils.htm

Skipping the debugger for now until I figure out how to use it myself ;-) Seems to work occasionally under win32, but it’s flaky.

Required Knowledge Assuming you already know C and have the appropriate chip documentation/datasheets.
Have a quick read-through of the mspgcc FAQ and manual. Both are
reasonably short for what they are.
FAQ: http://mspgcc.sourceforge.net/faq/t2.html
Manual: http://mspgcc.sourceforge.net/manual/

The manual contains a lot of advanced stuff you can skip at first, or
skip entirely. This includes (at minimum) the stuff about customizing
the startup/end procedures, stack, the entire ABI section, inline
assembly, and stuff about building mspgcc (the package you get is
already built).

Get familiar with ‘make’. Outside of kinky application-specific tools
like the Microchip assembler/compiler and ‘IAR Kickstart’, the rest of
the free world uses make to automate compiling, linking,
installing/running and packaging their code. Go into the mspgcc
‘examples’ folder and find the blinking LEDs example (e.g.
E:\mspgcc\examples\leds). Open up the file called Makefile in Wordpad
and have a look inside. This is the master script that will smartly
handle all your compiling, programming the chip, and avoid you rewriting
lots of code whenever you change chips. The contents will probably look
like gibberish, there are only a few parts that are important for our
purposes. The make tool installed by mingw32 is named ‘mingw32-make’.

How make works is you specify one or more ‘targets’, i.e. things make
can do. Running make with no target specified compiles your program.
Some other targets are ‘mingw32-make clean’ (delete your old build and
any scratch files), or ‘mingw32-make download’ (compiles your program,
downloads it to the chip and runs it). All the necessary commands to
handle each target are in the Makefile.

Since the top half of the ez430 kit is essentially the USB Sy-Bi-Wire programmer, you have to change the download command to:

msp430-jtag –spy-bi-wire -lpt=USBFET -e leds.elf

I.e. in the Makefile you’d find and change the download section to:

download-jtag: all
msp430-jtag –spy-bi-wire -lpt=USBFET -e ${NAME}.elf

As long as you have the Makefile open, now is a good time to find the
CPU= line and change it to match the msp430 variant you are actually
using. In the case of the eZ430 board:
CPU = msp430x2274

Now when you #include the base generic as you will for most any
mspgcc project, it will automatically switch in the correct headers and
peripheral support for that specific CPU.

DIY-Spy: a homebrew 2.4GHz wi-fi spectrum analyzer

I was reading the Thinkgeek catalog a while back and an interesting gadget caught my eye: “Wi-Spy”, a 2.4GHz spectrum analyzer on a USB stick. Coming from the world where “spectrum analyzer” refers to a big benchtop box with a name like Le Croyright, we can’t afford those Agilent on it, my first thought was, “A good spectrum analyzer in the GHz range is like a gazillion bucks; what’s really inside this thing?”

Not much, it turns out. After seeing the guts I would not use this device for anything remotely demanding accuracy, but on the bright side, it would be pretty straightforward to make your own that works just as well! Possibly with parts that are already on your board (*cough*XBee).

According to this review and a couple other tech sites, the innards of the original are nothing more than a Cypress WirelessUSB SoC (CYWUSB6934) and USB interface. According to this updated review, the latest version switches to TI/Chipcon’s CC2500 radio ($2.15 USD in quantity) and retails for $399.

The “WirelessUSB” and CC2500 radios are inexpensive 2.4GHz radio chips used in devices such as cordless mice, game controllers and remote controls. What it has in common with many other digital radios is an RSSI (Received Signal Strength Indication) register, which can be read out to provide a measure of how much signal (i.e. interference) is present on any given channel. Wireless gadgets normally use such a mechanism to find the cleanest channel to broadcast on. Most any radio chip with an RSSI readout should work here: XBee, TI/Chipcon’s CC25xx parts, Nordic, etc. I have a big nut going right now for Nordic’s nRF24L01, but unfortunately this does not have an RSSI measurement to speak of (there is a 1-bit “collision detect” flag that warns if the RF energy on the current channel is above a set threshold).

So essentially, the firmware running on the dongle consists of:

for (channel=0; channel<255; channel++)
{
WriteReg(RF_CHANNEL, channel);
signal=ReadReg(RSSI);
send_usb(signal);
}

Hell, why didn’t I think of selling $2 of chip and 4 lines of code for $400? ;-) (I’ve even used those old Cypress radios before on a work project – Unigen’s ready-made JUNO module shown here is about 7 bucks.)

The DIY-Spy

As proof of concept (and a cool toy for anyone who has one of these lying around), I have implemented a working Wi-Fi spectrum analyzer on TI’s ez430-RF2500 development kit ($50), a 2-part USB dongle which consists essentially of a CC2500 radio strapped to an MSP430 low-power microcontroller (detachable bottom half) and a USB interface which enumerates as a virtual serial port (top half). The top half doubles as a standalone MSP430 programmer, so this kit is a great cheap way to get started playing with them.

Being the lazy efficient person that I am, I grabbed mspgcc and an existing ez430 RF demo program (JM Kikori’s RF2500 test application – raw transceiver) and just tossed the infinite RSSI loop into the middle of it.

Here is the main addition (simple & sweet). Forgive WordPress’ complete mangling of the formatting.


static void dump_rssi()
{
int i;
char rssi;
for(i=0; i<256; i++)
{
hal_spi_radio_writeReg( MRFI_CC2500_SPI_REG_CHANNR, i); // Channel number. Default spacing is ~200KHz/channel
hal_spi_radio_cmdStrobe( 0x34 ); // enter Rx mode (not needed except to start autocal)
rssi = (hal_spi_radio_readReg(MRFI_CC2500_SPI_REG_RSSI));
uart0_polled_putc((rssi&0xFE) | (i==0)); // Cheap speed hack: write upper 7 bits of RSSI value (throw away LSB). Use LSB to signal start of 256-channel RSSI byte list
hal_spi_radio_cmdStrobe( 0x36 ); // enter IDLE mode (not needed except for autocal)
}
}

The only real divergence of this from the pseudocode loop above is that the CC2500 requires periodic (or frequent, depending who you ask) recalibration, which can be set to be performed automatically on certain conditions (such as entering Rx mode). This setting is enabled, and the code above toggles between Rx and Idle modes between each channel change to trigger auto-calibration. To make things faster (for me as well as the gadget ;-), rather than perform any kind of real serial handshaking to keep the dongle and the graphing script in sync, I just truncate the least significant bit of the RSSI reading (1/2dBm) and use it to flag the start of the 256-channel sweep.

A more efficient approach would be to perform such calibration once per channel and cache the results (writing them back along with each channel change), which would in theory allow for much faster channel changes. But it’s really a moot point since here the 9600-baud connection to the virtual COM port (MSP430 <–> USB controller) is the limiter of maximum speed.

Most of the time in this project went into tweaking around with the CC2500’s fifty billion or so configuration register bits, not all of which are really documented. In the end I just installed their win32 configuration wizard for the undocumented voodoo (e.g. correct IF setting) and annoying math, and hand-tweaked the remaining settings. For this I set the base frequency to 2400MHz, and the channel spacing to ~ 405KHz, providing the frequency range 2400MHz to 2505MHz across the 256 channel settings. This corresponds to the 2.4GHz ISM band and a little extra. All automatic gain control features are disabled.

Testing
I’ve actually been sitting on this project now for a couple months, since I wasn’t getting the results I expected initially (sitting close to my WiFi access point) and had no good way to test it. Luckily, as it turns out I was tasked with developing some RF gadgets (nRF24L01-based) at work, which could easily be set up to output a raw carrier wave at a programmable frequency. Sure enough, testing revealed some bugs in my initial CC2500 register settings, now corrected.

The video above shows the resulting spectrum output as the nRF’s naked carrier is swept through a handful of frequencies. As it progresses, it should also become evident where my WiFi access point is broadcasting. The green lines show instantaneous signal, the red shows the peak value at each frequency, and the blue shows a running average. The display script is written in Processing.

Downloads

Fairly undocumented; use at your own risk.
diyspy.zip – Source code and .elf binary for ez430 kit (use mspgcc to build from source), .inf file for virtual COM port (win32 only), and Processing script for display.

Protected: A decade of thoughts… // Two’s complement (one’s a crowd)

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Steppin’ Razor: Yet Another Cheap DIY, Homebrew CNC

After about an entire year of the parts sitting around, next-week, next-month, ya-I-been-meanin-ta, tonight I managed to get my homebrew CNC router* assembled into a usable (or at least testable) state. The entire design (if you can call it that! – it was really kind of ad-hoc) consists, as much as possible, of parts commonly available from any random big-box home improvement store (ours is the ‘Depot). The only ‘specialty’ (not available from the hardware store) parts are the electronics – stepper motors, driver boards, and power supply for the above – and machine parts such as ACME nuts and leadscrews, and some standard bearings to help hold the leadscrews in place. The machine’s linear bearings – commonly regarded as the holy grail of low-cost DIY CNC machines (good linear bearings are hard to come by and hard to make!) – are pairs of big industrial-style drawer slides (also from the Home Despot), carefully squared and bolted into place. Not a recommended approach for any remotely heavy-duty machine, but since I mostly intend to carve wood, plastics and the occasional PCB, this shouldn’t pose a huge problem.

Some videos of the machine running:
First test: carving a small face in a piece of foam
Closeup on the business end (Dremel-style rotary tool affixed to the Z axis)
The finished piece
Carving some zombies – here I got smart and attached a light to the machine
Bonus: Dry run (Dremel spindle turned off), showing the melodic sound of the stepper motors :-) (And in the background, the current-limit relay in my borrowed bench supply going nuts. The stepper motor drivers are now powered by a beefy 19V 6A power brick intended for a big laptop.)

Pics






The basic idea (for non-techies):
Imagine spinning a nut on a long bolt – the nut moves up or down the bolt depending which direction it was turned. The same can be done by holding the nut steady, fixing the bolt in place and rotating it – the nut will slide left and right. Attach a cutting head to this moving nut, and mount this assembly (that can move in one axis, e.g. up and down) to two more just like it that move in different directions (left/right, in/out), and you have a cutter that can be moved around in three dimensions by spinning the screws. Attach some motors and a computer can turn the screws automatically by driving the motors forward and backward, moving the cutter in a way that carves out a complex shape.

Components of interest (for techies):
3x Vexta stepper motors, PX245-02B-C8 (6V, 0.8A per phase): $5 each on AllElectronics (sold out shortly after I bought mine)
Stepper drivers: 3x Linisteppers, bolted to a pair of Pentium slot-whatever heatsinks and fan.
Lead screws: 1/2″ x 3′, 10 thread per inch ACME threaded rod (enco.com), with matching ACME nuts attached to the linear guides using J-B Weld (this stuff is amazing!). In retrospect, 10tpi is a bit overkill, and I have to spin the motors like crazy to move the axes at any speed (specifically, 10 rotations to move 1 inch), and stepper motors start losing a lot of torque at higher speeds.
Couplings (motor to leadscrews): Fat vinyl tubing sections and hose clamps

There are still some bugs to work out. For one, though the drawer slides on the X and Z axes are working well, the vertical orientation of the slides for the Y table produces unacceptable play. Basically, the internal part of the slide (the part that actually slides) can shimmy left and right slightly in addition to in and out of the rails that contain it, which gets worse the further these inner parts are extended out of the fixed rails. The force of the cutter pushing left and right into the material causes the table to skew a small amount, which both introduces inaccuracy in the cut and causes the Y table to bind (get stuck). I also still have not found a *good* way to hold down arbitrarily sized and shaped work pieces. Detailed build pics, yet-to-be-tested specs (accuracy, etc.), assembly guides(?) will be in a future post.

*What’s the difference between a router and a mill? Semantics, mainly. The terms are somewhat used interchangeably. From what I can gather reading forum posts on the subject, router implies higher spindle speeds, softer and thinner materials being cut (wood, PCBs), and higher speed overall, while a mill implies a heavy-duty, slower-moving machine cutting metal.

Stupid Excel Trick – amuse your friends & bore your enemies

What’s 1-2?

Today, MS Excel tells me it’s +39815. (Tomorrow it will tell me something different.)

Some while back a signup sheet went around the office for our annual lamb roast. Since every problem (nail) in an office environment has a preinstalled office-suite hammer, the signup list was an Excel spreadsheet. Once everyone has entered their number of guests, it totals up how many total guests. Here’s what I sent around before figuring out Excel’s flavor of crack.

Say you don’t know exactly how many guests you will have for the BBQ. Type a range (e.g. “1-2”) in and see what Excel computes for the total numbers of guests/folks.

For “1-2” guests by my name I get exactly 39084 total guests. Fixed by just saying “1”, but now I’m curious. How is it computing this number?

I can see that being parsed as “one minus two” and yielding a negative number of guests, but I can’t figure out what particular flavor of crack Excel is smoking to get 39,084. Anyone?

I mean, if it had returned NaN or +32767 (or some other signed-unsigned integer conversion failure), I might have understood.

An Excel guru eventually figured it out: The field was hard-set as a numeric field (no auto). Still, it parsed the expression, not as “one minus two” but as a date – “February 1, current year”, and since it was a numeric field, represented this numerically the best way it knew how: the number of days since January 1st, 1900.

The flavor is strawberry.

Firefox 3, SSL and self-signed certificates

First off, for those who know what I’m talking about and are just as pissed…the fix! (sorta)
Open about:config and set the follwing settings:
browser.xul.error_pages.expert_bad_cert: true
browser.ssl_override_behavior: 2

This brings you down from five clicks to “only” two. :-/

So, a while back I got sick of the nag dialogs, caved and updated to Firefox 3. It works pretty much just as well as FF2, but one thing has been bugging me: Encrypted sites are second-class citizens. In previous FF versions (and pretty much any browser known to mankind), if you visited a site which had SSL encryption turned on but no “respectable” certificate, you would get a simple warning dialog about it, with the option to stop or continue (one click). Now however, this one-click process has been replaced by an extremely cumbersome process of navigating through several warnings, examining the certificate, and adding a special exception to the browser settings for that certificate (permanently). Now, viewing any of the Web’s increasingly “encrypted for the heck of it” pages is a giant pain in the ass.

By “respectable” certificate, I mean something that has been purchased from a certification company such as Verisign with an annual maintenance fee (currently about $400/yr), after said company has (claimed to have) performed some background checks on you to ensure that you are really who you say you are. The certificate then vouches, to any random onlooker, that your site is actually operated by you. This makes great sense if you are a bank, of course. You want your customers to know you’re really the bank, not some guy who bought a bank-like domain. For everyone who isn’t a bank, though, the main purpose of SSL is to encrypt data between the server and the user’s PC, preventing any random monkey-in-the-middle (bored local-yokel ISP admins, airport Wifi no-goodniks) from viewing or tampering with the data flowing between them. Since random hobbyists and bloggers can’t or won’t (and, ahem, shouldn’t) pay $400 a year for a CA certificate just to give away free content, this has historically been accomplished for free by a self-signed certificate, i.e. a certificate generated by the webmaster himself. Obviously, while it performs the encryption task just as well, it cannot vouch for the identify the webmaster – but if Joe’s Blog is just trying to keep some braindead ISP / censorware from “re-expressing” the site, is Joe’s SSL-enhanced blog less secure than Joe’s plain unencrypted HTTP (which does not generate alarm bells from Firefox) blog?. Duh, of course not. So why treat it as though it is?

Some more correct solutions would be:

  • Present the Dire Warning Dialog matryoshka exactly once. At the third click is the “I know what I’m doing” checkbox for advanced users which reverts behavior to that of to FF2 and most every other browser in existence (i.e. single-click dismissal for users who understand the difference between encryption and authentication). This approach worked surprisingly well on my LSP-Fix utility, which allows advanced (potentially destructive) operations with an “I know what I’m doing” checkbox and appropriate warnings about how much fun it is to reinstall one’s OS.
  • Same as #1, but with a very brief SSL test the user must pass to enable the checkbox, to prove they really understand the difference between encryption and authentication – or for that matter, between either of those and security.
  • Keep the 1-click dismissal from the start, but fix the wording for novices: WARNING: This site is no more secure than Joe Blow’s random blog. Do not submit your credit-card number or anything else you wouldn’t put on the frontpage of the New York Times.
  • Display a bright red titlebar / address bar and the familiar “broken padlock” symbol for sites with unverifiable certificates. A Bright Red Something works very well as a persistent visual reminder, hours after the dialog-clicking has faded from memory (I use this approach on any GUI logged in as administrator/root, reminding me that I have the power to really screw myself.)
  • Release the SSL behavior fix for FF3 as an extension that must be manually installed, for clueful users who want to surf Comcast-proofed sites in peace Looks like a Moz developer’s already done it, though compatibility with different FF3 versions sounds a bit hit-and-miss.

A Mozilla developer’s (non-SSL-encrypted) blog on the subject explains some of the logic behind this UX nightmare, including the (semi-sensible, I must admit) rationale behind making exceptions permanent by defaut. (This, too, should have an advanced-user override switch – I for one don’t want to permanently accept bad certs as good.) Be glad for what you got though, apparently they had initially decided not to allow self-signed pages to be accessed AT ALL.

(Yeah, apparently I’m not the first person to take offense at this behavior, though my beef is not so much in the wording but the sheer ten-click time-wastage and the implication that some encrypted sites are somehow less secure than plaintext ones.)

Creepy government project…

Title: Virtual Dialogue Application for Families of Deployed Service Members

Objective: To develop a highly interactive PC or web-based application to allow family members to verbally interact with “virtual” renditions of deployed Service Members.

This RFP from the Office of the Secretary of Defense (OSD09-H03) floated across my desk the other day. After reading the first line I thought, “They want internet voice chat with avatars? Quit wasting my tax dollars, go download SecondLife.”

Then I kept reading. That is not the goal of the project. At all.

Description: The Defense Centers of Excellence for Psychological Health and Traumatic Brain Injury recognizes that family outreach and advocacy is pivotal for both the psychological health of the family and the resilience of the Service Member. Deployments put stress on the entire family, especially small children and communication is key. The ability to reach out and communicate with loved ones from areas of conflict is better than at any time in history. Nevertheless, the stresses of deployment might be softened if spouses and especially children could conduct simple conversations with their loved ones in immediate times of stress or prolonged absence. Historically, families have derived comfort and support from photographs or mementos, but current technology SHOULD allow for more personal interactive messages of support. Over 80% of American children between the ages of three and five regularly use computers, and 83% of families have a computer in their home. So, computer-based applications would resonate with children and capture their interest and imagination. The challenge is to design an application that would would allow a child to receive comfort from being able to have simple, virtual conversations with a parent who is not aivailable “in-person”. We are looking for innovative applications that explore and harness the power of “advanced” interactive multimedia computer technologies to produce compelling interactive dialogue between a Service member and their families via a pc- or web-based application using video footage or high-resolution 3-D rendering. The child should be able to have a simulated conversation with a parent about generic, everyday topics. For instance, a child may get a response from saying “I love you”, or “I miss you”, or “Good night mommy/daddy.” This is a technologically challenging application because it relies on the ability to have convincing voice-recognition, artificial intelligence, and the ability to easily and inexpensively develop a customized application tailored to a specific parent.

No, I don’t see any potential to scar a kid for life with this. Especially if a detached, AI “Dad” suddenly has no recollection of the existence of the family dog, or memorable recent events in the kid’s life. Or catching on that “Dad” is a fake, and for a long time after, never trusting whether he’s talking to his real parent or a computer simulation. Or, mid-conversation, the arrival of a letter apologetically informing the family that the person the kid’s currently speaking to was actually killed in combat three weeks ago.

Could the current state of AI not only fool someone into mistaking it for a human, but mistaking it for a human they’ve known intimately for their entire life? (Then again, I have known some humans that might not reliably pass a Turing test, either.)

We are seeking development of a tool which can be used to help families (especially, children) cope with deployments by providing a means to have simple verbal interactions with loved ones for re-assurance, support, affection, and generic discussion when phone and internet conversations are not possible. The application should incorporate an AI that allows for flexibility in language comprehension to give the illusion of a natural (but simple) interaction. The current solicitation is not aiming to build entertainment, but a highly accurate and advanced simulation platform. Voice-recognition and voice-interaction are required. The User Interface is a critical component for this program. Application must be user friendly and application must be easy to install and maintain. Verbal interactions should be as normal as current technology will allow. Proven track record for creating similar types of applications is desired, but not required. Development plans should include the use of trained psychological health and family advocacy experts with experience providing services to military populations. Project MUST include discussion of how personal information would be collected, recorded, and rendered as well as address issues about information content and complexity of proposed simulation application. If using a web-based application, security and maintenance issues must be addressed. Application must run on typical family-owned computer systems.

Hiking in the Middlesex Fells

Some pictures from our hiking trip a couple weeks ago (Krista, myself, Jane, and Matt). Holy crap, is it fall already? How did that happen?

Fun with High Voltage & Plasma

The other night I picked back up playing with insulated gas discharge tubes (IGDT), better known as plasma globes. The basic idea is to pump a sealed chamber filled with a noble gas (or air, in a pinch) down to low pressure (1s to 10s of Torr), and apply electricity at high voltage (a few kV) and frequency (a few kHz) to ionize the gas. Depending on the gas(es), pressure, voltage, and frequency, the results should range from a diffuse eerie glow to a bunch of lightning-like plasma streamers dancing around inside the chamber. The most well-known example are the Eye of the Storm novelty globes and their knockoffs.


[Photo Album]

Here are some pictures from tonight’s initial playing, using a scavenged fridge compressor as a vacuum pump and a cleaned-out glass pasta sauce jar as the globe. The effect inside the jar was generally unimpressive over a wide range of pressures, but the effect on the clear PVC tubing and the white plastic hose barb I used to attach it was certainly interesting! The hose barb connector glowed brightly and the plastic tubing lit up like a flexible neon sign, with a glow that crawled through the hose several feet toward the compressor as the pressure dropped. Nice poor-man’s neon effect, but I suspect air will outgas and/or leak through the walls of the PVC tubing rapidly (days?), ruining the vacuum and the effect. This calls for further study :-)

I didn’t play too much with additives except to revisit the combination of plasma globe and discrete mini Neon lamps. This looks much cooler with the neon lamps actually inside the evacuated chamber with the glowing plasma (and finally with a decent camera!). Everything so far has used plain old air.

Fridge Compressor as Vacuum Pump

The short story is yes, you can use the compressor from a refrigerator or dehumidifier as a quick & dirty vacuum pump (or light duty air compressor), provided the refrigerant has all been vented/leaked before you get to it (unless you have facilities to safely capture and recycle the refrigerant, which few do). The design of these things seems pretty universal, as well as ingenious: the “in” tube leads to a piston, which is driven by a big electric motor in the center of the compressor via a crankshaft. The output of this valved piston vents directly to the inside of the case, which is sealed and in facted welded shut, with the “out” tube being the only escape. The bottom 1/4 inch or so of this mechanism is submerged in a pool of light oil, which is sucked up by a cone on the bottom of the crankshaft mechanism, sucked through the shaft and flung out the top and against the outer walls of the compressor by centri[whatsit] force – providing simultaneous lubrication and transfer of heat from the pump mechanism to the outside case, which acts as a heatsink. This page has a very cool teardown of one of these compressors, complete with videos of the oil-slinging mechanism in operation.

As a side effect to this design, small amounts of oil are sometimes ejected from the outlet along with the air, necessitating some kind of primitive oil recovery/trap mechanism. For mine I attached a small length of vinyl tubing to the outlet, made a sort of drip loop in it, and attached the other end to a piece of plastic pipet taped vertically to the side of the compressor. The width of the pipet prevents oil from being blown out all the way to the top, while the drip loop in the tubing (intentionally seeded with a couple drops of oil) provides a simple but highly effective visual flowmeter, good for indicating the end of effective pumping (or a leaky system). A loosely fitting cap taped over the pipet helps reject dust.

It’s probably a good idea to eyedropper out occasional oil from this catcher and feed it back into the inlet to keep the piston lubed up. (I had to drain all the oil out of mine to transport it, then refilled it with an equal volume of some SAE 30 motor oil I had on hand. No ill effects thus far, but I’m pretty sure the original oil was a lot lighter.)

But how good is it? I have no actual meter that will deal in these pressures, so it’s hard to say. On this pump a jar of water would–just barely–start to boil at room temperature. According to this calculator, that approximates to roughly 20 Torr (.026 atmospheres). Not bad for free!

Possible sealing approach (haven’t gotten around to trying it yet)

Professional globes are all-glass affairs of a complex shape, with the glass fill tube(s) heated and melted shut while under vacuum to seal the globe. This is not really an option for hobbyists, since it must be connected to a live vacuum during sealing and a typical “globe” has a nonglass base (plastic or Plexiglas) where an equally nonglass fill tube emerges, since glassmelting is not compatible with the typical vinyl tubing connecting it to the live vacuum system in the process. Some just leave a small length of tubing and a closed valve permanently affixed. But good valves aren’t cheap, and cheap valves aren’t good. The approach I’d like to try is to epoxy a hose barb into the base with a very thin piece of hollow metal tubing (needle) epoxied inside of it, making the tube the only gas path into or out of the globe. This is connected via a short piece of vinyl tubing to one of two matching hose barbs on a small lidded jar (e.g. baby food – something with a “magic button” style rubberized lid), such that the needle snakes through the center of the tubing and just reaches the bottom of the jar. A small discardable “bucket” (e.g. soda cap) of 5-minute epoxy would be mixed up and placed inside the jar, the lid screwed on, and the needle sunk into the epoxy. The jar, and thus globe, are then evacuated via the 2nd barb in the babyfood jar lid. When the pump is switched off, the normal small leakage (maybe introduced via valve, if the pump setup is just that good) will allow the vacuum to relax slightly, forcing liquid epoxy up the metal needle, where it is allowed to cure and permanently seal the globe. The excess epoxy-filled metal needle and hose barb can then be cut off. Extending this setup to multiple flush/fill hoses on the globe would be easy enough, other than trying to hand-align these multiple needles at once.

Railway Supply Institute expo 2008, Chicago

I was there to demo my self-powered wireless brake health monitoring system at the FRA’s Advanced Concept Train booth. Despite the final assembly of this and the other 29 units occurring only a couple days before (and passing through the TSA’s loving hands), everything went perfectly! (Murrphy’s Law might have a surprise or two for me on back-order.)

The train show wasn’t all that exciting to me (not a train nut), but the food was good, and I got to visit the fam back home for a bit. :-)

[Pictures from the trip]

Worst User Agreement, Evar

And the winner goes to… The Terms & Conditions for use of the Hampton Inn’s complimentary WiFi. Weighing in at 47.4KBytes* and a whopping 90 screens (scrunching it all into a tiny browser text box did not help in this regard), this is quite possibly the longest, and most unilaterally evil, user agreement I have ever read.

(I would start here with a list of definitions of usage information (‘hereinafter … referred to collectively as the “Information”‘) gathered by the service, but man is it lengthy. Basically, your IP, lists of websites visited, transactions and purchases on 3rd-party websites, you name it.)


You agree that HHC shall own all Information.

By using the Service, you voluntarily, expressly and knowingly acknowledge and agree with all of the foregoing and further agree to each and all of the following: (I) such Information belongs to HHC and is not personal or private proprietary information; (ii) such Information, wherever collected, may be processed, used, reproduced, modified, adapted, translated, used to create derivative works, shared, published and distributed by HHC in its sole and absolute discretion in any media and manner irrevocably in perpetuity in any location throughout the universe without royalty or payment of any kind, without, however, any obligation by HHC to do so

I’m guessing the main “[iI]nformation” they’re interested in is clickstream data, but the definition of this [iI]nformation includes any piece of data transmitted through or “relating to” or “describing” the service (even prior to being presented with this contract), presumably including this blog post. (*Starts lawsuit clock*) So you might not want to use this service to email your just-finished Great American Novel manuscript to your publisher. Also, this is the first legal agreement I’ve ever seen explicitly covering the entire Universe.

Also, when you submit information (including the Information) to us in your use of the Service, you thereby (i) represent and warrant that such information is complete, truthful, and accurate, that you own all rights in such information, that the information, if applicable, is entirely your own original, unpublished work, is not based in whole or in part upon any pre-existing work or work of any other person,

Again, ass-uming they’re mostly after clickstream data, this makes it a legally-actionable offense to surf in such a way as to provide non-unique clickstream data, i.e. surfing the same sites you surfed yesterday. And apparently, you are forbidden from transmitting already-public data through the WiFi connection (even if you own it…err, would have owned it until the moment you sent a copy through Hampton Inn’s WiFi connection)…maybe they are fishing your packets for saleable manuscripts, leakable memos and not-yet-submitted patents after all.

Because we are not involved in the actual transaction between buyers and suppliers, if applicable, in the event that you have a dispute with one or more users, you also on behalf of yourself, your predecessors, if applicable, and each of their present and former officers, employees, directors, shareholders, parents, subsidiaries, alter egos, affiliates, partners, agents, attorneys, accountants, heirs, executors, administrators, conservators, successors and assigns, as applicable, hereby fully and forever releases and discharges the Indemnified Parties, from any and all claims, demands, liens, actions, agreements, suits, causes of action, obligations, controversies, debts, costs, attorneys’ fees, expenses, damages, judgments, orders and liabilities of whatever kind or nature in law, equity or otherwise, whether now known or suspected which have existed or may have existed, or which do exist or which hereafter can, shall or may exist, based on any facts, events or omissions occurring from any time on or prior to the execution of this Agreement which arise out of, concern, pertain or relate in any way to this Agreement or the Service.

Synonymania! Oh yeah, that is ONE SENTENCE.


Notwithstanding such provisions, this release shall constitute a full release in accordance with its terms. You knowingly and voluntarily waive the provisions of Section 1542, as well as any other statute, law or rule of similar effect. In connection with such waiver and relinquishment, You acknowledges that you are aware that you may hereafter discover claims presently unknown or unsuspected, or facts in addition to or different from those which you now know or believe to be true, with respect to the matters released herein. Nevertheless, it is your intention, through this Agreement, and with the advice of counsel, fully and finally settle and release all such matters, and all claims relative thereto, which do now exist, may exist, or have existed between and among the parties hereto, including the Indemnified Parties. You hereby acknowledge that you have been advised by your legal counsel, understand and acknowledge the significance and consequence of this release and of this specific waiver of Section 1542 and other such laws.1

Hereby, the party of the first part registers a parse error on Line 1. The remainder of this section has you agree to an end-run around a California law protecting you from getting screwed over by an omission from the contract or other omitted facts which, if known, would have materially affected your decision to enter the contract.

If there is any place that runs a “Worst User Agreements” contest, I saved a copy…

* This is about 15% of Pride and Prejudice by weight, according to Project Gutenberg, and >100% as dull, according to the party of the first part myself.