Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.
We read the original document in DC a few months ago, while doing the touristy thing. These days, that means submitting to a search on the way into each museum; Mary lost her forgotten-in-the-bottom-of-her-purse Swiss Army Knife to the Smithsonian guards.
We left town feeling that something has gone badly wrong in the last decade or so.
In the Mysteriously Missing Label category, we find three similar products with only one shelf label. Which one is the better deal?
Caffeine unit pricing
You might think it’d be the Wal-Mart Equate house brand. In order to find out, you’d have to haul all three offerings down the aisle and around the corner to the price scanner, which would reveal it’s the one on the far left, by a considerable margin. Oddly, that one says “Double Strength” even though it has the same 200 mg dose as the others.
In the Bizarre Units category, we have two very similar products with completely different unit-price units of measure. Seeing as how a “fluid ounce” is a unit of volume and a “pound” is a unit of weight (or, for the pedantic, force), even the dimensions aren’t compatible. Clicky for bigger pictures.
Vanilla unit pricing – 2 oz
And, just to show that wasn’t a one-off mistake that could happen to anyone, the smaller size containers continue the theme.
Vanilla unit pricing – 1 oz
Given that nothing in a Wal-Mart store happens by accident, someone was directed to remove two of those three labels and another someone deliberately chose incompatible units.
Of course, anyone I’ve ever asked has no idea why that would happen…
My Shop Assistant (who now merits a Proper Name) returned a fairly new measuring tape to the Basement Laboratory, reporting that the retracting crank handle fell off in “normal use”.
Stripped handle threads
Admittedly, this was a surplus find, but you’d think the build quality would be a bit higher. I’m sure I paid a minute fraction of list price: you could have bought it for much more in a reputable store.
Maybe this is why the whole lot got scrapped out:
Handle detail
I applied a bit of JB Industro Weld to the plastic (?) threads on the spool, twisted the handle in place, squared it up, then eased more epoxy around the top of the threads and let it cure flat on the bench.
Remounted handle
I’d say the original design wasn’t particularly good and the implementation left a lot to be desired. If the interior fittings have similar flaws, I’ll eventually regret applying JB Weld in such a cavalier manner…
Yellow / Light Cyan / Cyan / Light Magenta = 30 ml each
The waste ink container is now a bit more than half full: 90 mm high in a 40 mm diameter cylinder. That works out to 113×103 mm = 113 ml. Given that “high capacity” cartridges for this printer contain 11 ml, I’m looking at 10 cartridges worth of waste ink.
While I was printing handouts for Cabin Fever, the R380 had a brain spasm and announced it didn’t recognize any of its ink cartridges. A power cycle brought it back to its senses and all the continuous-ink cartridges reset themselves to Completely full once again. With another printer, that error message required a complete new set of cartridges, because the printer could (and did!) set bits inside the refill-prevention chips that rendered the cartridges unusable.
I wondered if the Thing-O-Matic would benefit from having its two high-current heaters on a separate +12 V supply than the DC Extruder, after finding that the heaters dragged the +12 V output down by nearly half a volt.
A bit of rummaging turned up a suitable ATX supply with a data plate that might justifiably lead one to believe that the supply provides separate +12 V outputs:
Turbolink ATX-CW420W power supply data plate
There’s no indication which of the four connectors might use +12V1 and +12V2, but, being that sort of guy, I applied an ohmmeter to the various yellow wires and found they were all exactly 0.0 Ω apart.
Huh.
So I opened the Warranty Void If Seal Removed top cover and found this situation:
All the yellow wires terminate in the same solder blob below the PCB
Two incoming wires got neatly spliced together in mid-air, despite having free holes in the PCB
This may not come as much of a shock: they lie…
Perhaps if you spend more money on your supply, it’ll actually live up to the data plate specs. Then, again, perhaps you’ll just be spending more money.
And, if you swap in a fancy supply for the MBI-stock one, it might not make much difference at all. I suspect the various power levels and current capacities have pretty much the same degree of integrity…
Y’know how some folks say they don’t wear a seat belt because they want to be thrown free in a crash? Here’s how that works in actual practice.
The air bag fires as the front bumper begins to deform and your body rises off the seat. Because you’re not belted in, the bag boosts your upper torso against the roof liner, bounces your head off the sunshade and bezel, then feeds you directly into the windshield glass.
Laminated glass doesn’t disintegrate, so your skull probably won’t completely penetrate the windshield. You’ll lose some scalp, though, as you slide down the crumbling glass and wedge above the dashboard.
Even if you survive a broken neck, the ensuing brain trauma means you won’t be the same person ever again.
News flash: massive brain trauma does not make you a better person.
Before laminated windshield glass became mandatory, your head would completely penetrate the windshield. Here’s what happened in 1937, from the incomparably grisly — And Sudden Death by J. C. Furnas:
Safety Glass Windshields
I read one of the many Reader’s Digest editions of that article during my formative years. Probably the one in October 1967, if a bit of Google-fu serves me right. You can’t get reprints of it from RD any longer, it seems.
However, unbelievably, while I was composing this post, I checked eBay and found a typewritten copy of the article, signed by Furnas, with 38 minutes remaining in the auction. I was the only bidder: for nine bucks (delivered) it’s mine.
Most likely it’s a publicity / fundraising copy, because the handwritten notation on the first page reads:
With best
regards to
[name]
J. C. Furnas
Oct 20, 1947
Those SUVs reside in the junkyard along the Dutchess Rail Trail near Creek Road, where I might get a new seat to rebuild my comfy office chair this spring.
In general, you cannot solve a bed bug problem by attracting and trapping bugs: there are simply too many bugs that are breeding ahead of their losses. We had (presumably) brought very few bugs home in our luggage, so every one we trapped was one less bug in the room. In any event, the number of bugs caught in the traps would give some idea of how much trouble we were in.
The bottom line: we trapped one or two bed bug instars and no adults.
Anything labeled for use against bed bugs carries a staggering markup and considerable smoke-and-mirrors marketing, but if you go back to the original sources (see the references in the first post), you’ll find out what actually works, which is quite different from what’s advertised.
The study by Wang, et. al., tested carbon dioxide, heat, and chemical lures. Tested singly: CO2 is pretty good, heat is OK, chemical lures definitely come in last. Basically, I think there are way too many significant figures in their results, but under idealized test conditions in a small arena, they collected about 80% of the bugs after six hours.
One key number: the CO2 flow rate was about 170 ml/min, roughly that produced by an adult human.
Another interesting number:
The visual inspections found ≤23 bed bugs in each apartment and they were considered as low levels of infestations.
CO2 mug and powder trap
Based on that, we decided to build some CO2 traps, which led to those observations. Our version of a dry-ice trap used a huge insulated mug filled with dry ice, perched atop an inverted dog food dish. We deployed two traps like that.
The dog dish has a cloth skirt (so the bed bugs can get traction on the way in) and a layer of talcum powder inside (so they can’t get any traction on the way out). The gas flow rate was in the right ballpark.
After several days, we had collected exactly zero bed bugs.
That wasn’t surprising, of course, because we knew we didn’t have all that many bugs, but we were still getting bitten in other parts of the house. Like, alas, the guest-room bed where we’d moved after gutting our bedroom.
Using dry ice as a CO2 source is relatively expensive and exceedingly inconvenient. We went through two iterations and decided that this was far too expensive, given the expected results.
It turns out that baker’s yeast metabolizes sugar into ethanol and carbon dioxide as the yeast gradually dies in a sea of dilute ethanol; if you have a distillation rig handy, you can probably get a decent yield of vodka from this project. Normally I use the carbon dioxide to stretch bread dough, but in this case it came in handy all by itself.
You can buy, for $50, a Bed Bug Beacon or you can build your own carbon dioxide lure and trap from ordinary household items for pretty close to zero dollars. Your choice.
I built and deployed four yeast reactor lures, built from gallon milk jugs and Tygon tubing from the parts heap. This picture tells you pretty nearly everything you need to know.
Yeast CO2 generator
I used a hollow punch to poke those the neat holes in the lids, but a razor knife will suffice. Seal the opening on the bottle cap with something sticky; nothing adheres well to polyethlyene and Tygon, although the contact cement I got with the dryer rear seal worked well.
Cap detail
Put three quarts / liters of warm water in the jug, add a cup of sugar (lots of sugar = longer production = more gas) and a teaspoon of yeast (lots of yeast = more production = live hard, die young), put on a solid cap, and shake vigorously to mix. Swap in the cap with the tubing and deploy. The recipe is totally non-critical and would make a great science fair project…
The dingus on the other end of the hose is the bottom of a cottage cheese container, artfully sculpted into a shallow dish with four small feet between low arched openings. Basically, it’s a little cover to trap the CO2 in a confined area and let it leak out in relatively concentrated streams. I have no idea if that’s how it works, but it was easy to do and keeps the hose from wandering away.
What they don’t tell you is that the gas production from a small yeast reactor is maybe 5%, tops, of the 150-200 ml/min required to mimic a human: I bubbled the gas into an inverted 60 ml syringe and used a stopwatch. The gas production varies strongly with time; after a week it’s down to essentially zero, so I’d say the “11 day” claims for the BBB’s lifetime are, mmmm, fanciful, at best.
Gas production is proportional to the total number of active yeast. Methinks a cup of sugar in three quarts of water will yield more yeast than a packet of sugar in, what, a pint jar? If you drop fifty bucks on a BBB, make some measurements and let me know, OK?
Maybe they use brewer’s yeast, which is an ethanol-tolerant strain of ordinary baker’s yeast. The end product, after a week, smells strongly of ethanol, so I’m not sure how much difference that would make.
In any event, my opinion is that such a minimal gas flow can attract bugs from only a very limited radius, so the results are far less conclusive than dry ice or pressurized-gas lures. Of course, if you have floors crowded with bed bugs, a few of them will stumble across the lure simply by accident.
Of course, there is one lure that’s absolutely guaranteed to attract bed bugs from across the room: you. I’ll discuss that after covering traps and barriers…
The Smell of Molten Projects in the Morning 