The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Oddities

Who’d’a thunk it?

Analon Slide Rule
Whenever I do anything even slightly out of the ordinary with magnetics, I must drag out my trusty Analon slipstick to make sure I haven’t lost a dimension.

Analon slide rule – front

Go ahead, you verify that the area inside a BH hysteresis curve is proportional to power loss in a given transformer core. I’ll wait…

Analon slide rule – back

My recollection is that I bought it in the Lehigh University Bookstore in the early 70s, but that doesn’t square up with the Analon’s history: they should have been out of circulation by then. I’m pretty sure I didn’t get it in high school, extreme geek though I was, and it’s for damn sure I wouldn’t have bought one after graduation. Come to think of it, if the LU Bookstore wasn’t among the last bastion of Analon holdouts, where would you look?

Over the decades I’ve penciled in a few handy dimensions they didn’t think of. Unlike most of the 600 597 (plus one in the Smithsonian) Analons in the wild, this one actually gets used, so it’s not New-In-Box (which means you collectors need not suffer from involuntary hip motions). It’s also not as grubby as it looks: I didn’t spend a lot of time futzing with the scans.

Anyway, that’s called beausage and it enhances the value.

Works that way with other antiques, right?

Links:
Yeah, OK, it’s a Slide Rule Gloat…
2009-02-27
Power Outlet Contact Failure

Burnt outlet expander

Ordinary AC power outlets have fairly robust contacts, designed to last basically forever. I have no idea what the actual design life might be, but it’s rare to have an AC outlet fail.

This one did…

It’s an outlet expander at the end of an extension cord that provides six outlets. I’d installed it at my parent’s house (I was their go-to guy for electrical things, of course) and everything was fine. One visit involved rearranging some appliances and the adapter went nova when I plugged something into it.

Me being their go-to electrical guy, I’m pretty sure this gizmo didn’t experience a whole bunch of mate-unmate cycles in my absence. Most likely it was defective from the factory, so sticking a plug in once or twice was enough to break the contact finger.

Detail of burnt socket

Here’s a contrast-enhanced detail of the outlet in the lower-right of the top picture. The broken finger bridged the brass strips carrying the two sides of the AC line in the left side of the compartment.

Blam: brass smoke!

Oddly, the fuse didn’t blow. It was pretty exciting to have a small sun in the palm of my hand until the contact finger fell to the bottom of the compartment.

The bottom picture shows the offending finger. It’s pretty obvious what happened.

Errant contact finger

I’ve read of folks applying silicone lubricant (spray, perhaps) to their AC line plugs to reduce the mating friction in the outlet. While that sounds like a good idea, I think it’s misguided: you don’t want to reduce the metal-to-metal contact area by lubing it up with an insulator. In any event, that sliding friction ensures the contacts have a clean mating surface with low resistance.

Maybe use some Caig DeoxIT, but not an insulating spray!

For what it’s worth, do you know that the durability of an ordinary USB connector is 1500 cycles? That’s far more than PCI backplane connectors at 100 cycles. Some exotic high-GHz RF connectors can survive only a few dozen cycles.

Moral of the story: don’t unplug your stuff all the time. Use switches and stay healthy.

This took place many years ago, so the picture quality isn’t up to contemporary standards.

2009-02-25
CD V-750 Dosimeter Charger Manual

V-750 Model 5b Manual Cover

My V-750 dosimeter charger came with two (!) copies of the manual and the modification instructions (stamped JUN–1965) for adding the anti-kick capacitor.

The paperwork didn’t fare quite as well as the metal-cased charger, sporting far more mildew on the pages than I want on my shelves.

I cut the worst-looking copy right down the middle, scanned it with some attention to detail, and now there’s a nice version that looks just as bad but lacks the mildew.

Clicky:

CD V-750 Model 5b Radiological Dosimeter Charger Operating and Maintenance Manual with Modification Instruction Sheet

If you’re really clever, you can figure out how to sequence the sheets and print them duplexed so they appear back-to-back, then bind them into a booklet just like the original. There’s a copy of a blank inside cover, too, so you can wrap your booklet in a nice Civil Defense Yellow cover.

The schematic shows what real engineers could do, back in the days when transistors came individually packaged with a ten-dollar price tag: 1.5 volts in, 200+ volts out, one transistor. Of course, they paid attention to their transformer lessons.

V-750 Dosimeter Charger Schematic

2009-02-24
Photo Tweakage: Mouse Tunnels in the Snow

Mouse tunnels in the snow

As the snow cover melts away in the spring, you discover how much activity has been going on.

The mice make elaborate tunnels with spaces for seed stores, latrines, and numereous secret entrances near the bushes. For a few months, at least, they can scamper all over the yard without worrying about becoming snacks for owls and hawks.

This kind of picture requires a bit of tweakage, because the default camera settings deliver an essentially gray picture with no contrast. The usual auto-exposure settings assume a more-or-less neutral background, so the camera adjusts the exposure to deliver a neutral result. Unfortunately, you really want most of the background to be white, so the default snow image will be grossly underexposed.

Set the camera to overexpose the picture by 1 or 2 EV; if your camera has a histogram display, adjust the exposure to put that huge bump on the white end close to the right side of the histogram. It helps if you frame the picture before doing this, as the LCD monitor will be pretty much retina-burn white.

Take the picture and get it into your PC.

GIMP Level Adjustment Window

Now, in your favorite photo-editing software (The GIMP on our desktops), adjust the photo’s levels & contrast. This screen shot shows the logarithmic histogram; the linear one is basically just one peak 3/4 of the way to the right side with a little grass on the rest of the chart. The two little buttons in the upper-right choose linear or log.

Drag the white point (the teeny white triangle on the right, just below the histogram) until it’s just a bit to the right of the abrupt dropoff’s foot. That sets the whitest part of the picture to real white, not half-a-stop-down light gray.

You can do the same with the black point (the black triangle on the left), setting it to just left of the black dropoff. In this case, we have some genuinely dark areas, so leave it alone.

Now, the key part: drag the middle triangle to adjust the gamma. Move it rightward to darken the overall image by decreasing the gamma and emphasize small differences on the bright end of the histogram. That makes the tunnels pop out of the image, although it also tends to make the snow look very contrasty.

Don’t go overboard with this sort of thing, but a little adjustment can reveal details and bring pictures back to life. It’s not for Ansel Adams quality pix, that’s for sure.

Here’s possibly more than you want to know about levels & gamma & contrast, but with much better illustrations and more descriptions: Unai Garro’s Blog. He has other useful tutorials, too.

2009-02-20
A Thorough Job of Hard Drive Data Destruction

Scrubbed hard drive platters

What’s wrong with this picture?

A friend rides herd on a college data center and reports that one of the hot spares in a drive array started complaining about errors. By the time he got to it, things had gone from bad to worse to worst: the drive was spinning, but its data was gone.

He removed all the head frippery before giving me the carcass, but the platters are exacty as they were when he ripped through those “Warranty Void If Removed” stickers.

Even though disk platters are now made of glass in order to achieve adequate flatness tolerances, you’re not supposed to be able to see through the things. There’s a bare millimeter of untouched plating on the inner and outer rims; everything else is finely ground glass.

Evidently the drive suffered a head crash or some part of the plating peeled off, after which the debris acted as grinding compound under the heads on the rest of the platters. Eventually the internal filters clogged and the ensuing dust storm scrubbed the glass platters clean.

He said the inside of the drive was filled with impalpable silvery dust. Another friend deadpanned “Oh, so all the data was still in the drive, right?

We decided that sorting all those dust grains into the right order would tax even Iranian “students”.

More than you likely want to know about hard drive platters resides there.

2009-02-17
Nonmagnetic Tweezers: Don’t Believe The Hype

A small package of 6000 SMD resistors just arrived from a Hong Kong eBay seller. It showed up promptly despite traveling halfway around the world, had neat packaging, and I’ll give ’em good feedback.

Also included was a free needle-tip tweezers, just exactly what you need for plucking those little ceramic rectangles from their packages. I already have a bunch of needle-tip tweezers in my rack, but you can never have too many tools and this one won’t go to waste.

Gooi TS-11 tweezers

The package has what appears to be comprehensive instructions in both Chinese and Japanese (to my untrained eyes, anyway). Not much in English, other than that Anti-magnetic, anti-acid and non-corrosive Stainless Steel line; perhaps this isn’t the export model. Indeed, it lacks the obligatory country-of-origin labeling, but, given where the package came from, one may reasonably assume the usual Chinese origin.

The tweezers are (almost illegibly) stamped STAINLESS NON-MAGNETIC and bear a tidy sticker: gooi TS-11 ANTIMAGNETIC.

Gooi TS-11 Antimagnetic sticker

The build quality and surface finish are, um, a bit rough, but Gooi seems really proud of their non/anti-magnetic properties.

Needless to say, a magnet sticks firmly…

I have no convenient way to test their anti-acid (whatever that is) and non-corrosive properties, but I’m betting these suckers are plain old Chinese mild steel, made from recycled US scrap. Perhaps the previous iteration was stainless and we’re stepping down the cost-saving ladder? If they would just change the packaging to match reality, that would be fine with me.

[Insert standard observations about Chinese quality control here.]

Y’know, come to think of it, I’m sort of wondering about those 6000 SMD resistors. With any luck they’ll actually work when I get around to using them. If not, I suppose it serves me right for buying direct from Hong Kong via eBay, eh?

And, yes, I know some stainless steel is magnetic.

2009-02-11
They’re Getting Bolder!

Turkey on the Patio

Got up this morning, looked out the kitchen window, and there stands a turkey on the patio!

They’ve been edging closer and closer for the last week or so; we think the snow cover is making the seeds under the feeder look more attractive. As nearly as we can tell, though, they have yet to venture across the patio to the feeder: no tracks in the snow.

What would be really impressive: a row of turkeys lined up on the patio railing, just like they do on our neighbor’s split-rail wooden fence.

2009-02-08