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?

Would You Pull the Tab?
So this device showed up in an envelope with a letter telling us we’d won a contest if, of course, the number on the device matched the number in the letter:

CodeKase device

I wonder if anybody else had second thoughts about pulling what’s obviously an insulating sheet holding two contacts apart? In this day and age, getting the victim to blow his own fingers off probably counts as a win.

Maybe it comes from having read The White Plague at an impressionable age. Who could resist getting a Nice Thing in the mail?

The number matched, of course, but the letter’s finer print said the prize would be one of:
- A new car of some sort
- A flat screen TV
- A cheap electronic trinket
- A three-day / two night vacation
In order to claim your prize, you had to call an 800 number. The much finer print revealed the odds of winning the first three of those prizes was somewhere around 300,000:1. “Winning” the vacation was essentially a slam-dunk proposition, of course, and probably tells you everything you need to know about the course of the phone call.

It’s apparently economical to send out this much hardware to reel in new “customers”:

CodeKase device – parts

Using the metal disk from a membrane switch as a spring to push the coin cell against the contact wires is a nice touch. This is apparently the optimized version that uses a single lithium cell in place of two alkaline buttons; the cell “socket” on the other end consists of vestigial lumps.

I harvested the lithium cell and the blue LED, of course…

More about CodeKase, direct from the source. I like “Step Five: Recycle Your CodeKase”…
2015-12-05
Neopixel Knockoff: Early Failure

About a week after First Light, one of the knockoff Neopixels (not a Genuine Adafruit Product) suffered an intermittent failure: it worked fine after being off for an hour or two, but eventually stalled at a fixed color, with all downstream pixels equally dead. Of course, it was the middle package in the string of three, buried in the hub (this is before the failure):

Hard Drive Mood Light – low angle

Spraying circuit cooler on the package brought it back to life for a few minutes, confirming the diagnosis. Reducing the maximum intensity to PWM 32 reduced the average power dissipation enough to let it run for as long as I was willing to let it, although it might not survive a hot summer day.

Not having glued the spacers onto the hub simplified extracting the strip, although warranty repair is always a nuisance. I daubed red Sharpie on the failing LED to avoid losing track of it, then resoldered the LED and capacitor connections to no avail:

Knockoff Neopixel Failure – overview

There’s nothing obviously wrong inside:

Knockoff Neopixel Failure – detail

The fine details of the WS2812B controller produce a horrible Moiré blur with the camera’s low-res image, but you get the general idea.

Most likely, one of those flying wires isn’t quite bonded, but we’ll never know…

2015-12-03
Why Friends Don’t Let Friends Run Windows

Perhaps this is not nearly as motivational as it’s supposed to be:

Win 10 Upgrade Popup

A friend sent that along after reading my efforts to squelch the Windows 10 nagware on an off-lease Dell Optiplex that will never, ever be updated.

She just turned off automatic updates, which means she must examine all the updates and manually install ones that don’t download Win 10 (which she doesn’t want), forevermore. Unfortunately, that means she won’t automatically get all the security updates that help make current versions of Windows much less hazardous then in The Bad Old Days.

Talk about a Hobson’s Choice: in practical terms, you must decide between automatic updates or not getting regular updates. OK, that’s actually a false dilemma, but you get the idea.

If you run automatic updates the way Microsoft recommends, you’ll soon be running a free operating system that tracks and reports your every move, so as to deliver precisely targeted advertisements right on your desktop. What could possibly be better?

Come the middle of next year, we may see an uptick in the number of people using Linux or running unpatched Windows boxes to cut down on nagware.

2015-11-29
Hard Drive Platter Thicknesses

It should come as no surprise that hard drive platters have different thicknesses:

Hard Drive Platter Thickness

The thicker ones measure 1.25 mm, which is near enough to 50 mils to suggest they date back to the Good Old Days. The three thinner ones in the middle are 0.77 mm = 30 mil and could be slightly younger than dirt. There’s more where these came from and I expect more variation on the theme.

The beveled edges make the platters look thinner than they really are; they’re firmly clamped together with no space between them.

As nearly as I can tell, the IBM 350 Disk Storage Unit on the IBM 350 RAMAC had platters about 25 mil thick. Those were two feet in diameter, so they definitely don’t make ’em like they used to!

The thickness wouldn’t matter, except that the OpenSCAD program producing the hub & spacer tabs for the Mood Lights needs to know.

2015-11-26
Provincetown Pilgrim Memorial: Lighting Ticky-tacky

This imposing memorial plaque stands in a small park in Provincetown MA, at the foot of the hill from which the Pilgrim Monument emerges:

Provincetown Pilgrim Memorial

It’s one of those 1920-ish things with the impeccable stonework and bronze casting that you couldn’t possibly duplicate nowadays. But, at least twice between then and now, somebody thought it’d be a Good Idea to decorate it with what look to be Genuine Christmas Tree Lights:

Provincetown Pilgrim Memorial – detail

The most recent lamps and wires seem to be restrained by plastic clips glued onto the face of the stone:

Provincetown Pilgrim Memorial – lamp detail

A previous generation drilled small holes and inserted metal pins that didn’t survive in a salt-spray environment, so I guess plastic seemed like the right answer.

Words fail me…

2015-11-22
New Countertop vs. Old Strut

Spotted this in a restaurant near Lowell, MA on our road trip:

Countertop trash cutout vs support strut

Somehow, it’s very hard to coordinate sinks, supports, and plumbing these days…

2015-11-21
Neopixel Current

Adafruit’s Neopixels are RGB LEDs with a built-in current-limiting 400 Hz PWM controller and a serial data link. Successive Neopixels aren’t synchronized, so their PWM cycles can produce serious current spikes.

Lighting up just the red LED in two Neopixels at PWM 16/255 produces this current waveform (at 10 mA/div):

Neopixel current 10 mA – 16-0-0 0-1

Each red LED draws about 20 mA, so when the two Neopixel PWM cycles coincide, you get a nasty 40 mA spike. When they don’t coincide, you get a pair of 20 mA pulses. Those pulses walk with respect to each other at a pretty good clip; the oscillators aren’t trimmed to precision.

Lighting up three Neopixels with PWM 16/255 on the red does exactly what you’d expect. The horizontal scale is now 100 µs/div, making the PWM pulses five times wider:

Neopixel current 10 mA – 16-0-0 0-1-2

The narrow spike comes from the brief shining instant when all three Neopixels were on at the same time. Now you have three PWM pulses, each with slightly different periods.

Remember that these are PWM 16/255 pulses. When they’re at full brightness, PWM 255/255, there’s only a brief downtime between pulses that last nearly 2.5 ms and they’ll overlap like crazy.

Obviously, the more Neopixels and the lower the average PWM setting, the more the average current will tend toward the, uh, average. However, it will have brutal spikes, so the correct way to size the power supply is to multiply the number of Neopixels in the string by the maximum possible 60 mA/Neopixel… which gets really big, really fast.

A 1 meter strip of 144 knockoff Neopixels from the usual eBay supplier will draw 144 x 60 mA = 8.6 A when all the pulses coincide. Worse, the supply must be able to cope with full-scale transients and all the fractions in between. A husky filter cap would be your friend, but you need one with a low ESR and very high capacity to support the transients.

No wonder people have trouble with their Neopixel strings; you really shouldn’t (try to) run more than one or two directly from an Arduino’s on-board regulator…

2015-11-18