Archive for category Science
The WS2812 RGB LED atop the Bowl of Fire Floodlight …
… failed in the usual way after a bit over a year of constant use.
I’d done an unusually good job of epoxying the ersatz heatsink in place:
I wrapped the bulb in a towel with only the heatsink sticking out, whacked the side of the heatsink parallel to the glass with a plastic-face hammer, and it popped right off:
The missing piece of the epoxy ring turned out to be a divot ripped out of the glass, which I didn’t notice until I’d chipped the fragment off the aluminum, so no pictures.
Given the relative strengths of epoxy and glass, pulling a divot seems impossible, but folks doing 3D printing on glass platforms have been reporting exactly that failure for years. The prevailing theory seems to involve small scratches and defects in the glass surface, with subsequent weakening, and stresses applied to the epoxy perpendicular to the glass surface pulling the cracks apart.
Replacing the RGB LED will require drilling it out and probably a complete rewiring, because I seem to have made liberal use of epoxy inside the heatsink and brass tube.
The best way to get a pure, non-reflective black uses optics, not pigments:
The shiny steel blades reflect light just fine, but the reflections have no way back out of the gap between adjacent edges: the angle of reflection always points away from you and the incoming light.
I always admire the blackness when I open that box.
Yes, I’m a member of the Society of the Easily Amused.
By August 2, a pair of caterpillars had hatched and grew to 3 mm:
A day later, they were 4 mm long:
They really were sort of blue-ish with green hints:
By August 9, one had had more mature coloration:
The other caterpillar had vanished; we assume it got out of the aquarium and wandered off.
Apparently, the front end of the caterpillar (at the bottom of the picture) has a hard windshield reflecting the ring of LEDs around the camera lens. The caterpillar eats its skin after each molting, except for the windshield:
We kept fresh milkweed branches in a vase and the caterpillar ate almost continuously:
By August 15, the caterpillar was ready for the next stage in its life. At 10 in the morning it had attached itself to the screen covering the aquarium and assumed the position:
It transformed into a chrysalis by 5:30 PM:
The discarded skin remained loosely attached until I carefully removed it.
What look like small yellow spots are actually a striking metallic gold color.
Eleven days later, on August 26 at 9 AM, the chrysalis suddenly became transparent:
The shape of the butterfly becomes visible in reflected light:
The gold dots and line remained visible.
The magic happened at 3 PM:
The compacted wings emerge intense orange on the top and lighter orange on the bottom:
The butterfly took most of the day to unfurl and stiffen its wings into flat plates:
By 8 PM it began exploring the aquarium:
As adults, they sip nectar from flowers, but don’t feed for the first day, so we left it in the aquarium overnight.
At 10 AM on August 27, we transported it to the goldenrod in the garden, where it immediately began tanking operations:
A few minutes later, it began sun-warming operations:
Mary watched it while she was tending the garden and, an hour or so later, saw it take off and fly over the house in a generally southwest direction. It will cross half the continent under a geas prohibiting any other action, eventually overwinter in Mexico with far too few of its compadres, then die after producing the eggs for a generation beginning the northward journey next year.
Godspeed, little butterfly, godspeed …
In the spirit of “video or it didn’t happen”, there’s a 15 fps movie of the emergence taken at 5 s/image.
An array of tiny eggs appeared on the outside of our bedroom window:
The patch measures 12 mm across and 14 mm tall. From across the room, it looks like a smudge, but it consists of hundreds of eggs, each on a tiny stalk glued to the glass:
The bottom image is two days later than the top one, both are scaled to about the same size and contrast. The critters look about the same, although I think the lines have more prominent ripples or bumps.
We have no idea what they’ll turn into, but they certainly look like they have two eyes and wings …
Datasheets loosely associated with the tuning fork resonators in hand suggest 1 μW maximum drive power, which works out to maybe 100 mVrms = 150 mVpk at about 10 kΩ ESR. If you inadvertently apply 500 mVpk = 375 mVrms, the resulting 14 μW does this:
I was applying a precisely tuned 60 kHz sine wave to the first pass at a crystal filter grafted onto the loop antenna preamp and wasn’t paying attention to the amplitude. For all I know, though, the poor thing died from a power-on transient. I’m pretty sure I didn’t break it during extraction, because it stopped being a resonator while in the circuit.
The missing tine fell out of the can:
Laser trim scars form a triangle near the tip, a T a bit further down, a slot just above the nicely etched gap.
A closer look at the fractured base:
The metalization appears black here and gold in person.
So, yeah, one down and 49 to go …
I set the Sony HDR-AS30V atop a tripod, told it to take photos at 5 second intervals, then stitched the images into a Youtube video. It won’t go viral, but watching the spider construct her web over the course of two hours was fascinating.
She finishes the spiral at about 1 m video = 1.25 h real time, settles down for what might be a nap (it’s hard to tell with spiders), and has an insect join her for supper at 1:28, half an hour later. Spiders go from “inert” to “death incoming” almost instantly, even in real time running.
Another orb weaver set up shop in the adjacent window, but moved out the next day. Perhaps there’s a minimum spacing requirement?
Two more orb weavers guard windows in the kitchen and laundry room. We sometimes leave the lights on for them.
YouTube has other web-building videos with far more detail, of course.
The magic incantation to create the video from a directory of images in the form
sn=1 ; for f in *JPG ; do printf -v dn 'dsc%04d.jpg' "$(( sn++ ))" ; mv $f $dn ; done ffmpeg -r 15 -i /mnt/video/2017-09-03/100MSDCF/dsc%04d.jpg -q 1 Orb-Weaving-2017-09-03.mp4
Histogramming all 50-ish resonator frequencies shows reasonably good distributions:
I don’t know what to make of the difference between the
parallel series-capacitor and basic serial resonant frequencies for each tuning fork:
Perhaps each resonator’s frequency depends on its (laser-trimmed) tine mass and follows a more-or-less normal distribution, but the
parallel-serial difference series capacitor changes the frequency based on (well-controlled) etched dimensions producing quantized results from three different masks / wafers / lots, with the motional inductance and capacitance incompletely modeling the physics?
For reference, the resonators look like this:
Producing the histograms uses the LibreOffice
frequency() array function, which requires remembering to whack
Ctrl-Shift Enter to activate the function’s array-ness.
[Update: Faceplant about “parallel” resonance, which is actually the shifted resonant peak due to the 24 pF series cap. Apparently I typo-ed the second histogram subheading and ran with the error; the figures are now correct.]