Archive for category Science
Monthly Image: Turkey Hen and Chicks
Posted by Ed in Photography & Images, Science on 2019-06-15
Mary saw a fox trotting behind the garden, gripping a (dead) turkey chick in its jaws, with the hen in hot pursuit. The fox dropped the chick, circled the pine grove, picked up the chick, and departed stage right. The hen eventually led her remaining chicks into the yard, but gathered them underneath while watching for danger:
She settled down for a few minutes:
With the fox safely departed, she released the chicks:
Then they returned to foraging, with one chick trying out its wings:
Two days earlier, she led nine chicks through the yard; we think the fox picked off a chick a day. She lost two more during the next four days, suggesting they rapidly improve their ability to scamper out of harm’s way.
Monthly Science: Water Bottle Refill History
This year’s Northern Star Quilt Guild show in the O’Neill Center at WCSU gave me an opportunity to update last year’s data points, although not quite in the way I expected.
The overview:
The left display is rotting out:
The center display seems undamaged:
The right display took a direct hit:
So the middle station refilled 3025 = 10460 – 7435 bottles, roughly eight bottles a day, every day, for a year. Seems like a lot of refilling, doesn’t it?
Unfortunately, I didn’t take pictures of the other watering hole last year, but here’s what it looks like now:
Overview:
Left:
Center:
Right:
Now, it’s entirely possible I have the two stations reversed, in which case I have numbers for all three displays:
- Left = 242 = 4758 – 4516
- Center = 633 = 8068 – 7435
- Right = 800 = 9689 – 8889
Does a bottle or two a day, every day, for a year, seem more reasonable? Hard to say, so, with a bit of luck, we’ll have more data next year.
For science!
MPCNC Drag Knife: PETG Linear Bearing
Posted by Ed in Machine Shop, Science on 2019-05-24
Having reasonable success using a 12 mm hole bored in a 3D printed mount for the nice drag knife holder on the left, I thought I’d try the same trick for the raw aluminum holder on the right side:
The 11.5 mm body is long enough to justify making a longer holder with more bearing surface:
Slicing with four perimeter threads lays down enough reasonably solid plastic to bore the central hole to a nice sliding fit:
The top disk gets bored to a snug press fit around the flange and upper body:
Assemble with springs and it pretty much works:
Unfortunately, it doesn’t work particularly well, because the two screws tightening the MPCNC’s DW660 tool holder (the black band) can apply enough force to deform the PETG mount and lock the drag knife body in the bore, while not being quite tight enough to prevent the mount from moving.
I think the holder for the black knife (on the left) worked better, because:
- The anodized surface is much smoother & slipperier
- The body is shorter, so less friction
In any event, I reached a sufficiently happy compromise for some heavy paper / light cardboard test shapes, but a PETG bearing won’t suffice for dependable drag knife cuttery.
Back to the laboratory …
Monthly Science: Weight
Posted by Ed in Home Ec, Recumbent Bicycling, Science on 2019-05-01
Progress is our most important product:
Now that we’ve begun bicycling more regularly, Winter Bloat is transmogrifying into thigh muscle.
The hills around here become noticeably steeper during winter; we attribute the additional elevation to frost heaves …
Monthly Science: Weight
Posted by Ed in Home Ec, Recumbent Bicycling, Science on 2019-04-01
We’d been eating a “healthy” high-carb / low-fat diet, which produced the more-or-less expected 1 lb/yr weight gain over the course of three decades. Given that we eat about 106 Cal/yr, being off by a mere 0.3% seemed fixable, but we were always hungry while trying to cut out calories.
In April 2016, we decided our tummies had come between us, so we switched to a mostly ketogenic diet (clicky for more dots):
Having a Master Gardener in the family complicates dietary choices along the ketogenic axis, but Mary raised more green-and-leafy veggies, less squash-and-corn, and we keto-ized our meals reasonably well. Moderation in all things works fine for us, so losing 25 pounds at about 1 lb/week wasn’t particularly stressful.
Continuing through 2017, you can see how regular bike riding season affects winter bloat:
Our cycling vacation in July 2018 produced a blip, but the rest of the riding season worked as expected:
It’s straightforward to crash-diet two dozen pounds, but maintaining a more-or-less stable weight for the next two years suggests we’ve gotten the annual calorie count about right. FWIW, my bloodwork numbers sit in the Just Fine range, apart from the somewhat elevated cholesterol level typical of a keto-ized diet.
Starting in late 2018, however, a stressful situation of a non-bloggable nature (at least for a blog such as this) produced an unusually high number of road trips, motel stays, and generally poor dietary choices:
The situation now being over, our lives / exercise / diet will return to what passes for normal around here and my goal is to lose another 10% of my current body weight, ending at 150 pounds, by the end of the year. In round numbers, that requires losing half a pound = 1700 Cal/week, 250 Cal/day. Not power-noshing an ounce or two of nuts a day should do the trick.
If it makes you feel more science-y, you can use the NIH Body Weight Planner, but it produces about the same answer: knock off 300 Cal to lose weight, 250 Cal to maintain it, at essentially the same exercise level as before.
We’ve been recording our weights as dots on graph paper every Saturday evening for the last four decades, so I know for a fact I averaged 148 pounds when I wore a younger man’s clothes. I’ll re-post the 2019 chart, adding four dots every month, during the rest of the year.
This way, you can help keep me on track … [grin]
Another WS2812 Failure: Broken Glass
Posted by Ed in Electronics Workbench, Machine Shop, Science on 2019-03-22
The WS2812 under the 5U4GB full-wave rectifier tube went into pinball panic mode:
It’s been running more-or-less continuously since late 2016, so call it
Because I’d be crazy to replace it with another likely-to-fail WS2812, I had to remove both of them before installing SK6812 RGBW LEDs and updating the Arduino Nano.
Unfortunately, I did a really good job of bonding the side light to the tube with epoxy:
The last tube manufacturing step involved flashing the getter onto the tube envelope, so as to remove the last vestige of air. Admitting air oxidizes the getter:
It was such a pretty tube, too …
RD JDS6600 Signal Generator: Warmup Time
Posted by Ed in Electronics Workbench, Science on 2019-03-18
An RD JDS6600 Signal Generator recently arrived from around the curve of the horizon, leading me to measure its warmup time:
Looks like it’s good to go after maybe 90 minutes and, after much longer, it settles to 10 MHz +36 Hz, for a correction factor of 0.9999964 on those days when you’re being really fussy.
The need for frequencies accurate to better than 4 ppm doesn’t happen very often around here, but it’s best to be prepared. It’s amazing what you can get for under $100 these days …
I measured the frequency by zero-beating against the Z3801 GPS Frequency Standard (purple trace in the middle):
Basically, trigger the scope on either trace, crank the JDS6600 frequency in 1 Hz, then 0.1 Hz steps, until the traces stop crawling past each other, and you’re done.
It’s worth noting you (well, I) must crank eleven 0.01 Hz steps to change the output frequency by about 0.1 Hz around 10 MHz, suggesting the actual frequency steps are on the order of 0.1 Hz, no matter what the display resolution may lead you to think.
The RDS6600 main PCB (Rev 15) sports a 24 MHz oscillator close to the Lattice FPGA:
The AD9850 step size worked out to 0.0291 Hz for the LF crystal tester. A 24 MHz clock would produce a 5.7 mHz step size, but that’s obviously no what’s going on. More study is indicated.
The bottom trace is the scope’s internal function generator, also set to 10 MHz. Zero-beating the JDS6600 against the scope’s output produces a similar result:
The scope’s function generator actually runs at (9.999964 MHz) × (0.9999964) = 9.999928 MHz, a whopping 72 ppm low. The on-screen frequency measurements don’t have enough resolution to show the offset, nor to zero-beat it with the Z3801 input, so it’s as good as it needs to be.
The Z3801’s double-oven oscillator takes a few days to settle from a cold start, so this wasn’t an impulsive measurement. Having the power drop midway through the process didn’t help, either, but it’s March in the Northeast and one gets occasional blizzards with no additional charge.
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