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Archive for category Science

Monthly Image: Turkey Hen and Chicks

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:

Turkey hen with chicks - alert
Turkey hen with chicks – alert

She settled down for a few minutes:

Turkey hen with chicks - resting
Turkey hen with chicks – resting

With the fox safely departed, she released the chicks:

Turkey hen with chicks - emerging
Turkey hen with chicks – emerging

Then they returned to foraging, with one chick trying out its wings:

Turkey hen with chicks - dispersing
Turkey hen with chicks – dispersing

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.

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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:

Gym water bottle refill station B - overview
Gym water bottle refill station B – overview

The left display is rotting out:

Gym water bottle refill station B - left
Gym water bottle refill station B – left

The center display seems undamaged:

Gym water bottle refill station B - center
Gym water bottle refill station B – center

The right display took a direct hit:

Gym water bottle refill station B - right
Gym water bottle refill station B – right

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:

Gym water bottle refill station A - overview
Gym water bottle refill station A – overview

Left:

Gym water bottle refill station A - left
Gym water bottle refill station A – left

Center:

Gym water bottle refill station A - center
Gym water bottle refill station A – 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!

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MPCNC Drag Knife: PETG Linear Bearing

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:

Drag Knife holders - detail
Drag Knife holders – detail

The 11.5 mm body is long enough to justify making a longer holder with more bearing surface:

Drag Knife Holder - 11.5 mm body - Slic3r preview
Drag Knife Holder – 11.5 mm body – Slic3r preview

Slicing with four perimeter threads lays down enough reasonably solid plastic to bore the central hole to a nice sliding fit:

Drag Knife - 11.5 mm body - boring
Drag Knife – 11.5 mm body – boring

The top disk gets bored to a snug press fit around the flange and upper body:

Drag Knife - 11.5 mm body - flange boring
Drag Knife – 11.5 mm body – flange boring

Assemble with springs and it pretty much works:

Drag Knife - hexagon depth setting
Drag Knife – hexagon depth setting

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 …

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Monthly Science: Weight

Progress is our most important product:

Weight Chart 2019-04 - Ed
Weight Chart 2019-04 – Ed

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 …

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Monthly Science: Weight

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):

Weight Chart 2016 - Ed
Weight Chart 2016 – Ed

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:

Weight Chart 2017 - Ed
Weight Chart 2017 – Ed

Our cycling vacation in July 2018 produced a blip, but the rest of the riding season worked as expected:

Weight Chart 2018 - Ed
Weight Chart 2018 – Ed

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:

Weight Chart 2019-03 - Ed
Weight Chart 2019-03 – Ed

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]

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Another WS2812 Failure: Broken Glass

The WS2812 under the 5U4GB full-wave rectifier tube went into pinball panic mode:

Failed WS2812 - 5U4GB Rectifier
Failed WS2812 – 5U4GB Rectifier

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:

Failed WS2812 - 5U4GB broken glass
Failed WS2812 – 5U4GB broken glass

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:

Failed WS2812 - 5U4GB getter oxidation
Failed WS2812 – 5U4GB getter oxidation

It was such a pretty tube, too …

5U4GB Full-wave vacuum rectifier - cyan red phase
5U4GB Full-wave vacuum rectifier – cyan red phase

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RD JDS6600 Signal Generator: Warmup Time

An RD JDS6600 Signal Generator recently arrived from around the curve of the horizon, leading me to measure its warmup time:

RDS6600 Signal Generator - Warmup plot
RDS6600 Signal Generator – Warmup plot

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):

RDS6600 Signal Generator vs. Z3801 GPS Frequency Standard
RDS6600 Signal Generator vs. Z3801 GPS Frequency Standard

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:

RDS6600 Signal Generator - clock oscillator
RDS6600 Signal Generator – clock oscillator

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:

IMG_20190312_130925 - RDS6600 vs SDS2304X frequencies
IMG_20190312_130925 – RDS6600 vs SDS2304X frequencies

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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