Archive for category Science

Blog Summary: 2019

Another year of being the Domain Expert of scam-by-mail gadgets, obsolete ABS codes, and water heater anode rods:

Blog Page View Summary - 2019
Blog Page View Summary – 2019

Plotting the log of page views against posts in descending order of popularity gives a power-law relationship of some sort:

Blog Page View Graph - 2019
Blog Page View Graph – 2019

The log-log view has odd discontinuities:

Blog Page View Graph - 2019 - log-log
Blog Page View Graph – 2019 – log-log

Overall page views are down 30% from last year: 205k vs 290k.

WordPress served 1 million ads (vs 1.2 million in 2018) on those 205k page views, nearly five ads per page view, which seems horrifying. If you’re not using an ad blocker, you surely have difficulty finding the blog post amid all the crap.

The implosion of on-line advertising continues apace, however, as WordPress paid only 63% as much per ad: $0.40 (vs $0.70 in 2018) per thousand views. Obviously, ads on WordPress blogs aren’t worth much these days.

Recommendations:

While I could pay WordPress their upgrade ransom to eliminate the ads, it’s better if you defend yourself by eliminating all ads, wherever they may be.

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Bird Feeder Icing

After a day of snow + sleet + ice, followed by overnight cooling, the bird feeder looked like this:

2019-12-19 - Ice on bird feeder - Day 0
2019-12-19 – Ice on bird feeder – Day 0

The ice generally doesn’t bond across the top, so the sheets slide off separately to the front and back. This time, they stayed together and began sliding off to the side.

The next two days were unusually cold and the glacier stopped sliding:

2019-12-21 - Ice on bird feeder - Day 2
2019-12-21 – Ice on bird feeder – Day 2

The temperature warmed enough during the day to let the glacier resume sliding, whereupon it fell and shattered on the patio.

No birds or squirrels were injured during this incident.

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Cheese Slicer: JB Weld Epoxy FTW

The JB Weld epoxy I slathered on our trusty hand-held cheese slicer a year ago continues to withstand daily washing and occasional trips through the dishwasher:

Cheese Slicer JB Weld 1 year - top
Cheese Slicer JB Weld 1 year – top

The bottom is in fine shape, too:

Cheese Slicer JB Weld 1 year - bottom
Cheese Slicer JB Weld 1 year – bottom

Compare it with XTC-3D epoxy, which admittedly isn’t rated for continuous water exposure, after a year:

Cheese Slicer - epoxy coating split
Cheese Slicer – epoxy coating split

JB Weld FTW!

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Monthly Science: Vegetable Ice Crystals

Mary made a batch of veggies in tomato sauce and froze meal-size portions as winter treats. The moist air inside the containers froze into delicate ice blades on the zucchini slices:

Veggie ice crystals - overview
Veggie ice crystals – overview

A closer look:

Veggie ice crystals - detail
Veggie ice crystals – detail

The blade cross-sections might be oblong hexagons, but it’s hard to tell with crystals melting almost instantly after the lid comes off. Some of the smaller hair-like blades reminded me of tin whiskers.

Yummy!

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Wasabi NP-BX1: End-of-Life

As a followup to the DOT-01 battery status, I found the last of the Wasabi NP-BX1 batteries in a drawer where they’d sat unused for eight months.

Recharge and test to get the blue lines, with the red lines from the DOT-01 batteries:

Wasabi DOT-01 NP-BX1 - 2019-11
Wasabi DOT-01 NP-BX1 – 2019-11

The double blue line came from a second recharge of that battery, just to see if more electrons would help. Nope, it’s still dead.

The Wasabi battery with the highest capacity also has the weirdly rippled voltage trace and, when I extracted it from the test holder, came out disturbingly warm and all swoll up. This is A Bad Sign™, so it spent the next few hours chillin’ on the patio and now resides in the recycle box.

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Monthly Science: Weight

After another two months:

Weight Chart 2019-10 - Ed
Weight Chart 2019-10 – Ed

The trend is definitely not uniformly downward, perhaps due to my increasing ability to accelerate (small) masses against the local gravity vector and, definitely, garden harvest season. My pants still fit fine, if that’s any indication.

I’ll add a skin-fold caliper dot to the weekly record after I can get repeatable measurements, perhaps by marking the test spot with a Sharpie.

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Alead Telecoil Receiver: Magnetic Field Check

I got an Alead / Nolan HearLinks (many adjectives) Telecoil receiver to boost my ability to hear music & presentations at Vassar, because they recently slotted telecoil loops into the floors of their public venues. It took a few concerts to get the appropriate volume setting, after which I wondered how sensitive the receiver was:

Alead T-coil receiver - test setup
Alead T-coil receiver – test setup

The small T in the upper right corner marks the receiving coil location, with the coil oriented parallel to the body’s long axis. It’s the secondary winding of an air-core transformer with a single-turn (perhaps using Litz wire) primary embedded in the floor, with the induced voltage obeying the usual transformer equation:

V = 2π µ₀ µr N A f H cos θ

Definitions:

  • µ₀ – vacuum permeability = 4π×10-7 H/m
  • µr – relative permeability
  • N – number of turns
  • A – receiver loop area, m²
  • f – signal frequency, Hz
  • H – magnetomotive force, A/m
  • θ – angle between windings

For a given installation and receiver position, pretty much everything is fixed, with the voltage depending only on the H field caused by the primary winding current.

The induced voltage is linearly dependent on the frequency, but the transmitter equalization filters apparently flatten the spectrum to get equal receiver amplitude between about 100 Hz and 5 kHz.

The coil in that picture has nine turns, with four passing through the Tek current probe. Applying 10 mVpp to the winding produces a corresponding current:

JDS6600 10mVpp 1 kHz - 4 turns - 1 mA-div
JDS6600 10mVpp 1 kHz – 4 turns – 1 mA-div

The scope sees 14 mVpp = 1.4 div at 1 mA/div = 1.4 mA. Dividing by 4 turns means the coil actually carryes 350 µA. The signal generator has a 50 Ω output impedance, so 10 mV should produce about 200 µA, which seems a bit low. On the other paw, the signal generator sees the coil as a dead short at 1 kHz, so I don’t trust the numbers.

Whatever magnetic flux it may be produces a 1 kHz tone at a somewhat higher volume (for the same receiver setting) than the fancy Vassar loops, so the flux is in the right ballpark. With a bit more attention to detail, perhaps I can tinker up a current-mode loop drive amplifier.

The Alead receiver has an internally generated tick audible at the audio volume I need for the Vassar loops, which is 5 to 7 steps down from the maximum volume at 15 steps. It seems related to the internal Bluetooth hardware, although it’s present even when the receiver is not paired with my Pixel phone and, in fact, is unchanged even when 100 feet from the nearest electronic device.

When I reported the problem, they said:

Yes, you can hear very minor tick sound on telecoil mode. It is caused by some electronic and current to make those tick sound. Sorry for this defective on the design.

It had one job that it doesn’t do well, so it’s on the way back for a refund.

Evidently, I must build an audio loop receiver to get what I want …

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