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.
If you measure something often enough, it becomes science
Thirteen months ago, that round table had self-enclosed:
We don’t have a good picture of the square table, but it had that same crater open to the central hole.
Other pictures show the topmost 14+ inches from that storm consisted of lovely, fluffy snow that cleared well, although I’d have settled for a bit less.
It’s winter in the Northeast US. Snow happens on a regular basis. I enjoy the shapes, not the shoveling…
The AA battery pack grafted onto the back of the Hobo datalogger recording groundwater temperature showed a 50% level during its most recent dump, so I swapped in a pair of new AA cells.
The pack hack dates back to 2009-09 and the Duracell Ultra cells have a “best used by” date of March 2013. Call it 5.5 years of service and, figuring an average current of 10 μA, that’s a total of 480 mA·h.
The datasheet shows many graphs at much higher currents, but a capacity of 3500 mA·h to 0.80 V at 5 mA seems pretty close. Given that they produce 2.87 V with no load, they’re still in decent shape.
However, the logger’s opinion of their voltage is what counts. To estimate that number, I checked the reports from the attic: the death planet for lithium cells.
Starting with an old Energizer failing after a few hours in December:
Two new Maxell CR2032 lithium cells also had trouble, with the first reporting a low voltage in January:
The second in February:
I think the Maxell cells failed from low temperature, but dead cell is dead.
That happens just above 2.85 V, so the attic datalogger now carries an AA alkaline battery pack.
The well pit definitely got cold during those nights when the air temperature dropped well below zero:
Match that against the attic air temperature:
The well pit has two vent holes made from old-school fluted steel downspout pipe embedded vertically in a half-foot concrete slab. They’re maybe five feet apart and the southwest hole seems to be the air inlet:
The northeast hole must be the outlet for all that ground-warmed air:
The logger hangs from the string entering from the center left, with a ring hung over an abandoned hose bib rising straight out of the concrete.
Surely it’s been that cold before without freezing the pipes, so I won’t worry too much…
A licensed bird rescuer gave a talk before a showing of Pelican Dreams in Rhinebck and presented some of her patients…
A Red Tailed Hawk with a broken left wing, just out of its bandage:
A Barred Owl who, despite having a left eye that no longer dilates, rapidly acquired weapons lock on my camera’s focus assist light:
And a pair of insanely cute Screech Owls, both with eye damage, atop their padded perch:
Most of her patients arrive after collisions with automobiles; it seems carnivorous birds don’t look both ways before pouncing on prey near the roadside.
Contrary to her impassioned claims, however, wind turbines kill essentially zero birds, at least compared to windows, HV power lines, and cats. Some reports with actual numbers that, obviously, won’t convince anybody who already knows what the results should be:
Low light, no flash, long zoom, handheld, good-looking subjects.
One of the four 40 W bulbs in the classic 1955 fixture over the front bathroom mirror burned out, leading to this discovery:
Yup, I installed that bulb in late September 1998, when we repainted that bathroom (for the first time since the original owners painted it in 1955). Getting a decade and a half from an incandescent bulb in regular use ain’t all that bad, sez I. Two other bulbs appeared in mid 2014, replacing bulbs with barely 6 years of service. Inexplicably, the third bulb has no date; I must be slipping.
Having burned through the 40 W bulb stash, I put two 60 W incandescents in the center sockets, leaving me with four new-old-stock bulbs on the shelf. Might be a lifetime supply for this house…
From a datalogger hanging on a string in the well pit, about three feet underground, in December:
The temperatures continue downward in January:
The corresponding attic air temperature record for January ends early:
When the air temperature dropped to +11 °F in the early hours of 17 January 2015, the well pit hit 35.5 °F. It was just over 35 °F in the wee hours of 29 January 2015, but the attic logger gave up as the battery voltage declined to 2.8 V.
Evidently, the new Maxell CR2032 lithium cells don’t do well in extreme cold. They’re rated to -20 °C = -4 °F, but that spec applies for a very low load that surely doesn’t include blinking a red LED.
I’ll take a look at that logger in a few days, then hack a pair of AA cells on the back if it’s dead again. Alkaline cells aren’t very good in cold weather, either, but they may have a better minimum voltage.
Or it’s just another batch of dud CR2032 cells…
All three Energizer CR2032 lithium cells installed at the end of November failed in December, with this being the most dramatic example:
Now, granted, it was mighty chilly in the attic, but failing after 18 hours seems unreasonable. So much for last month’s data.
I’ve started a batch of Maxell cells with the more reasonable date code 3O, which seems to indicate a manufacturing date of 2013 October.
We shall see…
The Smell of Molten Projects in the Morning 