Category: Science

If you measure something often enough, it becomes science

PolyDryer Humidity: September

After six months to see how much moisture entered from the 50%RH (±5%RH) basement air:

	2026-09-07
Filament	%RH	Weight – g	Wt gain – g	Gain %
PETG White	26	56.2	6.2	12.4%	Gel
PETG Black	28	57.3	7.3	14.6%	Gel
PETG Orange	34	54.1	4.1	8.2%	Alumina
PETG Clear	37	54.4	4.4	8.8%	Alumina
PETG-CF Blue	38	54.0	4.0	8.0%	Alumina
PETG-CF Gray	34	56.4	6.4	12.8%	Gel
PETG-CF Black	25	56.3	6.3	12.6%	Gel
PETG Blue	38	55.9	5.9	11.8%	Alumina
TPU Clear	34	56.3	6.3	12.6%	Alumina
TPU Black	32	55.2	5.2	10.4%	Alumina

Sorted by relative humidity:

PETG-CF Black	25	56.3	6.3	12.6%	Gel
PETG White	26	56.2	6.2	12.4%	Gel
PETG Black	28	57.3	7.3	14.6%	Gel
TPU Black	32	55.2	5.2	10.4%	Alumina
PETG Orange	34	54.1	4.1	8.2%	Alumina
PETG-CF Gray	34	56.4	6.4	12.8%	Gel
TPU Clear	34	56.3	6.3	12.6%	Alumina
PETG Clear	37	54.4	4.4	8.8%	Alumina
PETG-CF Blue	38	54.0	4.0	8.0%	Alumina
PETG Blue	38	55.9	5.9	11.8%	Alumina

Fairly obviously, there is no correlation between the humidity level and the amount of adsorbed water.

The silica gel beads were rather dark, not that that means much:

Silica Gel beads - 2026-09-07 — Silica Gel beads – 2026-09-07

All the boxes now contain 50 g of alumina beads.

2026-09-08

Yellowjacket Nest

Although I’d sealed the cracks around the front door after the previous Yellowjacket encounter, a cloud of Yellowjackets revealed their queen had set up housekeeping between two plants in front of our house. I donned my beekeeper suit, sprayed the obvious entrances with wasp killer, then repeated the dose over the next several days until, as Khruschev apparently didn’t say, the survivors envied the dead.

The nest was about a foot in diameter, with the top slightly above ground level and bonded into the leaf / mulch layer:

Yellowjacket wasp nest – top overview

It had two active layers below the top (positioned upside-down here):

Yellowjacket wasp nest – side view

The bottom view gives a better idea of its extent:

Yellowjacket wasp nest – bottom overview

I know nothing of wasp nest building, but if they’re similar to honeybees, then the much larger cells in the disk were intended to raise overwintering queens to start new nests next spring:

Yellowjacket wasp nest – new cell structure

The longer capped cells sticking out beyond the others may raise the few drones required to mate with queens from other nests:

Yellowjacket wasp nest – capped cells

That’s a fly over on the left; the scavengers wasted no time getting in there for the (perhaps still poisonous) goodies.

My wasp identification skillz are weak, but this looks like an American Yellowjacket:

Yellowjacket wasp nest – wasp dorsal view

The definitive test requires going face-to-face with a wasp to find the three dots on a German Yellowjacket.

However, all yellowjackets wear yellow-and-black livery and that’s enough ID for me!

2026-09-04
Jumping Spider

If Jumping Spiders like this one were much larger than 5 mm, they’d be terrifying:

Jumping Spider

It appeared atop a trash can and, as with all Jumping Spiders, it’s here or there without being anywhere in between.

I eased the trash bag inside, gently lowered the lid, bade it happy hunting, and we parted on good terms.

2026-08-27
E-Bike Brake Sensor Bench Check

A pair of brake sensors with LED indicators arrived and should improve the situation on Mary’s bike.

The connector pinout, as seen looking into the jack on the controller side of the cable:

Bafang Brake Sensor pinout

Of course, one cannot depend on color codes, but now we know it uses a 5 V supply. Some rummaging produced a suitable (“Julet”) connector, a cutoff USB cable, and a USB power supply:

Tour Easy LED brake sensor – bench test harness

You’ll note the sensor’s signal wire is blue, not white, but red = 5 VDC and black = common on both sides of the splice. This is not to be sniffed at.

With the disk magnet (supplied with the sensors) oriented edgewise to the sensor, so the magnetic field is largely cancelled, the maximum separation allowing the sensor to remain On is about 7 mm:

Tour Easy LED brake sensor – edge – max ON

The minimum distance allowing it to be Off is 8 mm:

Tour Easy LED brake sensor – edge – min OFF

Orienting the disk face-on to the sensor increases the distances, because the magnetic field is not cancelled out in that direction. Similarly, positioning the magnet either above or below the plane of the sensor changes the results.

The maximum On distance is now 20 mm:

Tour Easy LED brake sensor – side – max ON

The minimum Off distance is 22 mm:

Tour Easy LED brake sensor – side – min OFF

The other magnet has a similar field strength and the other sensor responds at nearly the same distances, so they’re reasonably matched.

The LEDs are, however, not well matched: one sensor is much brighter than the other. I only have one connector, so I cannot show both in the same picture. These pictures have the same exposure (1/120 s and f/1.7), with the top sensor appearing in the previous pictures:

E-bike Brake Sensors – LED Brightness comparison

The red LEDs show a similar difference. I’m certain this doesn’t rise to the level of a warranty claim, because, hey, maybe the brighter one should be dimmer.

Now, to fit them on Mary’s bike …

2026-08-14
Water Heater Anode Rod Replacement
The Bradford White AeroTherm heat pump water heater that Came With The House™ has been running for three years. Based on previous experience with the same City of Poughkeepsie water, it was time for a look at the anode rod.

Which, as always, required the Greatest Ratchet with a foot of extensions getting the 1-1/16 inch socket down to the rod:

Water Heater Powered Anode – socket wrench

Remember to:
- Turn off the water heater power
- Shut off the inlet and outlet valves
- Open the drain valve to relieve the tank pressure
- Only then loosen the anode rod
Seeing the first few inches justified extracting the rod:

Water Heater Powered Anode – old rod top

Due to low overhead clearance and inauspicious pipe locations, I had to hacksaw the bottom third off to extract the rod:

Water Heater Powered Anode – old rod overview

Water Heater Powered Anode – old rod bottom

With the rod out, draining a few gallons of water into a pan didn’t produce any notable gravel, so I didn’t do a complete flush. Much to my delight, the drain has a ball valve!

Given that this is a fancy water heater and I no longer regard anode rod maintenance as a fun-filled activity, I installed a Corro-Protec powered anode rod for cathodic protection without all the crud:

Water Heater Powered Anode – Corro-Protec parts

The wall wart proclaims 15 mA with a green LED indicating it’s hard at work:

Water Heater Powered Anode – Corro-Protec wall wart

The data plate on the back reports 24VDC 15mA, but, being me, I poked at it with a handful of resistors:

Corro-Protec power supply measurements

The electronics could be as simple as a 24 VDC wall wart feeding a 425 Ω series resistor and a transistor switch lighting the LED for currents a little over 6 mA.

A quick ohmmeter check shows the powered rod electrode is open-circuit with respect to the tank, as it should be without much applied voltage. Applying +24 VDC from the wall wart drives 15 mA into the water: the rod is hard at work.

I’ll take a look at it in a year or so just to see what’s going on in there …
2026-08-05
Bee Tunnel Nests: Emergence

On rare occasions I see a small bee or wasp investigating the bamboo tunnel nests at the windows:

Bee Tunnel Nest – wasp investigating

Several of the tubes filled & sealed in early June have served their purpose:

Bee Tunnel Nest – Small A

Bamboo tubes have a paper-thin liner around the edge, but the mud-sealed tubes have obvious small holes chewed through the end caps:

Bee Tunnel Nest – Small B

My assumption that various insects would pick their favorite tube from the assortment seems to be working:

Bee Tunnel Nest – Small C

The medium and large tubes haven’t seen much traffic:

Bee Tunnel Nest – Medium

We’re glad to help!

2026-07-03
New Wildlife
An inch-long Praying Mantis stood guard on a carton delivered to the front door:

Praying Mantis – early instar

We hope to see many more of its kind.

Two views of a one-turn snail found on a lettuce leaf from the garden:
One-turn Snail – right side
One-turn Snail – left side
Mary has developed a Zero-Tolerance Policy for snails & slugs, so this one must start over again from the bottom of the food chain.

With sparrows excluded, the House Wrens eventually began setting up their second nest of the season, with the male proclaiming both he and his lady’s chosen nest are the best in the land:
House Wren – second nesting – 2026-06-30
House Wren – second nest – 2026-06-30
Wrens are on our Most Favored Critter list!

Previous encounters with their ancestors and relatives:
- Mantis
- Snails
- Wrens
2026-07-01