Archive for category Oddities
Monthly Image: Organ Pipe Mud Dauber Wasp Nest
The side of our house seems to attract Organ Pipe Mud Dauber Wasps during nesting season.
One pair of wasps built this impressive structure behind the patio door, beside the bathroom window:
Organ Pipe Mud Dauber Wasp Nest – side view
The female wasp built six tubes over the course of an August week, carrying blobs of mud the size of her head and abdomen from sources about 30 seconds away (1 minute round trip). Each blob produces half of one serration around the tube, with a seam running down the middle, and requires 20 seconds to smooth into place. We got tired just watching her!
Each tube has many compartments, each containing a wasp larva and a paralyzed spider, with a mud cap inside the end:
Organ Pipe Mud Dauber Wasp Nest – bottom view B
We watched the wasps attack, sting, and remove spiders of a specific size from the corners of our window frames.
The young wasps in the innermost tube may not make it out alive, because they must chew through at least one outer tube before flying away:
Organ Pipe Mud Dauber Wasp Nest – bottom view A
Perhaps layering the outer tubes around a central tube makes for a more compact and durable nest, with the possible sacrifice of offspring in the center.
The new wasps will likely emerge next spring.
Excavator Family
Posted by Ed in Oddities, Recumbent Bicycling on 2018-09-09
We’re accustomed to seeing geese with goslings and turkeys with chicks around this time of year, but we didn’t realize excavators have a similar breeding season (clicky for more dots):
Excavator Family – Vassar College
The adult seems very protective …
Spotted on the Vassar College campus, in front of the dining hall.
Frayed Power Drop
Posted by Ed in Electronics Workbench, Home Ec, Oddities on 2018-09-06
The neutral conductor is down to its last three strands:
Damaged neutral – over Redondo near pole 62859
Perhaps the power drop got snagged twice, because there’s a splice only a few feet away:
Damaged neutral and splice – over Redondo near pole 62859
Spotted overhead on Redondo near Rt 376 during an evening walk. I reported it using Central Hudson’s dead streetlight page, because there seems no other way to get their attention. It may be the homeowner’s responsibility, in which case a second splice will surely appear after the next power outage.
Dutchess Rail Trail: Maloney Rd Trailhead vs. SUV
Posted by Ed in Oddities, Recumbent Bicycling on 2018-09-05
The driver gave us plenty of room, which is always nice:
Tire tracks at Maloney Trailhead – DCWWA SUV on Maloney 2018-08-20
But then the SUV turned into the Maloney Rd entrance to the Dutchess Rail Trail:
Tire tracks at Maloney Trailhead – DCWWA SUV entering – 2018-08-20
Which was specifically designed to exclude motor vehicles:
Tire tracks at Maloney Trailhead – DCWWA SUV tracks – 2018-08-20
Later, I was told it’s an “allowable access” for Water Authority vehicles and, in any event, because their SUV didn’t leave the biggest ruts and tracks, they think it’s all good:
Tire tracks at Maloney Trailhead – 2018-08-20
The ramp joins the trail at an acute angle, so the SUV required some backing & filling to get around:
Tire tracks at Maloney Trailhead – Tight Turn onto DCRT – 2018-08-20
Then it’s an easy drive to the water meter about 2500 feet down the trail:
Tire tracks at Maloney Trailhead – Dutchess Water Authority SUV – 2018-08-20
There’s an Official Vehicle Access gate one mile south of the Maloney ramp that’s about 3800 feet from the water meter. I’m told they use the Maloney ramp to reduce the distance they drive on the rail trail; evidently, destroying the entrance Just Doesn’t Matter.
I’m trying to develop an attitude between Zen and apathy, with just enough indifference to not care when somebody tells me how wonderful things will be in the future.
Headless Garden Bunny
A small rabbit, occasionally seen about the back yard and within the garden, met an untimely end:
Dismantled Garden Bunny
We credit one of the neighborhood hawks or owls.
Over the course of the next few days, the corpse lost more of its stuffings and eventually vanished.
Perhaps a similar event produced the bunnyless head we saw a while ago.
Go, birds, go!
Monthly Science: Monarch Caterpillars!
After several years of seeing few-to-no Monarch butterflies, last year we managed to save a single Monarch egg, raise the caterpillar, and release it:
Monarch on Milkweed – left
This year, we’ve seen more, if not many, Monarchs in flight. They’re not abundant, but perhaps there’s hope.
A Monarch evidently laid eggs in our milkweed patch, with at least two offspring surviving:
We decided to let them seek their own destiny; may the odds be ever in their favor …
Raspberry Pi: Nominal vs. Actual I2C Speeds
Posted by Ed in Electronics Workbench, Oddities, Software on 2018-08-29
Two lines in /boot/config.txt enable the I2C hardware and set the I2C bus speed:
dtparam=i2c_arm=on dtparam=i2c_arm_baudrate=200000
However, the actual SCL frequency comes from dividing the CPU’s core clock by an even integer, so you can’t always get what you want. The Pi 3 ticks along at 1.2 GHz (actually 1.1 GHz, because marketing) from a core clock of 550 MHz, so a 200 kHz clock calls for a 2750 divider: 550 MHz / 2750 = 200 kHz.
Actually measuring the SCL frequencies suggests something else is going on:
I2C 200kHz – actual 125kHz
D0, the bottom trace, is SCL, D1 is SDA, and D2 is a trigger output not used in this setup. The yellow analog trace is the current in the SCL line between the Pi and the BNO055, about which more later.
So a 200 kHz nominal frequency produces a 125 kHz actual frequency.
The BNO055 pulls the clock low (“clock stretching”), which can (and does) cause problems, but it’s not active during the main part of the transfer where the Pi determines the SCL frequency.
More measurement along those lines produces a table:
| CPU Core Clock: | 550 | MHz | |
| I2C SCL kHz | |||
| Nominal | Ratio | Actual | Ratio |
| 250 | 2200 | 156.20 | 3521 |
| 200 | 2750 | 125.00 | 4400 |
| 150 | 3667 | 92.59 | 5940 |
| 125 | 4400 | 78.12 | 7040 |
| 100 | 5500 | 62.50 | 8800 |
| 50 | 11000 | 31.25 | 17600 |
| 25 | 22000 | 15.63 | 35189 |
| 10 | 55000 | 6.25 | 88000 |
Apparently, the code converting the nominal I2C rate in config.txt uses a table of divider values intended for another CPU core clock. AFAICT, the boot code could divide the actual core clock by the desired I2C frequency to produce the appropriate value.
I have no particular desire to Use The Source to figure out what’s going on …
[Update: Perhaps this comes along with CPU clock throttling due to temperature. For completeness, I should dump the temperature and actual clock speed.]
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