Archive for category Oddities
Although the pair of Ortlieb Back-Roller packs on Mary’s bike make her look like a long-distance tourist, we’re actually on our way to her garden plot:
The left-side pack suddenly seemed unusually floppy:
One second later:
Another second and it’s visible under my right hand:
The view from her bike at about the same time:
I’m expecting to fall to my right, but it’d have been better if I hadn’t kicked the bag:
The pack went under the rear wheel and out the far side:
Where it came to rest in the middle of the trail:
Elapsed time from the first picture: just under 5 s.
Did you notice the other cyclist in the other pictures? She’s why I veered so hard to my right!
A pair of these latches hold the pack onto the rear rack:
When they’re properly engaged, they look like this:
When they’re not, they look like this:
Which is obvious in the picture and inconspicuous in real life.
The strap emerging from the top of the latch serves as both a carrying handle and latch release: pull upward to open the latches and release them from the bar, lift to remove the pack, and carry it away as you go. Installing the pack proceeds in reverse: lower the pack onto the rack bar, release the handle, and the latches engage.
Unless the pack is empty enough to not quite fully open the latches as you carry it, in which case the closed latches simply rest on the bar. We’ve both made that mistake and I generally give her packs a quick glance to ensure sure they’re latched. In this case, the plastic drawer atop the racks (carrying seedling pots on their way to the garden) completely concealed the pack latches.
Tree roots have been creasing the asphalt along that section of the rail trail: the bike finally bounced hard enough to lift the drawer and fall off the rack rod.
Memo to Self: In addition to the visual check, lift the packs using the strap across the middle holding the rolled-down top in place. Remember, don’t check by lifting the carrying handle, because it just releases the latches; another easy mistake to make.
OK, it’s not as exciting as a Strava KOM:
We’re at the top of an uphill section and, riding together, we’re not sprinting for town line signs.
The ESP8266 controller in Sophi’s blimp project suffered from random resets, which I was absolutely certain happened when the current for the three DC prop motors glitched the battery supply. So I hauled the Tek current probes + amps + scope to a Squidwrench meeting and, after considerable fiddling, we found a smoking … trace:
The purple trace shows the Li-Ion battery voltage at an inactive motor driver located on the far end of a known-to-be-too-small trace. In principle, there’s little-to-no current drawn through that trace, so it should represent the voltage at the regulator input.
The green trace shows the 3.3 V regulator output at its bulk storage cap.
The ground reference is at the PCB’s battery negative connection pad.
The bold dotted green cursor shows the regulator output hitting 2.57 V, entirely low enough to glitch the ESP. The scope triggers on negative-going edges below 2.6 V and this was the first trigger after starting and running the motors for a few seconds.
Conspicuous by its absence: any hint of a current glitch in the yellow trace from a Tek A6302 probe clamped around the battery positive wire. The current remains constant at the 400 mA (100 mA/div) level drawn by two DC motors, with no sign of any glitches whatsoever; she’s not using PWM speed control. The whole board draws about 80 mA DC and the ESP’s WiFi radio pulls 200 mA pulses, so all’s quiet on those fronts.
Which is why I like to measure actual circuit operation: I vastly prefer to solve actual problems, knowing what does (or doesn’t!) cause them helps, and I’m not at all bothered by being wrong.
The regulator output doesn’t go much above 3.3 V, which is comforting.
However, when the regulator’s input voltage falls below 3.3-ish V, its output voltage tracks right along down with it. Input variations above 3.3-ish V don’t make much difference in the output.
Although it’s a buck-boost converter, its response time isn’t fast enough to cope with something else on the PCB pulling enough current to spike its input voltage (shared with the motor driver) below 3.3 V. The dropout is barely 4 ns long, far shorter than the regulator’s switching period.
I have my doubts as to the accuracy of those voltage waveforms and, in particular, their pulse widths. IIRC, the scope can trigger on a pulse exceeding a specific width, but I’d devote more time arranging the test points and getting RF-quality connections / grounding before going further out on a numeric limb.
This single trigger event may not be the glitch causing the reset. What it does show is the regulator output dropping below the ESP’s absolute-minimum input voltage spec, at least briefly, which is cause for concern.
More testing is definitely in order …
A mutual staredown during a utility bike ride:
This is just after noon, when deer should be snoozing, just north of Paula’s Public House, with the deer on the creek side of the road. I’m towing the trailer with an empty propane tank, coasting down from 18 mph, and expecting the deer to jump in front of me, because it can. It waited patiently until I passed, hopped the guide rail, trotted across the road, then clambered up the steep hillside away from the Might Wappinger Creek.
Searching for deer will reveal many more encounters.
We heard God’s Own Weedwhacker off to the right as we approached Jackson Drive on the way home:
The chopper followed the power lines, just over the treetops, with the downdraft thrashing the leaves:
Long ago, I attended a talk about using choppers for power line inspection and maintenance. Apparently, someone with nerves of ice can replace insulator supports and aeolian dampers on high-tension lines while perched on a chopper hovering very very close to the conductors. Pilots with experience getting troops into and out of hot LZs are in high demand.
I’m sure they give the E911 call center a heads-up before taking off …
Spotted another big turtle ready to cross the Dutchess Rail Trail along Daley Rd:
This must be the best season ever for turtles crossing vast expanses of asphalt, because I don’t recall seeing this many turtles during any previous spring. Confirmation bias in full effect, to be sure.
The picture is a dot-for-dot crop from the Sony HDR-AS30V helmet camera, demonstrating why image compression has more to do with resolution than the number of dots.
The dark spot in the grass, barely visible over on the left, is a dinner-plate-size snapping turtle recently teleported from the middle of Rt 376 just north of Robinson Lane:
The driver of the white van managed to stop both lanes during the rescue and, judging from the lack of gore, handled the snapper without incurring organic damage.
Color me impressed!