Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
Some surreptitious brush clearing called for a tool larger than our wonderful Fiskars PowerGear pruner, so I unearthed a long-disused bypass lopper in the garage (it may have Come With The House). Alas, the pivot bolt lost its jam nut long ago:
Bypass loppers – OEM 10 mm bolt
That’s an M10x1.5 bolt, for which I lack a corresponding nut.
But 3/8-16 is approximately M10x1.5, for small values of thread engagement, and I do have an assortment of inch-sized stainless steel fasteners:
Bypass loppers – 0.375 inch bolt
The nylon lock nut jams the bolt against the left blade, with the split washer applying pressure to the tapered blade. Slobbering oil in the sliding joints restored it to perfect working order.
The weird round dingus on the far side of the pivot, up against the handles, is a bumper cushioning the fully closed position. It’s a nice touch and might work better if its rubber pad hadn’t aged out over the decades spent in the garage waiting for this very day.
It’s my kind of yard work: “What do you need killed next?”
That’s with the card jammed into an Anker USB 3.0 adapter and both devices plugged into the two USB 3.0 “Super Speed” ports in the front of my desktop box. Plugging them both into the adjacent USB 2.0 ports drops the data rate to 18 MB/s.
The Sandisk card claims read-write speeds of “up to” 20 MB/s, so it’s the limiting factor.
Getting reliable performance numbers is surprisingly difficult:
dd bs=4M count=1000 status=progress if=/dev/urandom of=/mnt/part/random.bin
4177526784 bytes (4.2 GB, 3.9 GiB) copied, 214.064 s, 19.5 MB/s
1000+0 records in
1000+0 records out
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 214.922 s, 19.5 MB/s
dd bs=4M count=1000 status=progress if=/dev/urandom of=/mnt/part/random2.bin
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 217.08 s, 19.3 MB/s
1000+0 records in
1000+0 records out
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 217.08 s, 19.3 MB/s
Obviously, prying bits out of the random number generator limits the overall write speed.
Zeros, however, are cheap and readily available:
dd bs=4M count=1000 status=progress if=/dev/zero of=/mnt/part/null.bin
4169138176 bytes (4.2 GB, 3.9 GiB) copied, 23.0091 s, 181 MB/s
1000+0 records in
1000+0 records out
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 23.1775 s, 181 MB/s
dd bs=4M count=1000 status=progress if=/dev/zero of=/mnt/part/null2.bin
4093640704 bytes (4.1 GB, 3.8 GiB) copied, 25.031 s, 164 MB/s
1000+0 records in
1000+0 records out
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 25.7781 s, 163 MB/s
But the caches take a while to drain, even after the command returns:
time ( dd bs=4M count=1000 status=progress if=/dev/zero of=/mnt/part/null3.bin ; sync )
4118806528 bytes (4.1 GB, 3.8 GiB) copied, 23.0004 s, 179 MB/s
1000+0 records in
1000+0 records out
4194304000 bytes (4.2 GB, 3.9 GiB) copied, 23.5305 s, 178 MB/s
real 0m35.887s
user 0m0.008s
sys 0m4.824s
Dividing 4 GB / 35.9 s says the mechanical write speed is close to 110 MB/s.
Reading proceeds a bit faster, while also running up against the effect of the many caches between the spinning platter and the screen:
time ( cp /mnt/part/random.bin /dev/null )
real 0m36.565s
user 0m0.048s
sys 0m1.712s
time ( cp /mnt/part/random.bin /dev/null )
real 0m29.157s
user 0m0.036s
sys 0m1.800s
time ( cp /mnt/part/random.bin /dev/null )
real 0m10.265s
user 0m0.028s
sys 0m1.040s
time ( cp /mnt/part/random.bin /dev/null )
real 0m0.608s
user 0m0.004s
sys 0m0.600s
time ( cp /mnt/part/random.bin /dev/null )
real 0m0.590s
user 0m0.008s
sys 0m0.580s
time ( cp /mnt/part/random2.bin /dev/null )
real 0m31.035s
user 0m0.056s
sys 0m1.816s
time ( cp /mnt/part/random2.bin /dev/null )
real 0m31.024s
user 0m0.052s
sys 0m1.860s
Unsurprisingly, copying a brace of 4 GB files in parallel takes twice as long as each cold-buffer read, so disk’s raw read speed seems to be around 130 MB/s.
The drive’s write speed won’t be the limiting factor while saving camera video data!
Mary used to mix up her oil-and-vinegar dressing using a measuring cup, then she drew markings on the bottle, then I added tidy labels:
Calibrated Oil-and-Vinegar bottle
The labels align with her process: she adds ½ C oil first, then ¼ C vinegar, then various other ingredients. The liquids swirl around, sort themselves out, and it’s all good.
Surprisingly, the labels survived uncounted dishwasher adventures.
When I rewired the guts of the digital tattoo power supply to eliminate the series foot switch, I kept the original wiring polarity, with the black wire to the sleeve and the red wire to the tip:
Tattoo Digital Power Supply – internal view
It’s the same color code I (strongly) recommend in the Squidwrench Electronics Workshops: use any color for the ground / common wire as long as it’s black, then, if you have a red wire, use it for the positive supply. You can use yellow for the higher supply voltage, but stop being clever.
I put suitably colored Powerpoles on the far end of the cable to replace the standard tattoo machine spring clip connector, so I can attach clip leads, battery test fixtures, and so forth and so on.
We wired the supply into a clip-leaded diode measurement setup with a current limiting resistor and a pair of multimeters to measure the diode current and forward voltage, whereupon we noticed all the meters displayed negative voltages and currents.
After a frenzy of wire-checking verified their setup was all good, I forced the simplest possible test, herein recreated on my bench:
Tattoo Digital Power Supply – polarity test
Which produced this display:
Tattoo Digital Supply – reverse polarity
Huh.
After a brief exploration of “Trust, but verify” territory, we swapped the clip leads from the power supply and continued the mission.
Back on my bench, I pulled the supply apart and measured the voltage at the jack terminals:
Tattoo Digital Power Supply – jack wiring
Still negative. Huh.
The bottom of the power supply PCB shows exactly what you should expect by now:
Tattoo Digital Power Supply – reversed color code
The red wire near the top of the board is, indeed, soldered to the trace labeled GND and goes to the jack’s tip terminal; the adjacent black wire goes to the front-panel LED. Similarly, the black wire just below it, soldered to the same trace as the yellow wire, goes to the jack’s sleeve terminal; that trace also connects to a resistor leading to the trace labeled LED+ and the LED’s red wire.
Although tattoo machines run from DC supplies, their motors or vibrators don’t depend on any particular polarity and will run fine with a backwards supply.
Resoldering the red and black wires where they should go produces the expected sign at the jack:
Tattoo Digital Supply – meter leads
Although measuring and plotting diode voltages and currents may seem tedious, actually wiring stuff together and taking data reveals how difficult the real world can be.
I trusted the supply’s internal color code and, although I’m certain I tested the Powerpoles, I obviously didn’t notice the meter’s sign.
We have several high-intensity / long-attention-span home projects scheduled this summer, all of which will keep me away from the Basement Laboratory.
We’re OK, all is right with our world, but painting rooms and yard maintenance always take way more time than they should, while having close to zero intellectual content.
Like, for example, the result of a strenuous morning devoted to removing a severely overgrown holly bush:
Mother of All Holly Bush Stumps
I’ll post odd & ends a few times a week until maybe mid-August, whereupon I should get back to more usual pursuits.
Despite what look like “squeeze here” markings, you must push the license plate bulb holders toward the center of the car:
Subaru Forester 2015 – license plate bulb holders
They were both stuck firmly to the trim plate, so I braced a screwdriver against the outboard edge of the trim panel, after which it becomes obvious how pressing inward compresses the (plastic) spring clip so you can pull the outward side of the holder away from the hatch.
The bulbs with conical ends, known as “festoon” lamps, (unsurprisingly) come in several lengths. The Forester bulbs are about 25 mm long, (unsurprisingly) much shorter than the 31 mm LEDs that seem to be the smallest available replacements, but (surprisingly) the socket tabs have barely enough compliance for the extra half dozen millimeters:
Subaru Forester 2015 – dome with 31 mm festoon LED bulb
The LEDs are much much much brighter than the incandescents, although I’d prefer warm white to cool white. The cargo compartment lamp in the back is still way too dim; I don’t understand how Subaru decided on a plastic cover tinted dark smoke gray.
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.
The Smell of Molten Projects in the Morning 