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
In preparation for the next time a task puts my head in a dark place, I got a cheap headband LED light:
Headband LED – overview
Unlike most of the others you’ll find, this one has a pair of 18650 lithium cells in the box on the back of the headband:
Headband LED – isolated cell
Contrary to what you might think, the cells are in parallel, with shorting plates connecting the battery compartment terminals. This works well for perfectly matched cells, which is not what arrives in the package.
The 3200 mA·hr capacity claimed (in one line of the product description) doesn’t match the 2200 mA·hr capacity (claimed in another line and) printed on the cells. As expected, both claims far exceed the actual 1500 mA·hr measured capacity.
LED Headband Light – 2022-01-12
The 1 A load is somewhat more than the 800 mA I measured at full brightness, but makes for easy comparisons.
I think they put the cells in parallel to reach the claimed 4-6 hours of run time, but in practice the connection discharges the better cell to match the weaker one with no assurance of equal load sharing thereafter.
So I conjured an insulator from the Box o’ Retail Clamshells:
Headband LED – cell isolator
In the unlikely event my head must remain stuck in a dark spot for longer than one cell lasts, I can move the insulator to the dead cell and continue the mission. Charging alternate cells isn’t much of a burden, either.
For unknown reasons, the (anonymous) manufacturer soldered the LED package at a jaunty angle inside the frame:
Headband LED – SMD alignment
The lens pulls in-and-out to zoom the focus. The tightest setting (all the way out) projects a bright tilted square out in front, which is somewhat unsettling.
The whole affair cost less than a pair of known-good 18650 cells from a reputable supplier, so ya get what ya get.
The top step of a folding step stool we’ve been (ab)using forever finally wore out, mostly because it was covered in vinyl and intended as a seat. We always used it as a step, despite knowing you should never stand on the top rung of a ladder: “Do not stand on or above this level”.
I tossed the ripped vinyl and warped particle board, cut a random chunk of wood-textured paneling (which Came With The House™) to fit, match-drilled four holes, and it looks OK:
Folding step stool – reseated
The original seat / step / whatever used press-fit studs with a flat flange covered by the vinyl, but I just slammed 10-32 tee nuts into the paneling:
Folding step stool – tee nut installed
That’s a ring of low-strength threadlock around the inside of the nut; I do not expect the screws to come out ever again.
I cut the screws to length with a Dremel cutoff wheel using a slightly shortened tee nut as a fixture:
Folding step stool – screw shortening fixture
Not visible: the vacuum hose clamped to the vise sucking up all the abrasive + metal dust.
Good for an hour of Quality Shop Time™ on a cold winter morning!
The Tektronix AM503 manual specifies a Special Adapter to inject a signal directly into the input connector in place of the A6302 Hall probe:
Tektronix AM503 Special Adapter
The intricate Amphenol plug might still be available at some phenomenal cost, but I’m willing to just jam a pair of wires into the AM593 connector and be done with it.
I combined a pigtail BNC sporting a male connector, two 51 Ω resistors in parallel, two snippets of 18 AWG wire (an exact match for the 40 mil connector pins!) with the ends filed smooth, and some heatshrink tubing to make a roughly equivalent adapter:
Tek AM503 – Crude Special Adapter
Because the pigtail didn’t quite reach the function generator, I joined it to a longer cable with a BNC bullet, whereupon a slight tug ripped the guts out of the bullet:
BNC Bullet – failed
A closer look:
BNC Bullet – parts
The center hole comes into play with their equally craptastic BNC tee connectors.
Comparing this bullet with others from the same eBay lot shows the outer shell didn’t get quite enough crimp around the metal ring. Because it’s not an electrical connection, I eased some epoxy onto the internal shoulder where that ring seats, then slid the guts back in place.
For the first time in a loooong time I (had to) set up remote desktop sharing, starting from an existing SSH login through a single-port pinhole in an immutable router firewall.
The remote PC runs Xubuntu 20.4 LTS and I verified it already had x11vnc installed. If that’s not the case, make it so.
In order to share / control the desktop of a different user (hereinafter known as kay), I must SSH into that PC as kay. My SSH session uses public key authentication and kay has no need for outbound SSH, so just use my PC’s public key in kay‘s authorized_keys file. On the remote PC, where I am signed in as me:
cd ~
sudo mkdir /home/kay/.ssh # kay does not have a public key
sudo cp .ssh/authorized_keys /home/kay/.ssh # so just copy mine
sudo chown -R kay:kay /home/kay/.ssh # transfer ownership
sudo chmod go-rwx /home/kay/.ssh # set proper permissions
Why You Shouldn’t Use Heat Pumps in the Northeast US
465
Baofeng UV-5R Squelch Settings
460
Mini-Lathe Tailstock: Alignment
449
Homebrew Magnetizer-Demagnetizer
446
Arduino Serial Optical Isolator
444
Mysterious Noise in Toyota Sienna Minivan: Fixed!
444
Baofeng UV-5: Squelch Pop Suppression
434
bCNC Probe Camera Calibration
432
Demolition Card GTA 5-10-9
431
Multimeter Range Switch Contacts: Whoops!
425
Realigning Tweezer Tips
421
Schwalbe Marathon Plus and Michelin Protek vs. Glass Chip
418
Kenmore Model 158 Speed Control: Carbon Disk Replacement
417
Kenmore Electric Dryer: Power Resistor Replacement
416
Old Kenmore Sewing Machine Foot Control Repair
414
Closing the Dmesg Audit Firehose
400
Blog Page Views
That adds up to 200 k page views from 122 k visitors, for an average of 1.6 pages / visitor, down slightly from last year. For a variety of reasons, I wrote only 242 posts over the course of the year, so more folks read only the single post matching their search terms.
To give you an idea of how awful online advertising has become, WordPress shoveled 817 k ads at those readers, slightly more than four ads per view. Given the toxicity of online advertising, I just started paying $50/year for a “personal” plan to get a few more gigabytes of media storage, which also let me turn off the ads. Most of you won’t notice, as you already run ad blockers, but it will calm the results for everybody else.
Fortunately, losing the $250 / year income from those ads won’t significantly affect my standard of living.
The sweep speeds run much slower to capture the complete envelope, which can be up to a minute long, with enough left over to show the end of the previous sequence and the start of the next. The Moire patterns come from the scope sampling rate, the display resolution, or changes in the pulse repetition frequency. Blame Siglent for not making the scope’s digital data accessible through the network; screen shots are the best I can do.
The descriptive headings for each screen shot come from The Auvon AS8016 Fine Manual, a PDF version of which you can get from Auvon’s support staff by asking nicely. I identify the modes as Mxx, rather than their Pxx, for reasons that made sense at the time.
P19 – Beating from low frequency to a little high frequency.
Auvon M19 Mod
P20 – Muscle twitches at a very low frequency. It feels like a tapping massage.
Continuous 250 µs pulse at 13.5 Hz.
Auvon M20 Pulse
P21 – This program activates the muscle in a short tingling cycle. It is smoother than P1/P2.
Auvon M21 Mod
P22 – This program gently warms up the muscles prior to exercise; it feels like a rhythmic massage. Increase intensity until you get a strong but comfortable muscle movement.
Auvon M22 Mod
P23 – This program uses a pulse frequency appropriate to fast twitching muscle fibers. It improves their anaerobic capacity and is used for improving maximum muscle strength.
Auvon M23 Mod
P24 – This program gently warms up the muscles prior to exercise; it feels like a rhythmic beating and comfortable tingling. Increase intensity until you get a strong but comfortable muscle movement.
Auvon M24 Mod
Despite the icons on the unit’s display, the manual suggests you can apply pretty nearly any pattern to any muscle, but now we all know what’s coming out of those jacks …
The Smell of Molten Projects in the Morning 