The Smell of Molten Projects in the Morning

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

Raspberry Pi: WLAN to Wired Network
The CNC-3018XL and MPCNC machines each have a Raspberry Pi feeding G-Code into an Arduino clone controlling the stepper motors. The former grew a USB WiFi interface in place of its internal WiFi hardware when it seemed to have difficulty connecting to the house router, while the latter pretty much worked. Of late, however, I’ve been trying to reduce the number of WiFi devices cluttering the airwaves, with the result of wiring both machines to an old Ethernet switch from the Box o’ Network Stuff:

LinkSys Switch for CNC machines

The blue puck is the KVM button to select one of the machines for the keyboard / mouse / monitor on the bench.

One key point I generally screw up: the WiFi IP address cannot become the wired IP address without rebooting everything else on the network. Instead, just change the IP addresses and be done with it.

Collecting all the pieces in one place:

Disable the both internal WiFi hardware and Bluetooth in /boot/config.txt, thereby eliminating the need to force the WiFi down in /etc/rc.local:
```
dtoverlay=pi3-disable-wifi
dtoverlay=pi3-disable-bt
```
Define the static IP address in /etc/dhcpcd.conf:
```
interface eth0
static ip_address=192.168.1.34/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.2
```
Kill IPV6 activity in /etc/sysctl.conf:
```
net.ipv6.conf.all.disable_ipv6=1
```
I very much doubt this information is either complete or correct, but it serves the purpose as of early 2022.
2022-02-08
Floor Lamp Shortening

A new floor lamp similar to the one I adjusted to suit my chair appeared next to Mary’s chair. It was, as I expected, much too tall, but shortening it required just removing one of the vertical tube sections (exactly one foot long!), as Mary was content with the flexy arm’s reach. Perhaps as a nod to the current chip shortage, this version of the lamp has a control consisting of a mechanical knob in a lump just under the flexy arm: push to turn on, rotate for intensity, tap for color, push-and-hold for off. This is much more usable than the finicky proximity pads on my lamp (and the slightly more expensive version of this one), which is why I picked it.

Because the coaxial power connector doesn’t fit through the bushing in the base of the vertical tubes and didn’t have a connector at the control lump, I had to dismantle the lump to disconnect the power cable to remove the pipe section, an operation deep in warranty violation territory.

So, we begin.

Loosen the screw clamping the power cord to the tube just below the control lump:

LED Floor Lamp – DC wire clamp

Remove the two screws holding the control lump together:

LED Floor Lamp – control case

Pull the front of the lump off the tube and peel off a protective foam sheet to expose the circuitry:

LED Floor Lamp – PCB silkscreen

Power comes from a 12 VDC 400 mA wall wart, so note the wire markings:

LED Floor Lamp – DC wire marking

In this case, the marked wire (with the dashed lines) is the positive conductor:

LED Floor Lamp – DC polarity PCB marking

Unsolder the cable and pull it out of the entire collection of tubing. The topmost section has two inner threads, so remove one of the other sections (with inner and outer threads) and reassemble the rest. Poke the cable through the tubes, solder to PCB, tighten clamp screw, reassemble lump in reverse order, then declare victory:

LED Floor Lamp – shortened

The business end now hovers 39 inches (a neat 1 m) over the floor, just below her eye level, where it belongs.

2022-02-07
Ottlite Conversion: Mini-Lathe LED Lighting

An ancient Ottlite fluorescent floor lamp (one of a pair bought during a closeout sale at a minute fraction of their absurd sticker price) finally aged out. Pondering what to do with the carcass led to this discovery:

Ottlite conversion – LED panel fit check

Half of a Samsung (!) LED panel (presumably sheared by the surplus supplier) fit so perfectly in place of the fluorescent tube that I just had to make it happen.

The original fluorescent ballast mounted in the smaller compartment:

Ottlite conversion – OEM fluorescent driver

I like the air-cooled triac sticking off the side of the PCB.

The lamp originally mounted parallel to the flex arm, but I wanted it at a right angle, so the molded bracket had to go:

Ottlite conversion – bracket milling setup

Which required a few minutes of manual jogging:

Ottlite conversion – bracket milled

Some coordinate drilling on the Sherline converted a rectangle of aluminum sheet into a backing plate inside the base (visible through the original holes) to spread the stress over a larger area:

Ottlite conversion – flex arm mount

The new 24 V 1 A power supply mounts pretty much where the OEM ballast came from, although I had to hack out the molded screw bosses and perch the PCB atop four aluminum standoffs anchored in globs of high-temperature hot-melt glue:

Ottlite conversion – power supply

You might think the white and black wires on the right are interchanged, because you’re not supposed to switch the neutral, but only if you also insist anybody cares about the colors of wires inside a molded cord. This one came from a nominally good-quality cord with an IEC connector now in the e-waste box: trust yet always always verify.

The LED panel sticks to the aluminum sheet with thermal tape and is clamped in place with a quartet of M2.5 standoffs:

Ottlite conversion – bottom view

I’ll eventually make a better cover than a strip of overhead projector film (remember overhead projectors?), as spattering the LEDs with cutting oil and random conductive swarf is Bad Practice™.

A little more cutting and drilling produced an angle bracket for the lathe backsplash panel:

Ottlite conversion – installed

Thing looks like it grew there, doesn’t it?

The end of the backsplash might need a 3D printed bracket to stabilize its right-angle bends and prevent wobbulation, although I’ll wait until that becomes a real problem before solving it.

The top of that stylin’ lamp shade tapers along its length and, unfortunately, appears directly in front of the MPCNC bench across the basement (out of sight at the top) as I stand at the lathe. Having the shade not align exactly parallel to the bench is more annoying than it really should be; perhaps I can get used to it after spending more time at the lathe.

I loves me some good LED lighting …

2022-02-04
Stylus Cover: Tiny Threading Tool

For unknown reasons, Mary’s Pixel 3a phone sometimes does not react to her fingertip, so she now has a stylus for such occasions. The cap covers the delicate fine-tip end (with the weird clear disk), leaving the rounded mesh end exposed to dock the cap.

I made a pair of covers for the mesh end, mostly because the styli came in a two-pack and I carry mine in a pocket pouch that will likely abrade the mesh:

Stylus Covers

They’re made from 3/8 inch = 9.52 mm acetal / Delrin rod, turned down to match the 9.4 mm stylus OD. The thread resembles a standard M8×1.25 with very rounded crests:

Stylus Covers – thread

While it’s possible to tap such a thinwalled cylinder with some exterior reinforcement, the (standard / normal / regulation / crispy) thread form of the hitherto entirely unused M8×1.25 tap cowering in the back of the drawer seemed a poor fit and, not being a bottoming tap, it wouldn’t cut full threads where they’re needed.

Besides, what’s the fun in that?

Lacking a threading tool small enough to fit inside the 7.4 mm bore, I gnawed one from a snippet of spring steel wire harvested from a dead box spring. The first pass was much too wide, but gave me the opportunity to make a few mistakes while shaping the tip:

Tiny Threading Tool – first pass

The discoloration on the shank betrays the torching required to knock the hardness down to something file-able. A little more Dremel cutoff wheel / grinder / file action produced a tiny tooth matching the rounded thread form on the stylus:

Tiny Threading Tool – second pass

A side / bottom view shows the crude grinding and excessive angles:

Tiny Threading Tool – side view

A real machinist would harden and temper it, but I didn’t bother for a tool cutting two non-critical threads in plastic.

Somewhat to my surprise, the mini-lathe can cut a 1.25 mm thread without any fancy metric change gears: a simple 35-40-45-50 train did the trick. Running dead slow gave me enough time to poke the power button and let it coast down as it approached the carriage stop marking the end of the thread: cutting plastic is much less exciting than, say, Real Steel.

When all the cutting was done, I beveled the cap for my stylus to fit better into the bottom of the pouch, but that’s definitely in the nature of fine tuning:

Stylus Cover – bevels

The second one went much faster and I should have made a third while I was hot.

A doodle giving the key dimensions:

Stylus Cover – dimensions

Another day of Quality Shop Time™!

2022-02-02
MicroMark Bandsaw Cover Screw Knobs

These descend directly from the LMS Mini-Lathe cover knobs:

Micro-Mark bandsaw cover screw knob

The top pair of screw heads aren’t quite flush with the cover, so the knobs have 1 mm extensions:

Micromark Bandsaw – cover screw knobs – upper

The bottom pair sit inside 4 mm recesses, so those knobs get matching extensions:

Micromark Bandsaw – cover screw knobs – lower

Attacking an anonymous 5 mm hex wrench with a Dremel cutoff wheel produced a quartet of 12 mm shafts and reduced drawer clutter by one unit.

In retrospect, I should have dismantled the cover, grabbed the screws in a vise with their shafts vertical, and epoxied all the knobs with perfect alignment. Next time, maybe.

2022-01-31
Tektronix AM503: Adjustment

Having put the Tek AM503 with the 4 MHz oscillation (B075593) on the shelf pending arrival of what might be the world’s last remaining NOS 2625 op amp in the “screened and tested” 156-0317-03 grade, I figured I might as well go through the adjustment procedure on one of the bench units (B064098) to reset the gain and reduce the peaky leading edges (green trace):

Tek AM503 – B031510 B064098 – 10mA-div

I conjured a low-budget Special Adapter to feed signals into the front-panel connector:

Tektronix AM503 Special Adapter

I also used a somewhat smaller resistor in place of the required 3 Ω 3 W wire-wound unit:

Tek AM503 – 3 ohm test resistor

It need only soak up a few seconds of the degaussing signal and never even got warm, so it’s all good.

To my surprise, the square-wave output of the JDS6600 Function Generator meets the 10 ns risetime requirement:

JDS6600 Fn Gen – risetime 50 ohm

Perhaps half an hour of adapter shuffling and trimmer twiddling later, the AM503 output looked better:

Tek AM503 – compensation adj

The (purple) input comes from the function generator output through a BNC tee and an unterminated foot of coax, so the leading edge ringing is perfectly normal.

With the scope input now providing the 50 Ω termination and the Hall probe clamped around one wire of a clip-to-clip pair of BNC-to-alligator-clip adapters, we’re still not talking RF-grade interconnection quality:

Tek AM503 – 1 MHz square

Even through it’s not factory spec, the output tracks the input well enough for my simple needs.

Good old Tek instruments: gotta love ’em!

2022-01-28
Headband LED Light: Cell Isolation

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.

2022-01-24