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.

Author: Ed

  • Naming Is Hard

    A recent update to the X Windowing System (or whatever it’s called) once again changed the names of its monitors / displays / output devices, so that my startup script no longer confined the tablet to the landscape display.

    In mostly reverse chronological order, here are various commands I’ve puzzled out:

    #xsetwacom --verbose set "HUION Huion Tablet stylus" MapToOutput "DP1-8"
xsetwacom --verbose set "HUION Huion Tablet stylus" MapToOutput "DP-1-8"
#xsetwacom --verbose set "HUION Huion Tablet Pen stylus" MapToOutput "DP-1"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen stylus" MapToOutput "DP-1"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen stylus" MapToOutput "HEAD-0"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen eraser" MapToOutput "DP-1"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen eraser" MapToOutput "HEAD-0"

    Over the last two years, the display name changed from DP-1 to DP-1-8 to DP1-8, and back to DP-1-8. I grew accustomed to this with the Wacom tablet (HEAD-0‽)and now know where to look, but I still have no idea of the motivation.

    Aaaand the tablet’s stylus name? The Wacom names were stable, but the Huion names apparently come from the Department of Redundancy Department.

  • Guten Tag, Deutchland!

    Guten Tag, Deutchland!

    Mostly, this blog ticks along with 400 to 500 page views per day, with 300-ish visitors looking at a page or two each.

    This week, something happened:

    Blog Stats - 2021-08-28
    Blog Stats – 2021-08-28

    Both of those spikes came from Germany:

    Blog Countries - 2021-08-28
    Blog Countries – 2021-08-28

    Traffic spikes generally come from a single post getting fifteen minutes of Reddit fame, with a zillion visitors hitting a specific page.

    In this case, a German “visitor” read nearly all of my 4461 posts on two days: 822 + 3561 = 4383. I’m reasonably sure no human finds my writing that interesting, so it’s likely a scraper capturing my text for the purposes of spinning it into a blog-like site with “unique content” for the purposes of SEO.

    Perhaps the first traffic spike was a targeting run?

    I’ll never know the rest of the story, but if you happen to stumble across a blog with an uncanny resemblance to this one, written by something with a wide vocabulary and no techie knowledge, let me know.

  • Tour Easy: Rear Brake Pads

    Tour Easy: Rear Brake Pads

    A horrible grinding sound from behind me suggested it was time to replace the Tour Easy’s rear brake pads:

    Tour Easy - worn rear pads - side
    Tour Easy – worn rear pads – side

    Yeah, about half of the “Wear Line” text remains visible; the actual line is long gone to dust.

    The retaining pin in the lower pad is twisted forward:

    Tour Easy - worn rear pads - face
    Tour Easy – worn rear pads – face

    The pad wore enough to let it scrape on the rim, which certainly can’t be good for it.

    The new Kool-Stop KS-MTTSA pads tout their leading wedge’s suitability for scraping mud off the rims, which isn’t a problem with my use case:

    Tour Easy - Kool-Stop MTTSA pads - 20873 miles
    Tour Easy – Kool-Stop MTTSA pads – 20873 miles

    The odometer reports 20873 miles since the last battery replacement fumble.

  • Arduino MEGA Debugging LEDs

    Arduino MEGA Debugging LEDs

    Kibitzing on a project involving an Arduino Mega (properly MEGA, but who cares?) with plenty of spare I/O pins led me to slap together a block of LEDs:

    Arduino Mega Debugging LEDs
    Arduino Mega Debugging LEDs

    The excessive lead length on the 330 Ω resistors will eventually anchor scope probes syncing on / timing interesting program events.

    Not that you have any, but they’re antique HP HDSP-4836 tuning indicators: RRYYGGYYRR. If you were being fussy, you might use 270 Ω resistors on the yellow LEDs to brighten them up.

    A simple test program exercises the LEDs:

    /*
  Debugging LED outputs for Mega board
  Ed Nisley - KE4ZNU
  Plug the board into the Digital Header pins 34-52 and GND 
*/

byte LowLED = 34;
byte HighLED = 52;
byte ThisLED = LowLED;

//-----
void setup() {
  pinMode(LED_BUILTIN,OUTPUT);
  
  for (byte p = LowLED; p <= HighLED; p+=2)
    pinMode(p, OUTPUT);

//  Serial.begin(9600);
}

// -----
void loop() {
  digitalWrite(LED_BUILTIN,HIGH);
  
  digitalWrite(ThisLED, HIGH);
  delay(100);
  digitalWrite(ThisLED, LOW);
 // delay(500);

  ThisLED = (ThisLED < HighLED) ? (ThisLED + 2) : LowLED;

//  Serial.println(ThisLED);

  digitalWrite(LED_BUILTIN,LOW);
}

    Nothing fancy, but it ought to come in handy at some point.

  • Sherline CNC Mill: Y-Axis Nut Mishap

    Sherline CNC Mill: Y-Axis Nut Mishap

    The need to gnaw a V groove into the side of two 60 mm aluminum bars led to this Sherline CNC mill setup:

    Sherline Y-Axis Nut Mishap - setup
    Sherline Y-Axis Nut Mishap – setup

    Milling the near end of the bars put the angle plate’s rear lock screw within a millimeter of the column; the vise fits in exactly one spot on the angle plate and that’s where the jaws must be.

    While controlling the mill with the Joggy Thing and some manual command entry, because it’s easier than real CNC programming, I overshot the near end and rammed the column with enough enthusiasm to dislodge the Y-axis leadscrew nut. An interlude of utter confusion ended with the backlash preload nut firmly jammed against the leadscrew coupler on the other end of travel:

    Sherline Y-Axis Nut Mishap - stuck preload nut
    Sherline Y-Axis Nut Mishap – stuck preload nut

    The paper shreds show where the bellows formerly stuck on the Y axis stage.

    The backlash nut chewed off a few star lock gear teeth on its way out, as seen here just above where they mesh:

    Sherline Y-Axis Nut Mishap - chewed star nut
    Sherline Y-Axis Nut Mishap – chewed star nut

    It’s been quite a few years since I took the thing apart to replace the nuts, so I used the opportunity to lube the otherwise inacessible X axis leadscrew inside its table upside down on the bench.

    The setscrew locking the Y axis leadscrew nut in place heaves into view with the X axis table off:

    Sherline Y-Axis Nut Mishap - setscrew
    Sherline Y-Axis Nut Mishap – setscrew

    I thought about jamming it in place with a second 10-32 setscrew, but the ones on hand were just an itsy too long and collided with the X-axis table:

    Sherline Y-Axis Nut Mishap - doubled setscrew
    Sherline Y-Axis Nut Mishap – doubled setscrew

    The thought of having the additional setscrew work loose, grind into the underside of the table, and require major surgery for recovery persuaded me to drop it back in the drawer.

    With everything in place, I adjusted the backlash (on both axes) down to a few mils:

    Sherline Y-Axis Nut Mishap - backlash test
    Sherline Y-Axis Nut Mishap – backlash test

    Tweaking the X axis preload nut under the table is not my idea of a good time, but it’s been quite a while since I had to do that.

    Folding the new paper bellows and installing them took about as long as repairing the mill.

    Milling the second V groove worked fine; all is right with the Sherline again.

  • Soldering Iron Spider

    Soldering Iron Spider

    I noticed something out of place when I fired up the soldering iron:

    Soldering Iron Spider
    Soldering Iron Spider

    It’s not obvious in a flat photo without depth perception, but here’s a closer look:

    Soldering Iron Spider - detail
    Soldering Iron Spider – detail

    A tiny spider had set up shop just over the tip cleaning port, with a delicate web linking the sponge to the iron holder.

    I tried to deport her outdoors, as is our custom with helpful critters, but she jumped off the web and scurried to an unknown spot on the bench. She’ll surely rebuild in an equally productive spot.

    Obviously, I’m not soldering enough electronic gadgetry …

  • Running Light: 1 W LED Switched Parallel Resistors

    Running Light: 1 W LED Switched Parallel Resistors

    Manually selecting the current through the 1 W amber LED with a switch actually intended for LED flashlights:

    1 W LED Running Light - switched parallel R
    1 W LED Running Light – switched parallel R

    The resistors on the low side of the LED use the MP1584 regulator for current control, with the orange wire feeding the resistor voltage into the error amplifier.

    The 15 Ω unswitched resistor sets the LED current at 53 mA = 0.8 V / 15 Ω, with the LED dissipating about 100 mW. The resistor dissipates 43 mW.

    Closing the switch puts the two parallel 4.7 Ω resistors in parallel with the 15 Ω resistor to produce 2.0 Ω, which sets the LED current to 390 mA and runs it at 950 mW. Each of the 4.7 Ω resistors dissipates 140 mW.

    That much power raises the aluminum body to 50 °C = 120 °F: definitely uncomfortable but probably survivable for the LED inside.

    Eyeballometrically, a decimal order of magnitude difference in the LED current produces an obvious brightness difference. My first try ran the LED at 500 mW (a binary order of magnitude less than 1 W) and wasn’t visually different. Given that the LED will run from the Bafang’s headlight output, saving power isn’t all that important.

    If this is the first time you’ve encountered parallel resistors, this is why your calculator has a reciprocal button: the total resistance is the reciprocal of the sum of the reciprocals of all the resistances:

    1/R = 1/R₁ + 1/R₂ + …

    A real engineering calculator does not have a shifted reciprocal function.