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

  • Useful Minicom Defaults

    I usually figure this stuff out for each minicom setup; now I can just refer here and get it right the first time.

    Run minicom -s the first time to set the internal configs:

    • Port typically /dev/ttyUSB0 for USB-serial adapter
    • 19200 8N1 for lack of anything smarter
    • No hardware flow control
    • Software flow control
    • Clear modem Init and Reset strings to blank
    • No DCD line
    • Set colors as below

    Your favorite colors will differ; these are Old-Skool:

    • Menu: white on blue
    • Status: black on cyan
    • Terminal: green on black

    Save that as the overall system default.

    Set command-line defaults in ~/.bashrc:

    • -m to use Alt+key rather than Ctrl-A and then the key
    • -c on to see those pretty colors

    Which will look like

    MINICOM='-m -c on'
export MINICOM

    And then it Just Works…

  • CPU Heatsink Fuzz

    My PC makes a seasonal migration: to the basement during the summer, to the living room in the winter. Those moves provide an opportunity to vacuum the fuzz out of the fan grilles and heatsinks.

    You’d think that, given the trouble caused by blocked air inlets, manufacturers would make it easy to get access to the grilles and trivially easy to remove the fuzz. Not so, alas.

    This time, I decided to see what the intake side of the main heatsink looked like. Two screws secure the shell to the circuit board and provide clamping pressure on the CPU heat spreader. The heatsink is a massive affair with liquid-filled heat pipes; I’ve never taken it out before because removing the screws exposes the CPU heat spreader, where you do not want to get fuzz.

    Heatsink fuzz
    Heatsink fuzz

    Oops!

    A bit of work with the vacuum and a brush greatly improved the situation. I think I kept the fuzz out of the heatsink-to-CPU joint, but there’s really no way to know because, as nearly as I can tell, Dell didn’t include any of the CPU temperature readouts on this system board.

    Memo to Self: Gotta do that more often …

  • American Standard Elite Kitchen Faucet: More O-ring Troubles

    Half a year after replacing the O-rings on the kitchen faucet, it’s dribbling again. This time, the symptom looked like a leak from the top of the faucet, which implied the three O-rings on the Spacer plate rather than big O-rings that seal the spout.

    You can see the O-rings look different on the old and new spacers …

    Old and New Faucet Spacers
    Old and New Faucet Spacers

    Indeed, the old O-rings are flattened out. It’s most visible over on the right edge of the lower ring; the top ring is new.

    Flattened O-ring
    Flattened O-ring

    Replacing them is no big deal; follow the directions in the earlier post to get everything apart. But: only half a year?

    Here’s a view of the diverter on the back of the column.

    Diverter viewed in mirror
    Diverter viewed in mirror

    Notice that the larger O-rings that seal the spout to the column had glued themselves to the column and left shreds when I removed them. A narrow strip of Scotch-Brite scouring pad, applied shoe-shine style, cleaned the O-ring debris off the column and made it nice & shiny. I suppose as long as they slip freely on the spout, then it’s all good, but there are new ones in place now.

    I used a bit more silicone grease on the O-rings this time; we’ll see if that makes it better or worse.

  • Monthly Aphorism: On Debugging

    • Whenever you find a problem, fix it

    Mad Phil taught me an absolutely fundamental rule for debugging electronic gadgets: when you find something unexpected, it’s either:

    • part of the problem you’re trying to solve
    • another problem you haven’t discovered yet

    In either case, ignoring evidence that something was just a little off or that you didn’t quite understand or that didn’t seem important was a sure recipe for missing the cause of the problem.

    That algorithm could trigger a depth-first search that distracts you from the real problem, which was where Mad Phil’s magic came in: he knew where the problem was and simply carved his way through the underbrush toward it.

  • Pin Spanner for 3.5 mm Audio Jack Nut

    The external antenna jack on the Totally Featureless Clock is, by necessity, recessed way down in a hole (because I can’t get to the inside of the now-finished half-inch-thick case to gnaw it out from there). Perforce, that puts the locking nut out of reach.

    Solution: a pin spanner wrench. I’m sure they’re available commercially, but what’s the fun in that?

    The male threaded part of the jack is 0.230 inch OD, the nut is 0.313 OD, and the notches are 0.030 wide and 0.020 deep. Raw material is about two inches of 5/16-inch air-hardening drill rod, not that I’m actually going to heat treat it for this application.

    Face off the end and drill the guts out with a 15/64-inch drill.

    Drilling central recess
    Drilling central recess

    Grab it in the 3-jaw chuck bolted firmly to the table, then mill off anything that isn’t a pin. Don’t grab it in the milling vise, which doesn’t have enough oomph to hold a slick steel cylinder in place; don’t ask how I know this.

    Milling pins in 3-jaw chuck
    Milling pins in 3-jaw chuck

    Set Z=0 at the top surface of the spanner-to-be and XY = 0 on the axis of the cylinder, of course.

    Manual CNC, feeding the commands into EMC2’s MDI slot and then mouse-clicking the stored commands to avoid reduce typing errors. For my setup, Y=±0.171 to produce the 30-mil pin and  X=±0.4 to clear on both sides.

    After cutting the first side at 3 k RPM, feed 2 inches/min, and 10 mils per pass, I whacked the other side off in one giant 20-mil bite. I’m such a sissy…

    A bit of heatshrink tubing improves the griptivity and it’s all good.

    Finished spanner engaged in nut
    Finished spanner engaged in nut

    This is the sort of thing you do once, drop in the baggie with the rest of the connector nuts, and use for years thereafter. I should’a done it years ago, but I’ve been able to not quite butcher the nuts with a needle-nose pliers…

    [Update: It turns out a commercial nut driver was available, at least in one special shop in one special place, but no longer. For my delicate uses, that shaft into the jack isn’t really needed.]

  • Sherline CNC Mill: Limited Headroom Thereof

    Cramped Headroom
    Cramped Headroom

    I had to drill a 1/4-inch hole in the Totally Featureless Clock’s case for the antenna jack. Fortunately, I have a 1/4-inch collet, because there was nowhere near enough room for the Jacobs chuck in there.

    Removing the tooling plate wouldn’t help: the chuck setup needed another inch!

    In truth, the headroom is rarely the limiting factor. Another inch or two of throat distance and maybe that much more Y travel would be nicer, while we’re at it.

    Ah, well, it’s all a matter of tradeoffs. If the mill were much bigger, I’d just want to make bigger projects, right?

  • IRQ Troubles on Razor

    The Dell Dimension 4560, a.k.a. razor, that controls my Sherline CNC mill woke up without network support. That’s a showstopper, because all the G-Code files live on the server across the basement.

    All my boxes have a network function dipstick test: the desktop background is an image on that same file server. When the NFS share wakes up dead, then the screen shows the default Ubuntu background: brown = down! (At least in Ubuntu 8.04 LTS, which is what EMC2 is built on right now.)

    Checklist…

    • NFS share isn’t mounted
    • … and can’t be mounted
    • ifconfig shows eth0 up & active
    • can’t ping the server
    • can’t ping razor from the server
    • Link lights on network switch nailed to floor joist overhead are green
    • Link light on NIC on back panel
    • Activity lights on switch & NIC blink occasionally (??)
    • Swapping ports on the switch = no change
    • Laptop works fine plugged into switch = switch OK

    So whatever is busted, is busted in the 4560. Drat!

    (Should have checked cable between switch and NIC. Sometimes you get a data failure without affecting the link & activity lights. Weird, but stuff happens.)

    Looking in dmesg shows that a bogus IRQ 11 occurred during startup:

    [   44.439932] irq 11: nobody cared (try booting with the  irqpoll" option)
... time passes ...
... bad IRQ log dump gibberish ...
[   44.440440] Disabling IRQ #11

    Fairly obviously, after that point nothing about the NIC or anything else on IRQ 11 will work: the hardware setup may be OK, you can write to it and read from it, but no actual data gets through.

    A reboot didn’t cure the problem. Reboots in Linux rarely solve a problem; you’ve got to actually find the root cause and fix it, rather than shake the dice to see if a better combination comes up.

    Anyhow.

    Restarted to get into Dell’s attenuated BIOS configuration routine, changed the NIC to IRQ 3 (just because it was first on the list), saved, restarted, and everything works. The bogus interrupt is gone, the NIC is running, NFS shares are OK.

    It absolutely beats me. But at least this is written down so the next time it happens, I’ll remember what I did.

    Oh, yeah. The Sherline CNC mill uses stepping motors and uses cutters, so it’s a Steppin’ Razor, of course, and is therefore named razor. I suppose I could have called it molly, but that’d be a stretch.