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: Memo to Self

Maybe next time I’ll get it right

  • 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 …

  • PTT Switch Contact Corrosion

    Corroded Pushbutton Switch Contacts
    Corroded Pushbutton Switch Contacts

    The PTT switch for the amateur radio on my bike got erratic: pushing the button didn’t seem to be producing reliable RF. I’d have sworn when I bought the switches that they were washable-during-PCB-assembly: at least moderately sealed.

    Wrong.

    Turns out there’s only the seal you get from snug-fitting mechanical parts. I carved off the square aluminum bezel and found an ordinary dome switch underneath, with contacts that actually looked better than you’d expect after half a decade on a bike. But, yes, I could see why it was erratic.

    Lacking anything smarter, I installed another one, just like the other one, with a square of Kapton tape over the button. Not a great seal, but maybe it’ll be Good Enough.

    Here’s what the button looked like in happier times…

    PTT Button
    PTT Button

    Memo to Self: Tape up the other PTT buttons?

  • New 1.5 TB USB Backup Drive

    Just got a new 1.5 TB USB drive (Western Digital Elements; every manufacturer has produced horror stores) for $85 delivered; I do not understand the economics of that business in the least. Anyway, this will become the external drive onto which the rsnapshot routine dumps the daily changes from the file server; the old 500 GB drive was 99% full, so it’s time to tuck that one in the fireproof safe.

    The NTFS partition had some weird-ass peculiarities that choked cfdisk, so I used parted to blow away the NTFS type=7 partition and create a new Linux type-83 partition. Strangely, the drive came with no shovelware, for which I’m grateful.

    sudo fdisk /dev/sde
Command (m for help): d
Selected partition 1
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-182401, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-182401, default 182401):
Using default value 182401
Command (m for help): w
The partition table has been altered!

    Then build an ext3 filesystem:

    sudo mke2fs -j -m 0 -L 'Backup-1.5TB' -O sparse_super /dev/sde1

    The sparse_super option seems to make sense; if the drive fails to the point where you must go rummaging for more than one spare superblock, you’re probably not going to find any of them.

    Turns out you really should unplug / replug a USB drive after walloping its partition table. Took me a while to figure that out. Again. You’d think I’d remember.

    Then you find the partitions’s new UUID using any of:

    ll /dev/disk/by-uuid/
vol_id /dev/sde1

    Then plug the UUID into fstab so the rsnapshot routine can mount the drive regardless of which device it wakes up as on any given day:

    UUID=77c75554-26a0-4bbc-a452-201c2150bf1a  /mnt/backup ext2 defaults,noatime,noauto,nodev,noexec,nosuid 0 0

    More on that from the last go-round there.

    The first backup took about six hours to copy 430-some-odd GB of data from the internal SATA drive. Call it almost exactly 20 MB/s; such a nice round number surely means a drive-limited data rate.

    Incidentally, if you need a shiny new UUID for some reason, uuidgen is your friend.

    Memo to Self: Just unplug the [mumble] drive.

  • Aztek Brake Pad Inserts: Glazing Thereof

    Went on a ride around the block and after about 4 miles discovered I had no rear brakes. Well, the brakes were there and doing the right mechanical things, but without much friction.

    Did an expedient repair by squeezing strips of paper between the pads and the rim, then rolling the wheel. Came out black and graphite-looking, not oily, but didn’t improve the braking.

    Rolled the bike into the shop after the ride; 23 miles without a rear brake gets my immediate attention. Wiped a lot of black graphite-looking schmutz off the rim using denatured alcohol, filed the well-glazed pads to a nice finish, and reinstalled.

    These are Aztek pad inserts, which I’m trying out to see how they work. So far, not much; they seem less grippy than the ordinary Aztek pads (on the front and previously on the back) and certainly much more prone to glazing.

    Memo to Self: 7792 on the odometer.

  • Casting Machinable Wax: Oops!

    Remelted machinable wax
    Remelted machinable wax

    I put a new bag in the vacuum cleaner while machining the prototype case for the bike radio adapters, which was a Good Thing: the swarf from those two halves filled the entire bag!

    I gutted the bag and dumped the swarf in a pot to melt down for another use. It started as a brick, but I figured having some rounds might come in handy. A bit of rummaging turned up some pill bottles of just about the right size.

    Unfortunately, I didn’t think quite far enough ahead: notice the shoulder around the right-hand end of the shorter cylinder? Yeah, the bottom of the bottle was bigger than the top…

    Fortunately, I don’t have a deep emotional attachment to the bottles, so carving it off the wax wasn’t a traumatic experience. Things would be different if I’d made a nice custom mold…

    Of course, the vacuum cleaner also sucked up the odd screw, paper snippet, older swarf left in nooks and crannies, and some of this and a bit of that. Most of the junk either floats to the top or sinks to the bottom, leaving the rest of the wax in good shape. I suppose I could filter the melt, but it’s pretty thick & gooey, even at 300 °F, and I doubt my cheesecloth is up to the task.

    Memo to Self: Do a better job of cleaning up before machining the wax, OK?

  • Bike Helmet Earbud/Mic Connections

    I’m in the process of reworking the interface box between the amateur radio HTs on our bikes and our helmet-mounted earbud & mic lashup. Mary needed a new helmet before I got the new interface ready, soooo there’s an adapter cable in the middle.

    This time around, the helmet cable uses a male USB-A connector, rather than a female 6-pin Mini-DIN PS/2 keyboard connector. Either one is cheap & readily available as assembled cables, which gets me out of soldering teeny little connector pins. These days, though, USB cables are more common.

    The motivation for a non-latching, low-extraction-force connector at the helmet is that when (not if) you drop the bike, the helmet doesn’t tie your head to the bike and snap your spine. Falls on a recumbent are much less exciting than on an upright bike, but you still want the bike to go that-a-way while you go this-a-way. Been there, done that.

    The old helmet cable connector: female 6-pin mini-DIN. The wire color code is not standardized. Viewed from rear of female connector or the front of the male connector, with the key slot up:

     ear com - Gn   5  |_|  6  K - ear hot
 mic com - Or   3  key  4  Y - mic hot
        gnd - Bn  1   2  R - gnd

    The new helmet cable connector: male USB-A. Mercifully, they standardized the wire colors. Looking at the front of the male USB-A connector with the tab down and the contacts up, the pins are 4 3 2 1:

    • 1 – R – ear hot
    • 2 – W – mic hot
    • 3 – G – mic com
    • 4 – K – ear com

    The female USB-A connector is exactly the same.

    That arrangement should produce the proper twisted pairs in a USB 2.0 cable, but all the USB cables I’ve seen so far lay all four wires in a common twist inside the shield. Maybe it’s the cheap junk I buy, huh?

    It’s worthwhile to scribble some color in the background of the trident USB symbol so it’s easier to mate the connectors.

    Easy-align USB connectors
    Easy-align USB connectors

    Memo to Self: verify the connections & proper operation before shrinking the tubing!

  • Continuous Flow Inkjet: Tank Topoff

    Just topped off the tanks again…

    • Yellow: 30 ml
    • Light Cyan: 20 ml
    • Cyan: 27 ml
    • Light Magenta: 22 ml
    • Magenta: 30 ml
    • Black: 30 ml

    Back in February I added 40 ml to the Black tank.

    The odd numbers are what was left in the bottom of the bottles

    Memo to Self: That’s about 8 oz = 250 ml of each color and 500 ml of Black since getting the printer in late Dec 2007. Figuring OEM ink at $2/ml: $3500. Current bulk ink cost is on the order of $20/bottle: $140. The continuous ink system was about $50 back then and $100 now.

    The backstory.