Adding a bit of trim to the bottom of the LED spider makes it look better and helps keep the strut wires in place:
It’s obviously impossible to build like that, so it’s split across the middle of the strut:
Glue it together with black adhesive and a couple of clamps:
The aluminum fixtures (jigs?) are epoxied around snippets of strut wire aligning the spider parts:
Those grossly oversized holes came pre-drilled in an otherwise suitable aluminum rod from the Little Tray o’ Cutoffs. I faced off the ends, chopped the rod in two, recessed the new ends, and declared victory. Might need better ones at some point, but they’ll do for now.
After about a year of streaming music, the music died over the course of a month, producing progressively bizarre symptoms on all the local Icecast stations. Killing the streaming server and yanking all the USB memory sticks produced this tableau:
The USB 2.0 32 GB SanDisk Cruzer Fit (tiny, black, upper left) holds images from various network cameras and is not involved with music. It’s nigh onto seven years old and, apparently, still going strong.
The USB 2.0 Centron (gray-and-retroreflective, upper right) was forgotten from the last time I set up a drive for our Forester’s player. There’s another one just like it in the car; they’re impossibly old, as you’d expect from their minuscule size.
The USB 3.0 64 GB Samsung Fit (small, white, lower left) is totally dead, to the extent it doesn’t even announce its presence when plugged into a USB socket. It’s 2.5 years into a five year warranty, but their new USB 3.1 version is twelve bucks; Samsung wins. It formerly contained an extensive selection of public-domain music.
The 64 GB Sandisk Cruzer (huge, black, lower right) suffered some serious damage:
sudo mount -o ro /dev/sdg1 /mnt/part
ls: cannot access '/mnt/part/PILZ': Input/output error
drwxr-xr-x 6 ed users 4.0K Nov 28 2019 ./
drwxr-xr-x 17 root root 4.0K Jun 7 2019 ../
-rw-r--r-- 1 ed ed 215K Mar 9 2019 CDClassical.m3u
drwxrwxr-x 56 ed ed 4.0K Mar 9 2019 Classical/
drwx------ 2 root root 16K Mar 9 2019 lost+found/
d????????? ? ? ? ? ? PILZ/
drwxrwxr-x 116 ed ed 12K Mar 9 2019 Pop/
-rw-r--r-- 1 ed ed 117K Nov 28 2019 Pop.m3u
It still contains a fair amount of music ripped from the CDs we’ve collected over the decades, but it’s obviously unusable. Just for fun, I tried reformatting and copying some files to it, but it eventually hard-crashed with I/O errors:
[37787.872410] usb 2-1: new high-speed USB device number 2 using xhci_hcd
[37788.013027] usb 2-1: New USB device found, idVendor=0781, idProduct=5530, bcdDevice= 1.00
[37788.013030] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[37788.013032] usb 2-1: Product: Cruzer
[37788.013034] usb 2-1: Manufacturer: SanDisk
[37788.013036] usb 2-1: SerialNumber: 4C530001151215101233
[37788.013604] usb-storage 2-1:1.0: USB Mass Storage device detected
[37788.014778] scsi host9: usb-storage 2-1:1.0
[37789.033409] scsi 9:0:0:0: Direct-Access SanDisk Cruzer 1.00 PQ: 0 ANSI: 6
[37789.034569] sd 9:0:0:0: [sdf] 120225792 512-byte logical blocks: (61.6 GB/57.3 GiB)
[37789.035820] sd 9:0:0:0: [sdf] Write Protect is off
[37789.035825] sd 9:0:0:0: [sdf] Mode Sense: 43 00 00 00
[37789.036137] sd 9:0:0:0: [sdf] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[37789.086533] sdf: sdf1
[37789.089418] sd 9:0:0:0: [sdf] Attached SCSI removable disk
[38035.071013] EXT4-fs (sdf1): mounting ext3 file system using the ext4 subsystem
[38035.183172] EXT4-fs (sdf1): mounted filesystem with ordered data mode. Opts: (null)
[38485.302549] usb 2-1: reset high-speed USB device number 2 using xhci_hcd
[38490.622285] usb 2-1: device descriptor read/64, error -110
[38506.195617] usb 2-1: device descriptor read/64, error -110
[38506.425616] usb 2-1: reset high-speed USB device number 2 using xhci_hcd
[38511.742339] usb 2-1: device descriptor read/64, error -110
<<< snippage >>>
[38548.845743] usb 2-1: USB disconnect, device number 2
[38548.858925] blk_update_request: I/O error, dev sdf, sector 99556320 op 0x1:(WRITE) flags 0x4800 phys_seg 30 prio class 0
[38548.858933] EXT4-fs warning (device sdf1): ext4_end_bio:309: I/O error 10 writing to inode 1531939 (offset 0 size 0 starting block 12444541
[38548.858937] Buffer I/O error on device sdf1, logical block 12444284
[38548.858944] EXT4-fs warning (device sdf1): ext4_end_bio:309: I/O error 10 writing to inode 1531939 (offset 0 size 0 starting block 12444542
<<< snippage >>>
[38548.858984] Buffer I/O error on device sdf1, logical block 12444293
[38548.859034] blk_update_request: I/O error, dev sdf, sector 99017520 op 0x1:(WRITE) flags 0x4000 phys_seg 3 prio class 0
[38548.859158] blk_update_request: I/O error, dev sdf, sector 99556560 op 0x1:(WRITE) flags 0x4800 phys_seg 30 prio class 0
[38548.859224] blk_update_request: I/O error, dev sdf, sector 99017760 op 0x1:(WRITE) flags 0x4000 phys_seg 2 prio class 0
[38548.859237] blk_update_request: I/O error, dev sdf, sector 99018000 op 0x1:(WRITE) flags 0x4000 phys_seg 2 prio class 0
[38549.230765] JBD2: Detected IO errors while flushing file data on sdf1-8
[38549.230920] Aborting journal on device sdf1-8.
[38549.231008] Buffer I/O error on dev sdf1, logical block 1545, lost sync page write
[38549.231011] JBD2: Error -5 detected when updating journal superblock for sdf1-8.
[38549.231325] Buffer I/O error on dev sdf1, logical block 0, lost sync page write
[38549.231332] EXT4-fs (sdf1): I/O error while writing superblock
[38549.231333] EXT4-fs error (device sdf1): ext4_journal_check_start:61: Detected aborted journal
[38549.231334] EXT4-fs (sdf1): Remounting filesystem read-only
<<< and so forth and so on >>>
The Icecast streaming server reads data continuously from the USB sticks and, given that I set up half a dozen “stations”, there’s plenty of reading going on. The drives are formatted as ext3 and mounted with the noatime option, so there shouldn’t be any writing going on, but it seems a year of constant reading can kill a USB drive.
Fortunately, the original data lives elsewhere, with scripts to copy the appropriate files to the right places, so rebuilding the drives on a pair of new USB sticks wasn’t a big deal.
For reasons not relevant here, I was asked to tweak an XFCE 20.04 installation to not ask for a password after the screen power-saver kicks in. There’s no need for a screensaver with an LCD panel, so this should be straightforward, as per the XFCE 18.04 setup:
Which had no effect.
For some reason, perhaps having to do with an upgrade from 18.04 to 20.04, Light Locker wasn’t actually handling the screen locking; some dedicated searching suggested this is a problem of long standing.
So tweak the Lock Screen settings of the screen saver that’s not in use:
If you’re doing this remotely, adding a stanza to ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-screensaver.xml should suffice:
It Would Be Nice to turn the various Raspberry Pi camera boxen around here into more-or-less full-automatic IP streaming cameras, perhaps using RTSP, so as to avoid having to start everything manually, then restart the machinery after a trivial interruption. I naively thought video streaming was a solved problem, especially on an RPi, particularly with an Official RPi Camera, given the number of solutions found by casual searching with the obvious keywords.
As far as I can tell, however, all of the recommended setups fail in glorious / amusing / tragic ways. Some failures may be due to old configurations no longer applicable to new software, but I’m nowhere near expert experienced enough to figure out what’s broken and how to fix anything in particular.
Doing RTSP evidently requires the live555.com Streaming Media libraries & test suite. Compiling requires adding -DNO_SSL=1 to the COMPILE_OPTS line in the Makefile, then letting it bake it for a while.
The v4l2rtspserver code fetches & cleanly compiles its version of the live555 code, then emits various buffer overflow errors while streaming; the partial buffers clearly show how the compression works on small blocks in successive lines. Increasing various buffer sizes from 60 kB to 100 kB to 300 kB had little effect. This may have to do with the stream’s encoding / compression methods / bit rates, none of which seem amenable to random futzing.
Running the RPi camera through the Video4Linux2 interface to create a /dev/video0 device seems to work, but controlling the camera’s exposure (and suchlike) with v4l2_ctl behaves erratically. Obvious effects, like rotation & flipping, work fine, but not the fine details along the lines of auto exposure and color modes.
Attempting to fire raspivid through cvlc to produce an RTSP stream required installing VLC on a headless Raspberry Pi, plus enough co-requisite packages to outfit world+dog+kitchenSink. After all the huffing & puffing wound down, the recommended VLC parameters failed to produce an output stream. The VLC doc regarding streaming is, to me, impenetrable, so I have no idea how to improve the situation; I assume RTSP streaming is possible, just not by me.
Whenever any of those lashups produced any video whatsoever, the images suffered from tens-of-seconds latency, dropped frames, out-of-order video updates, and generally poor behavior. Some maladies certainly came from the aforementioned inappropriate encoding / compression methods / bit rates.
The least horrible alternative seems to be some variation on the original theme of using raspivid to directly create a tcp stream or firing raspivid into netcat to the same effect, then re-encoding it on a beefier PC as needed. I’m sure systemd can automagically restart raspivid (or, surely, a script with all the parameters) after it shuts down.
So far, this has been an … unsatisfactory … experience, but now I can close a dozen browser tabs.
The stiffness of the bike helmet mirror mount suggested a similar clamp would have enough griptivity to immobilize the ball while cutting it in the lathe:
Building the clamp around the lathe’s three-jaw lathe chuck eliminates the need for screws / washers / inserts:
The Ah-ha! moment came when I realized the fixture can expose half of the ball’s diameter for drilling while clamping 87% of its diameter, because 0.5 = sin 30° and 0.87 = cos 30°:
That’s an orthogonal view showing 13% of the ball radius sticking out of the fixture; it’s 6% of the diameter.
Which looks like this in real life:
The socket is offset toward the tailstock end of the clamp (on the right in the picture) to expose half its diameter flush with the surface perpendicular to the lathe axis. The other side necks down into a cylinder of the same diameter to clear the drill bit.
This works nicely until the ball diameter equals the chuck jaw’s 20 mm length, whereupon larger balls protrude into the chuck body’s spindle opening. Although I haven’t yet built one, the 25 mm balls in my Box o’ Bearings should fit, with exceedingly sissy cuts required for large holes.
The fixture doesn’t require support material, because the axial holes eliminate the worst of the overhang. Putting the tailstock side flat on the platform gives it the best-looking surface:
The kerf between the segments ensures the jaws can apply pressure to the ball, whereupon the usual crappy serrated 3D printed surface firmly grabs it.
The fixture is a slip fit on the chuck jaws:
Tightening the jaws shoves them all the way into the fixture’s slots and clamps the ball:
Overtightening the chuck will (probably) compress the ball around the drill, which will (best case) give you slightly oversize holes or (worst case) cause the ball to seize / melt around the drill bit, so sleaze up to the correct hole diameter maybe half a millimeter at a time:
That fixture exposes 9.5 mm = 19/2 of the ball. The drill makes a 6 mm hole to fit the telescoping shaft seen above.
Obviously, you must build a custom fixture for every ball diameter in your inventory, which is no big deal when you have a hands-off manufacturing process. Embossing the diameter into the fixture helps match them, although the scribbled Sharpie isn’t particularly elegant.