Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
A semitrailer load of scrap metal pulled into an I-90 rest stop just after we arrived:
Metal scrap trailer – Cutting edge
Apparently, they dump the scrap into the trailer from a great height and, sometimes, a bar can gash the aluminum side wall. That slice obviously predates the current load, but you can see how it happened: dump a load atop a bar leaning against the side and you get a giant metal shear.
The trailer also had several puncture wounds:
Metal scrap trailer – Puncture wounds
I didn’t notice the circular feature at the bottom center until I looked at the picture, but it certainly reminded me of a bullet hole in glass plate. Close inspection of the original image suggests it’s a welded stress relief border around a drilled hole, perhaps with a boss on the inside of the trailer:
Verily, ImageMagick can do nearly anything you want to an image, as long as you know how to ask for it:
for f in *png ; do convert $f -density 300 -define jpeg:extent=200KB ${f%%.*}.jpg ; done
That converts a directory full of VLC’s video snapshot images from PNG format, which require nigh onto 4 MB each, into correspondingly named JPG files under 200 kB. The image quality may not be the greatest, but it’s good enough to document road hazards in emails.
Rt 376 2015-07-06 – Walker to Maloney – 3
The density option overrides VLC’s default 72 dpi, which doesn’t matter until a program attempts to show the image at “actual size”.
I didn’t realize that the define option existed, but it seems to be how you jam specific controls into the various image coders & decoders. Some of the “artifacts”, well, I can’t even pronounce…
VLC’s snapshot file names look like vlcsnap-2015-07-06-12h10m27s10.png, so bulk renaming and resequencing will be in order.
Lining the shield support box with copper foil tape turned out to be surprisingly easy:
Electrometer amp – shield – end view
The flat surface is two overlapping strips of 2 inch wide copper tape. I traced the exterior of the support box on the tape, cut neatly along the lines, slit the corners, bent the edges upward, peeled off the backing paper, stuck the tape into the box, pressed the edges into the corners, and didn’t cut myself once.
Applying 1 inch wide tape to the wall went just as smoothly, after I realized that I should cut it into strips just slightly longer than the hexagon’s sides.
The tape along the rim is adhesive copper mesh that’s springy enough to make contact all around the edge. I cut the 1 inch wide tape in half, which was just barely wide enough to reach::
Electrometer amp – shield – mesh soldering
Although you’re supposed to join the entire length of each seam for best RF-proofing, I tacked the corners and the middle of the long edge, then hoped for the best. The copper mesh seems to be plated on plastic threads that requires a fast hand to solder without melting, but I’m getting better at it. The adhesive is said to be conductive, but I loves me some good solder blob action.
The resistance from the flat bottom to the side panels and the fabric on the edge started out at a few ohms before soldering and dropped to 0.0 Ω after soldering, so I’ll call it a success. Didn’t even melt the outside of the PETG box, but I admit I didn’t take it apart to see what the copper-to-PETG surface looks like.
Covering the foil on the sides with 1 inch Kapton tape completed the decoration. I didn’t bother to cover the flat surface, because none of the circuitry should reach that far, and didn’t worry about covering the fabric tape for similar reasons. As madbodger pointed out, this violates the no-plastic-on-the-inside rule, but I’m still hoping for better results than having the entire plastic structure with all its charges on the inside.
A strip of horribly clashing orange plastic tape (which might be splicing tape for reel-to-reel recording tape) covers the outside edges of the fabric, prevents fraying, and gives the black electrical tape that holds the box down a solid grip:
Electrometer amp – shield – exterior
Yeah, like you’d notice mismatched colors around here.
Using black tape as an anchor seemed easier and better than messing with nesting pins & sockets. The copper fabric tape makes good contact with the rim of the PCB all the way around the perimeter and the black tape holds it firmly in place.
Early reports suggest the shield works pretty well…
We spent a pleasant evening hour walking & sitting on the town beach in North East PA on our way back from Detroit:
Sunset over Lake Erie – North East PA
The entire area smells strongly of the grapes that grow well in the hilly terrain south of Lake Erie. A local expert said that Welch’s (a major local employer) moved its CHQ to Concord MA to put a better hometown name on the company’s letterhead; being based in North East evidently didn’t have the same ring.
The Sony HDR-AS30V camera takes surprisingly good pictures in low light conditions, at least if you’re not too fussy about details like license plates…
At dusk, on our way to the City of Poughkeepsie’s Independence Day fireworks show:
Night Ride 2015-07-04 – AS30V – 0
Returning in full dark:
Night Ride 2015-07-04 – AS30V – 1
A light fog set in as we got out of the city:
Night Ride 2015-07-04 – AS30V – 2
The Cycliq Fly6 faces a major challenge from in-its-face headlights, even with some background streetlighting:
Night Ride 2015-07-04 – Fly6 – 1
In full dark, it’s enough for mood-setting:
Night Ride 2015-07-04 – Fly6 – 2
That ride marks the annual exception to our general Don’t Bike After Dark rule. We set our blinky taillights to the legally required steady mode, although I think a low-power blink mode would be more conspicuous. Perhaps an occulting light (constant bright with dim pulses) would be better, but I’m not sure that’s legal.
A roadie on a fancy bike, riding dark without lights and reflectors, passed us. Watching him dodge a car that entered an intersection without seeing him once again demonstrated that cyclists are, in general, their own worst enemy.
Although I’d thought of a Mu-metal shield, copper foil tape should be easier and safer to shape into a simple shield. The general idea is to line the interior with copper tape, solder the joints together, cover with Kapton tape to reduce the likelihood of shorts, then stick it in place with some connector pin-and-socket combinations. Putting the tape on the outside would be much easier, but that would surround the circuitry with a layer of plastic that probably carries enough charge to throw things off.
Anyhow, the hexagonal circuit board model now sports a hexagonal cap to support the shield:
Victoreen 710-104 Ionization Chamber Fittings – Show with shield
The ad-hoc openings fit various switches, wires, & twiddlepots:
The Smell of Molten Projects in the Morning 