Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Although the Superformula can produce a bewildering variety of patterns, I wanted to build an automated demo that plotted interesting sets of similar results. Herewith, some notes after an evening of fiddling around with the machinery.
The first two parameters set the more-or-less maximum X and Y values in plotter units; the plot is centered at zero and will extend that far in both the positive and negative directions. For US paper:
A = Letter = 11 x 8½ inch → 4900 x 3900
B = 17 x 11 inch → 8000 x 5000
The point_count parameter defines the number of points to be plotted for the entire figure. They’re uniformly distributed in angle, not in distance, so some parts of the figure will plot very densely and others sparsely, but the plotter will connect all of the points with straight lines and it’ll look reasonably OK. For the figures below, 10*1000 works well.
The travel value defines the number of full cycles that the figure will make, in units of 2π. Ten cycles seems about right.
The four parameters in between those are the m, n1, n2, and n3 values plugged directly into the basic Superformula. The latter two are exponents of the trig terms; 1.0 seems less bizarre than anything else.
Sooo, that leaves only two knobs…
With travel set for 10 full cycles, m works best when set to a value that’s equal to prime/10, which produces prime points around the figure. Thus, if you want 11 points, use m=1.1 and for 51 points, use m=5.1. Some non-prime numbers produce useful patterns (as below), others collapse into just a few points.
The n1 parameter is an overall exponent for the whole formula in the form -1/n1. Increasing values, from 0.1 to about 2.0, expand the innermost points of the pattern outward and turn the figure into more of a ring and less of a lattice.
So, for example, with m=3.1, setting n1= 0.15, 0.30, 0.60 produces this pattern with 31 points:
HP 7475A – Superformula – m 3.1 vary n1
Varying both at once, thusly: (m,n1) = (1.9,0.20)=green (3.7,0.30)=red (4.9,0.40)=blue
produces this pattern:
HP 7475A – Superformula – m 1.9 3.7 4.9 n1 0.2 0.3 0.4
Yeah, 49 isn’t a prime number. It’s interesting, though.
Note that n1 doesn’t set the absolute location of the innermost points; you must see how it interacts with m before leaping to any conclusions.
It’s still not much in the way of Art, but it does keep the plotter chugging along for quite a while and that’s the whole point. I must yank the functions out of the Chiplotle library, set my default values, add one point to automagically close the last vertex, and maybe convert them to polar coordinates to adjust the magnitude as a function of angle.
Yes, that poor green ceramic-tip pen is running out of ink after all these decades.
The step change in Week 22 shows when the replacement took over. After some poking around, Amazon Prime FTW.
The square-ish pulse starting in Week 26 marks a change from 55% RH to 60%RH and back again, to see how the front panel meter compares with the low end lab-grade hygrometer in the other side of the basement near the Hobo datalogger on the water inlet; they’re all off by a bit, but well within their expected tolerances. The 5% RH height of the step suggests a good match between their incremental calibrations.
It seems dehumidifiers last a few years, no matter which Brand Name you’ve decided to trust, so there’s not much point in developing a deep emotional attachment.
For the record, the old dehumidifier sported a GE label:
As it turns out, Electrolux bought Frigidaire a while ago, then absorbed GE’s appliances in 2014, so they’re all one big happy family now.
The various names notwithstanding, a recall notice suggests Gree Electric actually makes all the dehumidifiers badged with Brand Names you might think represent something significant.
Mary found a folding saw buried under a compost heap at Vassar Farms, where it had evidently been for quite a while. It cleaned up surprisingly well:
Folding saw – pivot shim
I made a crude brass shim to stabilize the crude blade in its crudely bent metal frame; the ugly hole came from freehand punching with the rebuilt leather punch tool. Probably spent as much time doing that as they did on the whole rest of the saw: it’s not a high-quality tool.
It could be an older version of the Harbor Freight Folding Saw, minus a fancy plastic-encased joint screw. I added a dot of Loctite to discourage this one from leaping to its doom.
As with the other pruning saws in my collection, that blade scares me just looking at it. I managed to avoid slicing myself open, although I did stab a finger with a sharp brass sliver…
As failures go, that one’s survivable; slightly larger epoxy dots should do the trick:
Silhouette temple – re-repair
The other temple worked loose inside the brass tube and rotated freely, so I yanked it out, bashed the tip slightly flatter, and epoxied it back in place, along with overcoating the epoxy dots on the lens to forestall another failure.
This has obviously blown right by the point of absurdity, but …
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:
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…
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 