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.
Armed with bags of electronic parts and boxes of meters, I’ll be helping folks at the CNC Workshop understand the electrical limitations of the Arduino microcontrollers they’re building into projects.
The presentation in PDF form:
Arduino Survival Guide – Workshop Edition – CNC Workshop 2015
We’ll wing it with the source code, because nothing’s more than a few lines long…
This afternoon at the CNC Workshop, I’ll be bootstrapping folks into creating 3D-printable solid models with Openscad.
The presentation in PDF form:
Practical Solid Modeling for 3D Printing with OpenSCAD – CNC Workshop 2015
The OpenSCAD source code for the exercises, in case you don’t want to type along:
Practical Solid Modeling for 3D Printing with OpenSCAD – Models.zip.odt
When you download that file, you’ll get something ending in .zip.odt. Rename it to remove the .odt extension, because it’s really a ZIP file; WordPress doesn’t allow users to uploads ZIP files.
If all has gone according to plan, I’m in Detroit today and will give a talk at the CNC Workshop on (my view of) the status of personal 3D printing, what to expect in the future, and what you can do with it today.
The presentation in PDF form: 3D Printing Status 2105-06 – CNC Workshop Detroit
Unfortunately, US Rt 44 is the only way to get from Adams Fairacre to the Stop & Shop, so we ride this section once a week. I’m towing the trailer with two bags of groceries:
A palimpsest of patches shows that they really don’t have staying power:
Gravel and a manhole cover keep cyclists off the shoulder:
We take the lane well before we encounter this section, because veering into traffic doesn’t work well:
The longitudinal crack marks the edge of the original paving. This is a common hazard on Dutchess County roads, as many were widened by simply paving the original shoulders into the travel lane, without actually rebuilding the substructure.
The map:
We noticed far more sparrows than usual in the garden, some flying clumsily, then saw both adults feeding a nestling peering from the nesting box:
Our presence interrupted the regular feeding pattern, stalling the male sparrow atop the utility pole with a tempting snack in his beak:
Even when it’s time to leave, just thinking about growing up and joining the world makes you tired:
May they all eat many garden insects!
Taken with the Sony DSC-H5 and tele extender lens, zoomed all the way in, with a touch of manual focus and exposure override.
Our Larval Engineer stopped by, on her way to a half-year co-op job out around Route 128, and devoted a few days to merge-sorting / triaging her possessions. Having shown her the HP 74754A plotter project, she later dropped a bag o’ stuff on my desk without comment:
The perforated pen holder stuck to the plotter case (hey, it would still fit!) in front of the carousel with a bit of foam tape on an angled bracket you can’t quite see. It held 15 pens at the ready: I really used that plotter.
The doodle on the yellow sheet sketches a bulky adapter between the spindle nose thread on the Sherline CNC mill and a plotter cartridge. The flange-less pen body might just fit into the spindle bore, but I remember concluding that machining pen bodies or adapters wasn’t worth the effort. Now it’s a simple matter of some OpenSCAD source code and a few hours of hands-off production, so perhaps I should re-think that.
No dates on anything, but I got the Sherline in 2004. The pen holder probably dates back to the late 80s, shortly after I got the plotter. Most likely, I gave her the bag o’ stuff and told her to make something interesting; it could still happen…
Using radiation to generate random numbers reminded me of some Victoreen 710-104 ionization chambers that have been in the pile basically forever:
The central contact seems to be double-insulated from the chamber with glass (?) seals in a soldered-in-place assembly:
That might be rosin left over from soldering, but you’d think they would have rinsed it off to reduce the leakage. Some cleaning will be in order.
A picture in The Fine Manual for the CD-V-710 Model 5 Radiation Survey Meter showed that the circuit board used point-to-point wiring, with the range switch soldered directly to that bent metal contact:
Another page gave some useful values and a simplified schematic:
Never fear, the manual also has the full schematic; they don’t write manuals like that any more.
The chamber bias voltage was +22.5, from one carbon-zinc battery available back in the 1950s. You can still get 22.5 V batteries at about ten bucks a pop, but 24 V from a pair of cheap & readily available 12 V A23 alkaline batteries should be close enough. There’s no current drain, so the batteries should last their entire shelf life.
The “HI-MEG” resistor represents a trio of glass-body resistors selected by the range switch:
As the saying goes, if you must select R7 in an actual emergency, you should sit down, put your head between your legs, and kiss your ass goodbye.
The steel-wall chamber responds only to gamma radiation, with a nominal current of 5 pA at 0.5 R/h. However, given an op amp like the LMC6081 with 10 fA bias current, maybe building an electrometer-style amplifier that can respond to background gamma radiation or maybe secondary gamma rays from cosmic ray air showers would be feasible; I haven’t done anything like that in a while and even a faceplant would be interesting.
Alas, radium-226 and its progeny, including radon-222 decay through alpha and beta emission that’s specifically excluded by the can.
This is not a new idea, by any means, as shown by some extensive discussion and well-done circuitry. Any amplifier that works with the Victoreen can will certainly work with a homebrew ionization chamber.
The Smell of Molten Projects in the Morning 