By turns: tinker, engineer, husband, author, amateur raconteur, recumbent cyclist, father, ham radio geek. So many projects, so little time!
With an AAA-to-AA adapter in hand, the Eneloop AAA cells looked like this:
The glitch comes from a not-quite-seated cell, showing that a poor connection matters.
The package touts “up to 800 mA·h, 750 mA·h min”, with asterisks and superscripts leading to “Based on IEC 61951-2(7.3.2)“, access to which requires coughing up 281 bucks. So it goes.
A full charge made them happier:
The as-delivered 530 mA·h capacity represents 73% of the 725 mA·h after the first charge, so I suppose they’re more-or-less within the “Maintains up to 70% charge after 10 years of storage” claim. The
16-10 date code suggests they’re hot off the factory charger, so they must ship with somewhat less than a full charge.
Comparing the capacity in W·h makes more sense, because most devices (other than the Planet Bike blinky light these will go into, of course) use a boost converter to get a fixed voltage from the declining terminal voltage.
They arrived bearing just over 600 mW·h:
After charging, that went a bit over 850 mW·h :
Call it 71% of full capacity on arrival. Close enough.
The Planet Bike blinky will be somewhat dimmer with two NiMH cells delivering 2.3-ish V, compared with the initial 3-ish V from a pair of alkaline cells. I generally burn the alkalines down to 1.1 V apiece, so perhaps they’ll be Good Enough.
Now, if I were gutsy, I’d install a rechargeable lithium AAA cell, with a dummy pass-through adapter in the other cell socket, and run the blinky at 3.7 V. At least for a few moments, anyhow …
We rode the Feeder Canal trail during a recent bike vacation in exotic Glens Falls NY:
The numerous downed branches along the trail and countless twigs on the trail came from a brush-clearing operation:
As luck would have it, a twig snagged between my front tire and fender, snapping the clips holding the fender in place:
Should it not be obvious, each ferrule formerly had two parallel jaws (on the left) gripping the fender, with the tiny screw digging into the fender. I affixed the fender to the broken clips with copious amounts of duct tape and we continued the mission.
It should be obvious why those ferrules are not suitable for 3D printing.
However, with the recent rear fender clip serving as inspiration, this didn’t take long:
The front fender fits a 20 inch wheel and is somewhat wider and flatter than the rear fender (I think they bent the same plastic strip around a smaller mandrel), so I did a quick copy-and-paste hack job on the OpenSCAD source code, rather than trying to parameterize the daylights out of the previous model.
The posts around the wire stays are 6 diameters deep and reamed to fit; the stays won’t be flopping around even without fiddly mechanical hardware retaining them. The holes extend about halfway into those posts to mimic the dimensions of the original ferrules.
All of us can predict where the next break will occur, right? That’s OK: I want this to break, instead of wrecking the fender, so the only question is how much abuse those simple joints can withstand. The printing orientation wraps the perimeter threads from the posts around the clip, making it about a strong as it can be.
The ferrules should splay outward by a few degrees to match the angle from the fender to the fork eyelets, but that’s in the nature of fine tuning.
The arch accommodates a strip of double-sided foam tape holding the clip in place along the fender curve, with those cute little hooks capturing the fender to keep the tape in compression:
I really must get some black foam tape …
The picture shows the fender sitting well away from the tire, due to the upper fender mount bending in response to the splash flap snagging on curbs and random debris; the wire stays didn’t seat completely into the posts.
The extender I made during the cracked fork episode remained perfectly straight, though:
So I re-bent the upper fender mount (not the extender!) to its original angle, thereby moving the bottom of the fender much closer to the tire. Now the stays seat fully, the clip holds the fender firmly in place with no rattles, and it’s all good.
The OpenSCAD source code as a GitHub Gist:
The Barbie-themed microscope light I built from an angel eye LED ring worked fine for the last six years (!), but a much brighter ring with 60 aimed 5 mm LEDs for $17 delivered from a US seller caught my eye:
Although this ring looks much more professional, it didn’t quite fit the microscope, being designed for a round snout rather than a squarish one. This snout has a 47-ish mm threaded ring intended for filters & suchlike, so I built an adapter between that and the 60 mm ID of the LED ring:
The ring came with three long knurled screws which I replaced with much tidier M3 socket-head screws going into those holes:
The part going into the snout threads is deliberately (honest!) a bit small, so I could wrap it with soft tape for a good friction fit. The Barbie Ring didn’t weigh anything and I wound up using squares of double-sticky foam tape; it could come to that for this ring, too.
The adapter features a taper on the bottom for no particularly good reason, as the field-of-view tapers inward, not outward:
Seen from the bug’s POV, it’s a rather impressive spectacle:
The control box sports a power switch and a brightness knob. Come to find out the ring is actually too bright at full throttle; a nice problem to have.
That was easy!
The OpenSCAD source code as a GitHub Gist:
An octet of Eneloop AAA cells arrived, I wanted to measure their as-delivered charge (the package says “Factory Charged With SOLAR ENERGY”, so you know it’s good), and discovered I’d given away my AAA cell holders. You can actually get inter-series adapters on eBay, but what’s the fun in that? Plus, I didn’t want to delay gratification for a month; you know how it is.
It’s basically an AA-size sleeve that fits over the AAA cell, with a lathe-turned brass post conducting juice from the + terminal of the inner cell outward:
Not much to look at when it’s assembled:
The AAA cell fits deliberately loose, because this goes into a metal clip holding everything firmly in place for the battery tester:
The source code tabulates the sizes of several cylindrical cells, exactly zero other pairs of which have been tested; I expect most won’t work correctly. In particular, the table entries should include the contact button OD and thickness for each cell, so that I can turn out the proper terminal for each pair of cells. If I ever need a different adapter, I’ll beat some cooperation out of that, too.
Discovered I needed an adapter after breakfast, started testing cells after lunch. Life is good!
The OpenSCAD source code as a GitHub Gist:
The original doodle:
The light switch for our attic turns on a single ceramic socket at the top of the stairs. The bulb burned out a few days ago:
To the best of my knowledge, that bulb has been in service since we moved in almost two decades ago. Most likely, it was installed when the house was built in 1955, because it matches several new-old-stock bulbs in a battered box that Came With The House™.
To be fair, the attic light doesn’t see much service, but … it’s been a great cost-performer!
The attic temperatures range from well below 0 °F in the winter to well above 120 °F in the summer, so it’s no place for CFL or LED bulbs. I swapped in a 60 W bulb from my heap, although I doubt it’ll be good for another half-century.
I’m towing a trailer of groceries southbound on Rt 376 (a.k.a. Hooker Avenue in this section), intending to turn right onto Zack’s Way for a library stop.
T=0.00 s, car @ 26.4 mph, me @ 19.8 mph
The transverse cracks through the asphalt are a convenient 60 ft apart, with the last one 20 ft from the stop line, and the frame numbers tick along at 60 frame/sec, so you can easily compute distances, times, and speeds.
I’ll be turning right at the intersection. The light is green.
T= 2.07 s, car @ 26.7 mph, me @ 19.7 mph
Now I can see the car’s right turn signal, so this might not end well. I can’t jam on the brakes and avoid a collision by dumping the bike at speed; I’ll slide under the car in the middle of the turn.
T=4.15 s, 15.2 mph
I’m 20 feet from the stop line and, suddenly, the driver also realizes this might not end well.
What he doesn’t know is that my trajectory must use the traffic lane: the shoulder around the corner is deteriorated, with several potholes, and vanishes completely where the intersection paving ends.
The driver is turning wide, into the opposing traffic lane, but if I weren’t lining up for the turn, we’d be on a collision course. My line will take me just to the left of the seemingly tiny, but very deep, pothole just ahead.
Leaning hard into the turn, but our paths won’t cross.
I’m back upright in the middle of the lane, with the shoulder ending in a pothole to my right.
Remember, I’m wearing a fluorescent (“safety”) orange shirt, running a blinky light (which is also the rear camera), and towing a trailer with a fluttering flag: I am not inconspicuous!
In case there’s any question:
The rest of the ride proceeded without incident …
The final installment of musings about building a large-format 3D printer …
(Continued from yesterday)
Perhaps they saw your blog post?
The old-old (original) high-resistance Kysan motor costs something like $45 and, apart from minor cosmetic differences, looks /exactly/ the same as the old-new low-resistance motor. If you were picking motors and didn’t quite understand why you needed a low-resistance winding, which would you pick? Hence, my insistence on knowing the requirements before plunking down your money.
To be fair, I didn’t understand that problem until the Thing-O-Matic rubbed my nose in it. With all four motors. Vigorously.
So, yeah, I think I had a part in that.
comes back to the same numbers over and over
The new-new leadscrews have something like half the pitch of the old-new and old-old threads; I don’t recall the number offhand. In any event, that gives you twice the number of motor steps per millimeter of motion and roughly twice the lifting force. This is pretty much all good, even though it may reduce the maximum Z axis speed (depends on your settings & suchlike).
When it moves upward by, say, 5 mm and downward by 5 mm, you’re measuring position repeatability. That level of repeatability is pretty much a given (for the M2, anyhow), but it doesn’t involve stiction & suchlike.
Can you move the platform up by 0.01 mm, then down by 0.01 mm, and measure 0.01 mm change after each motion?
Do larger increments track equally well in both directions?
Move upward a few millimeters, then step downward by 0.01 mm per step. Does the measurement increase by 0.01 mm after each step?
Repeat that by moving downward, then upward in 0.01 mm increments.
If the platform moves without backlash & stiction in both directions with those increments, it’s a definite improvement.
I wish I knew more
everything you learned is burned into your head forever
The way to learn more is exactly what you’re doing.
Two things I learned a long time ago:
1. Whenever you have two numbers, divide them and ask whether the ratio makes sense.
2. Whenever you don’t understand a problem, do any part of it you do understand, then look at it again.
Also, write everything down. When you come back later, you won’t remember quite how you got those results.
Which is precisely why I have a blog. I search with Google (site:softsolder.com microstepping) and /wham/ I get a quick refresher on what I was thinking. That’s why I keep link-whoring URLs: that’s my memory out there!
You’ll sometimes find scans of my scrawled notes & doodles. They won’t mean anything to you, but they remind me what I do to get the answers in that blog post.
modern controllers utilize much higher voltage and current bursts
More or less. Microstepping drivers apply a relatively high voltage, far in excess of what the winding can tolerate as a DC voltage, then regulate the current to a value that produces the appropriate waveform.
This may be helpful:
The mass of the bed APPEARS to be cancelling out any magnetic or mechanical stiction.
That can’t be true in both directions: the gravity vector points downward and the results aren’t symmetric. I think you’re reading noise. If the sequences of motions I described don’t produce the results I described, then you’re /definitely/ measuring noise.
From back in the Thing-O-Matic days:
E3D hot end setups vs MakerGear’s?
I’d want that groovemount post in an all-metal socket, though, rather than the traditional plastic, to get solid positioning and tolerance control. Makergear has the right idea with the aluminum V4 heater block mount.