Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Our Larval Engineer reported that her camera, which is my old Casio pocket camera, has begun fading away, so we’re getting her a shiny new camera of her very own. Being a doting father, I picked up a pair of Wasabi NB-6L batteries (and a charger, it not costing much more for the package) so she’s never without electrons, and did the usual rundown test on all three batteries:
Canon NB-6L – 2014 OEM vs Wasabi
Fairly obviously, the Wasabi batteries aren’t first tier products, but they’re definitely better than that bottom-dollar crap from eBay.
A few months ago I fired the Thing-O-Matic, only to have it wake up dead. Not exactly dead, but spitting out checksum errors on simple G-Code files sent from Pronterface, which used to work just fine. Trying a bit of this-and-that to no avail, I proposed to The Mighty Thor that I could loan the carcass to Squidwrench, reanimate it with a less bizarre set of hardware and firmware than the much-hacked Makerbot menagerie under the hood, and use it as an exemplar in my 3D Printing classes.
Fortunately, that particular Thing-O-Matic has the most well-documented hardware evah…
Matt suggested an Azteeg X3 controller, because it has thermocouple inputs that match the existing sensor, Thor ordered one, and I tinkered up a first-pass version of Marlin that could read the inputs and twiddle the motors. The firmware is on Github, not that you’ll need it for anything you’re doing; more on that later.
Here’s the Official Doc for the microstepping jumpers hidden under the driver boards:
Azteeg X3 – microstep jumpers
That’s XYZE = 16 16 8 4, respectively, with a spare slot (and spare driver, not installed) for the second extruder it’ll never have.
The extruder’s Type K thermocouple connects to the TC1 port on the shield, exactly reversed from the way you see the test thermocouple there: the red lead is to the left, the yellow lead is to the right. If you get it backwards, the indicated temperature goes down when you touch the bead. The printer’s thermocouple has some backstory.
The 10 kΩ thermistor bead connects to the BED port on the main board and isn’t polarized. The Heated Build Platform has a bit of backstory, too.
The gutted TOM286 carcass with the MBI hardware off to the side:
TOM286 – gutted electronics bay
After a few sessions, it looked pretty cheerful again:
This is what you see when looking down through the acrylic baseplate:
Azteeg X3 – inside TOM286
The blurry silver rectangle off to the left is an aluminum channel glommed to bottom of the acrylic baseplate with silicone snot to eliminate a nasty mechanical resonance.
The thermal cutout circuitry isn’t wired in yet; the ATX power supply has its -Power-On pin hotwired to the adjacent ground pin for now. The X3 gets its power directly from the +12 V supply, so there doesn’t seem to be any way to power the X3 from the +5 V Standby ouput, deliver +12 V to the motors, and switch the supply through the X3’s ATX output pin.
The heaters work fine, the motors turn properly, and the extruder feeds molten plastic; all the motor calibrations seem to be pretty close. The first test object was a total botch, of course, but the printer’s parts seem to work OK again.
The main reason for taking the FC1002 frequency counter apart was to replace the failed quad-AA NiCd battery pack. Rather than buy new cells with tabs, I recycled some low-discharge “ready to use” NiMH cells from the heap. Back in 2009, they looked like this:
Tenergy RTU Pack A Tests – Aug 2009
Nowadays, they’re a bit less peppy:
Tenergy RTU – 2014-01 – loose cells
The red blooper shows that you can’t trust a smart fast charger to get the right answer; it concluded that pair was fully charged. After the discharge test and an overnight C/10 charge, they regained as much enthusiasm as they’ll ever have.
They have slightly less capacity than in 2009 and also a somewhat lower terminal voltage. That shouldn’t matter here, as the frequency meter has a power supply to take care of that problem.
Although I’ve sometimes been able to (quickly!) solder directly to ordinary AA cells, a trial run on a defunct RTU cell showed that wasn’t going to work on whatever variety of steel they used, no matter how much I scuffed it and despite using aggressive flux that normally blends silver solder onto stainless steel.
Fortunately, the top half of a four cell case fit exactly in the space available, so I used woven copper fabric tape inside the case to interconnect the cells, then lashed everything together with the obligatory Kapton tape:
FC1002 Frequency Counter – battery pack
That cracked faceplate isn’t the nicest thing to confront, but it’ll suffice until I get more motivation:
I did five minutes of standup comedy at yesterday’s MHV Lug meeting, pointing out some of the more interesting ways to compromise a PC when you have an infinite budget for development and consumables.
You don’t get my patter with the PDF (unless you had access to the room’s bugging hardware), but the links may come in handy in the unlikely event you haven’t been following the story closely.
If you have a security clearance or are in line for one, you probably shouldn’t click on the link, because it contains copies of pages from the leaked NSA catalog:
A discussion on the Makergear Google Group about a heated enclosure prompted me to run the numbers for cooling stepper motors with water, rather than fans and finned heatsinks.
The general idea comes from my measurements of the air-cooled heatsink stuck to a stepper’s end cap. The metal-to-metal conductivity works surprisingly well and reduces the case temperature to slightly over ambient with decent airflow through the heatsink; epoxying a cold plate to the end cap should work just as well. A NEMA 17 stepper case is 42.3 mm square, so a standard 40 mm square CPU cooling plate will fit almost exactly.
The question then becomes: how much water flow do you need to keep the motors cool?
Some numbers:
Water’s heat capacity is 4.2 J/g·K
1 J = 1 W·s, 1 W = 1 J/s
NEMA 17 motors dissipate about 5 W (13 W if you’re abusing them)
We’ll cool all four motors in parallel, for a total of 20 W
Allow a 5 K = 5 °C temperature rise in each cold plate
Rub them all together:
(20 J/s) / (5 K * (4.2 J/g·K)) = 0.95 g/s
For water, 1 g = 1 cc, so the total flow is 1 cc/s = 3600 cc/h = 3.6 liter/h, which, here in the US, works out to a scant 1 gallon/hour. It’s tough getting a pump that small and cheap flowmeters run around 0.5 liter/m…
If you don’t want a pump. put an aquarium up on a (sturdy) shelf and drain it through the cold plates. A cubic foot of water, all eight gallons and sixty-some-odd pounds of it, will last 8 hours, which should be enough for most printing projects.
If you want reliability, drain the coolers into a sump with a float switch (high = on), put another float switch (high = off) on the aquarium, and have the pump top up the aquarium. If the pump fails, your steppers stay cool for the next 8 hours. Heating the water about 5 °C during 8 hours won’t require active cooling.
Now, managing the hoses leading to the X axis stepper may be challenging, but a cable drag chain would control the rest of the wiring, too.
One of the battery packs powering the GPS+audio interface on our bikes has completely failed, with zero volts at the output and no charge indication. The other five chug along as well as can be expected:
Initial-brand DVD External Packs – 2013-11
The push-to-test button on Pack 4 has become increasingly erratic over the last few months, rendering the charge status LEDs mostly useless, so it has two curves: the lower capacity came directly from the bike, the higher hot off the charger.
For reference, here’s what they looked like in May 2012:
External Li-Ion packs – 2012-05
And right after they arrived:
Initial External Li-Ion packs
Given their nearly constant use and charge cycling, I’m impressed.
The trio of batteries I built for the Sony DSC-F505V two years ago faded away; that camera seems particularly hard on the batteries, perhaps because they’re two cells in parallel that don’t share well. Two of the three seem pretty well gone:
Sony NP-FS11 2011 Packs – 2013-11 tests
Back then, I bought 12 cells, built six into those batteries, and left six charged cells sitting in a bag. After rebuilding the two worst batteries with those new-old-stock cells, it seems they maintained a substantial fraction of their charge while resting in the cool and the dark:
Sony NP-FS11 2011 Cells – 2013 packs – 2013-11-24
However, the camera would regard them as discharged, because it infers charge state from voltage. Squinting at the curves, their condition after a few minutes is roughly equal to a new & freshly charged battery produces over on the right when it’s nearly discharged.
The other curves show the result after their first charge in two years: basically, full capacity. The fact that both pairs of curves come pretty close to overlaying means they’re still well matched.
Sony NP-FS11 batteries – rebuilt
The third cell isn’t up to their spec, but it’s close enough to not bother rebuilding right now: 1.2 vs 1.4 A·h.
The Kapton tape pull tabs work wonderfully well, as the rebuilt batteries fit the compartment rather more snugly than the un-hacked cases.
The Smell of Molten Projects in the Morning 