Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
A bit over two years ago, those six 9 V 5.4 A·h lithium packs delivered around 4.5 A·h. They’ve been charged and discharged, run down until their undervoltage lockout tripped, severely jounced and bounced, and they still deliver about 4 A·h at 500 mA!
External Li-Ion packs – 2012-05
That’s a Good Thing, because I haven’t seen anything like those packs since then…
Never did get around to installing a cutoff switch, as we ride often enough that the penalty for not pulling the plug gets lost in normal use. The Wouxun KG-UV3D seems perfectly happy with 9 V delivered to its battery terminals, providing little motivation to hack into the battery case for a direct tap to the 7.4 V from the cells.
The relatively low capacity at 100 mA (black) shows that the boost converter isn’t particularly efficient; the discharge time is long enough that power loss in the booster outweighs the cell’s higher capacity at lower loads.
Surprisingly, the voltage drops to 4.5 V at 500 mA, which is what you should get from a typical USB port. If the device you’re charging expects the nominal 5 V at 500 mA, it will be sorely disappointed. Admittedly, that’s only 10% low, but …
The booster produces only 4.0 V at 1 A, with odd bumps as the cell discharges. Huh?
I know for a fact that my 1.8 A @ 5.0 V Kindle Fire doesn’t even notice it’s plugged into the Powermonkey. The voltage is probably too low to trigger the “External Power, Ahoy!” signal.
Bottom line: it’s not clear this thing actually works for contemporary devices. Maybe newer Powermonkey products behave better?
Here’s a great example of painting yourself into a corner…
Back in the day, I made a voice-only interface that adapted a helmet-mounted electret mic and earbud to an ICOM IC-Z1A HT. A pair of those let us talk companionably as we rode along.
Along comes our daughter, with her shiny-new Technician amateur radio license. I took an early version of the Z1A interface board, force-fitted it into an early version of the machined case that lacked a top, acquired an ICOM W32A HT and another TT3+, did some tweakage, and defined the result as Good Enough. Time passes, she’s promoted to Larval Engineer, goes off to college, and leaves the bike behind (a faired Tour Easy is ill-suited to being left out in the rain and is not a dorm-room-friendly bike).
Knowing that the Z1A on my bike is failing, I get a Wouxun KG-UV3D HT and modify the Z1A interface to match. Then I build an interface PCB for the KG-UV3D, conjure up a nice case (which is why I bought a 3D printer), chop the TT3+ out of the W32A lashup, put everything together, and it’s all good.
Here’s the carcass of the W32A interface in its half-case:
W32A PCB in case
Whereupon our Larval Engineer returns from college and once again needs a radio for her bike. At that point:
The W32A interface now lacks its TT3+.
The W32A PCB doesn’t fit in the Z1A case
The Z1A interface that would fit the W32A radio has the KG-UV3D modifications.
The Z1A radio has failed completely; it no longer even turns on.
Some alternatives:
Get another KG-UV3D, build another interface PCB + case, make it work
Transplant the TT3+ back to the W32A interface
Undo the KG-UV3D mods from the Z1A interface, put it on the W32A
Given that she’s going to vanish in another three months, tops, Choice 1 is out. Although the transplant in Choice 2 seems straightforward, it requires tedious soldering and produces an interface in a partial case.
So Choice 3 it is…
The Z1A board with the KG-UV3D modifications started out like this:
Z1A PCB modified for Wouxun KG-UV3D
Un-modified again and back in its machined case:
Z1A board minus mods – milled case
Buttoned up and ready to roll:
Z1A board on W32A – ferrite core
I put a clamp-on ferrite tumor around the GPS receiver cable to keep RF out of the TT3+, which seems quite sensitive to RFI; the poor thing locked up quite dependably on the bench with 5 W into a long rubber duck antenna, but not into a dummy load. The mobile antenna sits relatively far from the radio on the bike, but I think the TT3+ had problems in the early KG-UV3D lashup.
The TT3 audio level will probably require adjustment, as I’d cranked it up for the KG-UV3D, but that will require some on-the-air testing. Ditto for mic level.
When I get a KG-UV3D for Mary’s bike, I’ll buy two radios and build two interfaces, so as to finally have a working radio + interface on the shelf.
I’m mildly tempted by the new Yaesu VX-8GR, but that’s over $350 for a radio that also requires a new interface board design, a new case design, a new set of adapters, and other odds&ends. Not to mention that the radio’s built-in GPS antenna would live at the bottom of the seat frame beside the wheel and below my shoulder. I suppose I could conjure up an entirely new radio mount, but … the deterrents seem overwhelming.
Various versions of the schematics & PCB layouts for all those boards, plus solid models for the 3D printed case, are scattered here & there on other posts.
While doing something else, I rediscovered the fact that common 5 gallon plastic bucket lids have an O-ring gasket that seals against the top of the bucket. Some seals are hollow tubes, some are solid rods:
5 gallon can lid gaskets
The white O-ring has about the right consistency to serve as a quilting pin cap, along the lines of those 3D printed and silicone rubber filled cylinders. Although the rubber / plastic stuff isn’t quite as squishy as silicone snot, it holds the pin point firmly without much of a push.
Chopping the O-ring into 10 mm sections produced another small box of prototypes:
Lid gaskets as pin caps
Garden planting season remains in full effect, shoving all quilting projects to the back burner and delaying the evaluation phase of the project…
The general idea is to mention the things you need to know so you don’t kill your Arduino while fiddling around with the software side of the project.
It’s a rather dense collection of facts & figures and I expect a whole bunch of Q&A activity… which should result in a better Survival Guide the next time around.
Quite some time ago I got a Powermonkey Explorer set (the one with a solar panel charger) at a substantial closeout discount. After the marketspeak dissipates, it’s a single lithium-ion cell with a boost regulator and USB charger inside a screaming yellow case (the new ones seem more subdued) that’s somewhat water resistant, along with a kit of adapters for various widgets & phones. It stopped charging from the solar panel or a USB port, which suggested that I had little to lose by cracking it open.
It’s an odd shape, but grabbing it across the equator and applying gentle pressure cracked one side:
Cracking Powermonkey case
Wedging a screwdriver in the opening and twisting a bit freed the other side:
Enlarging Powermonkey case crack
Then it was just a matter of pulling gently to expose the cell & circuitry within:
Powermonkey interior
That seems to be a standard 18650, presumably similar to that 2.2 A·h cell.
I didn’t find anything obviously wrong, so I buttoned it up with screaming yellow silicone tape, put it on its wall-wart charger for a bit, and now it’s all good again: a shining example of a laying-on-of-hands repair.
The single button has much more travel than it should, so I think the internal foam supports have lost their springiness.
Mary uses an ancient paring knife (that, back in the day, my father had sharpened beyond all reason) to harvest garden veggies, which called for a scabbard to protect the blade, the bike pack, and the fingers.
I snagged a random block of acrylic from the heap, straightened the long sides, milled a channel just wide and thick enough for the blade down the middle, then added small recesses at the right end for the knife’s haft:
Garden knife scabbard – main block
The cover is an acrylic sheet, solvent-glued and clamped in place:
Garden knife scabbard – clamping cover
The cover exposes about 1/4 inch of channel so she can lay the point in place, rather than precisely aligning the point with the slot. I suppose I should have used gray acrylic to provide some contrast; maybe we’ll add a snippet of tape.
Then mill four sides flat, break the edges & corners with a file, and it’s all good (in a blocky kind of way):
Garden knife scabbard
The blade has become sufficiently bent over the years that simple friction holds it in the slot. It’s open on both ends so she can flush out the inevitable dirt.
I was going to engrave her name on the back, but came to my senses just in time…
The Smell of Molten Projects in the Morning 