Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
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.
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.
They’re rated at 600 mA·h, as are the much shorter 2/3 AA NiMH cells I also used for those phone packs:
Norelco T770 – rebuild
That’s a wrap of Kapton tape around the cells, plus a block of closed-cell foam to fill the cell holder. It’s not a high-stress environment, so this hack-job repair should work fine.
The trimmer’s charge / discharge cycle remains hostile to NiMH cells and I don’t expect a great lifetime from the new cells, either…
One of the batteries on the ancient Dell Inspiron 8100 laptop died completely and our Larval Engineer reports the other battery isn’t far behind; it gets her from outlet to outlet and not much more. Pursuant to that comment about harvesting reasonably good cells from dead batteries to build an extended-life external battery for the Canon SX230HS camera, I made a preliminary pack probe.
The label says it’s a 14.8 V battery, so you’d expect four 3.7 V lithium cells in series. The 3.8 A·h capacity suggests parallel cells:
Dell 75YUF battery – label
Indeed, peeling off the label shows four cells pairs in series:
Dell 75YUF battery – under label
The case joint seems firmly welded together and resisted simple attempts to crack it open. I might run a slitting saw around the edge, although I’ll probably just crunch it in the vise because the patient need not survive the operation.
A single cell should have a 1.9 A·h capacity, although in an awkward cylindrical form factor. The 3.5 A charging current would drop to 1.7 A for a (string of) single cells.
The Canon SX230HS uses a single 3.7 V, 1.1 A·h prismatic “battery”, which means replacing that with a single external cell wouldn’t be a major win; the size difference shows how much lithium energy storage tech has advanced in the last decade or so. A pair of cells in parallel would quadruple the runtime, which might be enough. Three in parallel would be fine, although that would require attention to matching their capacity; the nominal 5.2 A charging current (1.5 × 3.5 A) seems aggressive.
A long-forgotten toy emerged from the heap bearing a trio of corroded NiMH cells between the usual plated-steel contacts:
Corroded contacts – original
The toy wasn’t worth salvaging, but I extracted the contacts and applied Evapo-Rust to see what happened. After an overnight soak, some corrosion remained:
Corroded contacts – after Evapo-Rust
Scrubbing with a stainless-steel detail brush removed the flakes and left reasonably clean metal behind:
Corroded contacts – after brushing
Although it’s not beautiful, I think the contacts came out as well as one could expect. The longer contact plate has holes, thinned sections, and some corrosion inside the spring; I’d be mildly tempted to rebuilt the whole thing with some nickel shim stock and a new spring.
If I were salvaging the toy, I’d dab vinegar on the wiring to neutralize the creeping potassium hydroxide, rinse the whole thing with water, and clean out the case. Instead, it joined the consumer electronics recycling box with a thud…
The Smell of Molten Projects in the Morning 