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.

Author: Ed

  • Sony HDR-AS30V vs. Lithium Ion 18650 Cells

    These items came near enough to produce an irresistible force:

    Sony HDR-AS30V vs 18650 cells - side view
    Sony HDR-AS30V vs 18650 cells – side view

    How can you look at that layout and not jump to the obvious conclusion?

    The front view suggests enough room for a stylin’ case:

    Sony HDR-AS30V vs 18650 cells - end view
    Sony HDR-AS30V vs 18650 cells – end view

    You’d need only one cell for the camera; I happened to have two in my hand when the attractive force hit.

    The camera is 24.5 ⌀ x 47 tall x 71.5 overall length (67.8 front-to-door-seating-plane).

    The ATK 18650 cells are 19 ⌀ x 69 long, with the overlong length due to the protection PCB stuck on the + end of the cylinder. You can get shorter unprotected cells for a bit less, which makes sense if you’re, say, Telsa Motors and building them into massive batteries; we mere mortals need all the help we can get to prevent what’s euphemistically called “venting with flame“.

    Although I like the idea of sliding the cell into a tubular housing with a removable end cap, it might make more sense to park the cell over the camera in a trough with leaf-spring contacts on each end and a lid that snaps over the top. That avoids threaded fittings, figuring out how to get an amp or so out of the removable end cap contact, and similar imponderables.

    I think it’s possible to drill a hole through the bottom of the camera at the rear of the battery compartment to pass a cable from a fake internal cell to the external cell. Some delicate probing will be in order.

    In round numbers, those 18650 cells allegedly have three times the actual capacity of the camera’s flat battery and cost about as much as the not-so-cheap knockoff camera cells I’ve been using.

  • J5 V2 Flashlight: Current Draw

    Just for fun, I measured the J5 V2 flashlight’s current, by the simple expedient of unscrewing the cap and bridging the battery-to-case-threads gap with a multimeter:

    J5 V2 Flashlight - negative cell terminal
    J5 V2 Flashlight – negative cell terminal

    The results:

    • High: 3 A
    • Medium: 1.5 A
    • Low: 0.7 A

    As nearly as I can tell, they’re connecting the 18650 cell directly across the LED for High and PWM-ing it down to 50% and 25%. The PWM frequency is low enough to be visible during eye saccades and flashlight motions.

    The flashlight knows how to do all five modes without its tail cap, so the controller + FET must live behind the LED. I can’t tell if the switch in the tail cap is just a dumb pushbutton (with, it seems, a surprising & ill-controlled resistance) or doing something clever with resistive levels (because the resistance varies with each push); at some point this thing will fail in an amusing manner and I’ll take it apart to find out.

    The High setting dissipates 11 W (!) that pushes the flashlight well beyond uncomfortably warm within five minutes, so that’s not a useful long-term setting. The little alien egg beside the LED melted into a puddle during those five minutes; at least it won’t be moving anywhere else.

    Setting it to Low = 25% PWM duty cycle = 0.7 A (average, sorta-kinda), a freshly charged 18650 cell lasts for about five hours down to 3.6 V, which is pretty close to the cell’s 3.4 A·h rating (kinda-sorta, ignoring the decreasing cell voltage, etc). That suggests Medium would last maybe two hours, tops, and there’s not enough heatsinking to discover how long High would last.

    After 8.5 hours the cell was down to 3.2 V and the LED was, as you’d expect, rather dim. You could click to High for more light, of course, trading off runtime for brightness.

    The square LED emitter array produces a square light pattern that’s not aligned with the flats on the body, so if you happened to be thinking of clamping a holder onto those flats, be prepared for some custom rotation to align the pattern with the outside world. That obviously doesn’t matter in a hand-held flashlight, but a bike headlight might look weird.

    The zoom slider goes from a focused square (at full extension) to a well-filled round disk (at minimum length) with a diameter about five times the square’s side. I think the smooth zoom motion comes from grease-on-O-ring viscosity rather than precision machining.

    The original back of the envelope data:

    J5 V2 Flashlight - current and runtime
    J5 V2 Flashlight – current and runtime

  • Mica Compression Capacitor: Unsolderable Pins

    The mica compression capacitors have a finish on the pins that turned out to be completely un-solderable:

    Mica compression capacitor - solder vs pin
    Mica compression capacitor – solder vs pin

    Some casual searching suggests this is a problem with sulfur contamination of the tin-lead solder layer. I can’t vouch for any of that, as the flat areas forming the capacitor seem to be silver-plated, but …

    After some flailing around, I completely disassembled the capacitor, applied 800 grit sandpaper to remove all of the solder / flux / corrosion / tarnish / surface plating from the pins, dabbed on some RMA flux, then applied a thin layer of solder to both sides. Fortunately, the capacitor could be disassembled; they don’t make ’em like that any more.

    The solder layers must be thin, because the slots in the ceramic base must pass two or three pins apiece: four or six solder layers add too much thickness. Solder-wick is my friend!

    For reference, the 700 pF side looks like this:

    Mica compression capacitor - 700 pF disassembled
    Mica compression capacitor – 700 pF disassembled

    The steel washer does not have a mica washer underneath (as does the washer on the 400 pF right side). The two grayish steel plates go on the top.

  • Insouciant Squirrel

    Squirrels spend most of their time on all fours and, when they do pop up for a look around, generally seem hunched forward, ready to drop-and-run.

    Not this critter:

    Squirrel leaning back
    Squirrel leaning back

    Definitely brandishing a big leaning ‘tude…

  • Improvised Repairs Done Wrong

    Mary’s relatives encountered this repair in a rental flat during Thanksgiving week:

    Door handle - hex head bolt
    Door handle – hex head bolt

    Don’t have a hex bolt with the right thread? No problem: just use a sheet-metal screw, perhaps with a self-drilling point:

    Door handle - metal screw
    Door handle – metal screw

    Those hex heads let you apply more torque with less risk of stabbing yourself in the palm, which strikes me as an all-around Good Thing. I prefer socket-head cap screws, myself, but I’ll admit they’re an acquired taste.

    I’d like to think I wouldn’t do that …

  • J5-V2 700 lm Flashlight: QC FAIL, Redux

    The inside of the replacement J5 V2 Tactical Flashlight doesn’t have quite as much dirt on the LED emitter, but it’s still pretty bad:

    J5-V2 Flashlight - LED crud - second unit
    J5-V2 Flashlight – LED crud – second unit

    The small white dingus at about 10 o’clock seems to be a plastic shred stuck on end to the emitter lens. Here’s a better look, rotated a quarter-turn counterclockwise:

    J5-V2 Flashlight - LED crud detail - second unit
    J5-V2 Flashlight – LED crud detail – second unit

    There’s also an alien egg glued to the heatsink beside the LED:

    J5-V2 Flashlight - random pellet - second unit
    J5-V2 Flashlight – random pellet – second unit

    I’m hoping it’s another random plastic blob.

    There’s no point in returning this one; it’ll suffice for my purposes. However, given two random samples, I’d say the J5 Tactical Flashlight factory, wherever it may be in China, is really filthy.

    I’d hoped that paying a bit more for a “tactical” flashlight, instead of going bottom dollar, would yield a better product. Maybe it did?

  • Monthly Science: Bottled Water Evaporation

    These emerged from a hidden corner of a basement shelf, where they’ve been sitting undisturbed for far too long:

    Bottled Water Evaporation
    Bottled Water Evaporation

    I’ve known for a while that the PETE plastic used for nearly all bottles isn’t completely waterproof, but never had occasion to measure the results.

    The laser-etched date code  on the bottles says they “expired” in late August 2012, so, assuming one year of shelf life, they’ve been quietly evaporating for five years.

    Sampling a few bottles shows a nearly uniform weight of 459 g. A drained bottles weighs 13 g, so let’s say the bottles now contain 445 g of water. They should start out with 500 g, although I’d be mildly surprised if it wasn’t a bit over that to prevent some dork from complaining about getting only 498 g.

    Rounding in all the right directions, losing 60 g during five years works out to a tidy 1 g/month in a basement room at 60% RH.

    The surface area of those wonderfully convoluted bottles might be 300 cm², so they lose 3 mg/cm²·month.

    They’re near enough to 0.10 mm thick, which I’m sure is a compromise between reducing weight (and, thus, plastic cost) and incurring messy failures during normal handling. The evaporation rate surely varies as an inverse exponential of thickness, but I’m not going there.

    I’m certain water bottlers know those numbers to several decimal places and can plot them versus all the interesting variables.

    Memo to Self: don’t lose track of the water bottles!