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.

Category: Electronics Workbench

Electrical & Electronic gadgets

  • Crystal Properties

    Spent some Quality Shop Time measuring an assortment of crystals, some data from which will make up a Circuit Cellar column.

    And the raw numbers will come in handy one of these days, so here they are…

    12 MHz Asst HC-49/U Co+Cc/2 2Cc Fs BW Rs
    ECS 1 4.85 1.47 12.000162 787.5 40.1
    ECS 2 4.50 1.42 12.000150 725.0 40.1
    ECS 3 4.70 1.42 12.000325 1100.0 50.0 Rs out of range
    HC1 4 4.34 1.11 11.999000 600.0 36.0
    HC1 5 4.24 1.06 12.000137 537.5 36.9
    Sentry 6 5.14 0.96 12.000250 625.0 31.8 many spurs
    11.0592 MHz HC-49/U
    1 4.90 1.42 11.059275 562.5 9.3
    2 4.99 1.46 11.059112 575.0 14.7
    3 4.87 1.42 11.059275 512.5 9.6
    4 4.87 1.41 11.059125 550.0 10.0
    5 4.29 1.43 11.058935 750.0 18.1
    6 4.93 1.47 11.059000 537.5 10.7
    7 4.95 1.47 11.059200 525.0 8.1
    8 5.03 1.45 11.059037 575.0 11.1
    10 MHz HC-49/U spur +150 kHz
    1 2.57 1.36 9.997888 200.0 14.2
    2 2.61 1.30 9.997738 225.0 16.7
    3 2.75 1.30 9.997788 225.0 20.0
    4 2.67 1.30 9.997750 225.0 16.1
    5 2.75 1.26 9.997725 250.0 22.7
    6 2.69 1.27 9.997788 225.0 21.0
    7 2.69 1.26 9.997825 212.5 16.5 Circuit Cellar example
    8 2.69 1.22 9.997832 212.5 18.4
    9 2.72 1.24 9.997788 250.0 23.4
    10 2.68 1.20 9.997738 225.0 18.0
    18.43 MHz HC-49/US many spurs +10 +76 kHz
    1 3.86 1.33 18.432425 1.56 24.1
    2 3.79 1.22 18.432987 1.21 10.9
    3 3.93 1.39 18.432050 2.44 46.3
    4 3.97 1.40 18.431175 1.90 27.7
    5 3.89 1.33 18.431888 2.11 32.2
    6 3.92 1.39 18.430888 1.39 16.5
    7 3.99 1.35 18.431500 1.36 11.8
    8 3.97 1.35 18.431675 2.18 38.4
    9 3.95 1.31 18.430512 1.30 10.1
    10 4.04 1.50 18.431427 1.36 11.8

    The 18.43 MHz crystals are in the short /US cans with surprisingly high stray capacitance. Their bandwidths are in kHz and all over the map, as are the series resistances. Weird. Bad crystals? Bad technique?

    Capacitance measured with that fixture.

    Frequency & bandwidth from HP8591 spectrum analyzer with a fixture similar to the K8IQY design; the bandwidths seem to come in 12.5 Hz increments despite a (very narrow) 2 kHz span. The general process is there. Resistance measured from a cermet trimpot using a multimeter good for 0.1 Ω around 10 Ω.

    Crystal Test Fixture
    Crystal Test Fixture

    Useful equations, with column headings in boldface:

    • Lead-to-can capacitance for each lead: Cc = 2Cc / 2
    • Lead-to-lead capacitance: Co = Co+Cc/2 – Cc/2
    • Circuit Q: Q = Fs/BW
    • Circuit resistance: R = Rs + 25 (assuming 4:1 transformers)
    • Reactance XL = XC at series resonance: X = Q R
    • Motional inductance: Lm = X / (2 π Fs)
    • Motional capacitance: Cm = 1 / (2 π Fs X)
    • Parallel resonance Fp = Fs √(1 + (Cm / Co))

    More equations there.

    Memo to Self: Zero the capacitance fixture before critical measurements!

  • Generic Sony NP-FS11 Li-Ion Packs: Rebuild FTW!

    Herewith, the discharge test results for all the generic Sony NP-FS11 battery packs I have (click for a bigger image).

    Sony NP-FS11 Status - 2010-04
    Sony NP-FS11 Status – 2010-04

    The five mostly overlapping upper traces consist of:

    • Three packs (H, K, and L) rebuilt from the eBay junkers
    • F rebuilt from a deader in my collection
    • E is an older, no-name pack that just continues to work

    The rebuilt packs now have cells from batteryspace.com that are working fine: nominal capacity 600 mAh, actual around 1200 to 1400 for a parallel pair. It’s surprising to see a cell producing its rated capacity…

    The two lowest traces (G & I), plus the purple trace (J) are from the eBay source. The first two are obvious junk, but pack J is actually pretty good. The fact that it’s the best of six packs from that vendor tells you all you need to know about their QC.

    For those of you joining us via search engines, the rest of the story:

  • Li-Ion Battery Pack for the Bike Radios

    Battery Pack and Hacked Cable
    Battery Pack and Hacked Cable

    Finally got around to hacking PowerPoles into the coily cable from those Li-Ion packs, suitable for powering the amateur radio HT on my Tour Easy. The cable has surprisingly fat conductors, on the order of 22 AWG, that (when doubled over) half-filled the 30 A PowerPole terminals. I remembered to use the blue-and-black color code for 9 volt power on the second and third cables…

    The right-angle connector activates a switch that turns on the pack’s voltage regulator, which means that leaving the cable plugged in slowly discharges the battery. They self-discharge by about half in two weeks, which means that it’s not absolutely urgent to unplug the battery at every stop, but … I’d rather have an actual power switch.

    I also want to bypass that regulator, so as to get more voltage out of the pack. That may not be feasible, as I suspect they’re using the pass transistor as part of the over-current shutdown circuit, but it’ll be interesting to find out. So this is in the nature of a test to find out how well the lashup works before cracking the case.

    This view of the installed pack is looking down on the butt end of the bike, which is leaning against the Shelf O’ Crap in the garage.

    Battery on Tour Easy Rack
    Battery on Tour Easy Rack

    A four-inch length of adhesive-backed Genuine Velcro mates the battery to the rack, although I stuck both Velcro strips to some carpet tape in the hopes that’ll stick better than the OEM goo. Hooks on the bike and loops on the battery, which means the battery won’t affix itself to everything else in the universe while off the bike.

  • Generic Sony NP-FS11 Battery Packs: Surprising Contents Thereof

    So I dismantled the three junk packs I got from halfway around the world and rebuilt them with better-quality cells. Search for NP-FS11 and you’ll find the rest of the story.

    Some observations…

    These cases are the thinnest plastic that doesn’t actually break when you pick it up: to crack the case seam, you must push firmly. Two of the three packs were already cracked and the third yielded to a slight squeeze.

    What’s inside? Welly, welly, welly, what do we have here?

    DOA Battery Contents
    DOA Battery Contents

    The cells are labeled Sony Energytec, which ought to be a reputable brand name. Some possibilities:

    • Counterfeit cells
    • Quality test rejects

    I don’t know why you’d bother putting counterfeit cells inside a generic case; it’d be more profitable to sell a completely counterfeit battery with a fancy Sony label. So I’m guessing these came from a batch of cells that failed inspection and were miraculously saved from destruction.

    Battery Protection Circuit Board
    Battery Protection Circuit Board

    They have the usual protection circuit board on the top. What’s a bit tricky is that you must unsolder the three leads connecting to the case terminals before you can extract the cells. I unsoldered the strap from the negative terminal while I was at it; the positive lead is inaccessible beyond the black IC on the left.

    After that, it’s a straightforward rebuild.

  • Keeping Magnet Wire on the Spool

    Magnet wire wants to unspool itself, so it comes with a wrap of tape that eventually turns into a gummy layer. Rather than put new tape on the spool, gash a notch in the rim with a utility knife and capture the wire therein.

    Notched Wire Spool
    Notched Wire Spool

    If you’re really clever, you’ll angle the notch so the wire folds backwards and holds itself snug. If you’re not, well, there’s nobody going to notice having two opposing notches in the spool, right?

    They used to do this with thread and string, back in the old days when such stuff came on wooden spools, but it seems a lost art…

  • On Schematic Capture and PCB Layout Programs

    This useful comment thread showed up in relation to a post about a chainsaw repair, which would hide it from any rational collection of search terms. Here’s the thread in all its glory, as there doesn’t seem to be a way to move comments from one post to another.

    Feel free to continue the topic in the comments to this post…

    randomdreams

    Offtopic: have you ever used gEDA for schematic or pcb? I’m looking for something with reasonable abilities, and the crippled demo versions of orcad, eagle, and winqcad all look fairly crippled. I’ve zero use for autorouters and autoplacers (because they suck for analog design) but it’d be nice to have something that’s fairly usable for schematic and layout.

    Ed

    used gEDA for schematic or pcb?

    Nope. Every time I’ve looked at it, the status seems to be heartbreakingly close to being useful by someone who really doesn’t want to work around a morass of limitations. That’s becoming less true and maybe by now it’s practical… but I haven’t done a serious examination for maybe a year.

    I actually coughed up half a kilobuck for the Standard version of Eagle schematic & layout, as an autorouter doesn’t do much for the little bitty boards I build. Works fine, no complaints, but if I weren’t doing columns and suchlike, it’d be hard to justify.

    Neal H.

    andomdreams,

    I have used it for both a small project and a slightly bigger project,
    http://www.instructables.com/file/FPCHBLIG1M2BQTH (schematic)
    http://www.instructables.com/file/F6SYDYYG1M2KI8M (render of layout)

    It is quite usable, but the version that ships with most linux distros is pretty old, I had much better luck building it from source following the instructions on the gEDA homepage. The hardest part is creating symbols for the PCB tool, that is a little tricky to learn, but there are a lot of them pre-created for you on gedasymbols.org.

    randomdreams

    Thanks to both of you. I’ll probably give it a run. I currently spend much of my day creating symbols for Cadence, and I consider it impossible for any other part-creation process to be as painful or difficult as that. I’m more worried about general usability. Eagle’s the back-up plan.

    John Rehwinkel

    I still haven’t found a PCB layout program I like (and I’ve gotten tired of the truly primitive one I wrote 20 years ago). For schematics, I use DesignWorks Lite, which is apparently no longer offered (though DesignWorks Professional is still available).

    John Rehwinkel

    Ah, it is still offered (only $40), just not at the main Capilano site. The companion PCB layout program is Osmond ($200), which I keep meaning to try out. You can download the trial version at designworks4.com.

  • Monthly Aphorism: On Supplies

    • Never put a part back in the supply cabinet

    The Great Green, another excellent manager from my IBM days, mandated that very simple stockroom rule.

    He knew, even if we didn’t, that the next engineer would spend two days figuring out that the part you returned was defective, costing far more in the long run than just tossing the part.

    Of course, we never tossed the parts…