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

  • Wouxun KG-UV3D Plug Plate

    Based on those measurements that suggest spacing the plugs at 11.5 mm on center, I tweaked that parameter in the source code there and printed another one, just like the other one. Actually, I printed four of the fool things this time:

    Wouxun plug plates - 11.5 mm fixture
    Wouxun plug plates – 11.5 mm fixture

    With the plugs in the gluing fixture and the fixture in the vise, a ring of epoxy around the threaded sides holds them in place:

    Wouxun plug plate - wired
    Wouxun plug plate – wired

    A trial fit in the Wouxun KG-UV3D shows that the jacks prefer the 11.2 mm spacing I measured on the Wouxun headset, but they’ll accept plugs on 11.5 mm centers. I don’t know if that’s a real specification difference, a manufacturing tolerance, or what.

    FWIW, I’ve been using snippets of that cable forever, because it’s perfect for this application: two unshielded conductors and three more inside a braid, supple as a snake. It’s surplus, of course, with a gorgeous push-lock plug (and the jack!) on one end that must have cost a fortune… and which I’ll never to use for anything. Got two of them, just in case.

    Mushing an epoxy putty turd on the top anchors everything in place and protects the wires:

    Wouxun plug plate - epoxy cap
    Wouxun plug plate – epoxy cap

    In point of fact, the cable insulation isn’t anchored inside the blob and a minor tug could pull it loose. There will be a bit of slack at the case to allow for unlatching it from the radio, but the lashup will spend its entire life inside a snug pouch, so it shouldn’t come to any harm. We shall see.

  • Kenwood / Wouxun Headset Jack Spacing

    Wouxun plug mounting plate - overview
    Wouxun plug mounting plate – overview

    Try as I might, I cannot uncover a definitive answer to this simple question: What’s the center-to-center spacing of the mic and earphone jacks on the side of Kenwood and Wouxun HTs?

    The usual searches produce answers like 11 and 12 mm, both of which are obviously wrong, as can be determined eyeballometrically just by holding a scale against the plugs.

    Based on measurements I made on a Wouxun headset, the yellow plug mounting plate put the plugs on 11.2 mm centers and they fit into the KG-UV3D radio; it’s been working fine ever since.

    However, having just measured a speaker/mic and a headset, both from Kenwood, I come up with 11.5 mm. Frankly, I trust the Kenwood hardware a bit more: the plugs seem more rugged and the overall production values are higher.

    The calculation is simple: measure the pin diameters, then subtract half their sum from the outside distance across the pins. Cross-check by adding half the sum to the inside distance between the pins, which should give the same answer. It helps if the pins are actually round.

    The jacks in the Kenwood and Wouxun radios have enough compliance to accept either a Wouxun or a Kenwood headset plug without complaint. Maybe it doesn’t matter?

    Despite that, I made another gluing fixture with 11.5 mm spacing:

    Plug alignment plate - 11.5 mm spacing
    Plug alignment plate – 11.5 mm spacing

    Those are 0.1 inch grids; it’s a little bitty block of smoke-gray polycarbonate from the scrap heap. The plugs are nominally 3.5 mm (which is not 1/8 inch in this universe) and 2.5 mm, with clearance drills #28 and #39.

    Then I tried poking those 11.2 mm spaced plugs, now firmly epoxied in place in the yellow plate, and guess what: they don’t fit, no how no way. That’s not surprising, because there’s no compliance on either side of the joint and the plugs aren’t on the right centers for the fixture. Makes for a good No-Go gauge, I suppose.

    However, I think I’ll tweak the solid model spacing to 11.5 mm and run off another plug mounting plate for the next radio.

    FWIW, our ICOM IC-Z1A HTs use a sensible 10.0 mm spacing and that old fixture worked fine.

  • HT GPS+Voice: Battery Contacts

    For this version of the contacts (the old version is there) that make the GPS interface look like a standard Wouxun lithium battery, I left a bit more of the slot on the brass screw heads and increased the recess depth to compensate:

    HT-GPS Case - Battery contacts
    HT-GPS Case – Battery contacts

    The nuts all have fancy nickel plating, with washers & ring lugs silver-soldered in place:

    HT-GPS PCB - battery contact parts
    HT-GPS PCB – battery contact parts

    The trial fit looks OK:

    HT-GPS Case - PCB and battery contacts - end view
    HT-GPS Case – PCB and battery contacts – end view

    I even found the cutest little flat 1/4 inch wrench that fits 4-40 nuts, so I can do a better job of crunching the PCB between the nuts. That excess screw length has got to go, too…

  • HT GPS+Voice Circuitry: Bare PCB

    Drilling the PCB went fine, as did the etching & silver plating:

    PCB with edge wrap - front
    PCB with edge wrap – front

    The rear side has a fine ground plane:

    PCB with edge wrap - rear
    PCB with edge wrap – rear

    The small spots scattered over the rear mark vias that stitch the front and back planes together; lacking plated-through holes, I solder nippets of 24 AWG wires to both sides. The wrinkly edge comes from solder on the copper foil binding the entire perimeter.

    While I have no hard evidence that all of the fuss & bother matters, the most recent version of this circuit is the quietest yet: the machine noise from the TinyTrak3+ that plagued the first iteration has pretty much vanished.

    I’ll grant you that the silver plating doesn’t look very silvery in these pix, but it’s quite different from the bare copper in person. Here’s the front just after rubbing it in with a vigorous circular motion:

    HT-GPS PCB - raw plated - top
    HT-GPS PCB – raw plated – top

  • Panasonic CR123A Lithium Cell Capacity

    Picked up 25 Panasonic CR123A (more properly, CR17345) cells from the usual eBay supplier and put one to the test:

    Panasonic CR123A _ CR17345
    Panasonic CR123A _ CR17345

    Somewhat to my surprise, it delivers pretty nearly its full rated capacity at 400 mA discharge. It’d do even better at its 20 mA (!) rated current, of course, but I wasn’t up for a lengthy test…

    Yes, the nominal capacity spec is at 20 mA (C/77) discharge: one LED worth of current. Even the pulsed spec is only 900 mA at 10% over 30 seconds, which says a flashlight really puts the screws to the poor things…

  • USB Wire Color Code: Nobody Will Ever Notice

    A USB cable carries the analog mic and earbud audio for our bike helmets; the connectors are cheap, durable, and separate easily. I cut a 2 m “USB extender” cable (which, according to the USB guidelines, isn’t supposed to exist) near the A male connector, then wire that part to the helmet and the A female part to the GPS+voice board.

    The latest USB extender cable included a surprise:

    USB cable with yellow wire
    USB cable with yellow wire

    According to Wikipedia, there’s a standard color code for the wiring inside USB cables and yellow isn’t in the list. For this manufacturer, it seems that yellow is the new red.

    In previous USB extenders the red / black wires were a slightly larger gauge than the green / white data pair, but in this cable they’re not. That might matter if one expected the cable to carry, oh, let’s say an amp of battery charging current.

  • ThinkPad 560Z BIOS Battery Replacement

    Quite some time ago I picked up a trio of IBM Thinkpad 560Z laptops from the usual eBay suppliers as part of a DDJ column project. One turned into a digital picture frame, our Larval Engineer has another (because it was maxed out with 128 MB of RAM), and I just fired up the third (96 MB!) to discover whether it could serve as a text-only terminal without too much trouble.

    Alas, the BIOS battery was dead. I’d replaced the dead OEM cell some years back with a (surplus) lithium cell that’s a bit too small, so it only lasted a few years rather than a decade, but the cells were on the shelf. Soooo, I put in another one, just like the other one:

    Thinkpad 560Z BIOS battery
    Thinkpad 560Z BIOS battery

    After nudging the date & time into the current millennium, it then failed to boot Ubuntu 8.04: evidently the mighty 4 GB CompactFlash drive (jammed into a CF-to-IDE adapter) has bit rot.

    It’s a prime candidate for the text-only version of Tiny Core Linux, except that a 560Z can’t boot from either USB or CD-ROM, which means getting the files on the “hard drive” requires extraordinary fiddling. Drat!

    FWIW, when this battery fails, I think the (empty) main battery compartment has room for a CR123A cell that should outlast the rest of the hardware. I could blow two bucks on a replacement from eBay, but what fun is that?