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

  • Brother PT-1090 Tape Cartridge Innards

    Mad Phil gave me his Brother PT-1090 labeler, which I’ve been using rather often of late. The white tape cartridge (the TZ flavor) ran out, giving me the opportunity to pry it apart:

    Brother P-Touch TZ tape cartridge - disassembled
    Brother P-Touch TZ tape cartridge – disassembled

    Surprisingly, a few small pins molded into the cover, plus a few obvious latches, hold it together without a trace of glue or thermal welding.

    A detail of the little factory that assembles the label from several parts:

    Brother P-Touch TZ tape cartridge - detail
    Brother P-Touch TZ tape cartridge – detail

    Colored paper tape unwinds from the lower right and the top plastic layer from the lower left. Tape with thermal dye unspools from the upper left, the printhead (in the printer) heat-transfers pixels to the plastic tape in the opening right of center along the top, and the roller at the top right joins the just-printed plastic layer to the slightly sticky front surface of the paper tape. The used imaging tape respools in the gray cylinder near the middle.

    For those concerned with privacy, that gray spool of used imaging tape contains everything you’ve printed in order:

    Brother P-Touch TZ tape cartridge - imaging tape
    Brother P-Touch TZ tape cartridge – imaging tape

    I thought the thermal dye was part of the transparent tape cover layer, but in retrospect that doesn’t make sense: the printed tape would turn black in hot environments like, say, your car. So the printer must transfer the dye from a separate tape.

    The knockoff “ESD” tape cartridges from Amazon seem to have a slightly different tape path, probably to work around Brother’s patents. I’ll pry one of those apart in due course.

  • American Optical Microscope Illuminator: New Bulb!

    A classic American Optical microscope illuminator emerged from a box, minus its bulb. Some rummaging turned up a reference for AO bulbs, so I knew I needed a GE 1460 prefocused bulb. Those seem to be a bit rare these days, with 1460X bulbs sharing the same base with a slightly different glass envelope shape. As nearly as I can tell, as long as the filament sits in the same location relative to the base, it’s all good. Five bucks and a few days brought a new 1460X bulb to the bench, a few drops of Caig DeoxIT slicked the holder’s rather gritty contact patches, and the new bulb fit perfectly:

    Microscope Illuminator - 1460X bulb - detail
    Microscope Illuminator – 1460X bulb – detail

    And it lit up just fine, too:

    Microscope Illuminator - 1460X bulb - turned on
    Microscope Illuminator – 1460X bulb – turned on

    That’s running at the lowest of three selectable voltages: 5, 6, and 7.5 VAC, respectively. Given that the bulb spec says 6.5 V (at 2.75 A!), you best have a spare bulb on hand if you need the highest setting. At the nominal 6.5 V, it’s good for 100 hours; 6 V should eke out many more hours.

    A generously articulated arm holds the illuminator for desk work:

    American Optical Model 651 Microscope Illuminator - on base
    American Optical Model 651 Microscope Illuminator – on base

    That long snout fits into the pair of holes in the arm of my stereo zoom microscope to cast a bright light directly on the subject. The LED ring light makes that less necessary than before, although sometimes distinct shadows help pick out the details:

    Microscope Illuminator Test
    Microscope Illuminator Test

    That’s the failed WS2812B LED from the Noval tube, which again shows I need a USB camera with better resolution …

    The data plate on the bottom of the illuminator, should someone need it:

    American Optical Model 651 Microscope Illuminator - data plate
    American Optical Model 651 Microscope Illuminator – data plate

    The optics cast an image of that white-hot filament out into space, so I think the diffuse active area of a white LED wouldn’t produce the same amount of light on the target. I have some Pirhana LEDs, though, so (when this bulb fails) I’ll see about that.

  • Discrete LED Aging

    We all know that LED brightness decreases with age. An exit sign in Vassar’s Skinner Hall shows what that looks like in real life:

    Exit Sign - LED aging
    Exit Sign – LED aging

    The LEDs on the other side of the sign look about the same: a few very bright spots, a few very dim ones, and a whole bunch in the middle.

    It’s hard to judge by eye, but the brightest LEDs look much more than a factor of two brighter than the dimmest ones.

    An LED with a 50,000 hour lifetime will have 50% of its initial brightness at EOL and a year has 8,766 hours, so the LEDs will reach half-brightness in a bit under six years. I think discrete LEDs went out of style around the turn of the millennium, so it’s three half-lives old: the dimmer LEDs must be around 1/8 brightness.

    In case of an actual emergency, just follow me out the door, OK?

  • Vacuum Tube LEDs: Another Knockoff Neopixel Failure

    The WS2812B controller in this knockoff Neopixel failed:

    Failed W2812B Ersatz Neopixel
    Failed W2812B Ersatz Neopixel

    It used to live in the Noval socket:

    Noval socket - red phase
    Noval socket – red phase

    As with the one atop the big incandescent bulb, it failed by emitting random flashes of primary colors. This time, the Octal and Duodecar sockets were downstream and I got to watch four randomly flashing RGB LEDs, which says the controller failed enough to corrupt the data stream, but not enough to make the downstream controllers regard it as completely invalid.

    I replaced it with another one, just like the other ones, and it’s been running happily ever since.

    Fairly obviously, cheap knockoff Neopixels aren’t a good deal; the strip and these PCB versions have racked up three or four (I’m losing track) out of less than a dozen deployed. I won’t hold the overtemperature failures against the strip versions, but, still …

  • Sony HDR-AS30V Camera: Power Requirement

    A recent ride got rained out after 27 minutes:

    Rain Riding - 2016-03-25
    Rain Riding – 2016-03-25

    We didn’t get much more than damp and planned the ride with a bail-out route home, so it was all good.

    The camera ran from STK Battery A, which had gone flat 37 minutes into a recent ride, so I popped it in the battery tester and drained the rest of its charge:

    Sony NP-BX1 - STK A 27 min vs full - 2016-03-25
    Sony NP-BX1 – STK A 27 min vs full – 2016-03-25

    The dotted section says it had 0.85 W·h remaining after 27 minutes. Hand-positioning a copy of that curve against the full charge and discharge curve says the camera required 2.8 W·h. Eyeballometrically averaging the voltage over the leading part of the curve as 3.8 V says the battery delivered 0.74 A·h = 2.8 W·h / 3.8 V, then dividing that by 27/60 says the camera draws 1.6 A. That’s less than the 2 A guesstimate from previous data, but I don’t trust any of this for more than about one significant figure.

    Running the camera for 27 minutes requires 2.8 W·h, meaning 37 minutes should require 3.8 W·h. The curve says that’s the capacity at the 2.8 V test cutoff, suggesting the camera also has a 2.8 V cutoff.

    Looking at the discharge curves from yesterday’s post:

    Sony NP-BX1 - STK ABCD - 2015-11-03 vs 2016-03-24
    Sony NP-BX1 – STK ABCD – 2015-11-03 vs 2016-03-24

    If all that hangs together, the C and D batteries should run the camera for just slightly longer than the A battery, but that doesn’t seem to be the actual result: they’re much better than that.

    More rides are indicated …

  • Monthly Science: Five Months of Lithium Cell Wear

    I’ve marched the four STK NP-BX1 lithium batteries through the Sony HDR-AS30V camera in constant rotation since last November. The A battery drained 35 minutes into an ordinary ride on a pleasant day, so charging and measuring the entire set seemed in order:

    Sony NP-BX1 - STK ABCD - 2015-11-03 vs 2016-03-24
    Sony NP-BX1 – STK ABCD – 2015-11-03 vs 2016-03-24

    The dotted curves come from early November 2015, when the batteries were fresh & new, and the solid curves represent their current performance.

    It’s been a mild winter, so we’ve done perhaps 75 rides during the last 150-ish days. That means each battery has experienced under 20 discharge cycles, which ought not make much difference.

    The B battery started out weak and hasn’t gotten any better; I routinely change that one halfway into our longer rides.

    The A battery started marginally weaker than C and D, but has definitely lost its edge: the voltage depression at the knee of the curve might account for the early shutdown.

    Figuring that the camera dissipates 2.2 W, a battery that fails after 35 minutes has a capacity of 1.3 W·h. That suggests a cutoff voltage around 3.8 V, which makes absolutely no sense whatsoever, because the C and D batteries deliver at least 75 minutes = 2.8 W·h along similar voltage curves.

    The B battery goes in the recycle heap and we’ll see how the A battery behaves on another ride…

  • Raspberry Pi Power Heartbeat LED

    While looking for something else, I found a reference to the /boot/overlays/README file, wherein it is written:

            act_led_trigger         Choose which activity the LED tracks.
                                Use "heartbeat" for a nice load indicator.
                                (default "mmc")

        act_led_activelow       Set to "on" to invert the sense of the LED
                                (default "off")

        act_led_gpio            Set which GPIO to use for the activity LED
                                (in case you want to connect it to an external
                                device)
                                (default "16" on a non-Plus board, "47" on a
                                Plus or Pi 2)

... snippage ...

        pwr_led_trigger
        pwr_led_activelow
        pwr_led_gpio
                                As for act_led_*, but using the PWR LED.
                                Not available on Model A/B boards.

    Although the power LED isn’t (easily) visible through the Canakit cases I’m using (it’s under the barely visible hole in front of the small hole near the hacked RUN connector), turning it into a heartbeat pulse distinguishes the CPU’s “running” and “halted” states; whether it will also distinguish “crashed” is up for grabs.

    It’s not at all clear what other choices you have.

    To enable heartbeating, add this to /boot/config.txt:

    # turn power LED into heartbeat
dtparam=pwr_led_trigger=heartbeat
#

    I expected a simple 50% duty cycle heartbeat, but it’s an annoying double blink: long off / on / off / on / long off. Fortunately, it still isn’t (easily) visible …

    While you have that file open, reduce the GPU memory to the absolute minimum for headless operation:

    # minimal GPU memory for headless operation
gpu_mem=16
#

    Some further ideas, including a way to turn off the HDMI interface.