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: Oddities

Who’d’a thunk it?

  • Streaming Radio Player: OLED Garble

    Even in the dim light of dawn, it’s obvious slowing the SPI clock to 1 MHz didn’t quite solve the problem:

    RPi OLED display - garbled
    RPi OLED display – garbled

    The display started up fine, became encrypted during the next few hours, and remained garbled as the track information changed. This is almost certainly a bad SPI transfer trashing the OLED module’s control registers.

    Dropping the clock to the absolute minimum of 0.5 MHz didn’t help, either:

    serial = spi(device=0,port=0,bus_speed_hz=500000)
device = sh1106(serial)

    This particular display woke up blank after loading the new code, then worked OK after another reset. The other streamers lit up as expected on the first try, so the slower SPI isn’t making the situation instantly worse.

    Running the clock at 1 MHz definitely reduced the failure rate, which suggests it’s a glitchy thing.

    Good embedded systems practice suggests resetting the entire display from scratch every now and again, but my streamer code has no concept of elapsed time. Opening that particular can o’ worms would almost certainly result in an on-screen clock and I do not want to go there.

    I suppose I must get a new oscilloscope with SPI bus decoding to verify all the SPI setup and hold times …

  • Monthly Image: Red Sky in the Morning

    You can tell the day’s weather won’t be good when you see this:

    Red Sky in the Morning - 2018-02-07
    Red Sky in the Morning – 2018-02-07

    Taken just before the snow started …

    I wish I could run the snowblower up and down the driveway to preemptively level it at -5 inches, so the snowfall would end with almost bare asphalt.

    Long ago, they promised me heated driveways and sidewalks to eliminate snow shoveling, but it hasn’t worked out that way, either.

  • Stepper Motor Current Measurement Setup

    As part of installing the bar clamps, I packed away the Tek Hall effect current probes measuring the stepper winding currents:

    MPCNC Z Axis AB current probe - overview
    MPCNC Z Axis AB current probe – overview

    The hulking pistol is a Tektronix A6203 100 A probe, the little black pencil is a Tek A6302 20 A probe:

    MPCNC Z Axis AB current probe - detail
    MPCNC Z Axis AB current probe – detail

    The absurdity of measuring a 600 mA (peak!) current with a 100 A probe isn’t lost on me, but those things have become genuine eBay collectibles over the last few years.

    For low-frequency signals, you could probably get by with a Fluke i410 Hall effect current clamp.

    Yo, Eks, babes, remember me in your will … [grin]

  • Wouxun KG-UV3D: Enemy Action

    Once is happenstance, twice is coincidence, three times is enemy action:

    Wouxun KG-UV3D - failure 3
    Wouxun KG-UV3D – failure 3

    All of the (surviving) battery packs produce 9.0 to 9.2 V, a bit hotter than the pair of fully charged lithium cells the radio expects to see, but the first two radios lasted for six years under that abuse.

    This one failed after a few hours. It’s a new radio, but I’m willing to assume I killed the thing and will just eat the cost.

    I have no theories about what’s going on, but I must tweak my APRS interface to work with a Baofeng radio I have on the shelf.

    From now on, though, both radios will run from their stock battery packs.

    Maybe I’m just a slow learner.

  • Furiosa’s Home Away From Home

    You never know who or what you’ll meet on the road:

    Mad Max - Home Away From Home
    Mad Max – Home Away From Home

    A bit more detail:

    Mad Max - Home Away From Home - detail
    Mad Max – Home Away From Home – detail

    Maybe she’s on vacation?

    Spotted on one of our walks around the block.

  • Monthly Science: Wearable LED vs. Dead CR2032 Lithium Cell

    Eight months later, the dead CR2032 cell driving the “ruby” wearable LED has dropped to 2.15 V:

    Wearable LED - on window
    Wearable LED – on window

    It’s not a true red LED with a 1.5-ish V forward drop, but a white / blue LED with red phosphor or a red filter, with a forward drop well over 3 V.

    Against the sunlit backdrop from our kitchen window, the LED looks dark:

    Wearable LED - daylight
    Wearable LED – daylight

    Seen in a dim room, it’s still glowing:

    Wearable LED - dim light
    Wearable LED – dim light

    The current is now far below the 1 mA/div of my Tek A6302 Hall effect probe, so I have no way to measure the few microamps lighting the junction.

    The coarse grid outside the window is a swatch of deer netting we put up during feeder season to keep the birds from killing themselves on the glass.

  • Hawk vs. Squirrel Scuffle

    A light overnight snowfall revealed an early morning drama:

    Hawk vs squirrel scuffle - overview
    Hawk vs squirrel scuffle – overview

    I think a hawk stooped on a squirrel, perhaps launching from the utility pole by the garden, scuffled across the driveway to the right, and hauled breakfast off to a nearby tree:

    Hawk vs squirrel scuffle - approach
    Hawk vs squirrel scuffle – approach

    The driveway always shows many tracks, but the ones entering from the center-right don’t continue out the left:

    Hawk vs squirrel scuffle - tracks right
    Hawk vs squirrel scuffle – tracks right

    Another view:

    Hawk vs squirrel scuffle - tracks left
    Hawk vs squirrel scuffle – tracks left

    A pair of squirrel pups appeared in the last week. They’d make a good, easily carried hawk breakfast.

    Go, hawk, go!