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

  • Astable Multivibrator Blinkies: Radome Attachment

    Ping-Pong ball radomes tend to fall off their perches at the slightest touch:

    RGB LED - radome test
    RGB LED – radome test

    Because I planned to take my collection along to HV Open’s Mad Science Fair, I finally used a Round Tuit for some adhesive action.

    The general plan was to punch a ring from double-sided tape, thusly:

    Astable - Radome adhesive - poor surface
    Astable – Radome adhesive – poor surface

    The OD required touching up the edge of a brass tube punch I’d made a while ago:

    Astable - Radome adhesive - punch sharpening
    Astable – Radome adhesive – punch sharpening

    It worked exactly as expected:

    Astable - Radome adhesive - punching
    Astable – Radome adhesive – punching

    Unfortunately, the 3D printed spider’s “spherical” socket has such a rough surface that the adhesive had too few contact points to hold the ball in place.

    My fallback has become 3M outdoor-rated double-stick foam tape, so:

    Astable - Radome adhesive - 3M foam tape
    Astable – Radome adhesive – 3M foam tape

    This leaves a small black ring visible between ball and socket. Recessing the foam tape by half its thickness should improve its ahem optics, although it’s probably not worth the effort with black PETG.

  • Dell UG679 Lithium Battery Teardown

    The battery pack on my ancient Dell E1405 laptop finally died, so I tore it apart to see what horrors might lurk within:

    Dell UG679 Lithium Battery - teardown
    Dell UG679 Lithium Battery – teardown

    The case snaps apart without too much effort, although the delicate single-use latches won’t survive the operation. These certainly didn’t, which didn’t bother me at all, as I already had a replacement battery on order.

    One of the cells (in the front) seems to have leaked ever so slightly inside its wrapper:

    Dell UG679 Lithium Battery - leaky cell
    Dell UG679 Lithium Battery – leaky cell

    The three cells in that 3P section seem to have failed open: they pass no current at all.

    The other pair of 3P slices, charged at 4.2 V with a 700 mA current limit until the current dropped under 10 mA, still have some life:

    Dell UG679 3P sections
    Dell UG679 3P sections

    Perhaps recycling individual cells into LED glowies would be nice, as they have enough capacity remaining to run an Arduino for quite a while, and a 1S USB charger would make for a self-contained package.

  • Algorithmic Art

    This evening I’ll be showing off my Algorithmic Art at the HV Open Mad Science Fair.

    There’ll be glowing glassware:

    Vacuum Tube LEDs - halogen lamp - purple phase
    Vacuum Tube LEDs – halogen lamp – purple phase

    Ancient electronics with modern hardware:

    21HB5A - Guilloche platter
    21HB5A – Guilloche platter

    Blinking LEDs atop Brutalist analog electronics:

    Astable RGB LED - green phase
    Astable RGB LED – green phase

    A classic HP 7475A plotter hammering math onto paper from a Raspberry Pi running Chiplotle:

    HP 7475A Plotter - LED paper illumination
    HP 7475A Plotter – LED paper illumination

    Some take-home art:

    Superformula Plots - A-size paper
    Superformula Plots – A-size paper

    And, as always, a good time will be had by all!

  • KEDSUM LED Shop Lights: Cheapnification Thereof

    As the basement’s fluorescent fixtures and lamps gradually die, I’ve been rewiring the fixtures for LED tubes, all bought from KEDSUM through Amazon. The first few batches looked like this:

    Kedsum - good LED lamp
    Kedsum – good LED lamp

    The most recent two batches seem cheapnified:

    Kedsum - poor LED lamp
    Kedsum – poor LED lamp

    The tubes show similar changes, going from a stylin’ version to a simple cylindrical cap:

    Kedsum vs Kedsun - tube end caps
    Kedsum vs Kedsun – tube end caps

    The most recent carton label might lead you to think they’re counterfeits, but it could just be a simple typo:

    Kedsum vs Kedsun - LED lamp carton
    Kedsum vs Kedsun – LED lamp carton

    There’s absolutely no way to tell what you’re going to get from any vendor on Amazon (or anywhere else, for that matter), so there’s no point in returning them, but I’d hoped buying “the same thing” from “the same seller” would produce a consistent result.

  • Ooma Telo 2: Speaker FAIL

    The tiny voice inside our Ooma Telo 2 box died, although the VOIP phone service continued to work fine. A bit of searching showed the speaker seems to be the weak link.

    Well, I can fix that.

    Start by prying the recessed top panel off the case:

    Ooma Telo 2 - upper case latches
    Ooma Telo 2 – upper case latches

    Remove the circuit board to expose the tiny speaker, taking care not to rip the tiny wires out of the tiny connector:

    Ooma Telo 2 - OEM speaker to PCB
    Ooma Telo 2 – OEM speaker to PCB

    You can’t measure a dead speaker, but it seems to be an 8 Ω unit.

    The speaker sits in a rubber surround, with a foam rubber cushion against the PCB, tucked into a walled garden stiffening the case:

    Ooma Telo 2 - speaker port
    Ooma Telo 2 – speaker port

    I don’t happen to have a tiny 8 Ω speaker, but I do have a bunch of small speakers (Update: 28 mm OD), so I bulldozed those walls with a flush cutting pliers and a bit of cussing to make room:

    Ooma Telo 2 - modified speaker port
    Ooma Telo 2 – modified speaker port

    Nibble an adapter ring to match the rim of the new speaker, thereby routing the sound out those little holes, and hot-melt glue it in place:

    Ooma Telo 2 - speaker adapter
    Ooma Telo 2 – speaker adapter

    Hot-melt glue the new speaker in place atop the adapter, taking care to fill all the edges / cracks / crevices below it with an impenetrable wall of glop:

    Ooma Telo 2 - replacement speaker installed
    Ooma Telo 2 – replacement speaker installed

    The sealing part turns out to be critical with these little speakers, because a leak from front to back will pretty much cancel all the sound from the cone.

    Cut the wires off the old speaker, affix to the new one, replace the PCB, snap the case lid in place, and it sounds better than new.

    Millions of transistors in those ICs, but Ooma can’t spec a good speaker? Maybe they should have used a bigger speaker to begin with; ya never know.

  • Dell U2711 Monitor: FAIL

    My landscape monitor, a six-year-old Dell U2711, died after a few days of flickering and failure-to-start. As you’d expect with any old electronics, particularly from Dell, it’s the electrolytic caps:

    Dell U2711 Monitor - failed caps
    Dell U2711 Monitor – failed caps

    All of the black-cased caps on the board had bulged cases:

    Dell U2711 Monitor - failed FOAI cap - detail
    Dell U2711 Monitor – failed FOAI cap – detail

    They’re (allegedly) made by FOAI, for whatever that’s worth.

    They’re not really capacitors any more:

    Dell U2711 Monitor - 100 uF 5 ohm cap
    Dell U2711 Monitor – 100 uF 5 ohm cap

    I replaced all of them with cheap eBay caps to no avail. Spot-checking the other (“brown”) caps on the logic board showed they were still good, but the power supply board is firmly glued in place and I can’t get to the HV cap.

    A new monitor arrived two days later and it’s all good again.

  • Transistor Leads vs. Antistatic Foam

    Why you shouldn’t use antistatic foam for long-term storage:

    Anti-static foam - decades of corrosion
    Anti-static foam – decades of corrosion

    The lump emerged from Mad Phil’s parts stash, now residing under a bench at Squidwrench. The 952 date code on the HEP802 JFET suggests he tucked it in around 1980; you’re looking at nigh onto four decades of corrosion.

    Memo to Self: use it or lose it!