Advertisements

Archive for category Electronics Workbench

Vacuum Tube LEDs: Failed Tape, Failed USB Cable

While packing the vacuum tube LEDs for the HV Open Mad Science Fair, I noticed the knockoff Arduino Nano inside one had come unstuck from the base. It seems the double-stick foam tape I’d used had lost its sticky:

Vacuum Tube LEDs - unstuck foam tape
Vacuum Tube LEDs – unstuck foam tape

Replacing it with my now-standard black 3M outdoor rated tape ought to solve the problem forever more.

For whatever it’s worth, the SK6812 RGBW LEDs have had exactly zero failures in the last two years or so; I finally turned off the test fixture.

Before reassembling the light, I plugged the USB cable into the bench supply and watched the Nano reset erratically. Careful poking showed the USB cable was intermittent, so I carved it up:

Failed USB cable - autopsy
Failed USB cable – autopsy

As far as I can tell, the black wire (supply common) was cut mostly all the way through, with just a few strands remaining, before I peeled the insulation back.

A closer look at the solder joints doesn’t inspire much confidence in their QC:

Failed USB cable - solder joints
Failed USB cable – solder joints

If those pads tarnished along with their solder blobs, the overmolded plastic isn’t the right stuff for the job. If they started life like that … ick.

I must up my cable spend, although I have no confidence doing so will improve the quality.

Advertisements

Leave a comment

Exhibit Hand-Out Cards: QR Version

I’ve finally had it beaten into my head: any public exhibition requires paper handouts, if only for younger folks who are too shy to ask questions. Paper may seem obsolete, but it serves as a physical reminder long after the sensory overload of a busy event fades away.

Hence, I made up cards describing my exhibits at the HV Open Mad Science Fair, each sporting a QR code aimed at far more background information than anybody should care about:

Mad Science Fair - handout cards
Mad Science Fair – handout cards

The QR codes come from one-liners:

qrencode https://softsolder.com/?s=dso150 -s 5 -d 300 -o dso150.png

So, go ahead, shoot ’em with your phone:

  • Blog search QR code: astable
  • Blog search QR code: bowl-of-fire
  • Blog search QR code: dso150
  • Blog search QR code: halogen
  • Blog search QR code: hp7475a
  • Blog search QR code: tubes

Memo to Self: put the cards in the Big Box o’ Stuff the night before.

,

Leave a comment

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.

2 Comments

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.

2 Comments

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!

,

1 Comment

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.

,

6 Comments

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, 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.

,

Leave a comment