LED-ified Halogen Desk Lamp: DC LED Driver

Feeding half-wave rectified 12 V AC into the 4 W LED lamp I hung on the end of the halogen desk lamp worked at human scale, but produced dark bars across images made with my Pixel phones. Having solved that problem for the LED lighting on Mary’s sewing machines, I replaced the OEM transformer with a 12 VDC power supply:

LED Desk Lamp - Driver installed
LED Desk Lamp – Driver installed

The steel lump inside the base is the OEM weight that, in addition to two pounds of transformer, kept the whole affair from toppling over.

The transformer inside the DC supply weighs basically nothing:

LED Desk Lamp - Driver PCB
LED Desk Lamp – Driver PCB

The original 12 VAC transformer powered a 50 W halogen bulb and loafed along at 14.7 VAC (yes, RMS) into the 4 W LED. The light is somewhat dimmer at 12 VDC, but not enough to worry about.

Aaaaand the photo bars are gone!

Alpha Geek Clock: Battery Refresh

A pair of D cells can power an obsolete / out of production C-Max CMMR-60 WWVB receiver for about five years and, having the plastic pieces for a blinkie at hand, junking the faded case in favor of a test lashup seemed appropriate:

C-Max CMMR-60 WWVB receiver - AA alkaline test setup
C-Max CMMR-60 WWVB receiver – AA alkaline test setup

Given the fragility of that ferrite bar, I should conjure a wide D-cell base, a bar holder to cover the ends, and a PCB mount of some sort.

The receiver data pin drives the red LED of an RGB piranha through a 2.2 kΩ SMD resistor, so it’s visible in a dim room. Given that the thing flickers constantly during WWVB’s poor-reception daylight hours, reducing the LED current counts for almost everything.

The antenna has a cap under that heatshrink tubing, which called for a resonance check:

C-Max CMMR-60 WWVB receiver - antenna peaking - driver coil
C-Max CMMR-60 WWVB receiver – antenna peaking – driver coil

The blue dingus is an RF sniffer driven three orders of magnitude below its frequency spec:

C-Max CMMR-60 WWVB receiver - antenna peaking - function generator
C-Max CMMR-60 WWVB receiver – antenna peaking – function generator

The antenna response peaks where you’d expect:

C-Max CMMR-60 WWVB receiver - antenna peaking - scope
C-Max CMMR-60 WWVB receiver – antenna peaking – scope

Given the broad peak and typical tolerances, it’s spot on.

Alpatronix iPhone XS Max Wireless Charging Case: Battery Capacity

Mostly because I have the technology, here’s a battery rundown test for the (guts of the) Alpatronix iPhone case:

Alpatronix iPhone XS case - battery test setup
Alpatronix iPhone XS case – battery test setup

Bypassing the entire battery controller doesn’t tell you when it thinks the lights should go out, but does give an indication of the raw battery capacity:

Alpatronix iPhoneXS Charger - 2021-11-06
Alpatronix iPhoneXS Charger – 2021-11-06

Multiplying the nominal 3.7 V by the nominal 5 A·hr capacity says it should have a nominal 18.5 W·hr capacity at some unrealistically low discharge rate. Given that I found it at the end of the driveway with no provenance, I didn’t expect much.

To my utter astonishment, it delivered 17 W·hr at 500 mA!

It really ought to be good for something …

Shopvac QSP Motor Commutator Cleaning

The Greatest Shopvac emitted an intense smell of electrical death while inhaling fuzzballs from the Basement Shop stairs, prompting me to tear it down. For the record, it’s a Genuine Shop·Vac QSP 10 (Quiet Super Power):

Shopvac QSP - label
Shopvac QSP – label

Removing the handle and upper plate reveals a slab of (presumably) sound-deadening foam over the motor cooling fan. As far as I can tell, the last job this vacuum had before the previous owner discarded it was inhaling drywall dust without a filter:

Shopvac QSP - upper sound baffle
Shopvac QSP – upper sound baffle

Flipping the motor assembly over and removing the bottom plate revealed a pair of equally solidified foam slabs baffling the main exhaust path:

Shopvac QSP - sound baffle foam
Shopvac QSP – sound baffle foam

They eventually became Clean Enough™ after protracted rinsing, so maybe the thing now runs as quietly as the name would lead you to believe, if you believed in names.

Disconnecting and extracting the motor revealed the razor-sharp impeller disk. A shop rag prevents lacerations while torquing off the nut holding it to the shaft:

Shopvac QSP - impeller nut
Shopvac QSP – impeller nut

Rust on the washer below the impeller, along with the layer of caked white cement, suggested water accompanied the drywall dust:

Shopvac QSP - impeller washer
Shopvac QSP – impeller washer

Gentle suasion from the Designated Prydriver eventually eased the washer off the shaft and freed the motor:

Shopvac QSP - motor brush layout
Shopvac QSP – motor brush layout

It’s an old-school series-wound brushed universal motor. The plastic plate in the middle of the picture has a helical spring pressing the carbon brush against the commutator:

Shopvac QSP - motor brush detail
Shopvac QSP – motor brush detail

The rotor turned … reluctantly with the brushes in place and spun freely without them, suggesting the horrible smell of electrical death came from arcing across the gunk accumulated on the commutator:

Shopvac QSP - commutator as found
Shopvac QSP – commutator as found

Many iterations of diligent scrubbing with denatured alcohol on cotton swabs and old t-shirt snippets got rid of the crud, although that commutator will never look all shiny-clean again:

Shopvac QSP - commutator cleaned
Shopvac QSP – commutator cleaned

At least the brushes aren’t glued to it!

Reassembly is in reverse order, although I took the liberty of splicing a few inches of wire into the switch leads, because I’m not working under factory conditions with all the proper assembly fixtures:

Shopvac QSP - extended wires
Shopvac QSP – extended wires

The motor passed the smoke test and no longer smells like death, so it’s at least as good as it ever was.

It may run quieter with clean foam baffles, but I still turn off my power ears or don hearing protection when I fire up any shop vacuum.

Wireless Numeric Keypad vs. AmazonBasics AAA Alkaline

One of the streaming media players behaved funny, which always results in a numeric keypad battery replacement. This AmazonBasics AAA alkaline was down to about 0.5 V and long past its best-used-by date:

Numeric keypad - 5 year Amazon AAA Alkaline
Numeric keypad – 5 year Amazon AAA Alkaline

Nigh onto six years isn’t bad, particularly as it hasn’t leaked electrolyte all over the negative terminal.

Suggestions that Amazon monitors their Marketplace sellers to figure out what’s profitable, then promote a Good Enough house brand product to kill off the competition, seem to describe the situation just about perfectly.

CNC 3018 Tool Clamp Rehabilitation

The CNC 3018 Z-axis stage has a plastic clamp holding the spindle motor, so I just duplicated the motor diameter in the mounts for my diamond drag bit, cheap pen, and fancy pen holders. For obvious reasons, I tend to err on the small side for anything intended to fit into anything else, which led to each of the holders sporting a small strip of tape to soak up the difference.

While poking around the 3018, I once again noticed the clamp’s crappy fit around the holder:

CNC3018 tool clamp - top
CNC3018 tool clamp – top

The inside should be circular, but it’s definitely not:

CNC3018 tool clamp - top detail
CNC3018 tool clamp – top detail

The end of the 30 mm M3 SHCS bottoms out before the clamp closes, although I’ve managed to crank the screw tight enough to put enough of a dent in there to snug the clamp:

CNC3018 tool clamp - side
CNC3018 tool clamp – side

Some awkward scraping and filing eroded enough of the plastic to let a 25 mm SHCS close the clamp firmly around the holder:

CNC3018 tool clamp - revised
CNC3018 tool clamp – revised

The tool holders now slide in easily with the screw released and fit firmly with the screw tightened a reasonable amount, minus the tape snippets shimming the difference.

If I had the courage of my convictions, I’d take it all apart, bore the clamp out to a circular profile, realign the clamp screw passage to suit, then rebuild all those tool holders for the new diameter; it now works well enough to tamp that project down.

Alpatronix iPhone XS Max Wireless Charging Case Teardown

A battered Alpatronix iPhone XS Max wireless charging case emerged from the ground cover at the end of the driveway:

Alpatronix iPhone XS case - overview
Alpatronix iPhone XS case – overview

The iPhone was nowhere to be found, so harvesting its organs seemed appropriate:

Alpatronix iPhone XS case - opened
Alpatronix iPhone XS case – opened

I assume the four steel disks aligned the coil with the wireless charger.

A few hours of steady tension relieved enough of the sticky tape to release the battery:

Alpatronix iPhone XS case - battery removal
Alpatronix iPhone XS case – battery removal

Although its bag now sports a few wrinkles:

Alpatronix iPhone XS case - battery adhesion
Alpatronix iPhone XS case – battery adhesion

The alert reader will note the outside of case proudly proclaimed “Capacity: 5000 mAh” while the underside of the battery says “4920 mAh”, but that’s surely close enough for consumer electronics these days.

The battery charges through either the Qi coil or a (mercifully standard Micro-B) USB jack and everything seems to work.

Not sure what I’ll do with a bare lithium cell and its charger, but they ought to come in handy for something around here.