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: Machine Shop

Mechanical widgetry

SMD Measurement Tweezers

While fiddling around with those SMD capacitors, it occurred to me that I really needed some SMD tweezers: small forceps with isolated jaws, connected to the capacitance meter’s terminals. In the nature of a proof-of-concept, I sacrificed a (surplus) Tektronix banana plug cable and an old plain-steel tweezer (stamped Made in Japan back in the day when that had the same quality connotations as does Made in Pakistan right about now) and lashed them together:

SMD tweezers – overview

I chopped off the tweezer joint with a bolt cutter, scuffed up the steel with a file, soldered the cable wires, cut a small wood block to fit, and epoxied the whole mess together:

SMD tweezers – epoxy joint

When the epoxy cured, a generous wrap of silicone tape hid most of the hackage. Two lengths of clear heatstink tubing insulate the handles from my sweaty fingers:

SMD tweezers – joint detail

Part of the reason for picking this victim was its cheap-and-bendy steel: more easily soldered than stainless, no regrets about filing the jaws to suit. They’re flattened on the bottom and filed to grip SMD chips along their length:

SMD tweezers – tip shape

That’s on the top panel of my indispensable AADE LC meter. The stray capacitance of that cable is around 50 pF, but the meter can null it to a fraction of a pF. At least as long as I don’t change my grip, that is, which isn’t too severe a restriction. [Update: got the link right this time.]

That gorgeous Tek cable turned out to be entirely too stiff and the natural curve doesn’t lie in the correct direction. The next version will probably use a length of RG-174 mini coax and a dual banana plug. I think I’d like angled jaws, too, so as to attack the chips from the top down.

But even this version works wonderfully well, as I sorted out a few hundred random SMD caps in two half-hour sessions that I’d been putting off for far too long. This is the last batch; I’ve learned the hard way that it pays to transfer batches of chips to their storage bins long before I think I should:

Sorting SMD caps

Yeah, it’s false economy, but it keeps me off the streets at night. OK?

2011-12-08
Tux Cookie Cutter: It Works!

Sean reports that the first field test of the Tux Cookie Cutter went well:

Tux Cookies

I obviously need a few samples for QC purposes…

2011-12-07
Fruit Fly Traps

At some point we brought home a fruit fly starter kit that produced a zillion fruit flies in the worm compost bin; every time we opened the cover, half a zillion flies would emerge. After a bit of fiddling with the usual Internet recipes, I managed to produce something useful:

Fruit fly trap – overview

The trick involves making the liquid enticing enough to get the flies through the hole in the coffee filter top:

Frut fly trap – filter paper

I used about a cup of water, an ice cube of apple juice for sweetness (they are, after all, fruit flies), a tablespoon of vinegar for that delicious rotten aroma (they prefer damaged, easy to eat fruit), and a few drops of dishwashing detergent so when they hit the liquid they’re sunk.

The container must be tall enough to let them rise past the entrance opening on their way toward the light; I settled on the 2 pound ricotta cheese containers we have in abundance:

Fruit fly trap – results

That’s the catch after maybe a month at the end of the season, but it represents a week of activity back when we were breaking the infestation. I deployed four of those traps atop the compost bin to catch the half-zillion escaped flies and fired up the vacuum cleaner to extract the half-zillion remaining inside every time we opened the lid. After a few weeks of that, we’d managed to get ahead of their breeding cycle and the problem pretty much Went Away.

2011-12-05
Harbor Freight Digital Thickness Gauge: Lubrication Thereof

Picked up a Harbor Freight thickness gauge to measure Thing-O-Matic filaments and suchlike; it has a plastic piston and anvil, so it’s not well-suited to measure anything other than plastic parts. In fact, it’s all plastic and the various sliding surfaces produced a remarkable amount of friction.

Fortunately, the back cover pops off without too much of a struggle:

Harbor Freight Digital Thickness Gauge – cover removed

Dabs of silicone lube at all the contact points considerably improved its disposition.

The display offers 0.01 mm resolution, but I don’t believe that rightmost digit for an instant. The stated accuracy is ±0.1 mm, which is probably closer to the truth, and it agrees reasonably well with my considerably better quality digital caliper.

2011-12-04
Belt Sander Disk Tightening

As part of making that PCB, the sanding disk on the side of Mr Belt Sander made a lot more noise than usual; it’s hard to tell, because I wear 30+ dB ear muffs. Turns out that the setscrew had worked loose enough to let the disk walk outward, chewing up the plastic dust collector cover and the aluminum table:

Belt sander disk dust catcher

The setscrew gouged the shaft enough to prevent the disk from sliding off the shaft, which was probably a Good Thing, but that also meant I had to jam a big flat-blade screwdriver inside the guts of the dust guard and twist to pry the disk off:

Belt sander disk shaft

A touch of the file on the shaft, a bit of cleanup inside the disk hole, a dab of Loctite, and it’s all good again.

2011-12-03
GPS+Voice Interface for Wouxun KG-UV3D: PCB in a Box!

It always feels good when the parts fit together, even if they don’t actually do anything yet…

Bare PCB in Wouxun HT battery case

That’s the bare PCB in the first-pass 3D-printed battery case adapter, both of which need quite a bit more work. In particular, the case desperately needs some sort of latch to hold the yet-to-be-built contacts against the HT’s battery terminals.

Amazingly, all the holes lined up spot on, although I think the lower battery contact could move half a millimeter closer to the base of the radio. The battery case contacts are large enough to work as-is and, for what it’s worth, the Wouxun battery cases seem to differ slightly among themselves, too.

The PCB itself came out about as well as any homebrew PCB I’ve ever made, after getting the Logitech Joggy Thing working again to line the Sherline up for hole drilling:

Wouxun HT GPS-Audio PCB – copper

The circuit has provision for pairs of SMD caps on all the inputs, with which I hope to squash RFI from both the VHF and UHF amateur bands by choosing their self-resonant frequencies appropriately.

2011-12-02
Garden Sprayer Valve Spring Replacement

A garden sprayer awaiting repair emerged from the benchtop clutter. It’s an old one, with a metal shell and actual screws, so I could dismantle it to reveal the problem:

Garden sprayer valve – rusted spring

It’s evidently impossible to make a good, cheap, corrosion-resistant spring (pick any two, I suppose):

Garden sprayer valve – wreckage

Some rummaging in the Big Box o’ Medium Springs produced a slightly smaller spring that should last for a while; it’s good, free, and rust-able, if a bit too short.

Much to my astonishment, I found a length of 3/8 inch Marine Bronze rod in the stockpile and made a bushing to take up the remainder of the space:

Garden sprayer valve – new spring and bushing

It won’t get a good test until gardening season opens next year, but it seems to seal well enough.

2011-12-01