Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
This little utility knife lives in my belt pack for those occasions when I need a sharper blade than my long-suffering Swiss Army Knife can provide. Alas, I must have sliced up something awful in the recent past:
Corroded mini utility knife blade
Although the knife frame is slightly magnetic, it’s also reasonably noncorrosive and cleaned up pretty well after some Topsaver and wire-wheel brushing activity:
Mini utility knife – somewhat cleaned
Whew!
For whatever it’s worth, this is the same knife that made it through the Washington DC “security scans” that eventually confiscated Mary’s Swiss Army Knife. She didn’t look any more guilty than I did…
It seems that Wouxun KG-UV3D HTs require nearly 0 V to activate the PTT input, which I discovered after the radio on Mary’s bike began acting intermittently. The TinyTrak3+ would transmit correctly, but the PTT button on the handlebar began to not work at all / work intermittently / work perfectly. The switch and cable were OK, pushing the button produced nearly 0 Ω at the 3.5 mm plug, the connections seemed solid, but the radio didn’t transmit reliably.
I finally got the thing to fail on the bench, which led to the discovery that:
Shorting the PTT input to the GPS+voice adapter PCB to ground didn’t make the radio transmit and
Data bursts from the TinyTrack3 worked perfectly
Gotcha!
TT3 PTT In-Out
The TT3+ pulls its PTT OUT pin down from +5 V using a 2N2222A NPN transistor (off to the right in the schematic snippet), but, for reasons having to do with ESD, the input from the PTT switch on the handlebars goes through a 100 Ω series resistor, then passes to the TT3 board through PTT IN to D6 before joining the TT3 transistor collector. The low-active diode-ORed signal heads off through PTT OUT to a 10 Ω series resistor, thence to the KG-UV3D PTT input. D6 is an ordinary 1N4148, with the net result that the PTT input voltage at the radio dropped to 630 mV with the PTT button pressed.
Not finding anything else wrong, I replaced D6 with a BAT54 Schottky diode that pulled the PTT voltage down to 300 mV and the radio worked fine.
Of course, a BAT54 is a surface-mount diode, so I clipped off the unused no-connect lead (it’s the only way to be sure it doesn’t do anything) and tacked it down slaunchwise between the PCB thru-hole pads. If I had a BAT54C with common cathodes, I could replace both D5 and D6 in one shot, but D5 just pulls down a PIC input that has an ordinary logic-level threshold voltage.
I don’t know why the KG-UV3D PTT is so fussy, although it may really be a current-driven signal that requires more current than can flow through the 110 Ω + diode forward drop in series with the PTT button. Wouxun presents no specifications that I can find.
The identical circuitry on my bike works fine with the stock D6 diode and a presumably identical KG-UV3D. I should replace that diode before it gives me any trouble, but I’ll wait until I must take the box apart for some other reason.
The slop sink in the rental house developed a drip and, unlike our kitchen faucet, required only a new washer. Of course, choosing the right size from that assortment posed a bit of a problem:
Slop sink valve with washers
The old washer is in the upper right; you can see the indentation from the valve seat.
There’s a variety of sizes & shapes; these represent just the closest matches. I have no idea what 3/8, 3/8R, and 3/8L might signify, but they’re all slightly different, some with conical cross-sections that may also be slightly different. Worst case, of course, you can sand down the rim of a too-large washer to make the diameter come out right.
The washer just in front of the old one has information molded right into the back: GOLDEN STATE 10¢ 1/2. Now there’s a show of confidence in price stability that you don’t see much any more!
I found one that fit snugly in the recess of the valve stem, turned the screw tight, and it’s all good.
One of the myriad cheap LED flashlights around the house & shop stopped working. This one consists of an aluminum shell with a pushbutton switch in the screw-on rear cap; somewhat to my surprise, the switch worked fine.
Poking around the PCB in the front revealed the problem: only friction held it in place against the springs contacting the three AA cell battery container. Pushing a bit harder shoved the lens and the LED / reflector / PCB assembly out:
LED flashlight PCB
The spring in the middle contacts the positive battery terminal. Those three square pads pressing against a locating shoulder inside the shell, but two of the pads have a solder layer and one is bare. I don’t know if the long lead on the LED at about two o’clock is a deliberate attempt to form an additional contact.
Peering inside the shell reveals three teeny nubs on the locating shoulder that could, presumably, dig into the solder pads:
LED flashlight – shell contact points
If you’re having trouble spotting them, so did I. Running a fingernail around the shoulder helps: one is at the bottom, another about 10 o’clock, and the third at about 1 o’clock. They’re not evenly spaced at 120° to match up with the pads.
With only friction holding the PCB in place, I understand why the flashlight didn’t work; given enough of an impact, the battery would push the PCB just far enough forward to make the connection at least intermittent.
I aligned the two solder-coated pads with two nubs, shoved everything together, pressed the lens firmly in place, and we’ll see how long that lasts…
The handle cracked and fell off this ball valve while I collected the hoses and suchlike from the Vassar Farms plot:
Ball valve with broken handle
Surprisingly, it’s not plastic, but (most likely) some cheap & grainy pot metal that wasn’t designed for durability. Rather than throw out that nice brass and stainless steel valve body, I figured a new handle was in order.
To the Basement Laboratory Machine Shop Wing!
The ball rotates freely inside the valve with the handle missing, so I found an aluminum rod (which, IIRC, was the original kickstand from my Linear Mach III ‘bent) that exactly fit the ball opening’s ID:
Ball valve – removing nut
What with it being a dark and stormy night outside (and having shut down all the computers in anticipation of a monster thunderstorm), I decided to get medieval with some hand tools. The first step involved finding an aluminum plate of about the right size and thickness, with markings left over from whatever I’d been building when it last saw the ceiling lights:
Ball valve handle – initial layout
After carefully drilling & filing the shaft hole, it looked like it’d work fine. Then I realized that, for whatever reason, the original design aligned the handle parallel to the hose when the valve was closed, which made very little sense when analyzed according to the Principle of Least Surprise.
So I drilled-and-filed another hole on the other end at right angles to the first one:
Ball valve handle – proper alignment
The original handle had two bumps molded on the bottom that acted as stops at each end of its 90° rotation. I figured a pair of 10-32 screws would suffice, not to mention they’d provide a bit of adjustment in case I blundered the hole positions. I planned to chop these stubs to whatever set the proper length below the plate:
Ball valve handle – trial fit
It turned out that the proper length was just about exactly that of a 1/4 inch 10-32 set screw flush with the top of the plate, so that’s what I used instead. They’re located one radius out from the outline of the valve body; trace the body shape on the handle in each orientation, eyeball one setscrew radius out from those intersections, and drill the holes.
Lay out a nice handle shape by eye, rough it on the bandsaw, introduce it to Mr Belt Sander for final shaping, touch up the concave corners with a rat-tail file, scuff the flat surfaces clean with a Dremel stainless steel wire brush to produce a used-car finish (nice polish over deep scratches), and it’s all good:
Ball valve handle – top view
The knob on the end is actually a foot intended for the bottom of a widget case:
Ball valve handle – bottom view
It won’t get leak-tested until next year, but what could possibly go wrong?
One thing, perhaps: that screw likely lies too close to the hose, particularly one sporting a replacement connector. I may be forced to bend the narrow part of the handle up a bit…
It should go without saying, but you do not cut music wire with diagonal cutters intended for electrical wire or the low-carbon steel shears built into wire strippers. I use a bicycle cable cutter that easily slices through the hard wire used in brake cables and their housing:
Every now and again I touch up the jaws with a diamond file to get rid of small dings; despite being hardened, those fine points seem particularly prone to burrs.
When you see an ordinary wire cutter with matching half-moons in each blade, you know what happened…
Wrestling with those springs suggested the tips of the needle nose pliers needed attention, so I introduced them to Mr. Grinding Wheel:
That flattened the tips, but the jaws no longer meet flush at their ends. They’ve been reshaped a while ago, so (much though it pains me to admit this) it’s time to deploy the backup pliers…
The Smell of Molten Projects in the Morning 