Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
The tech reviewer for my Circuit Cellar columns on the MOSFET tester commented that the 32 kHz PWM frequency I used for the Peltier module temperature controller was much too high:
Peltier Noise – VDS – PWM Shutdown
He thought something around 1 Hz would be more appropriate.
Turns out we were both off by a bit. That reference suggests a PWM frequency in the 300-to-3000 Hz range. The lower limit avoids thermal cycling effects (the module’s thermal time constant is much slower) and, I presume, the higher limit avoids major losses from un-snubbed transients (they still occur, but with a very low duty cycle).
Peltier Turn-Off Transient
The Peltier PWM drive comes from PWM 10, which uses Timer 1. The VDS and ID setpoints come from PWM 11 and PWM 3, respectively, which use Timer 2. So I can just not tweak the Timer 1 PWM frequency, take the default 488 Hz, and it’s all good. That ever-popular post has the frequency-changing details.
Although it’s common practice to exchange your empty 20 pound propane tank for a full one, I vastly prefer to keep my own tanks: I know where they’ve been, how they’ve been used, and can be reasonably sure they don’t have hidden damage. Two of my tanks have old-style threaded connections, but the barby has a quick-disconnect fitting on the regulator and I’ve been using an adapter on those tanks.
The adapter comes with a plastic tool that you use to install it in the tank valve. In principle, you insert the tool into the adapter, thread the adapter into the valve, then tighten with a wrench until the neck of the plastic tool snaps, at which point you eject the stub and the adapter becomes permanently installed. I don’t like permanent, so I carefully tightened the adapter to the point where the O-ring seals properly and the tool didn’t quite break. I’ve always wanted a backup tool, just in case the original broke, and now I have one:
Propane QD Adapter Tool – in adapter
It fit into both the adapter body and the 5/8 inch wrench (the OEM tool is 9/16 inch) without any fuss at all:
Propane QD Adapters – OEM and printed
The solid model has a few improvements over the as-printed tool above:
Shorter wrench flats
More durable protrusions to engage the locking balls
Propane QD Adapter Tool
It took about an hour to design and another 45 minutes to print, so it’s obviously not cost-effective. I’ll likely never print another, but maybe you will.
The OpenSCAD source code:
// Propane tank QD connector adapter tool
// Ed Nisley KE4ZNU November 2012
include </mnt/bulkdata/Project Files/Thing-O-Matic/MCAD/units.scad>
include </mnt/bulkdata/Project Files/Thing-O-Matic/Useful Sizes.scad>
//- Extrusion parameters must match reality!
// Print with +1 shells and 3 solid layers
ThreadThick = 0.25;
ThreadWidth = 2.0 * ThreadThick;
HoleWindage = 0.2;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
Protrusion = 0.1; // make holes end cleanly
//----------------------
// Dimensions
WrenchSize = (5/8) * inch; // across the flats
WrenchThick = 10;
NoseDia = 8.6;
NoseLength = 9.0;
LockDia = 12.5;
LockRingLength = 1.0;
LockTaperLength = 1.5;
TriDia = 15.1;
TriWide = 12.2; // from OD across center to triangle side
TriOffset = TriWide - TriDia/2; // from center to triangle side
TriLength = 9.8;
NeckDia = TriDia;
NeckLength = 4.0;
//----------------------
// Useful routines
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,
h=Height,
$fn=Sides);
}
module ShowPegGrid(Space = 10.0,Size = 1.0) {
Range = floor(50 / Space);
for (x=[-Range:Range])
for (y=[-Range:Range])
translate([x*Space,y*Space,Size/2])
%cube(Size,center=true);
}
//-------------------
// Build it...
$fn = 4*6;
ShowPegGrid();
union() {
translate([0,0,(WrenchThick + NeckLength + TriLength - LockTaperLength - LockRingLength + Protrusion)])
cylinder(r1=NoseDia/2,r2=LockDia/2,h=LockTaperLength);
translate([0,0,(WrenchThick + NeckLength + TriLength - LockRingLength)])
cylinder(r=LockDia/2,h=LockRingLength);
difference() {
union() {
translate([0,0,WrenchThick/2])
cube([WrenchSize,WrenchSize,WrenchThick],center=true);
cylinder(r=TriDia/2,h=(WrenchThick + NeckLength +TriLength));
cylinder(r=NoseDia/2,h=(WrenchThick + NeckLength + TriLength + NoseLength));
}
for (a=[-1:1]) {
rotate(a*120)
translate([(TriOffset + WrenchSize/2),0,(WrenchThick + NeckLength + TriLength/2 + Protrusion/2)])
cube([WrenchSize,WrenchSize,(TriLength + Protrusion)],center=true);
}
}
}
After 30 years, IBM gave Mary a commemorative clock, after which she promptly retired. Back in the day, they used to hand out Atmos clocks (admittedly, on more momentous occasions), but this isn’t one of those. In fact, although it appears to have a torsion pendulum, that’s a separate motor-driven foo-foo which we immediately turned off:
Janus Clock – front
It normally sits on the living room coffee table (which actually holds a myriad plants next to the front window) where, after we scrapped all the upholstered furniture, the two of us can’t both see the clock face from our chairs. Having a spare clock insert from that repair, we had the same bright idea at the same time: we need a clock with two faces! We came up with Janus independently…
Despite its fancy appearance, the IBM clock consists mostly of brass and plastic, so I had no qualms about having my way with it in the shop. The new clock insert spanned the clock’s gilt plastic back cover, needing only a #1 drill hole for the adjustment stem, and exactly filled the available space between the back cover and the case. Both movements had enough interior clearance for 3-48 brass screw heads and nuts, so I eyeballed the right spots on the new cover, centered the Sherline spindle on the plate, and drilled two clearance holes 6 mm in from the edges on the vertical diameter:
Drilling clock insert cover
That put them 61.3 mm apart across the diameter, which would be awkward to duplicate by hand. Manual CNC makes it trivially easy to match-drill holes; I clamped down the gilt back cover from the IBM clock, aligned it to the table, located the center, and drilled two 3-48 clearance holes:
Drilling torsion clock cover
The glow from that polycarbonate packing block isn’t quite so nuclear in real life. The clamping force goes down the side panels of the cover, which had enough of a curve to be perfectly stable. Yes, I’m drilling into air, but came down real slow using the Joggy Thing and it was all good.
Assemble the two back covers (the holes matched perfectly), mark the adjustment stem hole, disassemble, hand-drill, reassemble, tighten nuts, and install:
Janus Clock – rear
It does look a bit lumpy from the side, but that’s just because I don’t have any gilding for the black tape wrap:
Those failures came from two separate cable snags that stalled the X and Y stepper motors for about 1 mm of travel. Fortunately, I wasn’t paying attention and, by the time I figured this out, the thing was nearly built, so I let it run to completion. The thick base plate accounts for most of the plastic, anyway.
First, the cable bundle on the right snagged on the socket-head cap screw just in front of the X axis limit switch (hidden behind the bundle here). This picture, taken after the +12 V pin in the HBP connector burned through, shows the typical snarl of wires inside a Thing-O-Matic:
Thing-O-Matic – HBP cable routing
The rewired thermistor cable snagged on the bulldog clip holding the top aluminum plate. This picture, taken after the thermistor pads fell off the HBP, shows the filler plate I put in place to prevent the cable (entering from the top and passing below the white cable on the HBP) from jamming in the gap between the Y axis stage and the case, but you can see how the bulldog clip handle could snag it when the platform moves rearward from the front left corner (+X +Y):
HBP Thermistor cable – snag shield and bulldog clamp
The fat gray cable flat against the case in that picture carries the X axis stepper drive signals up-and-over the Y axis. The thinner gray thermistor cable emerges from the electronics bay inside the case corner, then arches in from thetop.
My buddy Aitch recently gave me a few meters of corrugated wire loom, so I moved the bulldog clip rearward and bundled all those loose HBP wires in one tidy snood:
Thing-O-Matic – X axis cable loom
I’m sure something else will go wrong, but the machinery looks marginally less haphazard and the cables don’t snag while I’m watching…
Our Larval Engineer, evidently planning to serve some genuine home-style pizza to her compadres, asked for the Official Recipe.
It goes a little something like this…
T minus 2.5 hours
Blend (manually!) in mixer bowl:
1 Tbsp yeast (that’s two packets = crazy spendy → buy in bulk)
1 Tbsp brown sugar (or whatever sweet you have)
1-1/2 C warm water (1 minute in our microwave)
Add on top of liquid:
3 C whole wheat flour
1 C white flour
1 tsp salt
The original recipe called for:
4 Tbsp olive oil (or safflower, not vegetable / canola)
1/2 C additional flour only if you add oil
Don’t stir, just pause 5 minutes until the yeast gets up & running.
Run mixer until dough becomes rubbery and cleans the bowl.
No mixer? Stir, stir, stir, then knead, knead, knead.
Ed & Karen kneading bread dough – Raleigh 1995-ish
(As you can see, she has experience kneading bread…)
Cleave in twain, about 1 lb per lump.
Oil mixer bowl & one lump, let rise.
Flatten other lump in plastic bag & freeze for next week.
Put 1 unit homebrew pizza sauce on counter to thaw.
T minus 45 minutes
Roll crust to fit pan, generously flour bottom, let rise on countertop.
Grate cheese:
2 oz Sharp Provolone
2 oz Mozzarella
3 oz Monterey Jack
Cube meat:
2 oz Ham
4 oz Turkey / pork / what have you
Chop veggies:
handful Broccoli tips (save stalks for tomorrow’s stir fry)
1/2 Sweet pepper (Green / red)
3 Bunching onions (or small scallions, whatever)
1 big Mushroom (or 4 tiddly buttons)
T minus 15 minutes
Fire the Oven! to 500 F
Flour bottom of crust, flop on pan
Spread pizza sauce generously over crust, counter, walls, self
Distribute meat / veggies
Top with cheese
Slide onto middle shelf of oven
Set timer to 10 minutes if preheated, 12 minutes if not quite hot yet
Clean utensils / counter / walls / self
T minus zero
Remove from oven (top should be brown & bubbling)
Pause for coagulation
Cut
Distribute
Nom on!
The original recipe was about the same, plus foo-foo steps like putting oil in the dough, spreading cornmeal on the pan, oiling the crust before applying the sauce, and suchlike. You’ll need the book for all the details:
I’m sure something different has come along in the last third of a century, but you’ll never hear it from me. Mostly, build a few, tweak the ingredients to suit your style / what’s on hand, and it’ll be all good.
Our Larval Engineer may have a commission to fit her Speed-Sensing Ground Effect Lighting controller to another longboard. To that end, the case now sports mouse ears to spread the force from the cooling ABS over more of the Kapton tape, in the hope the plastic won’t pull the tape off the aluminum build platform:
Longboard Case Solid Model – mouse ears
That view shows the bottom slice that will hold the battery, but the ears appear on all three layers.
The plunger is basically a pin that eventually deforms the top of the switch membrane. Tee’s DSC-H1 had an exposed switch, although this picture shows that membrane was still in reasonably good condition:
Shutter Switch Closeup
My DSC-H5 has a thin black protective disk atop the switch, but the disk wasn’t particularly protective and developed a dimple that held the contacts closed even with the shutter button released (which is why I’m tearing the camera apart in the first place):
DSC-H5 Shutter Switch – dimpled protector
The C-clip around the plunger is now plastic, rather than metal, making it less likely to erode the thin plastic shaft. Pulling the clip off while holding the button down releases all the parts:
DSC-H5 Shutter Button – components
A few measurements from an intact shutter button, which may come in handy if you don’t have one:
DSC-H5 Shutter Button – plunger measurements
Mount three-jaw chuck on the Sherline table, laser-align chuck to spindle, grab shutter button by its shaft in a Jacobs chuck, grab shutter button in three-jaw chuck, release from Jacobs chuck:
DSC-H5 Shutter Button – in Sherline chuck
That’s not particularly precise, but it’s close enough for this purpose. I used manual jogging while testing the fit with a paper shim until all three jaws had the same clearance, then tightened the jaws.
I nicked the plunger at its base with a flush-cutting diagonal cutter, snapped off the plunger, and drilled a #56 hole through the button:
DSC-H5 Shutter Button – cap drilling
For reasons that made sense at the time, I repaired Tee’s DSC-H1 with a 1-72 brass screw. This time, I used an 0-80 (which I learned as ought-eighty, if you’re wondering about the indefinite article) screw and nut, because the screw head fit neatly into the bezel recess and I had a better idea of how to smooth out the threads.
This being plastic, I used the chuck to hold the tap in the proper alignment, then turned the tap through by finger pressure. This trial fit showed it worked:
DSC-H5 Shutter Button – 0-80 screw
Milling the nut down to a 2.8 mm cylinder required the usual manual CNC, with repeated iterations of this chunk of code in the MDI panel:
The 2.8 in the first line is the current OD and the 3.11 is the measured diameter of the 1/8 inch end mill. I started from a 5.0 mm OD that just kissed the nut, then worked inward by 0.2 mm at a time for very shallow 0.1 mm cuts:
DSC-H5 Shutter Button – 0-80 nut milling
The alert reader will notice, as did I, that the head isn’t quite centered: the cut trimmed the left side and left the right untouched, with an offset far larger than the centering error. As nearly as I can tell, the heads of those screws aren’t exactly centered on their threaded shafts, but the final result fixed that… and the overall error is a few tenths of a millimeter = maybe 10 mils, tops, so it’s no big deal.
With all that in hand, I applied a very very thin layer of epoxy to fill the threads below the now-cylindrical nut and convert the screw into a rod:
DSC-H5 Shutter Button – 0-80 plunger
My original intent was to use the screw head as-is atop the PET shield (per those instructions) on the switch membrane, but after reassembling enough of the camera to try that out, it didn’t work correctly: the half-pressed switch didn’t activate reliably before the full-pressed switch tripped.
The PET shield I used came from the side of a 1 liter soda bottle and turned out to be 0.27 mm thick:
DSC-H5 Shutter Switch – cover removed
I think the PET shield would work with the original plunger shape concentrating the force in the middle of the shield, but the nice flat screw head spreads the force out over a wider area. As a result, the force required to close the half-pressed switch contacts was roughly the same as that required to close the full-pressed contacts; remember the nub on the bottom of the black plastic tray concentrates the force in the middle of the full-pressed switch membrane.
So I removed the PET shield, added a dot of epoxy to fill the screw slot and compensate for the missing shield thickness, then filed a flat to make a nice pad:
DSC-H5 Shutter Button – epoxy on plunger
Reassembling the camera once more showed it worked exactly the way it should. In fact, the button seems more stable than the OEM version, probably because the slightly enlarged plunger shaft fits better in the bezel. Too bad about those scuffs on that nice shiny button dome, though:
DSC-H5 – repaired shutter button
Tossing the leftover parts seems entirely appropriate…
The Smell of Molten Projects in the Morning 