Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Although we had considerable success trapping voles during the last half of the 2024 gardening season, Mary found a description of what might be a better technique: a box with small entrance holes taking advantage of rodent thigmotaxis: their tendency to follow walls. The writeup shows nicely made wood boxes, but I no longer have machinery capable of cutting arbitrarily large wood slabs into pieces.
I do, however, have a vast pile of cardboard boxes:
Vole Box – large
That’s a rat-size trap.
A smaller box has room for two mouse-size traps (one hidden on the left):
Vole Box – small
The general idea: plunk the box in a garden plot, arm the trap(s), close the lid, and eventually a vole will venture inside, whereupon wall-following leads to disaster. Apparently bait is optional, as wall-following inevitably takes them over the trap pedal. I won’t begrudge them a walnut or two, should bait become necessary.
Cardboard is obviously the wrong material for a box in an outdoor garden, but I figure they’ll survive long enough to show feasibility and I can deploy a lot of small boxes before having to conjure something more durable.
Yes, those are laser-cut rounded-rectangle holes: 30 mm and 40 mm, assuming voles care about such things.
It has always seemed like a Bad Idea™ to run indoor air through the clothes dryer and dump it overboard, particularly during days when the indoor air has been painstakingly (perhaps expensively) heated or cooled. The dryer now lives in a separate room with two doors, so we can close it off from the rest of the house and let it inhale outdoor air through the screen on the storm door.
Except in winter, when a glass pane covers the screen. Propping the door open just a bit is unattractive, because an open door seems like an invitation to any field mouse looking to upgrade its domicile.
Given that the dryer exhausts through a length of 4 inch flexible duct, I figured a similar vent, facing inward, mounted on the storm door would admit enough air to keep it happy. Keeping insects and adroit mice out requires a screen:
Dryer Inlet Vent – filter retainer
After taking that picture, I rammed four threaded brass inserts into the holes, thereby eliminating the need for a handful of washers and nuts, some of which were absolutely certain to disappear through gaps in the deck.
The two blue-gray rings are PETG-CF:
Dryer Inlet Vent Filter Retainer – solid model
The small split makes the inner retainer just springy enough to fit over the two small tabs normally locking a dryer hose in place.
The OpenSCAD code gloms a few shapes together:
include <BOSL2/std.scad>
/* [Hidden] */
VentID = 102.0; // diameter at base of vent opening
VentOD = 107.5;
OpenAngle = 3;
LipWidth = 3.0; // lip around vent opening
LipThick = 7.5;
StrutWidth = 2.5; // wide enough to hold filter
StrutThick = 3.0; // tall enough to be rigid
NumStruts = 3;
Protrusion = 0.1;
NumSides = 360/6;
$fn=NumSides;
//----------
// Build it
union() {
linear_extrude(LipThick)
ring(NumSides,d1=VentID - 2*LipWidth,d2=VentID,angle=[OpenAngle/2,360-OpenAngle/2],spin=270);
linear_extrude(StrutThick) {
circle(r=StrutWidth);
for (i=[0:(NumStruts-1)]) {
a = 90 + i*360/NumStruts;
zrot(a)
right(VentID/4)
square([VentID/2 - LipWidth/2,StrutWidth],center=true);
}
}
linear_extrude(LipThick) // outside trim ring
ring(NumSides,d1=VentOD,d2=VentOD+2*LipWidth);
}
The overall union() keeps PrusaSlicer from identifying the thing as a multi-material model. Apparently, it still looks enough like a logo to qualify for special treatment, but I fought it to a standstill.
A LightBurn video suggested large scan line intervals for decorative effects, so I adapted the SCP warning labels to fit 4 inch CD/DVD discs, set up the fixture, and Fired The Laser:
CD Engraving – fixture
The overall effect is, in most lighting, subtle:
CD Engraving – samples 2
The pair on the right with inverted engraving areas are bolder:
CD Engraving – samples 1
From a distance these two look similar, but a line interval of 0.50 mm (on the left) produces a distinct lined effect compared to the overall frosty look for 0.25 mm (open in a new tab & zoom in):
CD Engraving – vary interval
The left and right edges of the disc warp upward as the surface melts and cools, pulling the disc into a potato chip shape. Doing large areas with 0.5 mm spacing produces less warp than 0.25 mm.
The laser barely fires at 10% power (on the right) and produces a line with a distinct granular look compared the smoother result at 20% (on the left), both at 0.50 mm interval to show the lines:
CD Engraving – vary power
A 2 mm border at 0.25 mm interval (on the right, with a DVD) appears lighter than the central area at 0.50 mm (the CD on the left does not have the border):
CD Engraving – interval passes
A closer look at the border:
CD Engraving – low power irregularity
The reason behind the granular effect at 10% power is more obvious with higher magnification:
The border and the central area happen on two different passes, so it’s comforting to see how closely the scan lines match.
I glued pairs of discs together with E6000 adhesive to discover whether it’s less awful than cutting and aligning adhesive sheets. Yup, much better, but white adhesive requires better path control to keep it out of the transparent ring around the hub and better quantity control to prevent blobs from squooshing out around the perimeter. Using clear adhesive would help, as would a fresh tube without a plug of cured gunk blocking the nozzle.
With the manual laser pulse button in place, I measured the beam power at the entry and exit planes of Mirror 1 and Mirror 2, with the differences indicating something about the reflectivity (or lack thereof) of the molybdenum mirrors. Given that the losses are on the order of a few percent, tops, I expected this to be below the repeatability of the measurements.
The Mirror 1 entry point is basically the same as the laser tube exit:
HLP-200B – Laser tube exit
The Mirror 1 exit plane is perpendicular to that, just behind the mirror, but there is no way I can get a picture of the arrangement. Suffice it to say I do not want to ever put any body parts that close to an operating laser tube again.
The HLP-200B meter turned out to be exactly the right length to stand on its own in front of Mirror 2, although I needed a few test shots to figure out the lateral positioning:
HLP-200B Mirror 2 entry check
The Mirror 2 exit measurements were hand-held, with the meter braced against the mirror mount brackets on the gantry:
HLP-200B Mirror 2 exit
Without further ado, the results:
M1 Entry
M1 Exit
M2 Entry
M2 Exit
35.5
31.2
30.3
32.9
28.3
30.6
29.1
32.6
31.8
22.8
27.8
28.9
30.3
29.0
29.4
28.5
26.9
28.4
28.7
27.0
31.1
31.7
28.6
26.9
30.7
29.0
29.0
29.5
2.99
3.27
0.84
2.67
The bold line gives the average of the six measurements at each position, with the sample standard deviation below that.
As expected, the pulse-to-pulse variations swamp any actual differences between the entry and exit power levels; Mirror 2 does not have a net power gain. A 2% loss in the mirror is 0.6 W at 30 W, obviously far too small for the HLP-200B meter to resolve.
The sediment and carbon filter cartridges in our house call for annual replacement and I wondered what was inside the big cartridge.
Much to my surprise, the white plastic cap unscrews easily after grabbing the filter in the bench vise and applying a strap wrench:
Whole house carbon filter – endcap
Water enters around the perimeter of the cap, flows through the media in the cylindrical cartridge, and emerges near the center at the other end. The filter is upside-down in the vise: the cap is on the bottom of the cartridge when it’s installed in the filter housing.
The brown stuff looks a lot like sand, but is probably KDF-85 media acting as a prefilter for the carbon:
Whole house carbon filter – prefilter
The white fiber pad separates the KDF-85 from the carbon granules filling the rest of the filter:
Whole house carbon filter – carbon
Atypically, I couldn’t think of anything to do with the empty cartridge, so I screwed the lid back on and lowered the whole mess into the trash can.
The light is unavoidably upside-down from the industrial standard, because I can’t don’t want to mount it on the laser cabinet, and my use of color does not match the industrial convention. Neither of which matter for my simple needs.
The blue and orange lights turn on when their inputs are active, so they positively show sensor satisfaction, rather than laser-disabling dissatisfaction. The entire stack lights up while the controller runs a job with assist air turned on, which is usually the case.
(See below for a slipstream update.)
The wiring diagram on the case is the only documentation enclosed with the stack light:
Stack Light – label diagram
Any power supply between 12 VDC and 24 VDC will work and, contrary to the label, the COM lead can be either polarity: the light works in either common-anode or common-cathode configuration. Because the laser controller inputs and outputs are all low-active, I wired the COM terminal to +24 V, so pulling the other leads to GND turns on their lights.
The overall connection diagram, in order from easy to hard:
Stack Light – wiring diagram
Some of the details behind the diagram explain what’s going on.
Stack Light – water protect wiring diagram
The water flow sensor is wired in series with the chiller, with a GND connection on the far end pulling the WP controller terminal low when both sensors are happy; the switches can handle another 50 mA of LED current with no problem.
Stack Light – L-ON wiring diagram
The HV power supply has an internal pullup to +5 V on its L terminal, which means the L-ON output terminal sits at +5 V when the laser tube is off. Connecting the stack light directly to the L-ON terminal dumps the LED current into the 5 V supply through the pullup resistor, producing a somewhat weak glow in the LED when it should be off.
Running the optoisolator input from 5 V solves that problem, as its diode will be off when the L-ON output is high. When it’s low, the diode turns on, the isolator’s output transistors conduct, and the stack light gets the full 24 V it expects.
Stack Light – lid sensor wiring diagram
The lid sensor normally goes only to the IntLock controller terminal, but I also ran it to the otherwise unused P terminal on the HV power supply, in the possibly misguided belief it would prevent the supply from firing with the lid up if it failed like the first one. Those two inputs have 5 V pullups, so the optoisolator handles the stack light’s 24 V supply.
Stack Light – status and assist air wiring diagram
When I added the dual-path air assist plumbing, diode D1 turned on the air pump when either the Statusor the AuxAir output turned on. When the job calls for assist air, the AuxAir output opens a valve to increase the air flow.
The Status output is active when the controller is running a job and that’s generally the only time the AuxAir output will be active, but the machine console has an Air button that manually activates it, so diode D2 isolates the Status output in that unusual situation.
Slipstream update: I realized swapping the green & orange lights would make more sense:
The little hex standoffs have M3 threads, although 6 mm screws are about as much as they’ll take. The recesses have clearance for the boost transistor underneath the PCB, but it’s your responsibility to not let random wires get in trouble with the exposed circuitry:
Optoisolator case
A strip of good foam tape sticks it to the controller:
Stack Light – controller wiring
Admittedly, the stack light wiring remains something of a hairball, but it’s in a good cause.
The OpenSCAD code can build as many cavities as you need:
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The Smell of Molten Projects in the Morning 