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.

Author: Ed

MPCNC: Button Box Wiring
The wiring hairball between the control button pendant and the Protoneer board looks like this:

GRBL – Control button wiring

The as-built schematic, such as it is:

GRBL Control button wiring – sketch

Yes, the SSR negative output goes to the Protoneer + Power Input.

I should drive the SSR from the Motor Enable output (in the external motor control header), rather than +5 V, to let GRBL control the motors, with a manual E-Stop override. The A4988 drivers require -Enable, so:
- -Enable to SSR -Control input (replaces GND)
- +5 V to BRS to SSR +Control input (as before)
The SSR Control input draws 13 mA at 5 V, suggesting I should drive the AC SSR (for the spindle motor) from the DC SSR output, rather than paralleling the two on a single Arduino output pin.

I belatedly recognized the E-Stop BRS as an instantiation of an SCP-001-J Keter-class anomaly; it is now appropriately labeled:

MPCNC EStop as SCP-001-J

I can attest to its effect on rational thought; a molly-guard may be required.
2018-02-27
Streaming Radio Player: Standard Galactic Alphabet
Prompted by Jacob’s comment about the most recent OLED garble:

RPi Streaming Player – Standard Galactic Alphabet

If ya can’t fix it, feature it!

That’s the First SGA Font from the Standard Galactic Font origin story. I copied the font file to one of the streamers, then re-aimed the font setup:
```
#font1 = ImageFont.truetype('/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf',14)
font1 = ImageFont.truetype('/home/pi/sga.ttf',14)
#font2 = ImageFont.truetype('/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf',11)
font2 = ImageFont.truetype('/home/pi/sga.ttf',11)
```
It looks surprisingly good on such a low-res display.

The user community seems divided over the update … [grin]
2018-02-26
J5-V2 Flashlight: Front End Rattle

After a year of fairly light use, the lens holder (and “attack ring”) of my J5-V2 flashlight worked loose and began to rattle. The ring holding the lens in place turned out to be finger-loose, but that wasn’t the entire problem, so I removed it and looked inside:

J5-V2 Flashlight – LED view

The mysterious alien egg resides on the upper-right side of the LED emitter.

The aluminum ring holding the LED assembly in place was also finger-loose, so I unwound it to take the whole front end apart:

J5-V2 Flashlight – front parts

Reassembly with a few dabs of Loctite in appropriate places should prevent future rattles.

Given the number of … issues … accompanying this thing, I’d say it’s not been a good cost performer. The Anker LC40 and LC90 flashlights work much better.

2018-02-25
Red Oaks Mill: Rt 376 Infrastructure Decay

NYS DOT’s recent Rt 376 repaving projects improved the road surface, but the infractructure seems to be crumbling apace, as we spotted on a recent walk across the bridge over Wappinger Creek:

Red Oaks Mill bridge – dangling concrete

The ragged edge of the deck shows other slivers have fallen into the creek.

My arms aren’t long enough to get a closer view:

Red Oaks Mill bridge – dangling concrete – detail

The concrete roadway is developing potholes in the right hand southbound lane, so the upper surface has begun crumbling, too.

I think the bridge dates to the mid-1990s, based on the aerial photo history from Dutchess GIS, so it’s a bit over twenty years old. Nothing lasts.

Repairing stuff is hard …

2018-02-24
MPCNC: Autolevel Probe, Tactile Switch Edition

So I intended to shrink the Autolevel probe with 1/8 inch drill rod and a tactile membrane switch:

MPCNC – Simple Z probe – pogo tactile switch

Unfortunately, it didn’t work nearly as well as I expected, because the switch membrane requires slightly less than the 180 g of pressure that pushes the P100 pogo pin entirely into its housing, leaving no overtravel worth mentioning. The membrane switch mechanism itself has much less than 1 mm of overtravel after the dome snaps, which left me with an uncomfortable feeling of impending doom.

I managed to figure that out before completely assembling the thing, saving me a bit of time.

The end of the pogo pin initially sported a dot of epoxy to spread the load over the switch dome:

Pogo pin with epoxy switch-pusher drop

I dismantled the pogo pin to see ~~whether I could substitute a more forceful spring~~ how it worked. As expected, a teeny spring drives the probe up against a trio of indentations in the brass housing. I didn’t expect the probe to have such an intricate shape, but it’s obvious in retrospect.

The OpenSCAD code for the housing required minimal tweakage from the larger version, so it’s not worth immortalizing.

2018-02-23

MPCNC: USB Camera Mount

The bCNC doc shows a camera mount made from acrylic and aluminum, but the MPCNC tool carrier lacks anywhere to secure such a thing. The camera should be reasonably close to the spindle axis, high enough to clear the work, and stable enough to hold its alignment. There’s a tiny flat spot next to the outer-lower Z-axis bearing supports (along the bottom of the picture), so that’s where it must go:

MPCNC - Central Assembly - detail — MPCNC – Central Assembly – detail

At least for now, anyway.

The USB camera originally mounted on a spring clip, with a 10 mm ball at the end of a 6 mm OD × 6 mm long stalk. Because we live in the future, building a matching ball socket isn’t particularly difficult:

MPCNC - USB Camera mount - Slic3r — MPCNC – USB Camera mount – Slic3r

3D printing FTW!

The stalk opening slants downward by 5°, because the camera PCB isn’t quite aligned with the stalk and I couldn’t get the first version to aim the lens directly downward.

A pair of brass inserts anchor the two M3 SHCS. The clamping force seems barely adequate to the task, but I’ll wait to see what else I don’t like before complexicating the situation.

A square of Genuine 3M sticky foam tape holds the mount to the MPCNC beside the DeWalt DW660 spindle:

MPCNC USB Camera - installed — MPCNC USB Camera – installed

The MPCNC bearing bracket doesn’t provide much surface area for the foam and it’s a bit more flexy than I’d like, but good practice probably requires verifying the spindle-to-camera offset before trusting the results, so we’ll see how it works.

The initial camera alignment consists of putting a mirror flat on the (pretty much level) platform:

MPCNC USB Camera - mirror alignment — MPCNC USB Camera – mirror alignment

Then you adjust the camera so its lens looks squarely at itself in the middle of the image:

bCNC - Camera - Mirror Alignment - first mount — bCNC – Camera – Mirror Alignment – first mount

The picture shows the camera aligned left-to-right (because the ball can rotate around the shaft axis), but the first mount didn’t allow the stalk to have enough downward tilt to center the lens image on the horizontal crosshair, thus the -5° tilt appearing in the second version.

With the camera lens centered on its reflection, you know the optical axis is perpendicular to the mirror. Because the mirror is flat on the bench, the optical axis must be perpendicular to the bench, which is parallel to the XY plane. Because we assume the MPCNC Z-axis moves perpendicular to the bench = XY plane, the distance between the spindle axis and the camera axis will remain constant, regardless of the Z-axis position.

Seems workable to me.

The OpenSCAD program as a GitHub Gist:

	// MPCNC USB Camera Mount
	// Ed Nisley KE4ZNU – 2018-02-16

	Layout = "Build"; // Build, Show, Mount

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//- Adjust hole diameter to make the size come out right

	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);
	}

	//- Dimensions

	CameraStalk = [6.0 + 1.0,10.0 + HoleWindage,4.0]; // stalk OD, ball OD, stalk length
	CameraAngle = -5; // stalk tilt, negative = downward

	MountBlock = [24.0,20.0,CameraStalk[OD] + 7.0]; // cube to hold ball, stick to MPCNC frame

	Insert = [3.0,4.4,4.5]; // brass insert

	NumSides = 6*4;

	//—–
	// Define shapes

	// Camera mount, enlongated for E-Z differencing
	// Origin at center of ball, stalk along +X

	module Camera() {

	union() {
	sphere(d=CameraStalk[OD] + HoleWindage,$fn=NumSides);
	rotate([0,90 – CameraAngle,0])
	PolyCyl(CameraStalk[ID],3*CameraStalk[LENGTH],NumSides);
	}
	}


	module Mount(Half="All") {

	Rounding = 2.0;

	ZShift =
	(Half == "Upper") ? -MountBlock.z/2 :
	(Half == "Lower") ? MountBlock.z/2 :
	2*MountBlock.z;

	difference() {
	hull()
	for (i=[-1,1], j=[-1,1], k=[-1,1])
	translate([i(MountBlock.x – Rounding)/2,j(MountBlock.y – Rounding)/2,k*(MountBlock.z – Rounding)/2])
	sphere(d=Rounding,$fn=3*4);
	for (j=[-1,1])
	translate([-MountBlock.x/4,j*MountBlock.y/4,-(MountBlock.z/2 + Protrusion)]) {
	PolyCyl(Insert[OD],Insert[LENGTH] + Protrusion,6);
	PolyCyl(Insert[ID],2*MountBlock.z,6);
	}
	translate([MountBlock.x/2 – (CameraStalk[OD]/2 + CameraStalk[LENGTH]),0,0])
	Camera();
	translate([0,0,ZShift])
	cube([2MountBlock.x,2MountBlock.y,MountBlock.z],center=true);
	}
	}

	//—–
	// Build it

	if (Layout == "Mount")
	Mount();

	if (Layout == "Show")
	Mount();

	if (Layout == "Build") {
	translate([0,0.75*MountBlock.y,MountBlock.z/2])
	rotate([180,0,0])
	Mount("Upper");
	translate([0,-0.75*MountBlock.y,MountBlock.z/2])
	rotate([0,0,0])
	Mount("Lower");}

view raw USB Camera Mount.scad hosted with ❤ by GitHub

2018-02-22

USB Camera Re-Cabling

The bCNC doc shows how to use a USB camera for XY alignment and I want to try it out. The Box o’ USB Cameras emitted a likely candidate with a focusing lens, six (!) white LEDs, and a ball mount attached to an aggressive spring clip, but its thick USB cable included a lumpy brightness pot for the LEDs and sprouted a mic plug (apparently, it predated cheap USB audio):

USB Camera – OEM wiring

The Box o’ USB Cables emitted a surprisingly long cable amputated from some random hunk of consumer electronics.

The LED brightness won’t need much adjustment after the first few minutes. I found a little 2 kΩ trimpot to fit the PCB holes:

USB Camera – inside – brightness pot

Miracle of miracles, the dial ended up almost centered behind the original mic pore. A few minutes of gentle filing embiggened the pore and moved it over the trimpot:

USB Camera – front with brightness pot

Yeah, the hole may need a plug or tape to keep the dust out, but there’s an even bigger gap around the lens.

It produces a 640×480 picture with pretty much the expected quality, which should suffice for its intended purpose.

Next step: stick it somewhere on the MPCNC.

2018-02-21

Author: Ed

MPCNC: Button Box Wiring

Streaming Radio Player: Standard Galactic Alphabet

J5-V2 Flashlight: Front End Rattle

Red Oaks Mill: Rt 376 Infrastructure Decay

MPCNC: Autolevel Probe, Tactile Switch Edition

MPCNC: USB Camera Mount

USB Camera Re-Cabling