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.

Tag: Improvements

Making the world a better place, one piece at a time

Devilspie2: Lua Scripts

Prompted by that suggestion, here’s the current collection of Devilspie2 scripts (in ~/.config/devilspie2/) that make my dual-monitor setup (left: 2560×1440 landscape, right: 1050×1680 portrait) usable with a single X session in Xubuntu 12.10. The window manager understands about the monitor layout, so maximizing a window will fill whatever monitor it’s currently occupying.

acroread.lua — maximized on portrait

if (get_window_name()=="Adobe Reader") then
      unmaximize();
      set_window_geometry(0,0,1000,100);
      set_window_geometry(2561,0,1000,100);
      maximize();
end

chromium.lua — right half of landscape

if (get_application_name()=="Chromium" and get_window_name() ~= "Print") then
   set_window_geometry(1400,0,1150,1200);
   maximize_vertically();
end

debugging.lua — handy with –debug option

debug_print("Window Name: " .. get_window_name());
debug_print("Application name: " .. get_application_name());

digikam.lua — right half of landscape, force large Search dialog, dammit

if (get_application_name() == "Digikam") then
	debug_print("DigiKam conditional - top");
	if (get_window_name() == "Advanced Search") then
		debug_print("Digikam - Adv Search");
		set_window_geometry(750,100,1000,1300);
	else
		debug_print("Main DigiKam window");
		set_window_geometry(0,0,1400,1000);
		maximize_vertically();
	end
end

firefox.lua — left half of landscape, enlarge dialogs

if (get_application_name()=="Firefox") then
	debug_print("FF conditional - top");
	if (get_window_name() == "Print") then
		set_window_position(700,350);
	elseif (0 == string.find(get_window_name(),"Password")) then
		set_window_position(0,0);
		maximize_vertically();
	end
end

gimp.lua — force Gutenprint dialog to the top, dammit

if (get_application_name() == "GNU Image Manipulation Program") then
	debug_print("GIMP conditional - top");
	if (string.find(get_window_name(),"Print")) then
		debug_print("GIMP - GutenPrint")
		set_window_position(700,350);
		make_always_on_top();
	else
		debug_print("GIMP - Main window");
	end
end

passwords.lua — put password dialogs in mid-screen

if (get_window_name()=="Password Required") then
	debug_print("Password");
	set_window_position(700,350);
end

pronterface.lua — force to middle-ish of Desktop 2

if (get_window_name()=="Printer Interface") then
   set_window_workspace(2);
   set_window_position(1200,750);
end

slic3r.lua — force to right side of Desktop 2

if (get_window_name()=="Slic3r") then
   set_window_workspace(2);
   set_window_geometry(1600,0,700,700);
end

terminal.lua — maximized on portrait

if (get_window_name()=="Terminal") then
   set_window_position(2561,0);
   maximize();
end

thunderbird.lua — left half of landscape, force big dialogs

if (get_application_name() == "Thunderbird") then
	debug_print("TBird conditional - top");
	if (1 == string.find(get_window_name(),"Print")) then
		debug_print("TBird - print...");
		set_window_position(700,350);
	elseif (string.find(get_window_name(),"Sending") or
			string.find(get_window_name(),"Confirm") or
			string.find(get_window_name(),"Processing")) then
		debug_print("TBird - generic dialog");
		set_window_position(200,600);
	elseif (string.find(get_window_name(),"Write:")) then
		debug_print("TBird - writing");
		set_window_geometry(1300,0,900,600);
		maximize_vertically();
	elseif (0 == string.find(get_window_name(),"Password")) then
		debug_print("Main TBird window?");
		debug_print(" name: ",get_window_name());
		set_window_geometry(0,0,1300,1200);
		maximize_vertically();
	end
end

2013-09-12

Improved M2 Heated Build Platform: First Light

Although the M2’s heated build platform works well enough, somebody who knows what he’s doing (you know who you are: thanks!) sent me an improved version. It’s a PCB heater, laid out to compensate for the usual edge cooling, firmly attached to a tempered glass plate with genuine 3M thermally conductive tape:

Improved M2 HBP – test setup

They designed the heater around the 30 VDC power supply used in their other equipment. Although I had ~~high~~ moderate hopes that a boost power supply would convert the 24 V supply I already had for the stepper driver bricks into the 30 V for the heater, it was not to be. So there’s a 36 V 9.7 A 350 W supply arcing around the planet that (I think) should work better: adjust the voltage down as far as it’ll go, soak up another few volts in the solid-state relay, and Things Should Be Close Enough to 30 V. One can buy a genuine 30 V supply, but it costs surprisingly more than either 24 V or 36 V supplies on the surplus / eBay market and won’t really provide the proper voltage without upward tweaking anyway.

I replaced their standard 0.156 inch square terminals with Anderson Powerpoles, soldered a length of shielded cable to the 100 kΩ thermistor pads, and gimmicked up a connection to the 24 V supply; it delivered 23.7 V at the PCB terminals. The thermistor is 100 kΩ at 25 °C and 11.4 kΩ at 77 °C. The PCB heater is 5.9 Ω at 25 °C and 7.3 Ω at 77 °C; it dissipates 77 W at 77 °C (no, that’s not a typo).

The ultimate temperature looks to be about 90 °C with a 24 V supply, which isn’t quite enough for ABS (which I’m not using in the M2 right now, but probably will eventually). The time constant, assuming the 1-e^-1 point is 66 °C, works out to about 9 minutes; it’ll be up to final temperature in half an hour. Those numbers aren’t quite as accurate as one might wish, because the heater power drops as the temperature rises and the copper resistance increases.

A 30 V supply would dissipate 120 W at 77 °C and rumor has it that the ultimate temperature is around 125 °C, which would be fine for ABS. Goosing the power a bit would produce more heat, but I’v been running the Thing-O-Matic at 110 °C and that’s good enough. More power, of course, gets it to the temperature setpoint faster, which is probably a Very Good Thing.

Obviously, you need PWM to control the temperature; given a 9 minute time constant, a bang-bang controller will work perfectly well.

The original data, including the thermistor resistance after I got my act together, plus a cute little temperature-vs-time graph:

Improved M2 HBP – 24 V supply

The colored flyspecks are part of the paper; I salvaged a stack of fancy menu cards from a trash can and padded them up as geek scratch paper.

2013-09-05
Basement Safe: Foam Door Seal

A bit of rummaging in the Big Box o’ Weatherstripping produced the stub end of a spool bearing 1/4 x 1/8 foam tape that exactly fills the gap between the Basement Safe’s door and liner:

Basement Safe – Foam door seal – latch side

The hinge side of the door has tape between the door liner and the safe wall, because that closes in compression rather than shear:

Basement Safe – Foam door seal – hinge side

There should be a big bump in the humidity record marking that installation, but I don’t expect any immediate difference. If the silica gel lasts more than two months, I’ll consider it a win.

2013-08-26
Public Facilities Maintenance: Progress

A day or so after kvetching about that informal DCRT vehicle entrance to the head planner developing the Dutchess County Master Plan for bicycle & pedestrian facilities, this appeared:

DCRT Overocker Crossing – block on informal entrance

Notice the blue electrical junction box on the right? That can’t possibly be a Good Thing… but, so far, it doesn’t seem to bother anybody enough to repair it.

Those missing ADA strips at Grand have been swept out, converting them into rough-bottomed trenches across the trail. At least they’re not quite so slip-prone, even if they’re still a tripping hazard.

2013-08-24

Air-gapped Ferrite Toroid Data

For an upcoming Circuit Cellar column on Hall effect current sensing, I slit another pair of toroids:

Then wound them with grossly excessive amounts of wire (the up-armored core on the right appeared earlier):

The smaller toroid is an FT37-43 that barely covers the active area of an SS49-style Hall effect sensor, but experience with the FT50 toroid suggests that’ll be entirely enough:

slit FT37 toroid trial fit to SS48-style Hall effect sensor

Data on the uncut toroids:

Property	FT50-61	FT37-43
Outer diameter (OD) – inch	0.50	0.375
Inner diameter (ID) – inch	0.281	0.187
Length – inch	0.188	0.125
Cross section area – cm²	0.133	0.133
Mean path length (MPL) – cm	3.02	2.15
Volume – cm³	0.401	0.163
Relative Permeability (μ_r )	125	850
Saturation flux G @ 10 Oe	2350	2750
Inductance factor (A_L) – nH/turn²	68.0	420

Those overstuffed windings improved the sensitivity, but increased the winding resistance far beyond what’s reasonable.

Data on the slit toroids:

Toroid ID	FT50-61	FT37-43	FT50-61
Measured air gap – cm	0.15	0.15	0.17

Winding data
Turns	120	80	25
Wire gauge – AWG	28	32	26
Winding resistance – mΩ	530	920	100
Predicted B field – G/A	872	660	163

Hall effect sensor @ 1.9 mV/G
Predicted output – mV/mA	1.7	1.3	0.31
Actual output – mV/mA	1.9	1.9	0.37
Actual/predicted ratio – %	+12	+46	+19

The last few lines in that table show the transimpedance (transresistance, really, but …) based on the winding current to Hall sensor output voltage ratio (in either mV/mA or V/A, both dimensionally equivalent to ohms), which is why the toroid’s internal magnetic flux doesn’t matter as long as it’s well below saturation.

Gnawing the 80 turn winding off the FT37-43 toroid and rewinding it with 15 turns of 24 AWG wire dropped the winding resistance to 23 mΩ and the transimpedance to 0.36 mV/mA:

FT37-43 with 15 turns 24 AWG - Hall sensor — FT37-43 with 15 turns 24 AWG – Hall sensor

However, applying a voltage gain of about 28 (after removing the sensor’s V_CC/2 bias) will produce a 0-to-5 V output from 500 mA input, which seems reasonable.

2013-08-08

Precision Wrench Rebuild

Decades ago, one jaw on my little 1/4 inch wrench that fits 4-40 nuts broke off. I brazed it back on, fully aware that one day it would break off again, because brazing isn’t really a suitable repair technique for a wrench, even one labeled as “Precision” in that time-honored manner of all low-cost tools.

Time passes, I’m tightening screws against 4-40 nuts, and the jaw gives way:

Precision wrench – broken jaw

So I sawed off a strip of bedframe steel that fit the nuts better than the original stamped steel, did a bit of hand filing, and came up with a reasonable replacement:

Precision wrench – detail

I rammed it into the handle, just as they’d done with the original stamped steel shape:

Precision wrench – rebuilt

That should last approximately forever…

2013-07-31
Water Heater Anode Rod Access Done Right

For reasons I won’t go into, I just installed another water heater. This one, nominally a GE that’s made by Rheem, has a perfectly aligned anode rod access port. This view shows the insulation filling the port, after removing the plastic cap:

GE Water Heater Anode Rod – as shipped

A bit of excavation reveals the top of the rod:

GE Water Heater Anode Rod – excavated

And the 1-1/16 six-point socket fits exactly through the port and mates perfectly with the rod:

GE Water Heater Anode Rod – socket in place

Unlike the never-sufficiently-to-be-damned Whirlpool, no metalwork is required.

Oh, and they have a very nice drain valve at the bottom, with wide opening that shouldn’t clog with the slightest trace of sediment:

GE Water Heater Anode Rod – drain valve

Overall, it looks like a definite win.

2013-07-22