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

  • Chair Reupholstering

    We were tasked with replacing the foam cushion and seat covering on a pair of kitchen chairs. Removing the existing fabric seemed simple, until I pulled a dozen staples holding the cardboard cover to the bottom of the chair and exposed the fabric stapled to the MDF plate:

    Chair reupholstering - stapled fabric
    Chair reupholstering – stapled fabric

    That’s just part of one corner. Obviously, whoever built the chair wanted to be very very very sure the fabric didn’t come loose!

    Removing the staples from one corner produced a pile:

    Chair reupholstering - one corner of staples
    Chair reupholstering – one corner of staples

    Piling up all the staples from the other chair looked even more impressive:

    Chair reupholstering - staple pile
    Chair reupholstering – staple pile

    I fired maybe a third as many staples into the new fabric, which seems secure enough.

  • ShopVac vs. Samsung Vacuum Cleaner Bags

    While cleaning the filter in the 1 gallon ShopVac for the bandsaw and lathe, I found the last few bags from the never-sufficiently-to-be-damned and long-gone Samsung vacuum cleaner that seemed about the right size for upcycling:

    Shopvac vs Samsung vacuum cleaner bags - overview
    Shopvac vs Samsung vacuum cleaner bags – overview

    They’re a bit bulky:

    Shopvac vs Samsung vacuum cleaner bags - trial fit
    Shopvac vs Samsung vacuum cleaner bags – trial fit

    It’s surely not worth buying bags just to cut ’em up, but, with a stock on the shelf, why not?

  • Motel Room Safe: Whoops

    We spotted a pile of room safes in one of the motel stairwells:

    Motel Room Safes in stairwell
    Motel Room Safes in stairwell

    Judging from what we found in the room, it’s out with the old and in with the new:

    Motel Room Safes - mounting pedestal
    Motel Room Safes – mounting pedestal

    Too bad about the mounting pedestal, though: same size, different orientation.

    Something unexpected always lurks in the datasheet …

  • Monthly Image: Wall Painting

    One day, long ago, this tree grew in a certain bedroom:

    Outlet tree
    Outlet tree

    And then a flower appeared in the laundry room:

    Outlet flower
    Outlet flower

    Much to our delight, she asked for forgiveness, not permission … which was, of course, granted immediately.

  • Astable Multivibrator: SMT LED Ballast Resistor

    The original astable multivibrator ran from a dead CR123 primary lithium cell:

    CR123A Astable - front
    CR123A Astable – front

    With a terminal voltage falling from barely 3 V, the LED drew about 3 mA (1 mA/div), tops, without a ballast resistor:

    Astable - CR123A 2.8 V - 1 mA -green
    Astable – CR123A 2.8 V – 1 mA -green

    Hacking in a charged NP-BX1 secondary lithium cell boosted the supply to 4 V:

    NP-BX1 Holder - SMT pogo pins
    NP-BX1 Holder – SMT pogo pins

    Which, diodes being the way they are, raised the LED current to nearly 400 mA (100 mA/div):

    Astable - NP-BX1 4V - base V - 100mA-div
    Astable – NP-BX1 4V – base V – 100mA-div

    Somewhat to my surprise, a few weeks of abuse didn’t do any obvious damage to the LED, but I added a resistor while I was soldering up another holder:

    Astable - 51 ohm SMD ballast
    Astable – 51 ohm SMD ballast

    There’s not quite enough room for a 1/8 W axial resistor, so why not blob in a surface-mount resistor?

    Which cuts the current down to a mere 15 mA (10 mA/div) from a lithium battery at 4 V:

    Astable - NP-BX1 - 51 ohm ballast - 10ma-div
    Astable – NP-BX1 – 51 ohm ballast – 10ma-div

    It’s still blindingly bright, but now I don’t feel bad about it.

     

  • Desk Drawer Stops

    The stops aligning the top two drawers of an old desk vanished, so I got the job of replacing them. They’re hammered into the wood frame:

    Drawer Stops - width measurement
    Drawer Stops – width measurement

    And stand up just enough to engage the back of the drawer face:

    Drawer Stops - height measurement
    Drawer Stops – height measurement

    Back in the Basement Laboratory Shop Wing, I harvested steel strips from a defunct PC case, rubber-hammered them flat, sharpened a cold chisel (un-hardened, so it always needs sharpening), and got to work:

    Drawer Stops - chiseled blanks
    Drawer Stops – chiseled blanks

    The pointy sides should have sharp edges, which you get for free with a chisel. You also get a bench full of little steel slivers perfectly suited for embedding in human flesh. Wearing eye protection is more than just a good idea, too.

    Introducing what will become the visible edges to Mr Disk Sander makes them marginally less hazardous:

    Drawer Stops - in progress
    Drawer Stops – in progress

    A slightly fuzzy picture of a test fit shows the stops should suffice:

    Drawer Stops - trial fit
    Drawer Stops – trial fit

    Which they did:

    Drawer Stops - installed
    Drawer Stops – installed

    Nobody will ever notice the blob of hot melt glue behind each one:

    Drawer Stops - glue blob
    Drawer Stops – glue blob

    Done!

  • Astable Multivibrator: NP-BX1 Base

    Adapting the NP-BX1 battery holder to use SMT pogo pins worked well:

    NP-BX1 Holder - SMT pogo pins
    NP-BX1 Holder – SMT pogo pins

    The next step is to add sockets for those 14 AWG wires:

    NP-BX1 Battery Holder - Wire Posts - solid model
    NP-BX1 Battery Holder – Wire Posts – solid model

    Start by reaming / hand-drilling all the holes to their nominal size and cleaning out the pogo pin pocket.

    Solder wires to the pogo pins and thread them through the holder and lid:

    Astable - NP-BX1 holder - pogo pin soldering
    Astable – NP-BX1 holder – pogo pin soldering

    That’s nice, floppy silicone-insulated 24 AWG wire, which may be a bit too thick for this purpose.

    The pogo pins will, ideally, seat with the end of the body flush at the holder wall. Make it so:

    Astable - NP-BX1 holder - pogo pin protrusion
    Astable – NP-BX1 holder – pogo pin protrusion

    Dress the wires neatly into their pocket:

    Astable - NP-BX1 holder - pogo pin wiring
    Astable – NP-BX1 holder – pogo pin wiring

    Butter the bottom of the lid with epoxy, clamp in place, set it up for curing, then fill the recess:

    Astable - NP-BX1 base - curing
    Astable – NP-BX1 base – curing

    While it’s curing, make a soldering fixture for the 14 AWG wires:

    Astable - drilling strut soldering fixture
    Astable – drilling strut soldering fixture

    The holes are on 5 mm centers, in the expectation other battery holders will need different spacing.

    Solder it up and stick the wires into the base:

    Astable - NP-BX1 base - detail
    Astable – NP-BX1 base – detail

    Jam a battery in and It Just Works™:

    Astable - NP-BX1 3.8V - 20ma-div - cap V
    Astable – NP-BX1 3.8V – 20ma-div – cap V

    The traces:

    • Green = supply current at 20 mA/div
    • Yellow = LED driver transistor base voltage
    • Purple = other transistor collector voltage
    • White = base – collector voltage = capacitor voltage

    The measurement setup was a bit of a hairball:

    Astable - NP-BX1 base - current probe
    Astable – NP-BX1 base – current probe

    For completeness, here’s the schematic-and-layout diagram behind the circuitry:

    Astable - NP-BX1 base - schematic
    Astable – NP-BX1 base – schematic

    I love it when a plan comes together!

    The OpenSCAD source code as a GitHub Gist:

    // Holder for Sony NP-BX1 Li-Ion battery
    // Ed Nisley KE4ZNU January 2013
    // 2018-11-15 Adapted for wire leads from 1.5 mm test pins, added upright wire bases
    // Layout options
    Layout = "Fit"; // Show Build Fit Case Lid Pins
    //- Extrusion parameters – must match reality!
    // Print with +2 shells and 3 solid layers
    ThreadThick = 0.25;
    ThreadWidth = 0.35;
    HoleWindage = 0.2;
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    Protrusion = 0.1; // make holes end cleanly
    inch = 25.4;
    BuildOffset = 3.0; // clearance for build layout
    Gap = 2.0; // separation for Fit parts
    //- Basic dimensions
    WallThick = 4*ThreadWidth; // holder sidewalls
    BaseThick = 6*ThreadThick; // bottom of holder to bottom of battery
    TopThick = 6*ThreadThick; // top of battery to top of holder
    //- Battery dimensions – rationalized from several samples
    // Coordinate origin at battery contact face with key openings below contacts
    Battery = [43.0,30.0,9.5]; // X = length, Y = width, Z = thickness
    Contacts = [[-0.75,6.0,6.2],[-0.75,16.0,6.2]]; // relative to battery edge, front, and bottom
    ContactOC = Contacts[1].y – Contacts[0].y;
    ContactCenter = Contacts[0].y + ContactOC/2;
    KeyBlocks = [[1.75,3.70,2.90],[1.75,3.60,2.90]]; // recesses in battery face set X position
    //- Pin dimensions
    ID = 0;
    OD = 1;
    LENGTH = 2;
    PinShank = [1.5,2.0,6.5]; // shank, flange, compressed length
    PinFlange = [1.5,2.0,0.5]; // flange, length included in PinShank
    PinTip = [0.9,0.9,2.5]; // extended spring-loaded tip
    PinChannel = PinFlange[LENGTH] + 0.5; // cut behind flange for solder overflow
    PinRecess = 3.0; // recess behind pin flange end for epoxy fill
    echo(str("Contact tip dia: ",PinTip[OD]));
    echo(str(" .. shank dia: ",PinShank[ID]));
    OverTravel = 0.5; // space beyond battery face at X origin
    //- Holder dimensions
    GuideRadius = ThreadWidth; // friction fit ridges
    GuideOffset = 7; // from compartment corners
    ThumbRadius = 10.0; // thumb opening at end of battery
    CornerRadius = 3*ThreadThick; // nice corner rounding
    CaseSize = [Battery.x + PinShank[LENGTH] + OverTravel + PinRecess + GuideRadius + WallThick,
    Battery.y + 2*WallThick + 2*GuideRadius,
    Battery.z + BaseThick + TopThick];
    CaseOffset = [-(PinShank[LENGTH] + OverTravel + PinRecess),-(WallThick + GuideRadius),0]; // position around battery
    LidOverhang = 2.0; // over top of battery for retention
    LidSize = [-CaseOffset.x + LidOverhang,CaseSize.y,TopThick];
    LidOffset = [0.0,CaseOffset.y,0];
    //- Wire struts
    StrutDia = 1.6; // AWG 14 = 1.6 mm
    StrutOC = 45;
    StrutSides = 3*4;
    StrutBase = [StrutDia,StrutDia + 4*WallThick,CaseSize.z – TopThick]; // ID = wire, OD=buildable
    //———————-
    // 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);
    }
    //——————-
    //– Guides for tighter friction fit
    module Guides() {
    translate([GuideOffset,-GuideRadius,0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    translate([GuideOffset,(Battery.y + GuideRadius),0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    translate([(Battery.x – GuideOffset),-GuideRadius,0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    translate([(Battery.x – GuideOffset),(Battery.y + GuideRadius),0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    translate([(Battery.x + GuideRadius),GuideOffset/2,0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    translate([(Battery.x + GuideRadius),(Battery.y – GuideOffset/2),0])
    PolyCyl(2*GuideRadius,(Battery.z – Protrusion),4);
    }
    //– Contact pins
    // Rotated to put them in their natural oriention
    // Aligned to put tip base / end of shank at Overtravel limit
    module PinShape() {
    translate([-(PinShank[LENGTH] + OverTravel),0,0])
    rotate([0,90,0])
    rotate(180/6)
    union() {
    PolyCyl(PinTip[OD],PinShank[LENGTH] + PinTip[LENGTH],6);
    PolyCyl(PinShank[ID],PinShank[LENGTH] + Protrusion,6); // slight extension for clean cuts
    PolyCyl(PinFlange[OD],PinFlange[LENGTH],6);
    }
    }
    // Position pins to put end of shank at battery face
    // Does not include recess access into case
    module PinAssembly() {
    union() {
    for (p = Contacts)
    translate([0,p.y,p.z])
    PinShape();
    translate([-(PinShank[LENGTH] + OverTravel) + PinChannel/2, // solder space
    ContactCenter,
    Contacts[0].z])
    cube([PinChannel,(Contacts[1].y – Contacts[0].y),PinFlange[OD]],center=true);
    for (j=[-1,1]) // wire channels
    translate([-(PinShank[LENGTH] + OverTravel – PinChannel/2),
    j*ContactOC/4 + ContactCenter,
    Contacts[0].z – PinFlange[OD]/2])
    rotate(180/6)
    PolyCyl(PinFlange[OD],CaseSize.z,6);
    }
    }
    //– Case with origin at battery corner
    module Case() {
    difference() {
    union() {
    difference() {
    union() {
    translate([(CaseSize.x/2 + CaseOffset.x), // basic case shape
    (CaseSize.y/2 + CaseOffset.y),
    (CaseSize.z/2 – BaseThick)])
    hull()
    for (i=[-1,1], j=[-1,1], k=[-1,1])
    translate([i*(CaseSize.x/2 – CornerRadius),
    j*(CaseSize.y/2 – CornerRadius),
    k*(CaseSize.z/2 – CornerRadius)])
    sphere(r=CornerRadius/cos(180/8),$fn=8); // cos() fixes undersize spheres!
    hull() // wire strut bases
    for (j=[-1,1])
    translate([0,j*StrutOC/2 + Battery.y/2,-BaseThick])
    rotate(180/StrutSides)
    cylinder(d=StrutBase[OD],h=StrutBase[LENGTH],$fn=StrutSides);
    translate([0,Battery.y/2,StrutBase[LENGTH]/2 – BaseThick])
    cube([2*StrutBase[OD],StrutOC,StrutBase[LENGTH]],center=true);
    }
    translate([-OverTravel,-GuideRadius,0])
    cube([(Battery.x + GuideRadius + OverTravel),
    (Battery.y + 2*GuideRadius),
    (Battery.z + Protrusion)]); // battery space
    }
    Guides(); // improve friction fit
    translate([-OverTravel,-GuideRadius,0]) // battery keying blocks
    cube(KeyBlocks[0] + [OverTravel,GuideRadius,0],center=false);
    translate([-OverTravel,(Battery.y – KeyBlocks[1].y),0])
    cube(KeyBlocks[1] + [OverTravel,GuideRadius,0],center=false);
    }
    translate([2*CaseOffset.x, // battery top access
    (CaseOffset.y – Protrusion),
    Battery.z])
    cube([2*CaseSize.x,(CaseSize.y + 2*Protrusion),(TopThick + Protrusion)]);
    if (false)
    translate([(CaseOffset.x – Protrusion), // battery insertion allowance
    (CaseOffset.y – Protrusion),
    Battery.z])
    cube([(CaseSize.x + 2*Protrusion),(CaseSize.y + 2*Protrusion),(TopThick + Protrusion)]);
    for (j=[-1,1]) // strut wires
    translate([0,j*StrutOC/2 + Battery.y/2,-(BaseThick + Protrusion)])
    PolyCyl(StrutBase[ID],StrutBase[LENGTH] + 2*Protrusion,6);
    for (i=[-1,1], j=[-1,1])
    translate([i*StrutBase[OD],j*StrutOC/2 + Battery.y/2,-(BaseThick + Protrusion)])
    rotate(180/StrutSides)
    PolyCyl(StrutBase[OD],StrutBase[LENGTH] + 2*Protrusion,StrutSides);
    translate([(Battery.x – Protrusion), // remove thumb notch
    (CaseSize.y/2 + CaseOffset.y),
    (ThumbRadius)])
    rotate([90,0,0])
    rotate([0,90,0])
    cylinder(r=ThumbRadius,
    h=(WallThick + GuideRadius + 2*Protrusion),
    $fn=22);
    PinAssembly();
    translate([CaseOffset.x + PinRecess + Protrusion,(Contacts[1].y + Contacts[0].y)/2,Contacts[0].z])
    translate([-PinRecess,0,0])
    cube([2*PinRecess,
    (Contacts[1].y – Contacts[0].y + PinFlange[OD]),
    2*PinFlange[OD]],center=true);
    }
    }
    // Lid position offset to match case
    module Lid() {
    difference() {
    translate([-LidSize.x/2 + LidOffset.x + LidOverhang,LidSize.y/2 + LidOffset.y,0])
    difference() {
    hull()
    for (i=[-1,1], j=[-1,1], k=[-1,1])
    translate([i*(LidSize.x/2 – CornerRadius),
    j*(LidSize.y/2 – CornerRadius),
    k*(LidSize.z – CornerRadius)]) // double thickness for flat bottom
    sphere(r=CornerRadius,$fn=8);
    translate([0,0,-LidSize.z/2]) // remove bottom
    cube([(LidSize.x + 2*Protrusion),(LidSize.y + 2*Protrusion),LidSize.z],center=true);
    translate([LidSize.x/8,0,0])
    cube([LidSize.x/4,0.75*LidSize.y,4*ThreadThick],center=true); // epoxy recess
    }
    translate([0,0,-(Contacts[0].z + PinFlange[OD])]) // punch wire holes
    PinAssembly();
    }
    }
    //——————-
    // Build it!
    if (Layout == "Case")
    Case();
    if (Layout == "Lid")
    Lid();
    if (Layout == "Pins") {
    color("Silver",0.5)
    PinShape();
    PinAssembly();
    }
    if (Layout == "Show") { // reveal pin assembly
    difference() {
    Case();
    translate([(CaseOffset.x – Protrusion),
    Contacts[1].y,
    Contacts[1].z])
    cube([(-CaseOffset.x + Protrusion),
    CaseSize.y,
    (CaseSize.z – Contacts[0].z + Protrusion)]);
    translate([(CaseOffset.x – Protrusion),
    (CaseOffset.y – Protrusion),
    0])
    cube([(-CaseOffset.x + Protrusion),
    Contacts[0].y + Protrusion – CaseOffset.y,
    CaseSize.z]);
    }
    translate([0,0,Battery.z + Gap])
    Lid();
    color("Silver",0.15)
    PinAssembly();
    }
    if (Layout == "Build") {
    translate([-(CaseSize.x/2 + CaseOffset.x),-(CaseOffset.y – BuildOffset),BaseThick])
    Case();
    translate([CaseSize.x/2,-LidSize.x/2,0])
    rotate(90)
    Lid();
    }
    if (Layout == "Fit") {
    Case();
    translate([0,0,(Battery.z + Gap)])
    Lid();
    color("Silver",0.25)
    PinAssembly();
    }
    view raw NP-BX1 Battery Holder – Wire Posts.scad hosted with ❤ by GitHub