Tag: Improvements

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

Power Supply Banana Jack Misfit

After butchering that fancy Tektronix test lead thing for the SMD tweezers, I hung the bitter end in my cable tangle. Turns out I needed a power cord to bring up the brassboard of the Wouxun GPS interface, so I soldered it up, went to plug it in, and … the Tek plugs didn’t fit the plated supply jacks.

Power Supply Banana Jacks

Now, if I had to choose whether Tek plugs are oversized or Made In China jacks are undersized, well, you can probably guess my answer.

Turns out that the jacks should be 4 mm ID, which is actually a 5/32 hard-inch size because banana jacks date back to the days before millimeters became a force to be reckoned with. They were actually 3.8 mm ID, which wouldn’t usually matter except for the fact that the Tek plugs have a nice solid bullet end that’s just about exactly 4 mm OD.

So I chucked up a 5/32 inch drill, perched the power supply on a block of wood (to clear the fuse & cord in on the back panel) on the drill press table, and hand-held it while clearing out the holes with a low spindle speed. You can see the nice, shiny brass inside those jacks in the photo; they used to have lumpy silvery plating inside that was probably responsible for much of the 0.2 mm shrinkage.

The jacks also don’t have the usual crosswise hole near the base to accept a bare wire, which is an occasional nuisance. I was tempted to drill that hole, but decided I’ll leave that project for another time.

2012-02-08
Geek Accessories: Cases Therefore

Mary made me several presents early this year: a new belt pack, a camera case for the Canon SX230HS, and a touchup for the Zire 71 case:

Belt pack – camera case – PDA case

The belt pack has an interior lining with many side pockets for the stuff I deem essential; it’s also large enough to hold both the camera and the PDA when I’m out biking around. The camera case includes a pocket nestling a battery against the camera’s front side, beside the lens cap. The Zire case, well, at some point I suppose I’ll be forced to get a phone, but, until then, this will suffice.

They’re all made from coated pack cloth, not that I expect to dunk myself in water (or that it’d do any good), but it seems to never wear out.

*hugs*

(And, yes, it probably should be “Therefor”, but …)

2012-02-04
Shower Basket Sucker Relocation

The outer suckers on the basket in the corner of the shower didn’t line up with the tiles; either tile dimensions have changed in the last half-century or it’s a hard-metric basket. It didn’t look right when I installed it (now that is a grandiose term if I’ve ever misused one), so (when the thing fell off and landed with a clatter a few days ago) I drilled two additional holes as far away from the corner as I could, using a step drill to prevent the plastic from shattering, and it’s all good.

Shower basket – redrilled

Sometimes, they’re easy…

You’ll note that I heroically resisted the urge to fire the Thing-O-Matic to print some kind of weird-ass safety-orange interposer plate, just because I could.

2012-01-24
HP 50g Calculator Screen Protector

A week or so after I got my HP 49GX calculator, I managed to drop a vernier caliper on it. Interior points downward, of course, putting a nice divot on the non-glare plastic over the LCD panel.

A week or so after I got my HP 50g calculator, I applied a screen protector sheet harvested from the lifetime supply I bought for my original Zire 71, back in the day.

HP 50g calculator screen protector

The fact that it’s an almost perfect fit and that the calculator sports a monochrome LCD with lower resolution is a sad commentary on the state of the calculator art.

Taking that picture in low-angle full sunlight makes the protector sheet look awful. In actual use, it’s nearly invisible. Haven’t dropped anything on it yet, either.

And, yes, I did cut it out around the HP logo button in the upper right corner.

2012-01-23

Zire 71 Printed Button Shield

After fixing that old plate, I just had to do this:

Zire 71 protector - solid model — Zire 71 protector – solid model

Which pretty much fills up the build platform:

Zire 71 protector - on build platform — Zire 71 protector – on build platform

And fits perfectly:

It’s printed with 100% infill to produce a solid plastic plate.

In retrospect, I think it’d work better if I put the notch on the bottom side with a bit of support, so that the glass-smooth surface faced the Zire. Maybe next time?

The OpenSCAD source code:

// Protector plate for Zire 71 PDA
// Ed Nisley KE4ZNU - Jan 2012

//-------
//- Extrusion parameters must match reality!
//  Print with +0 shells, 3 solid layers, 0.2 infill

ThreadThick = 0.25;
ThreadWidth = 2.0 * ThreadThick;

Protrusion = 0.1;           // make holes end cleanly

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

//-------
// Dimensions

$fn=8*4;

Length = 110;
Width = 73;
Thickness = IntegerMultiple(2.0,ThreadThick);
CornerRadius = 5.0;

NotchLength = 20;

PocketWidth = 22;
PocketLength = 12;
PocketRadius = 3.0;
PocketOffsetX = -1;
PocketOffsetY = 10;

SlotLength = 20;
SlotWidth = IntegerMultiple(8.0,ThreadWidth);
SlotDepth = IntegerMultiple(0.75,ThreadThick);

//-------

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);
}

//-------
// Outer section of plate
//  with nice rounded edges

module PlateHalf() {

  translate([0,0,Thickness/2])
    difference() {
      minkowski(convexity=3) {
        cube([(Width - SlotWidth)/2 - 2*CornerRadius,(Length - 2*CornerRadius),(Thickness - 2*Protrusion)],center=true);
        cylinder(r=CornerRadius,h=Protrusion);
      }
      translate([PocketOffsetX,PocketOffsetY - Length/2,0])
        minkowski() {
          cube([PocketWidth - 2*PocketRadius,PocketLength - 2*PocketRadius,Thickness],center=true);
          cylinder(r=PocketRadius,h=Protrusion);
        }
    }
}

//-------

ShowPegGrid();

translate([(Width - SlotWidth)/4 + SlotWidth/2,0,0])
  PlateHalf();

translate([-(Width - SlotWidth)/4 - SlotWidth/2,0,0])
  mirror([1,0,0])
    PlateHalf();

difference() {
  translate([0,0,(Thickness - SlotDepth)/2])
    cube([SlotWidth + 2*Protrusion,Length - 2*SlotLength + SlotWidth,(Thickness - SlotDepth)],center=true);
  for (Index=[-1,1])
    translate([0,(Index*(Length/2 - SlotLength + SlotWidth/2)),-Protrusion])
      cylinder(r=SlotWidth/2,h=Thickness + 2*Protrusion);
}

2012-01-20

Thing-O-Matic: HBP Rebuild

The basic problem with the heater on the Heated Build Platform is that the SMD pads must both make electrical contact to the Molex-style connector and withstand mechanical stress from the dangling wires & cables as the platform moves along the X and Y axes. Rather than replace the entire heater, I attached pigtail leads to the PCB, anchored those leads to the wood platform under the heater, and routed the cables through the deck under the Y axis stage a bit differently.

However, attaching pigtail leads to the PCB poses a problem, because ordinary electronic hookup wire has thermoplastic insulation that melts or deforms at temperatures well under my usual 110 °C platform heat setting; shorting the heater wires would be a Very Bad Thing.

Some concerted rummaging in the Big Box o’ Multiconductor Cable turned up a hank of Teflon-insulated shielded two-wire cable that, as nearly as I can tell, has pure silver conductors and shield braid: the ends were tarnished like silver and there’s nary a trace of copper in the fresh cuts. It must be military surplus and, based on a vague recollection, was most likely cough salvaged by my father, who worked as an avionics tech at Olmstead AFB in the mid-60s. Ya gotta have stuff, right?

[Update: Alas, it’s not pure silver, as shown in the comments.]

The general idea is to scuff up the shiny PCB surface enough to anchor blobs of JB Industro Weld epoxy that surround brass tubes holding the cables. A pair of tubes secure each cable and provide strain relief; the cable is free to move, but not by very much. The thermistor cable has a long arch that will, I hope, keep the cable at the platform temperature and reduce its cooling effect on the thermistor:

Thermistor rewiring – heat cure

The alligator clips connect to a bench power supply that delivered 4 V @ 2 A = 8 W that heated the PCB to about 40 °C in the rather chilly Basement Laboratory and encouraged the epoxy to cure in less time than forever.

The final result looked like this, with Anderson Powerpoles now attached to the heater cable:

Rewired HBP

The 24 AWG conductors in the cable may seem scanty for 6 A of heater current, but, hey, they’re silver.

The three-pin connector on the end of the thermistor cable is a pure kludge, built from a 4-pin header to match the CD-ROM audio pinout on the new cable from the Extruder Controller. I kept the default pinout on this end to provide some protection against plugging it in backwards:

Kludged HBP thermistor connector

With all that in hand, I screwed the PCB to the aluminum sub-plate, bolted it to the plywood platform, and stuck the cables onto the platform with adhesive clamps:

Rewired HBP – front

Reaming out the hole between the red and black Powerpole shells provided just enough room for an M3 screw to anchor them to the HBP: they won’t flop around under acceleration.

The thermistor cable exits to the left, the rest to the right, and I’m unhappy with the overall routing. I added a small bumper (made from bent steel shim stock) to keep the thermistor cable out of the gap between the Y axis stage and the left side wall:

Y Axis gap filler

So, yes, it works, but it sure ain’t elegant.

The first object was the revised platform level test pattern:

Rewired HBP with level test pattern

The platform is holding level within ±0.05 mm across build plates 1 and 2, somewhat better than before. On the other paw, the whole thing doesn’t have many hours on it…

2012-01-13
Thing-O-Matic: HBP Heat Shield

With the heater off for repair, I added a strip of self-adhesive stainless steel tape to the top of the plywood platform, directly under the heater. This should reduce the wood temperature and maybe, just maybe, reduce the thermal expansion that shifts the X axis location of the Z-minimum platform height switch.

HBP heat shield

It’s stainless steel because that’s what was in the Tape Lookaside Buffer; a hunk of aluminum tape, even a pair of 2 inch / 50 mm strips would work just fine.

Not shown here is the M3 screw through the front-center hole (invisible under the tape) that will eventually anchor the new heater connector.

2012-01-12