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

  • Fixing an MTD Gas Cap Splash Shield

    OEM plastic post
    OEM plastic post

    MTD used the same design for the gasoline tank caps on our leaf shredder and snow thrower: an aluminum cone (which evidently serves to keep splashes away from the tank vent) mounted on a heat-staked plastic rod molded into the cap. It’s straightforward, but a bit suboptimal for high-vibration yard gadgets.

    The aluminum cone eventually worries its way through the plastic post and falls into the tank, taking the heat-formed button from the post along with it. Trust me on this, fishing those things out of the tank is an exquisite little inconvenience.

    4-40 screw post - inside
    4-40 screw post – inside
    4-40 screw post - exterior
    4-40 screw post – exterior

    The fix is straightforward.

    Chop off the remains of the post, drill a snug 4-40 tapping hole straight through the cap, and tap it accordingly. Secure the cone to the screw with a nut tightened against the head, run the screw through the cap, run a pair of nuts onto it, trim to length, then jam the nuts together so the cone is about where it started out. Loctite on the nuts is a Good Thing, but I don’t know how it feels about gasoline immersion.

    The snowblower cone is getting wobbly; I must make a preemptive strike on it to avoid fishing the debris out of the tank.

  • Salvaging Old Photos: Gamma Boost

    We’re scanning a bunch of really old photographs to assemble a book of memories for Mary’s father. Most of the images are about what you’d expect for old photos: bad exposures, poor focus, and scratched emulsion. There’s not much you can do to save ’em, but one image really surprised me.

    Scanned at 600 dpi with the black and white points set to maximize the dynamic range, we got this image (reduced resolution for display here).

    Original
    Original

    The original image is somewhat brighter than that: there’s a figure visible in the upper-left, but you can’t see much more.

    After dramatically adjusting the gamma and switching to grayscale mode, her father popped out of the shadows.

    Gamma = 3
    Gamma = 3

    Now, it’s not a great picture, but it’s one of the few we have from that era… and it’s a much better picture than no picture at all!

    A similar trick can recover dull gray snow pictures, as mentioned there.

  • Holding Machine Screws for Trimming

    Screw in slotted nut
    Screw in slotted nut

    Some years back, I bought a lifetime supply of stainless steel machine screws in the usual sizes, all in 1- and 2-inch lengths. I was always cutting the things to length anyway, so why not start with nice screws?

    The problem with cutting a screw is holding it securely enough that it doesn’t fly off into a far corner of the shop, but without goobering either the threads or the head.

    The secret, at least as far as I can tell, is slitting a nut to make a secure clamp for sawing, filing, and grinding. I ran a slitting saw through a nut to get the result you see here. Although it’s awkward, a slit through a point means grabbing the nut on two parallel sides squeezes the slot closed: exactly what you want.

    Screw firmly under control
    Screw firmly under control

    Slit a bunch of nuts whenever you get set up to do this, because those ugly thread ends on the cut screws tend to chew ’em up. If you have any foresight, you’ll thread the nut on the screw before you cut it, but that doesn’t work for really short screws.

    Yeah, a lifetime supply of all different screw sizes and all different lengths would be nice, but I really don’t spend a whole lot of my life cutting screws…

  • Hard Drive Magnets for Debris Collection

    Magnetic Staple Collector
    Magnetic Staple Collector

    We took down the deer netting around the garden yesterday, which involves pulling a zillion staples out of the wood posts. I put some salvaged hard-drive head motor magnets to good use: one magnet inside my jacket sleeve to hold the other magnet in place, then just drop staples near them.

    Shazam… no staples in the ground!

    You can actually buy such things, with cute Velcro straps and all, but why? You’ve been saving those magnets for years: put ’em to use!

  • IBM Thinkpad 560Z CMOS Battery Connector Polarity

    Thinkpad 560Z Lithium Cell Polarity
    Thinkpad 560Z Lithium Cell Polarity

    Two years ago I converted a $20 Thinkpad 560Z (they’re more expensive now, oddly enough) into a digital picture frame for Mary’s parents, a process documented in two of my late, lamented DDJ columns there and there. It runs a stripped-down Slackware installation that boots directly into a picture viewer, so when you turn it on you get pictures and nothing else. Well, after you get a few screens of the usual white-on-black Linux boot messages, which I think adds a certain geeky charm to a digital picture frame.

    Anyhow, the thing failed just before Thanksgiving with BIOS error messages 161 and 163: its way of telling you that the lithium cell powering the clock chip has gone dead. I hadn’t replaced that cell when I did the conversion and it lasted just about exactly a decade; it was evidently the right size for the job.

    Not being constrained by the confines of the original laptop case, I replaced the coin cell with a grossly oversized CR123A cylindrical lithium cell (having a bunch of them on the shelf and some holders for another project). The connector is in an awkward location, below the IDE socket’s flex-PCB cable, and both wires popped out of the connector shell when I pulled on them. So it goes.

    The top picture shows the proper polarity, as seen inside another 560Z’s lithium cell compartment: red-for-positive on the right, with the circuit board positioned component side down (toward the keyboard). Our daughter did the soldering; she’s since learned about heatshrink tubing and cold joints; it’s good enough.

    This picture shows the CR123A all wired up and ready to go in the picture frame. The circuit board here is component side up, so the connector wires go the other way. Notice the small trace from the red-side pin on the circuit board; that’s your clue that it’s the positive battery connection. Measure the voltage at the backside of the connector to be sure you have those miniature pins properly seated in the connector, too.

    CR123A in 560Z Picture Frame
    CR123A in 560Z Picture Frame

    FWIW, I bought three 560Zs while they were cheap; our young lady installed Puppy Linux on the one in the top picture (hence her soldering) and seems reasonably content. They’re old & slow & cramped by contemporary standards, but just fine for most of the things you’d probably buy a fancy new netbook for.

    Hmmm…

  • Put Hand Wiring on EAGLE Layer 15

    Hand wiring on Layer 15
    Hand wiring on Layer 15

    Because nearly all of my printed circuit boards are for one-off homebrew projects, I tend to not obsess over getting the last air wire down on the copper. Instead, I route those pesky all-the-way-across-the-board stragglers on Layer 15 with big fat vias on each end, then solder a jumper wire across the board.

    In effect, my Layer 15 is outside the board.

    The screen shot shows a chunk of a board with some Layer 15 wires. I make ’em fat and use swooping semicircular arcs on the ends: they’re easily visible.

    I don’t worry about actually routing the traces; they’re just straight lines and arcs. This generates all manner of overlaps with the rest of the components & wiring, but after I go down through the DRC list and approve ’em all one time, that’s the end of that hassle.

    Two key advantages:

    • All the remaining air wires are genuine unrouted connections
    • I can print out Layer 15 separately to get a hand wiring map

    I make the vias fairly large (here, 100 mils) and a unique shape (octagonal) so that I know each one should get a wire.

    I usually wind up doing the power connections the same way; those vias are square. Conversely, ground vias stitching the top & bottom planes together are round; they get a short Z-wire through the board.

    This probably won’t work if you’re having the boards built by an actual PCB vendor, as they’ll try to make a three-layer board or kick the board out on layout rule violations… but, on the other hand, if you can afford a four-layer board, then most likely you won’t have any trouble routing the wires.

  • Terracycle Chain Idler: Status Report

    Stainless idler shaft in November 2009
    Stainless idler shaft in November 2009

    The 6 mm stainless steel shaft I installed in late June, for reasons described there, has been working just fine.

    Although the shaft has some discoloration, the idler bearing slides freely this way and that. No complaints about noises or bad shifting.

    I spritzed some silicone lube on the shaft and it’s way slippery again. That’s better than petroleum lubes that tend to turn road dust into grinding compound.