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

  • HT GPS + Audio: Revised Schematic

    This is a tweak to the previous design, based on some road testing.

    An attenuator on the output of the MAX4467 voice amp allows gains below unity. Right now, the MAX4467 has Av=5 and the attenuator cuts it back by about 1/5, so the overall gain is about unity. I have a bunch of surplus electret mic capsules and some have come through really hot; this allows backing the gain way down with the mic amp set to Av=1.

    That requires stiffening the Vcc/2 supply by swapping in a 33 µF cap for the original 1 µF unit. If you don’t do that, the amp turns into a oscillator: the attenuator jerks the Vcc/2 supply around, which feeds back to the non-inverting input of the MAX4467. In principle, the gain should be less than unity, but I wouldn’t bet on it.

    The MOSFET relay sometimes didn’t quite turn on from the piddly 4 mA available through the ICOM IC-Z1A’s mic power supply; it was vaguely temperature dependent. I returned to an ordinary optocoupler with a CTR of about 100% driving a 2N2907 PNP transistor, as in the first-pass design that you never saw.

    The two 2N2907 devices allow either a through-hole TO-92 or SMD SOT-3 package, depending on what you have and the power dissipation you need. In my situation, the SMD version suffices, with less than 100 mV of VCE saturation.

    Let me know if you need the Eagle PCB files or PCB layouts.

    Clicky for a bigger image…

    GPS + Voice HT Interface schematic - revised 15 July 2010
    GPS + Voice HT Interface schematic – revised 15 July 2010

    [Update: I’m not convinced the Vcc/2 supply is stiff enough. I ripped out the attenuator and cut the amp gain to 1.0. If I get some really hot capsules, I’ll think it over a bit more.]

  • Tour Easy Seat Clamp Doodles

    Tour Easy seat clamp doodles
    Tour Easy seat clamp doodles

    I’ve managed to lose enough weight off my butt (it doesn’t go away, it just becomes leg muscle for a few months) that I must move the seat on my Tour Easy forward maybe 5 mm. Alas, I’ve run out of adjustment room: the frame is a Medium Large and I probably should have gotten a Medium; that decision was forced by getting a much-too-small Linear many years ago.

    The general idea here is to bolt the seat to an aluminum circumferential clamp just forward of the plate and tubes that normally secure the seat to the frame. That moves the clamping bolts about 15 cm forward, but they slide in slots along the seat bottom.

    The bolts are 1/4-20 stainless carriage bolts, with the square shank under the head sliding in those slots. I think the clamp can be about the same thickness as the existing tubes, so the same bolts will work.

    The main frame tube runs slightly above the two small tubes that stiffen the rear triangle. It’s not clear those clearances in the clamp must be contoured to fit the tubes exactly; a simple flat cutout will probably work just fine.

    The top of the clamp must have two bosses to support the seat base around the clamping screws. A line of rivets down the middle secures the seat base to the contoured (carbon?) fiberglass pan holding the foam cushion.

  • Cutting Thin Rings: Homebrew Punches

    The Totally Featureless Clock is back for a refit: its preferred location turned out to have essentially no RF at all, so I must move the antenna out of the clock case on the end of a cable.

    Drat!

    I put the ferrite bar inside a length of PVC pipe, turned down to make it less ugly, with white plastic end plugs. Rather than fiddle around with complex mountings, I cushioned the fragile bar in closed-cell foam, which meant I needed some way to cut a bunch of foam rings.

    Some rummaging produced a thinwall brass tube with about the same ID as the PVC pipe. A brief trip to the lathe put a reasonably sharp edge on one end.

    Sharpening the brass tube
    Sharpening the brass tube

    That edge is more keen than it looks; while it’s not razor-sharp, it’s plenty good enough. I didn’t use it as a punch, just grabbed it in a rag to cushion my palm and rotated it through the foam against a plywood scrap.

    That produced a bunch of foam cookies.

    Foam cutouts
    Foam cutouts

    The bar diameter was close enough to a standard hole punch that I didn’t have to make one. Centering by eye and rotating by hand turned the cookies into donuts.

    Punched holes
    Punched holes

    And then they fit just fine…

    Cushioned ferrite bar antenna
    Cushioned ferrite bar antenna

    I made more donuts to swaddle the bar from end to end inside the PVC tube. I slipped the antenna in from the left, then pushed the donuts over the bar with Yet Another Brass Tube. The end result is an antenna compression-packed in foam, which ought to keep it in good condition through at least a minor oops.

    Finished antenna housing
    Finished antenna housing

    The screws pass through the end plugs to hold them against the pressure from the foam cookies at the bar ends. The holes are slightly counterbored on the top to blend the screw heads into the curve of the tube. There’s a 3/8-inch flat along the bottom that will eventually settle against the underside of a shelf.

  • Epson R380 Printer: External Waste Ink Tank

    Side cover latch and external tank hose
    Side cover latch and external tank hose

    Having reset the waste ink counter on my Epson R380 printer, I finally got around to installing the external waste ink tank that will prevent the printer from drooling all over its innards.

    Fortunately, rerouting the waste ink hose out of the printer doesn’t require the complete teardown mandated to remove the waste ink tank itself: you can do it by removing the cover, drilling a hole, moving the hose, and abandoning the tank in place.

    The recommended way to remove the right-side side cover (as you face the printer) involves jamming a steel ruler into the “vent” (it’s actually a decorative feature) and shoving a latch out of the way. I trimmed a bit of stainless steel strip, shoved it in, and it worked fine. The cover latch is the complex central feature in the vertical gap between the case and the cover. The hose is routed out through a new hole down in the lower right corner.

    With the cover off, it turns out that the “tank” is actually a “tray” (which is what it’s called in the maintenance manual) filled with absorbent fuzz. There’s no lid, so it appears they’re counting on evaporation to keep the total volume under control and surface tension on the fuzz to keep the ink from leaking when you tip the printer. I suspect if the printer spent a lot of time on its ear, though, things would get messy.

    Internal tank and OEM hose
    Internal tank and OEM hose

    Removing the hose from the barbed fitting goes easier with a small screwdriver pushing it along; you (well, I) can’t just pull the hose off. It’s a very flexible silicone rubber (?) hose with an internal liner: very nice stuff.

    The hose seems to drain only the head-cleaning station, not the long waste ink tank / tray across the width of the printer that catches overspray from borderless printing. That counter is at 5% of its rated maximum, so I’ll let it slide.

    The ink, being adsorbed in the fuzz, won’t leak back out of the tray, so there’s no need to plug the barbed fitting.

    Hole in case and rerouted hose
    Hole in case and rerouted hose

    I used the 1/4-inch tip of a fat step drill to poke a hole at the very bottom of the plastic case, behind the pillar holding the white printer mechanism. The far end of the hose connects to a pump somewhere back in the bowels of the printer and that hole position freed up the longest amount of hose.

    Much to my surprise, the tube wasn’t full of ink and didn’t bloosh blackness all over everything. Perhaps the hose drains back to the pump between head cleanings?

    Then it’s just a matter of buttoning up the case, joining the hoses with the supplied barbed fitting, sticking the external tank’s hook-and-loop strip to the printer, and trimming the hose to fit. It Would Be Nice If the new tank hose were the same flexy silicone stuff as the OEM hose, but it looks to be ordinary Tygon-ish tubing and is a bit stiffer than I’d like.

    External waste ink tank in place
    External waste ink tank in place

    No ink has reached the new hose yet, but I’m sure the next few head cleaning cycles will push out some oodge.

    The tank vendor suggests “recycling” the waste ink by diluting it with black ink, but I’ll just discard it. Bulk ink isn’t all that expensive, compared to OEM ink cartridges, and I’d rather not borrow trouble.

  • X10 Controller Lid Tweak

    The new X10 controller on our dresser has a nice lid over the buttons. Unfortunately, the lid lacks any affordance to raise it: smooth edges all around, slick surface, no notches or bumps.

    The obvious, albeit ugly, solution: add some black and very grippy rubber strips to the front and side edges of the lid. Now one finger suffices…

    Griptivity Enhancement
    Griptivity Enhancement

    Puzzle: how did the designers expect us to lift the lid?

  • Constraining a Sewer Snake

    Constrained sewer snake
    Constrained sewer snake

    Had the occasion to run the flexy snake through a kitchen drain that turned out to be not as plugged up as I expected, which is always good news. Replaced the cleanout plug, hosed off the snake, coiled it up, and applied the usual three nylon cable ties to keep the snake together.

    It took me years to figure out that last step. None of the old-school tricks work for me; I can’t tie knots in string / twine / rope while simultaneously holding those coils together and the snake resists any attempt to weave the loose ends into the bundle.

    Mercifully, I don’t use the snake all that often and I don’t feel at all bad about tossing three cable ties each time.

    You figured that out long ago, right?

  • OpenOffice 3.2 Graphics Cache Settings

    The default OpenOffice 3.2 graphics cache is probably large enough for ordinary documents. However, I put together a 9-page illustrated biography for a birthday party last year using (most likely) OOo 3.1 and that file dragged OOo 3.2 to its knees.

    The default cache settings are something like

    • 20 MB
    • 2 MB per object
    • 20 objects

    Crank those to

    • 256 MB
    • 5 MB per object
    • 50 objects

    Much better!

    I’m sure that depends on what you’re doing and how much memory your PC has, but when OOo gets really pokey on a graphics-intensive document, check the cache.