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.

Author: Ed

  • Water Heater Drain & Flush

    Flushing with Y hose connector
    Flushing with Y hose connector

    For reasons that aren’t germane here, I’m responsible for two water heaters. Having just replaced one of them, I figured I should do a preemptive drain-and-flush on the other and check its anode rod.

    In principle, you just hitch a garden hose to the drain valve, turn it on, and flush the sediment right out of the bottom. In practice, it doesn’t work that smoothly, as the valve has a teeny little opening that instantly clogs with grit.

    The first step is to shut off the water, open the drain valve, and disconnect both flexible couplings at the top of the heater. You will move the heater a little bit during this operation and that will cause the flexy connectors to leak, maybe just a little bit, but enough to cause Bad Things to occur.

    In the past I’ve used a Y hose connector with a homebrew double-female adapter to blow water into the bottom of the heater; the hose runs to a nearby sink with a male hose thread on the cold-water faucet. The two teardrop-shaped black handles on the Y adapter are ball valve handles (crappy valves, but good enough).

    It goes like this:

    • Close the Y hose valve
    • Turn on the water at the sink
    • Open the water heater drain valve
    • Open the Y drain valve
    • Watch a brief piddle of water hit the bucket
    • Close the Y drain valve
    • Open the Y hose valve to blast water into the tank
    • Close it again
    • Open the drain
    • Repeat as needed

    With any luck, you won’t have that much sediment and the drainage will clear after only a few iterations. That didn’t happen here…

    Water heater drain valve parts
    Water heater drain valve parts

    The next step is to apply a strap wrench to the drain valve, remove the cover and core, and see if the larger opening will produce more flow.

    Note that the drain valve, at least on this Whirlpool heater, is basically a coarse-thread plug that depends on a rubber disk to seal against the valve body. I’d really rather have a full-flow ball valve down there instead of this piddly little thing.

    it is possible to replace the drain valve entirely, but the last time around I applied far more force than I thought prudent to the plastic valve body and got exactly bupkis in the way of rotation. Not wanting to break the damn thing off, I gave up.

    Valve cleanout with copper wire
    Valve cleanout with copper wire

    Anyhow, with the guts of the valve out of the way, the flow was still fairly weak. I rammed a copper wire up its snout and dislodged a truly disheartening amount of crud. The opening kept jamming shut, which meant there was a great pile of sediment atop the opening, so I spent quite  while wiggling the wire to keep the water flowing and the grit emerging. The pic at at the bottom shows some of the pile; there’s a heaping double handful of sediment on that shovel.

    The bottom of the tank is flat, with the valve pretty much flush with the bottom. That means you’ll leave a huge pile of sediment inside unless you swish some water around. That, of course, will clog the valve. Repeat until tired.

    When you go to put the valve back together, don’t be surprised if it doesn’t seal. Tighten the cap, put a hose plug on the outlet, and move on.

    You can tell by the color of the water that Something Is Not Right inside the tank… more on that tomorrow.

    Some of the water heater sediment
    Some of the water heater sediment

  • Forgotten Alkaline D-cell: Corrosion!

    Alkaline D-cell corrosion
    Alkaline D-cell corrosion

    Found this toxic spill while I was looking for a gadget on another shelf: it seems I left an alkaline D cell standing on my electronics parts & tools carousel for much too long.

    Amazingly, although the cell’s leakage blistered the paint pretty badly, it didn’t affect the steel carousel!

    I wiped most of the crud and dead paint off, then applied white vinegar (which is essentially dilute acetic acid) to neutralize the cell’s potassium hydroxide. The grabber tool sticking  out from between the boxes had a pretty good dose of corrosion up the side, but soaking it in vinegar (wow, the bubbles!) removed that and a shot of penetrating oil expelled the rinse water.

    It’s definitely not Duracell’s fault: the cell had a best-used-by date in 1997.

    Memo to Self: throw ’em out!

  • LED Bike Light Doodles

    LED Bike Light Notes
    LED Bike Light Notes

    I need an LED taillight (and maybe headlight) with a metal case and far more LEDs than seems reasonable. This is a doodle to sort out some ideas… not all of which will work out properly.

    The general notion is that one can put today’s crop of ultrasuperbright 5 mm LEDs to good use. While the Luxeon & Cree multi-watt LEDs are good for lighting up the roadway, they’re really too bright and power-hungry for rear-facing lights. Mostly, you want bright lights facing aft, but the beam pattern & optical niceness really aren’t too critical as long as you’re not wasting too many photons by lighting up the bushes.

    I think, anyway. Must build one and see how it works. I know that a narrow beam is not a Good Thing, as cars do not approach from directly behind and it make aiming the light rather too finicky.

    The problem with commercial bike taillights is that they use piddly little LEDs and not enough of them. If you’ve ever actually overtaken a bicyclist at night with a blinky LED taillight, you’ve seen the problem: they’re too damn small. Automobile taillights must have a very large surface area for well and good reason.

    But who wants to lug the taillight off a ’59 Caddy around?

    So the diagram in the pic explores the notion of arranging a bunch of red & amber LEDs in a fairly compact array. The shaded ones are red, the open ones are amber (with two more side-facing ambers to meet legal requirements), and there are eight of each. The OD is about 40 mm. Figure 5 mm LEDs with 2.5 mm of aluminum shell between them. If the center four LEDs were spaced right, an axial (socket-head cap?) screw could hold the entire affair together.

    Turns out both the red & amber LEDs in the bags of 100 I just got from Hong Kong run at 2 V forward drop @ 30-ish mA, so that’s 16 V total for eight in series.

    Four AA NiMH cells fit neatly behind the array, so the supply will be 4 – 5 V, more or less. The outer casing could be plastic pipe.

    What to do for a battery charging port? Must be mostly weatherproof. Ugh.

    Rather than a regulated supply and a current sink / resistor, use an inductor: build up the desired forward current by shorting the inductor to ground, then snap the juice into the LEDs. The voltage ratio is about 4:1, so the discharge will happen 4x faster than the charge for a duty cycle around 20%. At that ratio, you can kick maybe 50 mA into the poor things.

    Governing equation: V = L (ΔI/ΔT)

    If they’re running continuously, 2 V x 50 mA x 0.2 = 20 mW. The full array of red or amber is 160 mW, 320 mW for both. If you’re powering them at 10% duty cycle, then the average power dissipation is pretty low. Not much need for an external heatsink in any event.

    A 1 kHz overall cycle means a 200 µs inductor charging period. With low batteries at 4 V and 50 mA peak current, the inductor is 16 mH. That’s a lot of inductor. I have a Coilcraft SMD design kit that goes up to 1 mH: 12 µs charge and 16 kHz overall. Well, I wouldn’t be able to hear that.

    No need for current sensing if the microcontroller can monitor battery voltage and adjust the charge duration to suit; three or four durations would suffice. Needs an ADC input or an analog window comparator.

    Automotive LED taillights seem to run at about 10% duty cycle just above my flicker fusion frequency; say between 50 – 100 Hz. If that’s true, red & amber could be “on” simultaneously, but actually occupy different time slots within a 100 Hz repeat and keep the overall duty cycle very low.

    I’d like red on continuously (10% of every 10 ms) with amber blinking at 4 Hz with a 50% duty cycle. When they’re both on the total would be 60% duty.

    The legal status of blinking taillights is ambiguous, as is their color; more there. Motorcycles may have headlight modulators. Bikes, not so much.

    Battery life: assume crappy 1500 mAh cells to 1 V/cell. Red = 50 mA x 0.2 x 0.1 = 1 mA. Amber = 50 mA x 0.2 x 0.5 = 5 mA. Thus 1500 / 6 = 250 hours. Figure half of that due to crappy efficiency, it’s still a week or two of riding.

    Rather than a power switch, use a vibration sensor: if the bike’s parked, shut off the light after maybe 5 minutes. It wouldn’t go off when you’re on the bike, even stopped at a light, because you’re always wobbling around a little.

    Memo to Self: put the side LEDs on the case split line?

  • Audio Headset Hanger

    Headsets Off the Desk
    Headsets Off the Desk

    For obscure reasons, I have a pair of headsets attached to the PC: one USB that’s used for phone calls and one plugged into a sound card for everything else.

    They’ve been cluttering up the corner of the desk for far too long, so I bent up a rack from a surplus coat hanger. Nothing critical, as long as it’s tall enough to hold the mics off the desk and wide enough they don’t clunk together.

    The trick is to just drill a hole in the top of the desk and poke the end of the rod into it. That works because my desk has a notch along the edge just exactly the right width to hide the hole!

    Hanger Mounted Under Desk
    Hanger Mounted Under Desk

    Maybe you don’t want to do this to the top of your desk, in which case maybe you can bend the hanger around the edge and put a screw in the bottom or the desktop. If you don’t look under there very often, the spiders will take over; this one is from the basement desk that I haven’t used for far too long.

    Details of the hanger, not that you can’t figure it out on your own:

    Headset Hanger
    Headset Hanger

    I suppose you could actually buy these things…

  • Tour Easy: Tightening the Coolback Seat Lace Cord

    Every now and then I notice the pedals are getting further away on my Tour Easy recumbent, which means it’s time to snug up the seat lace again. The lace cord has a Kevlar core, so it’s not very stretchy, but over the course of a few thousand miles either it stretches or the seat mesh relaxes.

    Here’s the only tool I’ve found that works for this purpose:

    Stanley 82-113 Hook Tool
    Stanley 82-113 Hook Tool: "The Hemorrhoid Picker"

    That’s what a friend calls his, anyway.

    It’s from Stanley and not in their current website listing, but they do offer the 78-393 – 4 Piece Hook and Pick Set, which looks to have a tool sporting the same hook end with a different (and much smaller) handle. IIRC, I got this one several-many years ago at Wal-Mart; maybe it’s a special-issue part number just for their shelves?

    What you do is work your way from the bottom of the seat lacing on one side all the way to the top, pulling out the slack as you go. At the top of that side, pull the accumulated cord into the knot, then start at the bottom of the other side. When you’ve got both sides pulled taut, knot up the slack again and you’re done.

    Needless to say, you can give yourself a King Hell puncture wound with that thing…

  • Credit Card Privacy Choices

    Just got a new credit card, which arrived with the usual “Privacy Policy” flyer describing how they’ll keep our sensitive bits safe & secure. Except, of course, that by default they’ll share those bits with nearly any organization that asks, if there’s even the least bit of money to be made in the process.

    The flyer explains how we can tell them of our privacy choices. Oddly, in this Internet Age, none of the banks have figured out how to put our privacy policy choices on their websites. Maybe that would be entirely too efficient.

    Anyhow, we’re supposed to either:

    • Pick up the phone to deal with their customer service apparat or
    • Pick up a pen, fill out a form, cut it out, and mail it to them

    For our joint accounts, if I forget to say “And this also applies to my wife”, well, then they’re free to share her sensitive bits.

    I’m sure they know that when they make “choosing” difficult enough, nobody will bother.

    Ya think?

    For the record:

    • Chase: press 0 to short-circuit the account info blather and get to a rep
    • Citi: press 6 for that purpose. Why not 0? Huh…

    The Chase folks tell me this may require up to 90 days to take effect. Wow, do they fill out forms and hand-carry the paperwork to Galactic HQ for further transcription?

    Memo to Self: Remember to tell the nice voice…

    • This applies to both account holders
    • Turn off all information sharing options
    • Turn off “convenience checks” (is anybody stupid enough to use those things?)
    • Turn off automatic credit line increases

    This takes about four minutes for each account on a Sunday morning.

  • Digital Caliper Disassembly

    Caliper Back Side - Label Removed
    Caliper Back Side – Label Removed

    Just in case I spill a sticky liquid on the caliper and must disassemble it again…

    This was a relatively inexpenive, but not dirt cheap, caliper that has worked fine all along, apart from the issue with the thumb roller frame.

    After removing all the obvious screws, taking off all the various doodads, and extracting the sliding jaw, it still doesn’t come apart. The trick, as always, is to peel the label off the back side to reveal the five crucial screws that secure the electronics package to the metal scale.

    These screws don’t have the best heads in the world, but a #2 Phillips driver, solid pressure, and steady torque gets them out. All but one of the screws are pointed; the one in the lower-left corner (as above) is a machine screw that, I think, ensures a good electrical connection between the metal frame and the electronics package.

    Caliper Disassembled
    Caliper Disassembled

    With those screws removed, the electronics package pulls off to expose the innards. Note the cough delicate hand-forging that secures the tang to the back plate.

    The schmutz on the far right matched up with a similar patch of rust on the sliding scale. Some TopSaver rust treatment applied with a scrubbing pad reduced the problem to mere discoloration; the rust wasn’t all that deep.

    Reassemble in reverse order, with dabs of lubricant on the obvious wear points along the way. The thumb roller must go on after securing the electronics package, not before.