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.
If you measure something often enough, it becomes science
If Jumping Spiders like this one were much larger than 5 mm, they’d be terrifying:
It appeared atop a trash can and, as with all Jumping Spiders, it’s here or there without being anywhere in between.
I eased the trash bag inside, gently lowered the lid, bade it happy hunting, and we parted on good terms.
A pair of brake sensors with LED indicators arrived and should improve the situation on Mary’s bike.
The connector pinout, as seen looking into the jack on the controller side of the cable:
Of course, one cannot depend on color codes, but now we know it uses a 5 V supply. Some rummaging produced a suitable (“Julet”) connector, a cutoff USB cable, and a USB power supply:
You’ll note the sensor’s signal wire is blue, not white, but red = 5 VDC and black = common on both sides of the splice. This is not to be sniffed at.
With the disk magnet (supplied with the sensors) oriented edgewise to the sensor, so the magnetic field is largely cancelled, the maximum separation allowing the sensor to remain On is about 7 mm:
The minimum distance allowing it to be Off is 8 mm:
Orienting the disk face-on to the sensor increases the distances, because the magnetic field is not cancelled out in that direction. Similarly, positioning the magnet either above or below the plane of the sensor changes the results.
The maximum On distance is now 20 mm:
The minimum Off distance is 22 mm:
The other magnet has a similar field strength and the other sensor responds at nearly the same distances, so they’re reasonably matched.
The LEDs are, however, not well matched: one sensor is much brighter than the other. I only have one connector, so I cannot show both in the same picture. These pictures have the same exposure (1/120 s and f/1.7), with the top sensor appearing in the previous pictures:
The red LEDs show a similar difference. I’m certain this doesn’t rise to the level of a warranty claim, because, hey, maybe the brighter one should be dimmer.
Now, to fit them on Mary’s bike …
The Bradford White AeroTherm heat pump water heater that Came With The House™ has been running for three years. Based on previous experience with the same City of Poughkeepsie water, it was time for a look at the anode rod.
Which, as always, required the Greatest Ratchet with a foot of extensions getting the 1-1/16 inch socket down to the rod:
Remember to:
Seeing the first few inches justified extracting the rod:
Due to low overhead clearance and inauspicious pipe locations, I had to hacksaw the bottom third off to extract the rod:
With the rod out, draining a few gallons of water into a pan didn’t produce any notable gravel, so I didn’t do a complete flush. Much to my delight, the drain has a ball valve!
Given that this is a fancy water heater and I no longer regard anode rod maintenance as a fun-filled activity, I installed a Corro-Protec powered anode rod for cathodic protection without all the crud:
The wall wart proclaims 15 mA with a green LED indicating it’s hard at work:
The data plate on the back reports 24VDC 15mA, but, being me, I poked at it with a handful of resistors:
The electronics could be as simple as a 24 VDC wall wart feeding a 425 Ω series resistor and a transistor switch lighting the LED for currents a little over 6 mA.
A quick ohmmeter check shows the powered rod electrode is open-circuit with respect to the tank, as it should be without much applied voltage. Applying +24 VDC from the wall wart drives 15 mA into the water: the rod is hard at work.
I’ll take a look at it in a year or so just to see what’s going on in there …
On rare occasions I see a small bee or wasp investigating the bamboo tunnel nests at the windows:
Several of the tubes filled & sealed in early June have served their purpose:
Bamboo tubes have a paper-thin liner around the edge, but the mud-sealed tubes have obvious small holes chewed through the end caps:
My assumption that various insects would pick their favorite tube from the assortment seems to be working:
The medium and large tubes haven’t seen much traffic:
We’re glad to help!
An inch-long Praying Mantis stood guard on a carton delivered to the front door:
We hope to see many more of its kind.
Two views of a one-turn snail found on a lettuce leaf from the garden:
Mary has developed a Zero-Tolerance Policy for snails & slugs, so this one must start over again from the bottom of the food chain.
With sparrows excluded, the House Wrens eventually began setting up their second nest of the season, with the male proclaiming both he and his lady’s chosen nest are the best in the land:
Wrens are on our Most Favored Critter list!
Previous encounters with their ancestors and relatives:
Mary wanted less pressure in the spray while watering her plants and I suggested replacing the nozzle’s washer with a flow restrictor:
The 3D-printed TPU base is squishy enough to act as a hose washer:
A 1.5 mm thick acrylic orifice plate snapped into the opening takes advantage of the laser cutter’s precision:
For lack of anything smarter, the holes have areas that are powers-of-two smaller than the nozzle’s 14.2 mm = 158 mm² internal passage: the hole labeled 8 is 158/256 mm² = 0.62 mm² → 0.9 mm diameter.
Rather than figuring each hole’s diameter, just divide the previous diameter by √2 or rescale it by 100%/√2, which LightBurn can evaluate directly in its Numeric Edits fields. The as-cut holes are larger than their nominal size by about 0.1 mm, but any errors that might cause are definitely in the nature of fine tuning while watering the plants.
The nozzle’s Shower pattern (on the left in the picture) has a 6.8 L/minute = 110 ml/s flow through an ordinary garden hose washer. The four smallest aperture plates produced these flows:
The flow should scale with the square of the aperture diameter, which I could bully those points into suggesting, but the measurement accuracy produced by filling a gallon jug while tapping my phone’s stopwatch doesn’t justify anything fancier.
The two smallest apertures reduce the Shower pattern to a very gentle spray requiring far too long to put enough water on the plants. Mary now uses an old plastic sprinkler head with enough holes to produce a dense spray with very little force, with the flow set by fifty feet of PEX pipe running across the width of the house from the town water inlet to the hose bib.
It was a fun exercise and I learned a little more about printing TPU and fitting acrylic parts therein:
I am so glad methanol is a liquid, not a crystalline powder, because this could be totally misinterpreted:
A recent LightBurn forum discussion pointed out methanol is a good solvent for borax to produce dark-brown to black laser engravings in wood. In round numbers, 20% w/w borax will dissolve in methanol at room temperature.
I understand the toxicity warnings and don’t plan to spray it indoors. OK?
The Smell of Molten Projects in the Morning 