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.
Electrical & Electronic gadgets
The Bafang battery charger uses an AC line cord “binocular” connector with what must be the weakest spring contacts ever made, which finally annoyed me enough to fix:
Also, the case now sports four thick fuzzy felt feet to keep it from sliding around quite so easily.
Another customer-does-the-last-ten-percent product …
A gusty thunderstorm knocked out power across Dutchess County, including half the service to our house. Being glad the refrigerator and freezer were on the live phase, I shut off the affected breakers on the dead phase, as well as all the 240 V breakers, and, with the living room darkened, we skipped our evening storytime.
By the next morning, a quick lamp test showed the recloser out on the pole had worked its magic, so I flipped all the breakers back on. The living room remained dark, prompting an investigation of the fuse box feeding the original house wiring:
Yup, another blown fuse.
Given what happens while wind and falling branches knock power lines askew, anything is possible. I have no idea where the fault current went, but replacing the fuse brought the living room back to normal.
None of the various UPS / lamps / phones seem damaged; I admit not peering inside the outlets to check for arc damage.
The truck side marker lights I’m thinking of using as daytime running lights have a pentagonal lens, so they should have a pattern with a bright central beam surrounded by five lobes. The one on Mary’s Tour Easy produced an oddly shaped blotch on the garage wall, so I ran the others though a simple test setup:
The lights sit horizontally in a small vise to keep them level and in the same position, although in no particular rotational orientation, and 100 mm from the graph paper. It’s running at 6 v to keep the brightness down enough to avoid blowing out the image. All of the images were exposed based on the central spot, so the surrounding paper gives some idea of the relative brightness: darker paper = brighter LED spot.
The front view of the lights comes from the stereo zoom microscope, with the wires gripped in a Third Hand and rotated to put the (inverted) TOP label where you’d expect it. They’re all roughly at the same position and pretty nearly lined up with the lens axis. The bubble-looking thing behind the central pentagon is the lens on the Piranha LED package, which should be centered but rarely is. You can see the dark orange square of the amber LED chip in some of the pictures.
Without further ado, the nine truck side marker lights that aren’t on her bike:
Side Marker E has a blob that looks like a cataract atop the LED lens, but it might be a mold imperfection.
Obviously, paying a buck a light doesn’t get you much in the way of build quality these days.
Plotting current against voltage for the amber truck side marker lights produces the expected straight-ish line:
The slope suggests a 330 Ω resistor, but the internal PCB sports a pair of 150 Ω SMD resistors.
I don’t believe the X-axis intercept for a moment, but 1.5 V seems about right for an amber LED.
Oh, and the DMM fuse doesn’t have a ceramic body. You’re seeing the vaporized remains of a 315 mA fuse neatly deposited over the inside of the glass tube after being shorted across a 3 A bench supply.
I hate it when that happens. Replacing it emptied the little bag of those meter fuses; next time it’ll get a half amp fuse.
Having seen a few bikes with amber “headlights” and being desirous of reducing the number of batteries on Mary’s bike, this seems like an obvious first step:
It descends from the fairing flashlight mount with an entry to suit a 15 mm truck side marker body:
LightBodies = [
["AnkerLC90",26.6,48.0],
["AnkerLC40",26.6,55.0],
["J5TactV2",25.0,30.0],
["InnovaX5",22.0,55.0],
["Sidemarker",15.0,20.0],
["Laser",10.0,30.0],
];
The rest of the code gets a few cleanups you’d expect when you compile code untouched for a few years using the latest OpenSCAD.
The markers are allegedly DOT rated, which matters not for my use case: SAEP2PCDOT.
The mount is grossly overqualified for a wide-beam light with little need for aiming:
Eventually, the marker should slip into a prealigned cylindrical holder, with a dab of epoxy to keep it there.
The lights are a buck apiece, so there’s no reason to form a deep emotional attachment. They are the usual poorly molded and badly assembled crap, although the next step up from a nominally reputable supplier is a factor of five more expensive.
It’s generated for the left side of the fairing, although I think having a pair of them would improve conspicuity:
Being automotive, it runs from a 12 V supply, which comes from a boost converter driven by the Bafang 6 V headlight output. The absurdity of bucking a 48 V lithium battery to a 6V switched headlight output, then boosting it to 12 V to drive a single amber LED with a 1.5 V forward drop does not escape me.
It’s possible to slice the lens off (using a lathe), remove / replace the resistor, then glue it back together, which would be worthwhile if you were intending to drive it from, say, an Arduino-ish microcontroller to get a unique blink pattern.
Given the overall lack of build quality, it might make more sense to slap a condenser lens in front of a Piranha LED.
Bonus: contrary to what you (well, I) might expect, the black lead is positive and the white lead is negative.
Although Gee’s Terry Symmetry is sized for female bodies, I managed to ride it up and down the driveway while watching the power display:
| Voltage | 52.5 | ||||
| Rated Current | 24 | ||||
| Max current | 18 | ||||
| Power | Power | ||||
| PAS | Assist | Amp | Calc | Observed | Ratio |
| 0 | 0% | 0.0 | 0 | 0 | ~ |
| 1 | 4% | 0.7 | 38 | 26 | 69% |
| 2 | 6% | 1.1 | 57 | 52 | 92% |
| 3 | 9% | 1.6 | 85 | 78 | 92% |
| 4 | 13% | 2.3 | 123 | 104 | 85% |
| 5 | 20% | 3.6 | 189 | 182 | 96% |
| 6 | 30% | 5.4 | 284 | 258 | 91% |
| 7 | 50% | 9.0 | 473 | 453 | 96% |
| 8 | 85% | 15.3 | 803 | 675 | 84% |
| 9 | 100% | 18.0 | 945 | 900 | 95% |
The variations in the last column suggest my data-taking is … wobbly, at best.
I think the displayed power does not come from actual current and voltage measurements, because recalculating the power using the nominal 48 V battery value produces an unnatural agreement:
| Voltage | 48 | ||||
| Rated Current | 24 | ||||
| Max current | 18 | ||||
| Power | Power | ||||
| PAS | Assist | Amp | Calc | Observed | Ratio |
| 0 | 0% | 0.0 | 0 | 0 | ~ |
| 1 | 4% | 0.7 | 35 | 26 | 75% |
| 2 | 6% | 1.1 | 52 | 52 | 100% |
| 3 | 9% | 1.6 | 78 | 78 | 100% |
| 4 | 13% | 2.3 | 112 | 104 | 93% |
| 5 | 20% | 3.6 | 173 | 182 | 105% |
| 6 | 30% | 5.4 | 259 | 258 | 100% |
| 7 | 50% | 9.0 | 432 | 453 | 105% |
| 8 | 85% | 15.3 | 734 | 675 | 92% |
| 9 | 100% | 18.0 | 864 | 900 | 104% |
The motor controller may measure the actual winding currents while generating the BLDC waveforms, but the values may not be available to the display at the end of the cable. If Bafang documented the commands & responses, we’d know for sure, but they don’t.
Those assist values come from Mary’s Tour Easy, a much heavier bike than the Symmetry, but the first few levels work well in my limited tests. The highest levels may be too peppy for Gee’s normal routes, but having some serious boost in reserve can defang (hah) the worst hills.
IMO, the bike would burn rubber at the motor’s full 24 A current …
These two discrete LM3909 circuits recently stopped blinking:
The green LED (on the left) took six months to wear its pair of not-dead-yet AA alkalines from 2.7 V down to nearly zero.
The blue LED in the radome took two months to go from 1.0 V (!) to nearly zero. It didn’t start very bright and went decidedly dim along the way, but the LM3909 circuitry still managed to jam a few microamps through the LED.
In both cases, one of the cells was reverse-charged by a few hundred millivolts, although neither leaked.
Both got another set of not-quite-dead AA cells and they’re back in action.
The Smell of Molten Projects in the Morning 