The general idea is to hold the wave washer (it’s mashed under the flat washer, honest) above those bumps on the plate holding the mirror and stalk balls. It’s a few millimeters from the end of a ¼ inch brass rod, drilled for the M3 screw, and reduced to 4.5 mm with a parting tool to clear the bumps.
While I was at it, I made two spare mirrors, just to have ’em around:
Long ago and far away, I moved the keyboards off our desk surfaces to a more convenient location on a tray under the middle drawer. Mary’s desk recently gained a somewhat thinner keyboard with a thumbwheel volume control, so she wanted the tray moved up:
The supports on either side started out as 2×4 lumber with a slot cut (using the radial arm saw I no longer have) for the aluminum sheet:
For the record, a pair of screws hold each support to the drawer:
Not elegant. Works fine. Good enough!
Tiny Bandsaw™ wasn’t designed for ripsawing lumber, but the same Proxxon 10/14 TPI blade I use for aluminum worked better than I expected to lop a 1-¼ inch strip from the wood slats:
That’s a reenactment based on a true story. The wood scraps clamped on the bandsaw table leave enough clearance for the 2×4 slide to freely, yet not enough for the blade to wander off track.
You can tell how long ago I built the original trays: nary a trace of 3D printing!
In truth, that vise is intended for small cylinders, not flattened nuts, but I figured it’d suffice for light-duty use. Grate parallel to the vise screw, reclamp as needed, and it worked out reasonably well.
Eventually, you have a pile of powder and one cubic nutmeg:
I’m sure there’s a way to grate the remaining cube, but I’m unwilling to shred my fingertips.
Tip the powder into a small jar and repeat as needed. Each nutmeg produces about 5 grams and I did three of the things this time.
(*) We omit the cloves and knock the sugar down by half. Your tastes will surely differ.
Scaling it down for a 10 mm polypropylene ball around the base of the 30 mm inspection mirror’s shaft simplified everything:
I’m reasonably sure I couldn’t have bought 100 polypro balls for eight bucks a decade ago, but we’ll never know. Drilling the hole was a complete botch job, about which more later. The shaft came from a spare mirror mount I made up a while ago; a new shaft appears below.
The solid model, like Gaul, is in three parts divided:
The helmet plate (on the right) has a slight indent more-or-less matching the helmet curvature and gets a layer of good double-stick foam tape. The clamp base (on the left) has a pair of brass inserts epoxied into matching recesses below the M3 clearance holes:
A layer of epoxy then sticks the helmet plate in place, with the inserts providing positive alignment:
The clamp screws pull the inserts against the plastic in the clamp base, so they can’t pull out or through, and the plates give the epoxy enough bonding surface that (I’m pretty sure) they won’t ever come apart.
I turned down a 2 mm brass insert to fit inside the butt end of the mirror shaft and topped it off with a random screw harvested from a dead hard drive:
At the start, it wasn’t obvious the shaft would stay stuck in the ball, so I figured making it impossible to pull out would eliminate the need to find it by the side of the road. As things turned out, the clamp exerts enough force to ensure the shaft ain’t goin’ nowhere, so I’ll plug future shafts with epoxy.
The front side of the clamp looks downright sleek:
Well, how about “chunky”?
The weird gray-black highlights are optical effects from clear / natural PETG, rather than embedded grunge; it looks better in person. I should have used retina-burn orange or stylin’ black.
This mount is much smaller than the old one and should, in the event of a crash, not cause much injury. Based on how the running light clamp fractures, I expect the clamp will simply tear out of the base on impact. In the last decade, neither of us has crashed, so I don’t know what the old mount would do.
The clamp is 7 mm thick (front-to-back), set by the M3 washer diameter, with 1.5 mm of ball sticking out on each side. The model has a kerf one thread high (0.25 mm) between the pieces to add clamping force and, with the screws tightened down, moving the ball requires a disturbingly large effort. I added a touch of rosin and that ball straight-up won’t move, which probably means the shaft will bend upon droppage; I have several spare mirrors in stock.
On the other paw, the ball turns smoothly in the clamp and it’s easy to position the shaft as needed: much better than the old Az-El mount!
The inspection mirror hangs from a double ball joint which arrives with a crappy screw + nut. I epoxied the old mirror mount nut in place, but this time around I drilled the plates for a 3 mm stainless SHCS, used a wave washer for a bit of flexible force, and topped it off with a nyloc nut:
I’m unhappy with how it looks and don’t like how the washer hangs in free space between those bumps, so I may eventually turn little brass fittings to even things out. It’s either that or more epoxy.
So far, though, it’s working pretty well and both units meet customer requirements.
With a pair of fresh AA alkaline cells producing 3.1 V (not the NiMH Duracells you see in the picture), the blue LED blinks brightly.
The 610 mV peak voltage across R1 shows the LED starts at 25.4 mA:
The capacitor reaches 1 V, then goes about 150 mV into reverse charge during the flash (note the different horizontal scales):
The Darlington version of Q1 seems to do a decent job of keeping the cap out of reverse charge. A Shottky diode would add a few hundred mV, but I doubt there’s anything nasty going on inside the cap as it stands.
Taking all those pictures of the DSO150 screen reminded me it has a data dump function: press the V/Div and ADJ buttons to squirt configuration, measurements, and trace data from the TX pad on the main board, just in front of the red-black power wires hot-melt glued in place:
The picture shows the “before” stage, while I was figuring out where to carve another hole in the case.
NB: The 113-15001-111 DSO150 firmware version includes the serial output option, so you won’t need third-party firmware. Similarly, current PCBs bring the serial pins to neatly labeled header pads. You should refer to the JYETech DSO150 / DSO Shell product page for the details.
After all the cuttin’ and filin’ was done, it looked like this:
The power switch on the back of the case (top of the picture) disconnects the lithium cell from the charge controller board (now tucked behind the battery) to eliminate any trickle current discharge. Charging the battery thus requires turning that switch on and turning the scope off with its own power switch (along its front edge). Capturing trace data requires having both switches on (duh), whereupon the scope’s normal operating current convinces the charge controller that the cell hasn’t reached full charge. Turn the scope off and, most likely, the controller will tell you the cell is fully charged.
An intro blurb squirts from the port at 115200 in good old 8N1 format when you turn the scope on:
It’s all in neatly comma-separated-value format, so you can slam it into a spreadsheet and have your way with it. Utilities also exist to capture the data, extract the values, and send them directly to GNUplot, etc.
If I expected to do a lot of that, I’d boldify the traces and embiggen the text, all of which is in the nature of fine tuning.
It’s hard to reproduce the beauty of the DSO150’s display, though:
The DSO150 remains pretty good for being the worst oscilloscope I’m willing to use …