Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
All eight cells were within 3 mV of each other, so I sorted them by voltage and picked two from the middle of the lineup. Shorting them together in parallel produced a few microamps of current, so they’re as well matched as seems reasonable.
Rather than attempt to solvent-bond the case back together, I wrapped a layer of Kapton tape around the whole thing. The case doesn’t have quite enough meat to bond, anyway, because the width of the slitting saw turned that much plastic into dust.
A bunch of cutouts along the bottom edge key it into the charger, so I cut out the tape over those sections. Despite what it looks like, the small metal tab between the two terminals (on the top) is not covered in tape; that’s the snazzy InfoLithium contact that tells the camera that this is a valid battery.
The camera reported the pack had about 15 minutes of life remaining, which makes sense given that the cells spent quite a while in transit. I ran it down to empty, put it in the charger, and it seems to be perfectly happy. I’ll do a capacity test after a round or two of picture-taking.
I doubt the tape will prove to be a permanent fix, but as far as the camera is concerned, that slick Kapton makes it go in and out like anything…
I’ve been mulling over adding a tool length probe for a while and finally decided that the simplest approach might be the best: a momentary-contact pushbutton switch that pulls a parallel port input pin to ground.
The motivation is that a simple switch seems to be repeatable enough for tool length probing and it’s cheap enough that I won’t form a deep emotional bond to it. When a probe crashes the switch, I can just pop another one in place without any heartache or putzing around for a day or three to build another over-elaborate probe station.
The catch is that the Sherline motor driver box doesn’t include connections for any of the parallel port input pins.
The choices seem to boil down to:
Adding a breakout board between the parallel port and the driver box or
Hacking the driver box to get access to the port pins
Well, I’ve already pretty well hacked up my controller, as I wrote up in Circuit Cellar magazine (Aug & Oct 2004), so I don’t have much to lose… and the box is already in the shop!
Probe to port pin 15
This picture shows the connection to pin 15 of the parallel port on the Sherline driver PCB. The driver doesn’t use that input pin (or any of the others, for that matter), which means the PCB doesn’t have a trace leading anywhere convenient. I ran the new wires through the connector mounting hole, rather than around the edge, and soldered them directly to the connector pins on the bottom of the board.
The jack is an ordinary 1/8″ (3.5 mm, these days) stereo (3 conductor) jack, with lah-dee-dah gratuitous gold-flavored flashed plating; anything similar will work just fine.
Connections:
Sleeve -> driver box
Ring -> circuit ground (pin 19 is convenient)
Tip -> pin 15, the probe input
The cable shield connects only at the plug into the driver box, not at the switch end. That ensures there’s no current flowing through it and it can do a marginally better job of shielding the two conductors within. I’m reasonably sure that makes no difference whatsoever in this application.
The cable got chopped out of an AV-interconnect dingus with all sorts of fancy connectors on the other end. It’s a surplus find, cost maybe a buck, and has the redeeming feature of sporting molded plugs that I don’t have to solder.
The switch connections are soldered and insulated with heat stink shrink tubing. The general idea is that the driver box provides all the power, there’s no electrical contact with the mill table or spindle, and thus no reason to use fancy circuitry to solve a problem that’s not there.
I did not add a capacitor across the switch contacts, figuring that I’d solve that problem when it happened. The common practice of putting a honkin’ big cap across switch contacts is bad practice: it effectively shorts the power supply across the contacts for a brief moment every time the switch closes. Some stored energy is good (it keeps the contacts clean), too much simply burns them away. ‘Nuff said.
Probe jack – inside
I marked a hole on the front panel symmetric with the LED, eased the circuit board out of the case and wrapped it in a shop rag to keep the swarf out, propped the case on the drill press table, and rammed a 1/4″ hole through the spot marked X with a step drill. Yeah, hand-held on the table, just like you’re never supposed to do.
The force is strong with me…
The (well, my) Sherline.hal file connects pin 15 to the probe sense input (maybe I defined that when I set things up; I don’t recall now), but it assumes the pin will be high when active. The parallel port pin has a built-in pullup resistor and a switch to ground makes it active when low. These two lines in my custom_postgui.hal file disconnect the high-active pin signal and connect the low-active pin signal.
unlinkp parport.0.pin-15-in
net probe-in parport.0.pin-15-in-not
You do it that way to avoid changing the Sherline.hal file, which will be overwritten if you ever run the automagic configuration program again.
If you’re doing this from scratch, just configure the whole thing using the configuration tool, it’ll set the HAL file properly and you won’t need any of that fiddling around.
Tweak the Sherline.ini file to add support for tool changing with the G30 command:
[EMCIO]
TOOL_CHANGE_AT_G30 = 1
Button everything up, then do a quick
G91 G38.2 Z-10 F10
and poke the button while the Z axis is in motion. The Z axis should stop instantly. If not, check your wiring.
Now, some Orc Engineering is in order: I need a low-budget fixture to put the switch in harm’s way.
Went to roll the bike out of the garage and the rear tire was dead flat. You don’t even need to look at the tire, you just instantly know something’s wrong: the bike feels funny with a flat tire.
The picture shows the problem: a pinhole in the tube. Nothing penetrated the tire, nothing went wrong with the tire liner (you can see this was a few mm from the edge, so it’s not an abrasion flat), there are no problems anywhere. Just a tiny hole in the tube.
As nearly as I can tell, the tube simply failed at that point, without any external aggravation.
Popped in another tube and it’s all good, but … I guess it’s time to buy some new tubes: the new one came from a box dated May 90.
Finding a flat in the garage is much much better than finding a flat on the road.
The snows have retreated and it seems the mice have been busy tunneling in the back yard. If we cared more about the lawn, I’m sure I’d be outraged. As it is, the tunnels will be gone after a few mowings and life will move on.
I didn’t spot their grainery, but I’m sure the grass will be greener around the latrine…
Certainly these were different mice than the ones who made far more extensive living quarters out front, but they’re definitely relatives.
So Mary was going to apply the long-disused Sears Craftsman electric hedge trimmer to the decorative grasses she’d planted on either side of the (equally disused) front entry, but when I deployed the thing it didn’t run. A quick walk through the debugging tree: GFI green, extension cord OK, so it must be the trimmer.
Off to the Basement Laboratory Repair Wing…
Two tricks to getting it apart, after removing all the obvious screws:
The handle comes out of the sockets after great persuasion
Remove two of the three hex-head-with-lockwasher screws on the bottom and the case pops apart. The third screw holds the motor plate into that half of the case.
The switch is, of course, not intended to be repairable, but that’s something of a motivator around here. It uses those awful poke-and-pray spring clamps, which you could, in principle, release with a small screwdriver, but I cut the wires on the motor side of the switch, leaving plenty of room to graft connectors onto them.
Next time, I’ll be able to release the wires more easily.
Congealed grease on switch contacts
A rivet holds the switch together, but attacking it with a drill removed enough of the head that I could whack the rest of the body out with a drift punch. A 2-56 machine screw fits neatly into the hole and there’s enough clearance on both sides for the screw head and a nut; hack the screw to length with a Dremel abrasive cutoff wheel.
Notice that the switch trigger button visible from outside the case acts on a push rod that slides the movable contacts (in the top part in the picture) back-and-forth atop the copper contacts (with the wires). A pair of springs loads the movable contacts against the copper strips.
The problem turned out to be, as expected, congealed grease inside the switch. The black gunk on the right halves of the copper contacts was essentially solid; you can see that it formed a nice insulating layer. I cleaned that out, polished up the moving contacts, reassembled it, and … the switch still didn’t work.
At least I discovered that with an ohmmeter, before reassembling the entire trimmer!
Switch contact slider
The movable switch contacts have a small ramp, just about in the middle, that rides up on the black hump between the copper strips when the trigger button is released. That mechanically breaks the connection, but also allowed the grease to congeal in the air gap. The grease also formed a lump that prevented the movable contacts from pressing firmly against the copper strips, despite the springs.
I gnawed out that crud with a small screwdriver, dabbed on more contact oxidation prevention grease, buttoned it up again, and now the switch works perfectly again.
New switch wires
I spliced in somewhat longer lengths of hookup wire with butt-splice connectors I’ve had for years and it’s all good.
The post with the screw hole just below the wires matches another in the opposite half of the case; the post actually fits inside the ring you see here, so it doesn’t crunch the wire. However, the wire must be pushed in far enough to avoid interfering with the switch action rod.
Saw this mountain at Marist College. I wonder how many will go directly to the recycling bin?
I can’t recall the last time I used a phone book; it’s faster and easier to type the name & location into that little search field, whack Enter, and click the obvious hit.
If you look hard enough, somewhere in the first few pages you’ll find the instructions to turn off next year’s phone book. We’ll see how that works out…
I tote around an ancient Palm Zire 71, which suffices for my simple calendar & to-do lists. This is my second, as the first failed when the flexible cable connecting the guts to the charging / USB connector crapped out; turns out that the slide-to-open feature that reveals the crappy camera also stresses the flexy cable to the breaking point. Now I don’t do that any more.
The battery (well, it’s actually a single Li-Ion cell, but let’s not be pedantic) finally stopped taking a charge, so I did a full backup, tore the thing apart, and popped in a new battery. This being my second Zire 71, things went smoothly…
I got a stack of surplus Palm batteries some years ago, but they’re readily available from the usual suspects for prices ranging from $5 to $50. We’ll see how well mine survived their time in isolation.
The connectors don’t match, which means you just chop off them in mid-wire, then solder the old connector onto the new battery. A few dabs of Liquid Electrical Tape and it’s all good.
Some teardown instructions are there, with fairly small pix.
General reminders:
Stick the teeny little screws on a strip of tape
Watch out for the tiny plastic switch fin on the side
Torx T06 screws on either side of the camera
The silver shield around the shutter button snaps under the sides with more force than you expect
There’s a metal strip over the connector that can be taped back in place after the plastic posts snap off
Gently pry the flexy cable up off the base, using the tabs on either side
The speaker seems to be held in with snot
The battery shield is not soldered in place!
The battery adhesive comes off with a sloooowww pull
Screws under label
Components around shutter button
Back side
Although it may not be obvious, I replaced the crappy plastic window over the camera with a watch crystal. Much better picture quality, although much worse than my pocket camera.
Backup and restore with various pilot-link utilities:
The Smell of Molten Projects in the Morning 