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.
After the hinge repair described there, those old sunglasses have been working fine and I use them regularly. The screw recently worked its Loctite loose and was held in largely by blind faith.
It’s obvious why:
A tiny dab of JB KWIK should solve that problem for the foreseeable future:
In the highly unlikely event I must remove that screw, I’ll just refer to this picture and mill the epoxy out.
While I was fiddling with the camera to get that first spectrograph, it began coughing up an assortment of Memory Stick errors, including the dreaded C:13:01 error. Having had this happen several years ago, I knew it came from the ribbon cable contacts in the Memory Stick socket and the only way to fix it involves taking the camera apart.
At the time, I used the guide at http://hbar.servebeer.com/text/f707/, which is now a dead link; you can use archive.org to retrieve it. There’s an exact copy at http://batteringram.org/misc/f707repair/ and a bit of rummaging suggests the same person is running the new site.
Anyhow, here’s my version of the teardown and fix. This is a bit more aggressive than what you’ll read above, in that I disconnect all the cables to get straightforward access to the guts of the camera, but I think it makes everything easier. In any event, re-plugging the cables in those connectors will probably be a Good Thing.
Remove the battery, Memory Stick, and all the straps and doodads. This fix will reset the camera to its factory defaults; you must eventually reset everything, so review your settings.
If your filing system depends on the camera’s numbering system: heads up! This will reset the image sequence numbers; the next picture will be DSC00001.JPG.
Remove the four Philips-00 screws that hold the rear case in place. Note that they are not identical…
Two on the left.
The rear screw on the right side.
The screw on the right side of the bottom passes through the front part of the case.
Ease the whole rear half of the case, display and all, away from the front half, until you can disconnect the three-wire cable from the power jack. A needle-nose pliers may be helpful, but be gentle!
Now things get nasty.
The flat paddle in the lower right plugs into a socket on the display board in the rear case: pry it out if it hasn’t popped out of its own accord.
Disconnect the ribbon cable on the left side by prying the gray latch away from the cable; the ribbon will pop out with no effort.
Put the rear part of the case somewhere out of the way.
Peel the static shield off the main circuit board. The black strip is a surprisingly strong adhesive tape that’s stuck to the ribbon cables along the top edge of the board. Peel gently!
Pull the three cables out of the sockets along the top of the board. The blue cable seems to be much more fragile than the others, but they all come out by just pulling directly upward: parallel to the board.
Unscrew the two P-00 screws holding the main board in place: upper left and center of the board.
Flip the camera over and ease the main board away from the case to expose the white connector on the bottom. This is stuck firmly in place, so try to not brutalize anything around the connector when it pops out.
That leaves only the ribbon cable on the right of this picture (left of the camera) connecting the optical section to the main board. Push the two ends of the gray latch bar parallel to the cable (it is not the same as the connector on the other side of the board shown above) away from the connector until the bar releases the cable and it pops out.
Put the main board somewhere safe.
Now you can actually see the Memory Stick socket behind all the ribbon cables!
Remove the two P-00 mounting screws, one to the upper right and the other to the lower right in the steel retaining bar.
Remove the socket from the camera. Whew!
Here is the offending cable entry into the Memory Stick socket. Pull the mumble cable out.
The socket pins evidently move just a little bit, every time you put in a Memory Stick, eroding teeny divots in the cable contact pads. I generally use the USB connection, so the socket doesn’t see a lot of motion. Your mileage may vary.
I cleaned off the ribbon cable pads with Caig DeoxIT, although I’m not convinced that really does anything in this situation.
This guy dismantled the socket to clean the internal contacts, which would probably make sense while you’ve got the hood up. I didn’t do that this time, though.
Then you reassemble everything in reverse order, after which the camera Just Works. Probably for another few years.
The puzzling part of this failure: the camera has literally hundreds of ribbon cable contacts, but only the Memory Stick cable goes bad. If any other cable failed, the camera would go Toes Up, right? Next time around I may try soldering thin copper pads on the cable or applying a thin backing layer to improve the resilience, but that sounds pretty risky even to me.
If you haven’t done so already, put a write-protected image of your biz card / contact info on every Memory Stick you use with your cameras to make it easy for an honest person who finds your camera to get in touch with you. The dishonest ones won’t change their behavior one way or the other.
Take a picture of your card now: the camera will set up the folders and name it DSC00001.JPG. If you’ve already got such a file, take a picture anyway, delete it, then copy your existing file to the camera as DSC00001.JPG. In either case, write-protect the file.
Memo to Self: next time, take the socket apart and cast some epoxy around the contacts to prevent further motion.
Having gotten a spectrometer image from the crude camera lashup, the next task is to (figure out how to) extract some meaningful data. The general idea is to use ImageMagick and Gnuplot as much as possible, so as to avoid writing any actual software.
The original image is the high-res version of this:
Use ImageMagick to crop out a slice across the middle and convert it to lossless PNG:
convert -crop 2500x100+0+1000! dsc00273.jpg dsc00273-strip.png
I can’t figure out how to reset the image size using -extract, but -crop gets the job done.
The default ImageMagic PNG compression is 75, so I should include a -quality 100 option, too.
Because we have colors separated spatially, all we need is a grayscale intensity plot. The easy and, alas, wrong way to convert the color image to grayscale goes like this:
convert -colorspace GRAY dsc00273-strip.png dsc00273-strip-gray.png
That grayscale value is a weighted sum of the RGB components that preserves human-vision luminosity:
Gray = 0.29900*R+0.58700*G+0.11400*B
I think it’s better to simply add the RGB components without the weights, because we care more about the actual spectral intensity. That might allow overly high intensity in some peculiar situations, but I’ll figure that out later. First, get the red / green / blue channels into separate files:
convert -separate dsc00273-strip.png dsc00273-strip-chan%d.png
That looks better: the intensities resemble the original colors.
Then add those three files together, pixel by pixel, to produce a single grayscale file:
convert -compose plus dsc00273-strip-chan0.png dsc00273-strip-chan1.png -composite dsc00273-strip-chan2.png -composite dsc00273-strip-spect.png
Extract a one-pixel row from the middle and write it as a raw binary file. You could extract the row from the original image, but I think some blurring might be appropriate, so later is better. There’s no point in trying to display a one-pixel-tall image, so I won’t bother.
convert -crop 2500x1+0+50 dsc00273-strip-spect.png gray:dsc00273-line.bin
Fire up Gnuplot and have it plot the grayscale intensities:
gnuplot plot 'dsc00273-line.bin' binary format="%uint8" record=2500x1 using 1 with lines lt 3
And there’s the spectrogram…
A quick-and-dirty bash script to persuade ImageMagick to make something similar to that happen, including all the commented-out cruft that I’ve been copying forever so I don’t forget the magick incantations when I need them again:
#!/bin/sh
base=${1%%.*}
echo Base name is ${base}
convert -crop 2500x100+0+1000! $1 ${base}-strip.png
convert -separate ${base}-strip.png ${base}-strip-chan%d.png
convert -compose plus ${base}-strip-chan0.png ${base}-strip-chan1.png -composite ${base}-strip-chan2.png -composite ${base}-strip-spect.png
convert -crop 2500x1+0+50 ${base}-strip-spect.png gray:${base}-line.bin
export GDFONTPATH="/usr/share/fonts/TTF/"
gnuplot << EOF
set term png font "arialbd.ttf" 18 size 950,600
set output "${base}-spect.png"
set title "${base} Spectrum"
set key noautotitles
unset mouse
set bmargin 4
#set grid xtics ytics
#set xrange [0:1400]
set xlabel "Red <- Colors -> Violet"
#set format x "%3.0f"
#set logscale y
set ylabel "Light intensity"
#set format y "%3.0f"
#set yrange [0:60]
#set ytic 5
#set datafile separator "\t"
#set label 1 "mumble" at 1600,0.300 font "arialbd,18"
plot \
"${base}-line.bin" \
binary format="%uint8" record=2500x1 \
using 1 with lines lt 3
EOF
display ${base}-spect.png
It turns out that the flat topped peak in the middle was in the original green channel data: that color was overexposed.
If I had a camera that could do RAW images, this whole thing would work even better. Using 16-bit intensity channels would be exceedingly good; the original JPG file has only 8-bit channel resolution: 1/256 = -24 dB, which isn’t anywhere near good enough. That’s assuming the camera + JPG compression has 24 dB dynamic range, which I doubt.
That blue / violet peak over on the right looks great: the optical focus is fine & dandy. I focused the spectrometer at roughly infinity, set the camera to infinity, then tweaked the spectrometer to make the answer come out right.
FWIW, I think that deep blue-violet line is the mercury G-line emission at 435 nm, which would explain why it’s so narrow. The others are rather broad phosphor emissions from the CFL tube’s surface.
LEDs can provide spectral wavelength calibration markers, although their peaks are rather broad in comparison to mercury emission lines. A 400-450 nm “UV” LED puts out a broad blue-violet blur on the left (reddish) side of the emission line. Maybe it’s really the mercury emission H-line at 404 nm?
An IR LED puts a line on the far left side, about twice the distance to the left of the red line as the green line is to its right. I don’t know the exact wavelength, but it’s around 900 nm. The camera (my old DSC-F717) can do IR + visual images, but it insists on auto-setting the exposure and focus, which wipes out the other lines. The line is barely visible with the camera’s internal (and highly effective) hot mirror in place. Maybe with a more stable setup that would work.
Diode lasers in IR, red, green, and blue? Hmmm…
ImageMagick (probably) can’t detect those LED markers and scale the output file width, as it deals with intensity over a regular XY grid. A Python script could swallow the output binary file and spit out a scaled binary file with the bump peaks set to known locations. Actually, I’d be willing to bet there’s a perverse way to get IM to do X-axis scaling, but I’m even more certain the command-line syntax would be a wonder to behold.
Inject the LED images with a beamsplitter or teeny mirror across the bottom of the spectrometer slit and get intensity calibration, too. Vary the LED intensity with a known current for decent calibration over several orders of magnitude. That could compensate for the crappy dynamic range: as long as the LEDs aren’t saturated, you can correct them to a known peak value. IM can probably do that automagically, given known regions on the input curve.
Blur the strip image to get rid of color noise and irregularities in the slit. Perhaps a vertical sum in each channel along (part of?) the entire strip, then divide by the strip height, which would completely avoid blurring along the horizontal axis. If, of course, the entrance slit is exactly vertical with respect to the camera sensor.
IM knows how to deskew / rotate images. Apply that before summing, so as to correct small misalignments?
Different cameras have different entrance pupils. A quick check shows the DSC-H5 has a much smaller entrance pupil at full zoom: the spectrum covers more than the full screen, so the spectroscope won’t work well with that camera. Normally, you’d like to fill the entrance pupil with the image, but …
Getting all the optical machinery supported and aligned and oriented will require an optical bench of some sort. Perhaps my surface plate with magnetic sticky bases?
I think this is going to work…
This is a proof-of-concept lashup for a camera-mounted spectrometer; I wanted to find out if the image processing would work, but needed some images without devoting a lot of time to the hardware.
The general idea is that a direct-view spectrometer produces a focused-at-infinity image for your eye. Substitute a camera for your eye and you get an image with the spectral components laid out in a spatial array, suitable for measurement and calculation.
The trick is holding the spectrometer on the lens axis while blocking ambient light. I figured that I could mount the spectrometer in a disk that fit into the camera’s 58 mm filter threads, then hold it in place for the few pix I’d need to get started.
The end result was Good Enough for the purpose, although it’s definitely a kludge…
The (admittedly cheap) prism-based direct-view spectrometer has a slide-to-focus mechanism that substitutes heavy grease for mechanical precision. A guide screw in a slot prevents the focusing tube from rotating in the body tube, so I decided to replace that with a locking screw to clamp the tubes together. It’s a very fine thread, undoubtedly metric, screw, but a bit of rummaging in my teeny-screw drawer turned up a match (those are mm divisions on the scale):
I think the spectroscope makers filed down the head of an ordinary brass screw to fit the slot, rather than using an actual fillister screw. That’s a Torx T-6 head on the flat-head screw, which probably came from a scrapped hard drive. I eventually found a round-head crosspoint screw (requiring a P-1 bit) that worked better, with a brass washer underneath for neatness.
That got me to this stage:
Making the adapter disk involved, as usual, a bit of manual CNC to enlarge the center hole of a CD from 15 to 15.75 mm, then cut out a 57 mm cookie. A stack of CDs makes a perfectly good sacrificial work surface for this operation, with some fender washers clamping the pile to the tooling plate. Those homebrew clamps are smaller than the Official Sherline clamps and work better for large objects on the small table.
I briefly considered milling a thread into the OD, but came to my senses… I still have that pile of 10-32 taps, but now is not the time!
While in the Machine Tool Wing of the Basement Laboratory, I bored a short plastic bushing to a tight slip fit on the focusing tube to clamp the disk to the eyepiece, with the intent of keeping the eyepiece from whacking the camera lens. That’s the small white cylinder in the first picture.
As it turned out, I had to mount the whole affair on a sunshade that screwed into the camera filter mount, because the eyepiece protruded far enough to just barely kiss the lens.
A liberal covering of black electrical tape killed off all the stray light. Hand-holding all the pieces together and aiming it at the CFL tube over the Electronics Workbench produced this First Light image:
Believe it or not, that’s pretty much in focus. Much of the width in the red & green lines seems to come from the phosphors, as there’s a bar-sharp narrow blue line to the far right, beyond the obvious blue line.
Settings: manual focus at infinity, manual exposure 1/60 @ f/2.4, auto ISO = 100. Maybe 30 cm from the 27 W CFL tube: way more light than I’ll ever get through a liquid sample in a cuvette.
Now to fiddle with ImageMagick and Gnuplot…
So there you have it: the bugs that killed three months.
We’ve gone a month without a bite and are only now restoring furniture to the bedroom. Each piece goes up on powder traps and gets a week in isolation to reveal any bugs before we reload the drawers with clean clothing. After vacuuming and washing there shouldn’t be any bugs left on the furniture, if the piece had any to begin with. Almost certainly that is wasted effort, but …
Maybe next year we’ll buy new chairs and a couch for the living room. For sure, they won’t have plush, overstuffed upholstry.
With any luck (and the regular use of a hot box disinsector), you won’t go through what we did.
However, should you discover a row of bites across your body, the actions you take during the next few days will determine the level of catastrophe during your next year. The problem will not go away by ignoring it; if you get a breeding population going in your house / apartment / condo, you will definitely need a commercial pest-control service.
If you think tossing out some furniture to get rid of a few bugs is expensive: just wait.
Good luck!
The rest of (this chapter of) the Bed Bug Story:
Now, having seen what we’ve been living through, you might ask yourself
Wouldn’t It Be Nice If there was some way to be absolutely sure that mumble does not happen to me?
There isn’t, but you can stack the odds in your favor by disinsecting everything that enters your house. In particular, when you return from a trip, you must treat your luggage with the same casual regard as you apply to any lump of highly radioactive waste.
Because all bed bug stages die when exposed to temperatures over 45°C (113°F, which I round to 120°F), the simplest way to ensure that you’re not bringing any passengers home is to heat your luggage / packages / clothing / whatever to an internal temperature around 120°F, then let it soak for maybe an hour to ensure all the occupants get the message.
What you need is a box that gets hot on the inside, but not hot enough to set your luggage on fire. As with all things sold for bed bug problems, the commercial solution seems grossly overpriced for what looks like an uninsulated ripstop nylon bag containing a rack, a heater, and a fan.
It should come as no surprise that I built something that’s bigger, uglier, and harder to use… but it produces data and you can do science. And, with liberal use of my parts heap, the overall price is maybe 10 dB down from the commercial version…
I figured that this widget is going to be a major part of our lives from now on, so a foldable / storable heater wasn’t particularly useful. In point of fact, we’ve been using it heavily and I don’t expect that to stop any time soon.
It’s a rigid box made of Dow Tuff-R rigid polyisocyanurate foam insulating board, held together with 4-inch wide aluminum HVAC tape. The rim around the top is sealed with opposing strips of felt weatherstripping, held on with double-stick tape.
Inside, I used lengths of wire shelving to support the thing-to-be-baked. After we’ve used it a bit more, I’ll conjure up permanent supports for the second level shelving (stacked on the right of the exterior picture); right now, they’re supported on wood blocks as needed.
The interior dimensions work out to 34x22x24 inches: it’s made from a single 4×8 foot sheet of insulating board. Here’s my working sketch showing how the parts lay out and fit together. (clicky the pic for more dots).
The only waste is the 1-inch strip along the right edge; the slab I bought came with a molding imperfection, so discarding that edge was OK.
I cut the sheet into four 2×4 foot strips, cut a 13-inch strip off each plank, then trimmed the 1 inch waste. That seemed less prone to catastrophic blundering than (trying to) make a pair of 8-foot cuts and whack each resulting strip in quarters. An ordinary razor utility knife worked fine, although I found that making two passes along each cut produced cleaner results than trying to do it all in one.
I assembled it with the heavy / shiny aluminum foil side inward, although I doubt it makes any difference. Cover all the edges with tape, tape all the joints both inside and outside, and it becomes a nice rigid box when you’re done. Pay attention to getting the sides at right angles; I used a framing square.
The board allegedly has an insulating mojo of:
R = 6.5 ft2 • h • °F/Btu
Figuring a surface area of 32 ft2 and a temperature differential of 120 – 60 = 60°F, the box should require 295 BTU/hr = 87 W to maintain that temperature.
Which, as it turns out, is pretty close to how it worked out:
The lower curve shows a 60 W bulb with a 10 W 120 VAC fan heats the interior to a bit over 100°F in 100 minutes, where it looks to be stabilizing. That was the first test and showed that I was on the right track.
The second test, with a pair of 60 W bulbs and the fan produced the two upper curves: one for air, the other inside some cloth jammed inside a plastic bucket to simulate a (tiny) suitcase. The combined 130 W heats the box over 150°F in two hours, with the somewhat insulated bucket trailing neatly behind as you’d expect.
Without opening the box, I connected the bulbs and fan to a Variac plugged into my Kill-A-Watt meter and dialed it for 100 W total dissipation. The temperature fell to slightly over 130°F in 80 minutes and looks like it would stabilize near there.
Ambient temperature was 67°F, so
R = 32 ft2 • 67°F / (341 BTU/hr) = 6.3
Close enough, I’d say. Given those few data points, it looks like the temperature sensitivity around 130°F is 0.7°F / W. [Update: typo in the equation. Doesn’t change the answer much at all.]
I swapped in a 100 W bulb, removed the Variac, and heated the cushions from my office chair.
One thermocouple is hanging in mid-air, the other is wedged inside one of the cushions. After nearly 5 hours the cushion is up to killing temperature and I turned the heater off. The air temperature drops rapidly, but the cushion stays over 120°F for another two hours.
The light bulb is just a proof of concept, because it’s entirely too hot: if the fan fails, your luggage ignites. I plan to build a rather subdued heater with a surface temperature around 140°F and a controller that monitors several sensors to ensure the contents reach killing temperatures and stay there long enough.
But that’s a project for another day…
[Update: If you’re arriving from a link, start at the overview to get The Whole Story.]
Even half an inch of masking tape forms an impenetrable barrier for small creatures; you could splurge on 2-inch tape to get more surface area if you’re squeamish. I did see a spider stepping daintily along a barrier, but, for the most part, all these specimens became mired within a few millimeters of an edge. That made it easy to decide which direction they were traveling: incoming insects stuck near the floor and a (very few) outbound insects stuck at the top, just after leaving the non-sticky surface.
This is, we think, a well-fed first- or second-instar bed bug caught on a tape barrier; it’s not quite the right shape for the book louse seen below. A powder trap caught the only other bed bug in our collection.
In addition to that sole bed bug, the tape barriers captured a steady stream of critters that were not bed bugs. The trick is sorting through all the false positives…
Given the number of books in the house, we caught many book lice. These have a disturbing resemblance to bed bugs, but are basically harmless to humans. You don’t really need books to have book lice, although we captured most of them adjacent to our bookshelves.
This scary critter is a carpet beetle larva. They survive on any fabric surface and can infest upholstery as well as carpets.
Dust mites, at least for their first few instars, are transparent little bags of bug stuff. The first instar may have six legs, just like a first instar bed bug, but successive instars have eight.
Here’s a close up view, showing it has eight legs:
We have no idea what this cute little thing might be. It’s about 0.5 mm in diameter and, to the naked eye, looks like nothing so much as bed bug crap. But it’s alive!
This terrifying apparition sprinted across the (non-isolated) kitchen table, whereupon I mashed it with a magazine. It’s most likely not a bed bug; we’re guessing a spider of some sort. That stylet in its proboscis doesn’t look spider-ish, though.
It might be related to this eight-legged critter; the lancet on the front end is similarly scary. The legs aren’t the same, though.
All in all, we found a bewildering variety of insects, bugs, and spiders wandering around in our house. None of them are particularly harmful, although I now have a (most likely pyschosomatic) allergy to dust mites.
We’re not entomologists: if you know what the mystery critters are, I’d like to hear from you!
Up next: a Hot Box that might forestall all this excitement.
The Smell of Molten Projects in the Morning 