Silicon Valley Redneck

Doing the math

I recently discovered Mythbusters... fun stuff!

Anyway, I'm currently partway through Pilot #1 - the episode with the JATO Impala.  They reenacted the fabled event with an actual Impala and three HPR motors fired in sequence.  The results were impressive, but fell far short of the legend.

Just for giggles, let's look at the best case.  We'll attach the rocket to the car and fire it off in outer space, thus eliminating air resistance, road friction, engine braking, and all that stuff.

If we apply 1500 pounds of thrust to a 3000 pound car for 15 seconds, that's, er, half a gee (call it 5 m/s²) times 15 seconds, or about 75 m/s.  The handy-dandy units program says that's around 168 MPH.  Faster than your average Impala, but hardly into mythical territory.

Curiously, the Mythbusters result is consistent with this BOTE calculation.  Funny how that works out.

Oh, one thing grated: they kept referring to "pounds thrust" and "horsepower" as if there were a constant conversion factor.  In fact, they're not convertible; thrust has units of force, and horsepower has units of force times distance per unit time, so instantaneous vehicle speed has to be factored into any conversion.  Or, you can take the energy expended by the rocket to be your "horsepower" number, whether it's accomplishing anything or not.  Remember, exerting 1500 pounds of force against a stationary object can be accomplished with zero horsepower in the steady state!

Later: Pilot #2 examines the tale of the autodefenestrating lawyer, and addresses the question: how could a window stand up to repeated lawyer impacts, and then one day succumb to the same impact?  A structural engineer raised the issue of HVAC-related pressure differences, at which point two words sprang into my mind: Hancock Building.  The issue of outside wind speed and building aerodynamics didn't even get mentioned on the show!

Happy Castoff Day!

Free of cast!  Free of cast!  Thank Dr. Reitman, I'm free of cast!

The follow-up X-ray shows the radius healing well, properly lined up.

Now that the restraint has been removed, I have some seriously stiff muscles, and moving the wrist beyond what the cast allowed is painful, for the moment.

Also, I have a case of peeling dead skin worthy of Mr. Morden (but only on the one forearm & hand).

Now I can type again... and clean the bird cages without futzing around with a vinyl glove... though doing any two-handed heavy work is probably a couple of weeks off.

Now to do some of that stuff.  Then, I guess, I should go to the lab (at a different Kaiser facility, in the opposite direction) and get my potassium checked.

Update: serum potassium is bang in the middle of the normal range.

Health gradually improving...

Well, I got my doctor to switch my blood-pressure pills, effective last Friday morning, and the Lisinopril cough is mostly gone now, though I still have some lingering crud - dunno how much is cold leftovers, how much is heating-season indoor allergies or similar, and how much is residual irritation from the coughing fits.

Anyway, I've progressed from sounding like Coffin Henry (when I had the cold) to sounding like General Grievous (post-cold, but with Lisinopril) to sounding like a normal person with a minor throat irritation, so I guess that's good.

The new pills don't seem to be quite as effective (and potentially have a dangerous side effect; I'm supposed to go in this week to get my potassium checked), but they're working OK, and once I lose some weight my blood pressure should come down a bit more.

My wrist doesn't bother me any more unless I try to turn it too far outward.  Lifting a 10-pound sack of groceries is no problem.  I surmise that, under the cast, it's pretty much healed, though I still lack the strength to crush the part of the cast that runs across my palm.

Ah, well - time to run some errands before the storm arrives.  Happy Boxing Day, all!

Happy Hogswatch!

I'm still here... and still not typing much.  Blogging will resume Thursday, when I should have both hands working, unless I have something particularly interesting to say before then.

Meanwhile, it's time to wake up and head for the Christmas festivities!

Oh, there's the problem!

The recent crop of SneakySpam had been confusing Spamassassin's Bayesian autolearner.  I'm using spamd, so the actual global Bayes database belongs to user "nobody."  I'd been shuffling the missed spam into its own mailbox, then attempting to correct its misclassification via

# sa-learn -u nobody --showdots \
   --spam /home/*/Maildir/.spam/cur/

Well, it didn't seem to be working.  I finally did some investigating, and discovered that it'd been busily building a database for root, which of course spamd wasn't using.

Apparently the "-u username" option isn't doing anything useful.

The following, however, does result in the spam being learned in the right place, with the desired effect:

# sa-learn -u nobody --showdots \
   --dbpath /var/nobody/.spamassassin/ \
   --spam /home/*/Maildir/.spam/cur/

That oughtta cut down on the amount of pump'n'dump spam that gets through!

Off my meds

My blood-pressure pills came with a variety of warnings, including "may cause a dry cough."

Just after I started taking them, I came down with What's Going Around, which involved a runny nose, post-nasal drip, and a productive cough.  It's a very persistent WGA, as others have noted.

Well, the WGA has mostly gone away now, but now a dry cough is exposed.  I'd suspected it was hiding behind the cold-like symptoms of WGA, and maybe this explains why the amount of coughing was out of all proportion to the amount of congestion.

So, I skipped my pill this morning, to see what would happen.

The upside: the cough is nearly gone now, and what remains is consistent with the degree of lingering crud.

The downside: my blood pressure is creeping back up into 140/90 territory, after having been around 100/67 yesterday.  Guess I'd better resume the pills tomorrow.

If the cough returns, I'll have to pester my doctor.

Oy. There's always someone worse off.

With all my kvetching about my recent illnesses and injuries... Stephen Green has had a much worse time, in the same few months.  Like, at our respective worst points, his weight was just about half mine... and (a) he's two inches taller, and (b) I wasn't exactly spherical.

The good news is, his condition is treatable.  The bad news is, it's a lifetime of treatment.  (My problems can most likely be managed, in the long run, with minor lifestyle adjustments.)

I was going to complain about having developed sore muscles on today's piddly 7-mile hike with moderate hills.  Compared to someone who's struggling to do one pushup... hey, I don't have it so bad.

Get well, Steve!

'Tis the season for colorful geblinkenlights

So, I had thirty assorted itty-bitty LEDs and an ATmega16... and it was December...

I soldered the AVR to an adapter board the easy way: goober on solder paste; place chip; zap with hot air; clean up with slobber-wick.

I should have done the bypass caps the same way - after all, paste + hot air is the approved method for soldering SMT caps - but instead went and used my usual method, soldering iron in the right hand and tweezers in the left.  This turns out not to work too well when the left hand is in a cast.

Snakes!  I used the most flexible twisted-pair I could come up with easily, which was 26 gauge stranded.  Once upon a time, I had a spool of 30 gauge stranded twisted pair, with nice thin flexible insulation, which was perfect for this sort of thing, but that's long since used up, and I've never come across a replacement supply.

Not wishing to hot-glue the LEDs directly to my cast, I stuck them to the inside of a cut-off pajama sleeve which fits over the cast, thus:

Happy Winterfair!  Also Saturnalia, Christmas, Yule, Hanukkah (by whatever spelling), Hogswatchnight, and any other seasonal events for which festive lights may be appropriate.

(Yeah, it's not the neatest lighting job ever seen.  Let's see you do better with a busted wrist.)

Oh... y'want the software?  Here are the key parts.

; Set up a timer...
; Timer 1: prescale by 1024, to run at 7812 Hz, with TOP=OCR1A

	ldi	r16,0x00
	out	TCCR1A,r16
	ldi	r16,0x0D
	out	TCCR1B,r16

; Foo faddle.  TIMSK is out of range of SBI.
	ldi	r16,0x10	; OC1A
	out	TIMSK,r16

; Set OCR1A to a suitable value (vaguely 1 second-ish)
	ldi	r16,high(TICKTIME)
	out	OCR1AH,r16
	ldi	r16,low(TICKTIME)
	out	OCR1AL,r16

	sei		; *** Interrupts ON!

	ldi	r20,0x11
	ldi	r21,0x24
	ldi	r22,0x34
	ldi	r22,0x98

; Buzz around the main loop
main:
	rjmp	main


; Timer 1 OCRA interrupt:
irq_t1cmpa:
	push	r16
	in	r16,SREG
	push	r16
;
; This happens at some human-speed interval.
; Go update the lights.

	lsl	r20
	rol	r21
	rol	r22
	rol	r23
	brcc	nocarry
	inc	r20
nocarry:


	out	PORTA,r20
	out	PORTB,r21
	out	PORTC,r22
	out	PORTD,r23

	pop	r16
	out	SREG,r16
	pop	r16

	reti

Eye. Mote. Blunt instrument with rough edges.

Assembly not recommended.

At least this one didn't (yet...) end up with Yet Another Trip To The Emergency Room, though it sure felt like it for a while there.

I woke up a bit past midnight with considerable pain in my left eye, as if there were something in it.  After splashing water on it, I still couldn't see properly, though the pain was fading quickly.  That eye just wouldn't focus.

An hour later, my vision was nearly back to normal - whew!

Since, when I woke up, I had the vague sense that I'd been rubbing my eye with the back of my hand, my best guess is that I'd been rubbing it with the cast... maybe to remove a bit of dust or a stray eyelash, or maybe the hand and eye had just ended up in the same location.  Funny how a wrist injury can lead to eye damage....

Anyway, to prevent further eyeball scratchery, I've just carved up an old sock to make a nighttime cast cover.  No more exposed rough edges!

still mostly one-handed

yes, my left hand will be mostly out of commission for some time yet... though i've been regaining use of the fingers.  using the hand for typing is problematic, for various reasons - can't position the hand properly, can't see past the cast, etc.

here's the x-ray from last sunday:

...funny, now my arm glows in the dark.  well, the outer layer of the cast does, anyway.  guess it's supposed to warn me if there are orcs about, or maybe russian spies.  is a luminous overcast some sort of omen?

anyway, i'm feeling somewhat better, and it must be time to play pimp my cast!  christmas lights are the obvious thing to add... parts on order, and i'll need a bit more use of my fingers.  meanwhile...

hmmm...

where's a roll of double-sticky tape and that ipod?

it's the svr podcast!