For more topics, scroll down,
press Ctrl-F to search the page,
or check previous months.
For the latest edition of this page at any time,
use this link: www.covingtoninnovations.com/michael/blog
Note:
The ads that you see here are not controlled, sponsored
or endorsed by Covington Innovations. They are brought to you by Google
and will vary depending on your personal browsing history.
2013 November 30
Short notes
As my consulting business ramps up to at least 100% capacity at the
beginning of December, I'm going to close out the month with a few
short notes.
I've revised my earlier
notes about shopping on Thanksgiving
as it became evident that the people opposing it didn't have the
same thing in mind that I did. We agree that a certain amount of commercial
activity helps people have a better holiday. It's not a Sabbath on which
all work is forbidden. The Black Friday shopping frenzy,
however, is for the birds, whether or not it spills over into Thursday.
It smacks of of replacing a holiday in honor of God with a
frenzy in honor of Shopping.
In other news: I said
Bitcoin would get hacked when the stakes got high enough,
and
it did. The people running it were
overconfident.
And a last note on Comet ISON: As of this moment, we don't know what it's
going to do next. At least part of it survived perihelion passage and will
reappear in the morning sky, probably not as a spectactular sight, but
hopefully as something I can photograph.
The lost art of electronic troubleshooting and repair
In my youth, I learned a lot about electronics from books about how
to repair radios and TVs. The 1960s were the height of the TV repair era,
and component-level repairs were frequenly needed.
But another force was at work. Recently, in an old magazine, I came
across someone around 1958 opining that cheap, reliable silicon transistors
would result in "disposable appliances" — our radios and TVs would work
so well, and be so cheap to make, that we would simply throw them away and
get new ones when the time came. Minor failures would no longer happen,
and a radio or TV wouldn't die until something big, like the picture tube,
bit the dust.
That prediction was exactly right, of course.
But many of us feel that the pendulum has swung too far. It may not always
be economical to repair equipment at the component level, but the art of doing so
should be preserved, for several reasons:
Respect for craftsmanship. I know economics dictates it, but I still feel
a twinge of sadness when something elaborately and beautifully made is
thrown away.
Sometimes economics tilts in our favor. We would at least like to be able
to screen "trash" for things that might be very easy to fix. Sometimes a
$200 gadget gets junked when all that is wrong is one broken cable.
Some people might be glad to get a good stereo for $5 and an hour's labor.
Sometimes there is a real need. Just like people who restore antique cars,
some of us put a high value on keeping old electronics alive. Sometimes a
particular piece of equipment has historical or sentimental value even if
it is not rare. For example, I'm going to try my best to repair my father's
Hallicrafters shortwave radio from the 1950s, even though its performance will
never be more than mediocre by today's standards.
(Today, a $140 Sony
is one of the best shortwave radios ever built and will outperform any old-technology receiver.)
It's satisfying. Although I haven't had much time to put into it in recent
years, I've always enjoyed bringing an old piece of equipment back to life.
The antique-car community has similar feelings and motives. There are beginning
to be 100-year-old cars that are still roadworthy, and 75-year-old radios that still work.
Industrial and medical electronic repair is, of course, still a thriving art.
It's consumer electronics that have been left out.
So where do you learn how to fix things? Around 1980 to 1990, a lot of mediocre books
were published — experienced writers were asked to write about new
technology, and they had so little experience that they didn't tell us anything
unobvious. But since then, two high points have appeared.
One is Sam Goldwasser's Repair FAQ, although it's looking a bit
dated by now — the pace of updates has slowed. Read it; save a copy.
The other is this book,
which I've just read with interest and enjoyment. The author, Michael Jay Geier, is a lot like me — he was running
a repair business when he was 8 years old — I could fix things when I was 8 but didn't think of
making money doing it. He shares a lot of practical knowledge about what components are likely to fail
and how to test them.
By the way, from that book I got one technique that was genuinely new to me: "current flooding."
If a piece of equipment has a short circuit across its power supply, causing its power supply to
shut down, the short can be almost impossible to locate. But "current flooding" provides a way.
Disconnect the original power supply and connect a lab supply, set to the right voltage, capable
of delivering many more amps without shutting down. This will fry the shorted component,
often making it actually catch fire, and won't damage anything else because the correct voltage
has never been exceeded. Shorts to ground are a common fault in cards for PCs — the symptom
is that the PC won't boot with the card installed — and I would have used this technique a
few months ago if I'd known about it.
Suppliers of electronic parts have started to look better, too, and just as in the 1960s, they've
gotten in touch with hobbyist ("maker") culture.
Look for instance at MCM Electronics
and Parts Express (which has to add a hyphen
between "parts" and "express" in its URL because some search engines were objecting to a
certain sequence of three letters!).
Melody, Sharon, and I are celebrating Thanksgiving together.
Our extended families are gathering elsewhere, and of course
Cathy, Nathaniel, and Mary are up in Kentucky.
I'm looking forward to a day off work.
We have much to be thankful for. Without going into detail,
several family members have a good prospect of overcoming
some chronic health problems. My consulting business is up
and running. We have a granddaughter who is nearly a year old.
All around, things are looking up.
I also want to wish all my friends (not just my Jewish friends)
a blessed Hanukkah, a holy day that commemorates events
that are an inspiration to freedom-loving people everywhere.
To conclude the series of astrophotos taken November 3, here is another view of the field of Mu Cephei,
with the large, mysterious-looking red nebula (compare last month's photo).
This is a stack of fifteen 1-minute exposures, Sigma 105/2.8 lens,
Canon 60Da at ISO 3200, iOptron SkyTracker, at Deerlick.
Car key remote transmitter mysteriously loses range
A couple of months ago, the key remote transmitter for my Ford Escape
mysteriously lost range. It used to work reliably from 50 feet away, or more.
Suddenly, depending on the location, I often had to walk right up to the car
in order to get it to respond.
I replaced the battery in the transmitter, but that didn't make a difference.
And Melody's transmitter was just as afflicted as my own.
Today (Nov. 26) I had a flash of insight.
The trouble started when I started keeping my GPS device plugged
in all the time.
So I unplugged the GPS from the lighter socket, and that was that!
The transmitter has regained its old range.
Presumably, either the GPS itself or the power supply is producing
RF interference. I actually suspect that the cheap lighter-socket-to-USB
power supply is the problem; it's not the one that originally came with
the GPS device. Next experiment: Go back to the original power supply
for the Garmin Nuvi GPS. It probably has better filtering.
[Update:] The problem is present whenever my
Scosche brand dual USB power adapter is plugged into the lighter socket
(which is energized all the time). It doesn't matter whether the GPS
is plugged into it. I don't know if this adapter is defective or if
this is a design problem with it. More news soon...
How to prevent a Radio Shack PRO-95 scanner from overcharging its batteries
Here's the gadget I built this evening (Nov. 25).
I had gradually become aware that my Radio Shack PRO-95
scanner radio overcharges its NiMH batteries.
That is, whenever it's connected to its 9-volt power
supply, it pumps 160 mA into them, which is too much
for continuous trickle charging.
So I inserted this gadget in the 9-volt power line between
the radio and
the power supply ("wall wart" — incidentally, it's an old Sony one
and outputs 9 volts).
At the flip of a switch I can either charge the batteries (with 160 mA)
or maintain them on a trickle charge (30 mA).
On "maintain," it charges the batteries very slowly and can continue indefinitely
without harm. This is for topping up batteries that are only slightly run down.
It would take a couple of weeks to charge a completely empty battery.
Also, on "maintain" there is not enough current to power the radio; you can't
listen to it.
On "charge," the batteries charge completely in about 12 hours but would be
damaged if the charging continued for days. This is also the setting for
listening to the radio with the power supply plugged in.
What's more, the red LED lights up on "charge" to remind me not to leave
the switch set that way indefinitely. I built the gadget in an old
translucent plastic 35-mm film can (remember those?) so that the LED is
visible from all directions.
Like all my published electronic circuits, this is intended for people
who understand how and why it works. It's not intended to be built blindly.
In other news: My technical accomplishment for November 24 was
soldering under a dissecting microscope in order to fix Sharon's Intuos
graphics tablet. The tiny USB connectors are soldered to the printed
circuit board and can be ripped loose any time anything tugs on the cord
hard enough to peel the copper traces off the board. After my repair,
there's some epoxy helping to hold things together.
And
I'm quoted in Popular Mechanics.
Somehow, a rumor got out that Wolfram Research had invented a way to write
computer programs in plain English. My take?
That doesn't seem to be what Wolfram is claiming, and anyhow, it's not a good idea.
We don't use plain English to express algebraic equations, or house plans, or
musical scores. English just isn't precise and concise enough; special notations
are much better.
A rich Milky Way field in Cassiopeia and Cepheus, showing the star cluster M52
at the upper left and the (red) nebulae Sh2-157 and NGC 7380. Same technique
as the picture I presented yesterday, but only 5 exposures were stacked,
and the picture is presented with rather high contrast to bring out the
faint nebulae.
Another example of galaxy photography with inadequate equipment under excellent
conditions. This is a stack of 13 one-minute exposures with a Canon 60Da at ISO 3200,
using a Sigma 105-mm f/2.8 lens wide open and an iOptron SkyTracker, at the
Deerlick Astronomy Village.
This is another of my pictures from November 3, and there are still
more to come!
This lizard was contentedly basking on a fence in our back yard when
the temperature read 48 F on my own thermometer and 45 F at the Athens
weather station. This may be the same lizard that was
our temporary pet last December.
[Addendum:] This is indeed an American chameleon, Anolis carolinensis.
He can change color, and in the chilly air, he turned so brown as to practically
disguise himself as a fence lizard, Sceloporus, whose behavior he
also seems to be imitating.
I've photographed the Andromeda Galaxy many times before, but this might be
the best example of a good picture taken with a small aperture.
Same technique as the picture of the Helix Nebula that I presented yesterday
(below); with a 105-mm lens at f/2.8, the total clear aperture was 1.5 inches.
Compare that to the 200-inch telescope on Mount Palomar...
This is the Helix Nebula (NGC 7292) in Aquarius, photographed with inadequate equipment
— but still, I got something.
Stack of six 1-minute exposures, Canon 60Da, ISO 3200, Sigma 105/2.8 lens wide open,
iOptron SkyTracker, postprocessed with DeepSkyStacker and PixInsight. The pixels were
binned to make one pixel out of every four, and you are looking at the central 600 × 400 pixels.
Ghost story: My Asus laptop won't turn on when it's resting on top of my
folded-up Lenovo laptop.
The reason? Both of them use magnets to sense when the lid is closed,
and the Asus is fooled by the Lenovo's magnet. At least, that's my best guess.
Fixing up old gear: In the next few weeks I'm going to be repairing and maintaining
some older electronic equipment in my workshop
(such as the Fabulous Fifties audio generator).
Here are a couple of hints about parts.
(1) For replacing resistors in vacuum-tube equipment, I recommend
Yageo 2-watt flameproof resistors,
which are rated at 500 volts and cost about 20 cents apiece at
Digi-Key.
They are hardly any bigger than traditional half-watt resistors.
Most modern resistors are rated at only 1/4 or 1/8 watt, 250 volts
maximum.
(2) I am going to replace every electrolytic capacitor that is more
than 30 years old, even if it seems to be working perfectly.
I have some in use, in equipment, that are more than 60 years old!
Unfortunately, there is a real risk that they will
fail catastrophically and take other
components with them when they go. And modern capacitors are
much higher-grade than the older ones were even when new.
Since it does no harm for filter and bypass capacitors to be higher
in capacitance and voltage than originally designed, I'm not going to try to match
them all. Instead, I'm buying 47-microfarad and 22-microfarad, 450-volt,
capacitors in quantity.
Now back to the pictures I took on November 3 at Deerlick.
This is the Double Cluster in Perseus (at the bottom) and,
above it, some faint emission nebulae (hydrogen gas clouds, red)
and also some dark nebulae (dust clouds obscuring the more distant stars).
Stack of twelve 1-minute exposures, Sigma 105-mm lens at f/2.8,
Canon 60Da, ISO 3200, iOptron SkyTracker.
"Can you see any mountains from your home in North Georgia?" friends sometimes
ask. Yes — these, for example — they're on the moon.
The lunar Apennine mountain range is named for a mountain range in Italy.
Like other recent moon photos, this is a stack of about 1300 video frames
taken with a Canon 60Da and a 5-inch telescope on back on November 11.
A couple of years ago, we had some trees taken down near my telescope pier,
only to find that we were relying on them to block some lights farther up
the hill. Today I had a tree planted that will, in a few years, do the same
job again. It is a Cryptomeria of some sort.
Should we boycott or ban shopping on Thanksgiving?
[Revised again.]
This year, several major department stores are going to be open on Thanksgiving Day.
This announcement has aroused controversy. Should this heathen practice be boycotted
or banned?
Well — I'm not planning to shop on Thanksgiving. I've always shied away
from artificially-created "Black Friday" frenzies, and this sounds like more of the same.
I suspect not many people will want to shop on Thanksgiving.
But I'm not going to circulate pledges or demand boycotts or bans.
I want to point out that there is another side to the story.
Let's not forget that we rely on a certain amount of commercial activity for the benefit of
everyone. Gas stations and some restaurants and pharmacies stay open. Nobody objects to
TV stations or the NFL working and making lots of money on Thanksgiving.
It can be quite inconvenient if too many businesses shut down — I remember
having trouble getting something to eat one Thanksgiving when I was in college
a long way from home, and of course all the college staff got the day off
and all the local businesses closed.
So let's not talk about activity on Thanksgiving Day as if it were Sabbath-breaking.
I think the people who are against "shopping on Thanksgiving" are aiming at
slightly the wrong target. The real risk is the abolition of
Thanksgiving itself, not some kind of secular Sabbath violation.
I'm alarmed by the way "Black Friday" seems to have spread to England
(even though Thanksgiving is not a holiday there) and the calls to make it
an official holiday in some states.
A holiday to honor God (or at least our human benefactors) is being
replaced by an artificial commercial frenzy.
The real problem is the Black Friday circus, whether or not it spills over
to the preceding day.
Another moon picture, again a stack of about 1300 video frames taken through
my 5-inch telescope on November 11. The crater just left of center, with
a single central peak, is Alphonsus, named in honor of King Alfonso X of Castile (Spain),
patron of astronomy.
At the lower left you see the Straight Wall, which is not a wall but a cliff
and is correctly described by its Latin name, Rupes Recta.
Should you use bargain batteries?
Are cut-price dollar-store batteries any good?
A name-brand 9-volt battery like the one on the left costs about $3.
The one on the right cost me 50 cents, or rather 2 for $1, at a
dollar store.
Which one is the better deal?
Well, the one on the left contains about 6 times as much electricity.
It also costs 6 times as much.
And it's from a manufacturer with a proven record of reliabilty.
(Sunbeam is just an importer; we don't know who makes their batteries.)
So the one on the left is the better deal. Right?
Maybe, maybe not. It depends on how you're going to use the battery.
If you're going to use up the battery in a high-load device,
then definitely buy the better one. High-load devices include anything
that plays music through a speaker, runs a motor, or produces more
than momentary light or heat. Camera flashes are high-load devices
because although the flash is instantaneous, it is very bright.
Cameras are high-load devices because of the focus motor and the bright display.
And always use top-grade batteries in smoke alarms.
But if the battery is going into a low-load device, such as a clock,
calculator, or multimeter, or will be used only occasionally, as in a
penlight or test instrument that actually runs only for a few minutes
per year, the cheaper battery may be the better buy. Either battery
is probably going to die of old age rather than by being used up.
And if the battery is likely to be run down by someone accidentally
leaving the equipment turned on, not actually using it, you might
opt for the cheaper battery, even in a high-load device. (This is often
the case with toys.) If any battery is doomed to be exhaused accidentally,
you might as well make the accident less costly.
A word of caution: don't leave a battery in place for months after it has been
partly run down by a high-load device. That's what makes them leak.
Partial exhaustion by a heavy load, followed by age, leads to leakage.
I've never seen a 9-volt battery leak. Its cells are enclosed in a
rectangular box. But 1.5-volt batteries leak, in my experience,
more readily now than they did in the 1970s! You are handling the
cylindrical cell itself; it's not in a box.
By the way, the cheapest batteries you can buy today are equal to the
best ones you could buy in 1970. Sunbeam is not lying when they describe
their 50-cent battery as "super heavy duty." It is equal to the "heavy-duty"
carbon-zinc batteries of 40 years ago.
This will provide some context for the images of lunar regions that I took
on November 11. This is the full face of the moon with the same telescope
during the same observing session. One image of a smaller region appeared
here two days ago; the others are coming.
This is a stack of 8 exposures taken with the camera direct-coupled
to my old Celestron 5. Because of field curvature, the picture is
sharper at the center than at the edges; I focused on the center, which
was probably a mistake, since "compromise focusing" on an off-center area
might have yielded a picture that was acceptably sharp all over.
Compare this to the picture taken with a big telephoto lens
a few days earlier — but the comparison
isn't entirely fair because the air was considerably steadier
for this newer picture.
I wish I could go, but I'm stuck in Georgia... The cultural highlight of Lexington,
Kentucky, this week is Shakespeare's King Lear,
performed by the Actors' Guild of Lexington,
with my son-in-law, Nathaniel Barrett, playing the role of Edgar.
In the picture, he's the one in the middle.
Speaking of things theatrical, when I was taking pictures of the comets on the morning of November 11,
I stepped out into my backyard wearing slippers, pajamas, and a dressing gown.
A particularly big, fancy, royal-looking dressing gown that I've had for years;
I had it at Cambridge thirty-five years ago, where it looked like
(and was mistaken for) a foreign academic gown.
So I felt a bit like Tycho Brahe, who reportedly observed wearing the
full regalia of a nobleman.
The battery charger that I described recently
was reviewed in QST, April 2009, and they really liked it.
Although Chinese-made, it is an American design.
QST also tells me that the most unreliable part in
modern electronic equipment can easily be the solder,
especially if the equipment failed after being exposed repeatedly
to vibration or changes in temperature. Everything else is so
reliable nowadays that a broken piece of metal is actually likely
to be the problem! Gone are the days when your TV needed a new
tube every few weeks.
An advantage of an analog oscilloscope that I didn't mention —
and the reason the digital one will never do all the work — is that an
analog oscilloscope responds instantly, while a digital oscilloscope often
takes a visible fraction of a second to process and display a waveform.
That means you need an analog scope if you want to see a change instantly.
An example arises when looking for loose connections — the analog
oscilloscope will tell you whether changes in the signal are synchronized
with your tapping on the circuit board; a digital oscilloscope won't.
The evening of November 11 was shaping up to be the last (moderately) warm
evening of the year (47 F), and ClearSkyChart
was predicting "good seeing" (steady air), so I got out my old Celestron 5 (now a third of a
century old) and let it cool down to the temperature of the surrounding air.
Then I photographed the moon and got very good results. I'll unveil the pictures one
by one as this month goes by — along with more pictures from my last trip to Deerlick —
but here's one to get started with. This is the southern region of the moon, with the craters
Tycho and Clavius prominent at the left. Stack of about 1300 video frames taken with a
Canon 60Da.
Commercial software is getting serious competition from free software —
and the latest one I want to try is
Audacity,
an audio editor.
It includes a tool for
removing the noise from vinyl records.
I have yet to try it, but I'm going to.
Because of patents, you have to get add-ons if you want to handle MP3 files,
but they, too, are free.
Offhand I can't remember observing two unrelated comets in the same
short observing session, although I suppose I've probably done it before
now. This morning (Nov. 11) I got up at 5 a.m. and carried the iOptron
SkyTracker out into the yard (with one hand), then put my Canon 60Da
on it, with a 105-mm f/2.8 Sigma lens wide open.
Here's Comet Lovejoy C/2013 R1, which is about sixth magnitude
and is a fine sight in binoculars. This morning it was near
the star Kappa Leonis. This is a stack of four 30-second exposures.
You're looking at an enlargement of just part of the picture.
And here's Comet ISON C/2012 S1, the "comet of the century" that
is shaping up to be nothing of the sort. I couldn't even see it
in binoculars (under unfavorable conditions). This is a single
30-second exposure, enlarged and cropped.
This is in the field of the star Eta Virginis.
After I photographed the first comet and before I photographed
the second, the International Space Station flew over, looking
like a second Jupiter moving across the sky. I took a 30-second
exposure, showing it as a trail:
How to fix electronics when batteries have leaked in them
I've just rescued my venerable old Nikon Coolpix 990 (my first pro-grade
digital camera, circa 2002) from a horrible fate, and to celebrate,
I used it to take the picture that you see above.
Batteries had leaked in it.
Whenever batteries leak in a piece of equipment, they ruin it, right?
Well, it's true that the equipment has had its life shortened.
Contacts that have had corrosive chemicals on them will eventually corrode again,
even if you do a good job of cleaning them up.
However, it may take years for this to happen, and your gadget
may give you many years of good service before any further problems arise.
The white crust that comes out of alkaline or rechargeable batteries is
mostly potassium carbonate, which is
is not highly toxic, although you should wash your hands after any
contact with it, especially because there may be some potassium
hydroxide mixed in.
Most "contact cleaner" solutions, including pure alcohol, do not
dissolve potassium carbonate. Water does, but water is not good for
electrical equipment — it takes too long to dry. So I use rubbing
alcohol, which is 70% alcohol and 30% water.
Do not drench electronic parts with any liquid unless you have no other
choice. The way I clean up battery crust is first of all to remove it
by poking with toothpicks, pins and needles, and whatever else will dislodge
it. (A dental pick is handy; pretend you're a dental hygienist getting tartar off
teeth.) Canned compressed air helps get the crumbs out of the way once you've
loosened them. (Protect your eyes!)
Rubbing alcohol softens the crust nicely — let a drop of
alcohol soak into the crust and stay there a few minutes, then use a pick
on it. An old toothbrush also comes in handy. Use canned compressed air
again at the end of the procedure, to remove moisture, and then let the
equipment dry before trying to use it.
It is often neither possible nor necessary to remove every trace of residue;
what's important is that the metal battery terminals need to be clean and
make good contact. Plastic and metal surfaces will often continue to look
corroded after they're clean because the surface has been roughened.
With the Coolpix 990, fortunately, almost all the crust was on the
battery-compartment door, which I could wash (carefully, with a small
squirt bottle) without getting liquid inside the camera. There was some
crust deeper inside the battery compartment, but I got it out with a pick
and a piece of moist tissue paper.
Then I used a Dremel tool with a rotating wire brush to polish up the
metal contacts. They didn't look as good as new, but they were clean
where it mattered.
Metal needs to be protected from further corrosion by adding a thin
coating of oil. Sliding plastic parts need lubricating.
You can do both of these with silicone oil (Armor All and similar
products), applied very carefully with a toothpick or rag.
If you don't have silicone oil, mineral oil will do.
Other oils designed for lubrication often have additives that aren't good
for plastic.
For now, the Coolpix 990 works. It may need further contact cleaning later
— or it may not. In 1987 I bought a camera flash for 25 cents because
batteries had leaked in it and the store considered it unsalable.
I cleaned it up inside, and as far as I know, it still works.
As I've remarked about astronomy software, the overwhelming
advantage of free software is that I don't have to buy
multiple copies for multiple computers. Back when I had
only one PC, I was more willing to spend $200 for a good
piece of software for it. Nowadays I want to put everything
on the desktop machine and two laptops, or maybe more, and
I don't want to pay triple prices!
TINA-TI is a cut-down version of TINA,
a commercial product, to which you can upgrade for
a few hundred dollars (depending on options).
But TINA-TI is quite usable by itself.
It includes a good selection of components
(including common ones such as NE555, TLC555, IRF501)
and can import SPICE netlists. Essentially, it uses
the same device models and computation engine as all
the other circuit simulators. In a brief trial,
I found it very easy to use.
The license terms for TINA-TI are a little quirky. You supposedly get a
one-computer license, but it's free, and there's nothing to prevent you
from downloading more than one copy. More curiously, I had to attest
that I am not a student or educator. (Thank goodness I'm retired!)
They don't want people outfitting student labs with free copies of
TINA-TI.
Of course, LTSPICE and Multisim are still out there. Multisim is hard
to track down — the web site was actually down yesterday —
and is expensive. It is facing serious competition from freeware.
[Addendum:] A correspondent points out that I need to explain what on earth
this is all about. This is software that engineers use to design electronic
circuits. Traditionally, the way to test any circuit design is to build a prototype.
But a good computer simulation — using the computer to calculate how
the circuit will behave — is also helpful. It's quicker; you don't actually
have to possess the parts; and if you make a mistake, nothing burns out or
catches fire. Circuit simulation software came into use in the 1970s when engineers
started designing integrated circuits that couldn't be prototyped in advance.
Now it's used for discrete-component circuits, too.
I'll get back to the Deerlick pictures soon, but first,
here's a picture of the moon taken with the huge
Olympus Zuiko 600-mm f/6.5 telephoto lens that I picked up
at the hamfest. Single exposure with a Canon 60Da in
"silent shooting" mode, vibrationless, better than any film SLR
ever could be. This was taken at f/11 and postprocessed
with RegiStax and Photoshop.
I don't know if you have as many NiMH AA and AAA cells as we do.
We use them in the cameras, the cell phones, a radio... and they
wear out. They gradually lose capacity and eventually won't take
a charge at all. We usually use them in sets of four and don't
know which one of the four has worn out. A voltmeter will tell us,
of course, at least roughly.
Enter the PowerEx Wizard One.
This device charges and tests NiCd and NiMH cells in several
different ways. Straight charging is easy, but the most useful
mode is "refresh and analyze" — that is, top up the charge,
discharge the cell while measuring its capacity, and charge it
up again. This takes about 24 hours, and at the end, you get a
reading of the measured capacity in milliamp-hours.
It may be less than the rated capacity because you may be
testing at a different discharge current than the manufacturer did,
but it will tell you whether the battery has lost capacity and,
most important, whether the four in a set are alike.
Each cell is handled separately, so one odd cell in a set
won't harm or affect the others. Separately discharging and cycling
the cells in a set will often make them match each other again,
when they had begun to drift apart because charging them in series,
the way other equipment often does, tends to magnify small differences
between cells.
Highly recommended.
[Addendum:] If you put in a battery that hasn't been used for a while
and choose "refresh and analyze," the display may say HIGH
(meaning high resistance — the battery isn't taking a charge
at the expected rate). Charge it (in "break in" mode) first.
Also, the default charge and discharge rates (1000 mA and 500 mA respectively)
are suitable for high-capacity AA cells (1500 mAH and higher), but you should
cut them in half for AAA cells and older-style AA cells.
[Further addendum:]
This charger will often read HIGH and shut down, or simply turn itself off,
when presented with a battery whose internal resistance is more than 0.5 ohm.
This is a safety mechanism to avoid charging batteries that aren't NiMH.
It also rejects older, deteriorated NiMH batteries, even those that seem to
be taking a charge in a more primitive type of charger.
The logic is apparently similar to what is described in
this Texas
Instruments presentation.
If you have a laboratory power supply, you can check the resistance of an
NiMH cell as follows. Set the power supply to at least 5 volts with a current
limit of 500 mA. Watch the voltage as you connect it across the cell.
Within a few seconds, it should drop down to 1.6 V or a little less.
If it stays in the 1.7-volt range or higher, the cell has developed
high internal resistance.
The other important addition to my workbench — made this very day,
November 7 — is a digital oscilloscope.
Unlike an analog one, a digital oscilloscope can record a transient (one-time)
waveform and store it. It can also do computations on the data, including
Fourier transforms (turning a waveform into a spectrum).
And it can save its display onto a USB flash drive.
This one was an eBay bargain and I'm the fourth (I think) owner, but the first
one actually planning to use it! It arrived in its original packaging and had
only been powered on a few times, according to the internal log.
You might guess I'm finally finding time to get back into electronics,
and you'd be right.
By the way, for a while I had a TDS 220 digital oscilloscope on my workbench,
but it was technically on loan to the University, not to me, and has been
returned to them now that I'm retired. So this instrument is not a totally
new world for me, but it does have some features the other one didn't. And it's
more colorful; they even provided little plastic pieces to snap onto the probes
to match the colors of the traces and the knobs.
A while back I thanked our church friend Raynette Noles
for giving me a Tektronix 2245A oscilloscope that she had inherited. Today I want to say a
little more about it — partly because I've just finished figuring out some of its features myself!
It is an analog oscilloscope with some digital measuring circuitry added.
(For the wider audience I should add that an oscilloscope draws a graph of
voltage versus time. It is an instrument for investigating electrical signals
of all kinds; you will see them in laboratories and repair shops.)
Because it's analog, it relies on a recurrent waveform. It doesn't record or store the
wave that it's displaying. To stay on the screen, the wave has to be doing the same thing,
over and over, and the oscilloscope synchronizes to it and keeps regenerating the display.
The good thing about analog oscilloscopes is that nothing weird can happen to
the input signal. If it gets distorted, it will get distorted in a predictable way.
Strange digital sampling effects will not happen.
The 2245A has two modes, A and B. In A mode, it is simply a four-trace oscilloscope:
Channels 3 and 4 have a limited range of input amplitudes — they're mainly
for logic signals, although here you see that they are fully analog, just like the
others.
The interesting part is that there are cursors for measuring voltage, frequency,
and time. Here you see them measuring frequency. They have to be put in place
by turning dials, and then they tell you the voltage or time difference between the
two points where they intersect the wave.
Then there's B mode. In B mode, you see the same waveform as in A mode, but
you only see part of it, magnified horizontally, and you can choose what part
to look at.
B mode by itself is less useful than alternating A and B mode, which you see here:
The upper trace is the whole waveform, with part of it highlighted, showing what's
magnified in the lower trace. Obviously, this would be more helpful with a
more complicated waveform — and most waveforms are indeed a good bit
more complicated than this one.
Here's the California Nebula, so called because of its shape.
It's a gas cloud in the constellation Perseus. Elsewhere in the picture
you see a bright cloud of stars and two dark nebulae (dust clouds in
interstellar space). North is to the upper right.
This is the first picture that I've processed from my trip to Deerlick
on Sunday, November 3. Stack of sixteen 1-minute exposures with a Canon
60Da (at ISO 3200) and Sigma 105-mm f/2.8 lens on an iOptron SkyTracker,
corrected with dark frames, flat fields, and flat darks using DeepSkyStacker.
Because DeepSkyStacker was used in "sigma clip" mode to reject deviant
pixels, the computer deftly edited out the effects of poor tracking in
a couple of frames, and even an airplane that flew through the field.
I did the postprocessing with PixInsight — this one hasn't been touched
with Photoshop. Although people complain about its "steep learning curve,"
I think PixInsight is as easy to learn as Photoshop, if not easier.
The secret to both of them is that there are hundreds of tools, most of
which you're not going to use.
Sunspots on November 3. Mostly, this is proof that my new Thousand Oaks solar
filter works well. Celestron 5, stack of three 1/2000-second exposures postprocessed
with RegiStax and Photoshop.
There's a lot going on here... I went to Deerlick on November 3 and took quite a few
good astrophotos, which you'll eventually see here. I'm also getting my electronics
workshop back into action after some months of neglect... more about that soon.
And although I don't often write about politics, I do want to refer you to
this.
Besides the expected economic feasibility problems
with Obamacare, and the unexpectedly inept implementation of the web site,
we also have an issue with false claims or, at best,
culpable ignorance. "If you like your present
insurance you can keep it" — says who? Regardless of
whether it's conservative or liberal, this is not competent, honest government.
I wish people (especially Congress)
were thinking about making urgent changes and corrections rather than
just demanding total repeal or nothing.
Has anybody noticed that the quality of the U.S. government has
fallen in recent years? Apart from questions about what policies they want
to implement, they have fallen down in practical ability to make anything
run smoothly.
Today (Nov. 2) I went to the Lawrenceville (Stone Mountain) Hamfest, which is
primarily a ham radio swap meet, for the first time since 2009.
I scored big. The items of most interest to me are the offbeat ones — not
common radio or computer gear, but unusual laboratory items and the like.
What I ended up with was an Olympus
Zuiko 600-mm f/6.5 telephoto lens
in a custom-fitted carrying case, with an OM-2 camera body.
For $40. Probably resalable for $800 immediately — it is so rare
that KEH doesn't have one in stock — but I plan to use it for
astrophotography (on a Canon DSLR body with an adapter).
That, in turn, will take a while, because I do not yet have an equatorial
mount capable of carrying it. (It's essentially a 4-inch refracting telescope
with a 6-element multicoated optical system.) But I can use it on a fixed
tripod for full-face shots of the moon, and I can test it on star trails
(and plan to do so right away).
Unexpectedly nice feature of this lens: The stiffness of the rack-and-pinion
focuser can be adjusted by the user, by turning the knobs in opposite directions.
(Turning them in the same direction changes the focus.)
I will test the OM-2 camera body later. It is a pro-grade camera and I don't
see any obvious problems, although I haven't opened it up to look for
crumbling foam or the like, nor have I put batteries in it.
It is a close relative to the only camera body I came close to wearing out.
I used an OM-2S incessantly from 1985 to 1998 and it looks visibly worn,
although when last used, it was still working fine.
Motorola 3360 DSL modem — "Internet" LED stays dark
If you are an AT&T customer using a Motorola 3360 DSL modem,
and you've connected it to a router, and the router is in charge
of logging into your AT&T account, then
your Internet connection will work fine but the "Internet" LED
will remain dark and not light up green.
Contrary to all documentation, this is apparently perfectly normal.
Now you know.
We replaced our 5-year-old Westell modem, which had become slightly
unreliable. No settings has to be made on the Motorola — we
just plugged it in, powered it up, power-cycled the router, and gave
it a few minutes to find the connection.
[Update:] The "Internet" light only blinks green when data packets are
being sent or received from the Internet. Now you know.
To set up this modem for use with a router, where the router stores your
DSL username and password, do the following:
(1) Factory-reset the modem per instructions. (With power on, hold down
the reset button for several seconds, then let the modem power up.)
(2) Connect the modem directly to the Ethernet port of a PC. For now,
leave your router unused.
(3) In the advanced menu, choose "PPP location" and tell the modem that
you are using it in bridged mode, i.e., the router, upstream from it, will
take care of logging into DSL.
(4) Save settings.
(5) Connect the modem to the "Internet" connector on your router, and
connect your PC to the router in the usual way. From there, do the setup
on the router if you have not already done so.
Five years ago, our nation was brought to its knees by a bad
mortgage underwriting system.
Today, I'm involved in reinventing it and fixing the problems.
I work with Formfree Holdings, Inc., which has received
a major
award from Mortgage Technology magazine.
A token of good things to come...
This is a private web page,
not hosted or sponsored by the University of Georgia.
Copyright 2013 Michael A. Covington.
Caching by search engines is permitted.
To go to the latest entry every day, bookmark http://www.covingtoninnovations.com/michael/blog/Default.asp
and if you get the previous month, tell your browser to refresh.
Entries are most often uploaded around 0000 UT on the date given, which is the previous
evening in the United States. When I'm busy, entries are generally shorter and are
uploaded as much as a whole day in advance.
Minor corrections are often uploaded the following day. If you see a minor error,
please look again a day later to see if it has been corrected.
In compliance with U.S. FTC guidelines,
I am glad to point out that unless explicitly
indicated, I do not receive substantial payments, free merchandise, or other remuneration
for reviewing or mentioning products on this web site.
Any remuneration valued at more than about $10 will always be mentioned here,
and in any case my writing about products and dealers is always truthful.
Reviewed
products are usually things I purchased for my own use, or occasionally items
lent to me briefly by manufacturers and described as such.
I am an Amazon Associate, and almost all of my links to Amazon.com pay me a commission
if you make a purchase. This of course does not determine which items I recommend, since
I can get a commission on anything they sell.
If what you are looking for is not here, please look at
previous months.
Five years ago, our nation was brought to its knees by a bad
mortgage underwriting system.
Today, I'm involved in reinventing it and fixing the problems.