Re: Extech EX410A DVM Don't Buy

On Sun, 06 Oct 2024 06:04:58 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Sat, 05 Oct 2024 17:30:03 -0700) it happened Jeff Liebermann
<jeffl@cruzio.com> wrote in <ugj3gjp918lmu1b7fipb2vqe4a2kucgf5q@4ax.com>:

There are also consistence problems and matching issues with NiMH:
<https://eneloop101.com/batteries/eneloop-test-results/>

>
Wow, some test site.

Yes.  I find the best web sites when I'm looking for something else.

Eneloop looks good, oldest onces I have are AAA from 2010 ...
still going fine, some in remotes, one in an inside/outside temperature meter
I have a DCF radio-clock with eneloop too.

Will your DCF radio clock operate at 1.2VDC (or less) at the radios
"normal" current drain?  Actually, yours probably uses two cell in
series, so that should be 2.4VDC.  The better NiMH cells provide 1.2V
with a very light load:
<https://eneloop101.com/wp-content/uploads/eneloop-sanyo-white-1900-mah-cell-2007-2017-10-year-battery_-capacity-test.png>
Disabling the receiver for most of the day and only operating it for a
few minutes when propagation is good (after midnight), isn't
sufficient.  The battery voltage might be higher than 1.2V when the
receiver is off, but as soon as the receiver comes on, and the current
drain increases, the voltage will drop below 1.2V.  I forgot how much
lower.  I did some polarization testing with an Oregon Scientific Time
Machine using WWVB.  It ran on two AAA cells.  Alkaline and
carbon-zinc worked well, but NiMH lost considerable sensitivity as the
battery aged:
<https://www.learnbydestroying.com/jeffl/WWVB%20test/>
<https://www.ebay.com/itm/387144016757>
I just found the device.  If I get ambitious or bored, I'll put the
clock on a variable voltage power supply and see how it handles low
battery voltages.

Fun with shorting alakline batteries:
<https://www.learnbydestroying.com/jeffl/pics/Duracell/index.html>

>
I gave up on Duracell long ago, when the AA rechargebles I bought for a lot of money
did not keepd their charge even for a few days!
I still have those, repeated test once .. some result.. crap.

The photos are not of a common Duracell leaking electrolyte, but
rather of a premium Duracell exploding inside its metal case.  There's
a small chance that this 9V battery was a counterfeit, but it's too
late to check.

No generator here, but I am considering buying something like this:
https://tesup.com/uk/tesup-vertical-wind-turbines-for-homes
there is more wind than sun here :-)

Ummm... A tiny desktop vertical rotating turbine is not likely to
produce 10 Kw of power.  The unspecified size solar panel might
produce 10 Kw, but a small desktop device will only deliver a few
watts at best.

I've had some experience with vertical turbine generators.  In a
strong wind, they can't be feathered and will usually rip the base out
of the roof or whatever it's mounted on.  They also make far too much
noise.  When ground mounted, the part of the vertical turbine blades
near the ground don't contribute much power.

I suggest you do some reading before you waste your money:
<https://en.wikipedia.org/wiki/Vertical-axis_wind_turbine>

I have two LiFePO4 batteries:
<https://www.bioennopower.com/products/12v-20ah-lfp-battery>

>
That is very expensive,
I payed $872.14 for my 12 V Lifepo4 250 Ah battery pack from Aliexpress.

I didn't pay anywhere near full price for the two batteries.  I don't
want to explain how I obtained the batteries but I will assure you
that I didn't steal them.

Well, I am more lucky with a huge garden where the wind can blow,
A wind generator on the roof would produce a LOT of power here,
but might blow away in the next storm, we just had one.
But in the garden, why not?
Can you not mount something on top of an old tree?

Again, you can't easily feather a vertical wind turbine.  There's no
easy way to point the vertical turbine blades perpendicular to the
wind.  The only way to slow down the rotation is with some form of
brake, which essentially converts the wind energy into heat.  Imagine
your turbine dissipating 10 Kw of heat continuously.

I solved that problem a few years ago by convincing a neighbor to buy
a "no moving parts" weather station for about $300.
<https://tempestwx.com/station/76665/grid>
<https://shop.tempest.earth/products/tempest>
I get to play with it and he gets to deal with maintenance issues.

>
Better than mine, mine only does temperature and humidity, sends data via RF to an in-house receiver.
I also log it to a file, receive it with an RTL-SDR stick connected to a Raspberry Pi.
I have been experimenting with wind speed - and direction sensors based on temperature differences:
https://panteltje.nl/panteltje/pic/wind_pic_thermal_udp/
and by using ultrasonics:
https://panteltje.nl/pub/wind_speed_by_differential_2_ebay_distance_meters_IMG_4891.JPG
 these are 2 dolar ultrasonic distance meters from ebay..

That's roughly the way the Tempest weather station works.  I suggest
you look at the available data sheet, feature list, and software
before you reinvent the device.  Communications is via Wi-Fi:
<https://shop.tempest.earth/products/hub>
<https://www.youtube.com/watch?v=lks6lIb5gGM>

See "Technical Questions" near middle of FAQ:
<https://tempest.earth/frequently-asked-questions/>
How does the ultrasonic anemometer work?
The ultra-sonic anemometer is composed of 4 transducers housed in the
top of the device. The Tempest measures wind speed and direction based
on the time of flight of ultrasonic pulses between pairs of
transducers. This allows for a high degree of accuracy especially in
variable wind conditions. An ultrasonic sensor is very good at
detecting light winds and has an advantage over mechanical sensors
which require momentum to rotate their bearings. Tempest’s ultrasonic
anemometer has an upper detection limit of 100mph (~160 kmph). Any
wind speeds above this threshold may be outside of accuracy
specifications.

Well, I did some testing writing quadcopter code, these days useful for bombing I guess:
https://panteltje.nl/panteltje/quadcopter/index.html

Sorry, but exploding drones have been replaced by exploding pagers. 

I'll pretend to be polite and not say anything about the wiring.

>
Ah, how 'bout this then?
https://panteltje.nl/pub/z80/sound_card_bottom.jpg

The wiring is (barely) tolerable.  However, whatever animal droppings
you used for flux is beyond disgusting.  I suggest baptizing your
wiring maze in some alcohol, which should remove the brown goo and
make your masterpiece presentable.

As a kid I started with 4.5 V batteries...

>
I'm still a kid. 

>
Sure, almost 80 here ...

I'm 76 and holding.
<http://www.learnbydestroying.com/jeffl/pics/jeffl/jeffl-wolf.gif>

I am still running around, biking, writing code and soldering with 60/40.
lead bad?
;-)
Inhaled resin smoke all my life,

I've given up running and cycling and downsized to walking and hiking.
<https://www.strava.com/athletes/103870441>
<http://www.learnbydestroying.com/jeffl/pics/bicycles/5bikes.JPG>
I don't write code.  Many years ago, I had to choose between a career
in hardware or software.  I chose hardware because it was less likely
to be automated into insignificance.  So far, I think I made the right
choice. 

I still use 63/37 tin-lead solder, but have forced myself to tolerate
using ROHS dross.  I have separate soldering and desoldering stations
on my bench, one for each blend.  There's are two small fans blowing
the fumes towards the wall behind my bench, which has slowly changed
from white to brown.  I make my own rosin flux from pine tree sap and
isopropyl alcohol.  It's very organic, substitutes nicely for incense
and might even be healthy.

BTW that Voltcraft soldering iron has adjustable preset temperatures,
so no special tips needed like a Weller.
Also I >never use a wet sponge< on the tips,
I clean tips with a piece of kleenex or even toilet paper, or rub it against the lead..
Using wet sponges kills your soldering tips, it is a sales trick.
I have tips that still look fine after 24 years.

I didn't know that.  I use cellulose sponges and water for tip
cleaning.  I also use some brass "wool" tip cleaners.  For the big
irons, I use a sal ammoniac (ammonium chloride) block.  When I bought
the box of Weller soldering station parts many years ago, it came with
about 50 dirty Weller tips.  I soon determined that the company that
provided me with these irons had a policy of not cleaning tips.  When
a tip became dirty with burned flux, it was replaced with a new tip.
After some experimenting, I managed to clean almost all the tips, some
of which I still use today.

--
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558