chip swelling up and getting fried

[CWatters]

"Andre" <testing_h@yahoo.com> wrote in message
news:2c2cf14c.0408191002.5138004e@posting.google.com...

Hi group.

With all the computers being scrapped, there must be literally
thousands of useless HDD's dumped every week in the UK alone.

The motors from CD drives have been rewound and used to power small indoor
RC model aircraft. Perhaps you could also do that with an HD motor?

 

[John Larkin]

On Fri, 20 Aug 2004 07:37:44 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

Placing an ammeter across a battery is not only dangerous, but gives
no meaningful info as related to working loads.

It places an upper limit on how much current the battery might
possibly be putting into the electromagnet, or into any load. And it's
interesting to me, since I now know the fault current envelope I might
see if, say, I had a battery-powered gadget and a tantalum capacitor
failed or an IC latched up or something.

And it was obvious that this particular measurement could not have
been dangerous, even before I knew the results.

Roger the combat boots.

John

 

[andy]

On Fri, 20 Aug 2004 07:40:21 +0000, Robert Baer wrote:

andy wrote:

On Tue, 17 Aug 2004 23:11:39 -0700, Chad Waldman wrote:

I posted a message a week back but never received the answer I was
looking for.

I have an electromagnet hooked-up to a 9V battery. The magnet is
strongest when the battery is at full charge. I want to replace the
battery with an adapter to run the magnet from an outlet. What I am
wondering is, what is the max current the battery is outputting when it
is new? If you have an ammeter, can you please test the output of a new
battery.

Thank you,
Chad

I've managed to get good results with a standard 250g coil of 24 swg wire
(0.56 mm) unwound from the bobbin, split in 3 equal lengths, and then
wound back on again, with the coils connected in parallel. The coil
resistance is around 1 ohm. With a 1.2Ah 12V lead acid battery, this gives
a peak current of about 10-11 amps. (The battery voltage drops to around
10.5 volts from about 12.5)

I'm using a piece of rebar (concrete reinforcing rod) as the core - this
works the best out of the metal objects I've tried. Bolts are no good.

With this setup, it's strong enough to push a neodymium magnet off the end
of the core, and lift the core against gravity. Guessing about 50-100
grams force when you try to pull the core out of the magnet with the
current on. To make a proper push/pull solenoid, you'd need a permanently
magnetised core, I think, which would be harder to find.

--
http://www.niftybits.ukfsn.org/

remove 'n-u-l-l' to email me. html mail or attachments will go in the spam
bin unless notified with

 or [attachment] in the subject line.

Try connecting the three windings in series; see if you can make a
meaningful comparison of the relative strengths (series VS parallel).
[/QUOTE]
I think I can guess that one - 3 3.3 ohm coils in parallel makes one ohm,
so the current is around 12A. In series would make about 10 ohm, with a
current of around 1.2A. So the strength would be about 9 times less.

-- 
http://www.niftybits.ukfsn.org/

remove 'n-u-l-l' to email me. html mail or attachments will go in the spam
bin unless notified with [html] or [attachment] in the subject line.

 

[KevinR]

Get a sheet of plywood, paint it black and glue lots of platters to it
to make a 60s style mirror.

Get a really big sheet of plywood and mount loads of platters at such
an angle that they all reflect the sun to the same spot and use it as
a solar power thingy. I suspect it might actually be cheaper to buy
mirrors though and you might have trouble keeping Bond's light fingers
off the Solex.

I have actually used some parts in real life.
I used a bearing as a cam follower in a PCB etching agitating machine
I built and I used the motor spindle thingy as a boss to allow me to
use a puller to extract a bearing from a CCTV panning gear.

I have dozens of the incredibly strong magnets, as we scrap a hell of
a lot of drives here and I always strip out the magnets, as I still
haven't got over the novelty of them yet (well I am only 40). Still
trying to come up with a use for those, they're not an ideal shape
(well, I supose they are an ideal shape for hard drives)

 

[Tim Auton]

testing_h@yahoo.com (Andre) wrote:

With all the computers being scrapped, there must be literally
thousands of useless HDD's dumped every week in the UK alone.

So, things to do with them.

If it's merely obsolete (as opposed to broken) put a transparent
window in it with some LEDs for illumination and put it to work (real
or simulated). Watching the heads do their stuff is cool (well, it is
if you're a bit sad like me).


Tim
--
Google is not the only search engine.

 

[John Larkin]

On Fri, 20 Aug 2004 17:42:16 +0100, andy
<news4@earthsong.free-online.co.uk> wrote:

Try connecting the three windings in series; see if you can make a
meaningful comparison of the relative strengths (series VS parallel).

I think I can guess that one - 3 3.3 ohm coils in parallel makes one ohm,
so the current is around 12A. In series would make about 10 ohm, with a
current of around 1.2A. So the strength would be about 9 times less.

Um, I think it's 3.3 times less.

But the big picture is that the amount of field you can sustain
longterm depends on how well you can cool the coil. So for a fixed
copper cross-section and surface area, there's some maximum number of
watts you can pump into the copper before you toast it, and those
watts set the field strength. So series/parallel or wire size doesn't
change the basic limit on field strength so long as the power supply
can be adjusted.

John

 

[Clint Sharp]

"Andre" <testing_h@yahoo.com> wrote in message
news:2c2cf14c.0408191002.5138004e@posting.google.com...
Hi group.

With all the computers being scrapped, there must be literally
thousands of useless HDD's dumped every week in the UK alone.

So, things to do with them.

1) Maglev (take off heads, use one of the actuator magnets)
2) Hard drive speakers (see Afrotech's site for this one)
Damn, forgot all about this, I first did this with a Conner CP344 HDD

about 12 years ago! Mind you, I only used a portable transistor radio as
the sound source so you had to get pretty damn close to hear it, but it
did work!

--
Clint Sharp

 

[gothika]

On Fri, 20 Aug 2004 15:10:14 +0930, "Boozo" <no bones@bogpond.com>
wrote:
You could easily convert that emergency light to rechargables.
I've got a couple I did this with.
Just wire in coaxial power jack and use a wall wart to keep the
rechargables in them charged up to peak.
I use the six volt flashlights that normally use the 6v lantern
battery and have subbed various 6v nicad packs(old style 6v batteries
for camcorders mostly.) instead.
This leaves plenty of room for wiring in the coax jacks.
A 6v 50-100ma wall-wart will keep them permanently topped off and
ready for a moments use.
If your light is the standard 3-6v barrel type you could sub AA nicads
in a cluster as well.

"Louis Bybee" <louistroutbybee@comcasttrout.net> wrote in message
news:8AELc.140328$IQ4.75275@attbi_s02...
"jtaylor" <jtaylor@hfx.deletethis.andara.com> wrote in message
news:tlELc.36510$vO1.168875@nnrp1.uunet.ca...

Louis Bybee <louistroutbybee@comcasttrout.net> wrote in message
news:vzDLc.135950$a24.68446@attbi_s03...

Good customer relations on their part. I suspect I will lean towards
Duracell as I buy batteries in the future.

The differences between brands of alkaline batteries are so small that
they
are dwarfed by the price differences. Duracell will replace your
whatever happily - they are on their way to the bank with your money and
don't want
you to even look at another brand.

How much does a <whatever> cost? How many batteries that cost $2 each
versus ones that cost 39 cents each wiil it take to buy you a new one?
"Coppertop" - "Titanium" - sheesh, whada buncha suckers.

I rarely buy primary cells anymore as the price/performance ratio of
rechargeables is getting so low.


Like you, I use rechargeables more and more these days, but there are
instances where an Alkaline battery is a "better fit".

In the case of my flashlight that was damaged its primary function is to
rest quietly beside the bed until it is desperately need some night when
the
need is immediate, and one needs to depend on the flashlight working
instantly. The flashlight frequently sits unused for great periods of time
between uses (it still lights up even after the cells leaked). Much longer
than many rechargables would maintain a charge. The correct, or best
battery
for one application usually isn't the best for another, and the same
application with different people's use patterns could warrant a different
battery type.

This "sucker" will continue to use Alkaline batteries in my "emergency"
flashlight. I do however, appreciate your concern for my potential state
of
unwise financial exposure. :-]

Louis--
********************************************

In the last 5 years I've had 6 or 7 items damaged by leaky batteries.
Even have a couple of Duracell AAA cells which expire in 2006 with
a negative reading on the battery tester and multimeter.
All of the damaged equipment had current (before use by dates)dates
stamped on the cells.
Only one of those was caused by me plugging in a PSU to the wrong
socket, the rest were battery faults.

Is the quality control getting slack or are they using cheaper seals etc...?

Never had a leaky battery in the previous 30 years until recently.

Boozo.

 

[John Larkin]

Think about it this way: we have three coils. Parallel, there's 10
volts across any given coil. Series, there's 3.3 volts across each
coil. So the current in any bit of wire is

3.3<<xxx s/b 3.0 times higher in the

parallel case. And the total ampere-turns product makes magnetic flux.

Oops: that makes the field ratio 3:1.

John

 

[Chaos Master]

It was written by KevinR[me@privacy.net] in message
<85mci0t9e44c8o6tp16t44p5fpcm5joepk@4ax.com>:

[what to do with dead HDD]

I have dozens of the incredibly strong magnets, as we scrap a hell of
a lot of drives here and I always strip out the magnets, as I still
haven't got over the novelty of them yet (well I am only 40). Still
trying to come up with a use for those, they're not an ideal shape
(well, I supose they are an ideal shape for hard drives)

The magnets, if strong enough, could be used as "hangers" for tools.
Just don't put it near a working HDD.

I have a 2GB hard drive here that is dead. ah, if I was able to open it without
breaking it (really tight screws)....

[]s
--
Chaos MasterŽ, posting from Brazil. REPLY TO GROUP!
MSN: wizard_of_yendor[@]hotmail[.]com http://marreka.no-ip.com
"People told me I can't dress like a fairy. I say,
I'm in a rock band and I can do what the hell I want!" -- Amy Lee

 

[Robert Baer]

andy wrote:

On Fri, 20 Aug 2004 07:40:21 +0000, Robert Baer wrote:

andy wrote:

On Tue, 17 Aug 2004 23:11:39 -0700, Chad Waldman wrote:

I posted a message a week back but never received the answer I was
looking for.

I have an electromagnet hooked-up to a 9V battery. The magnet is
strongest when the battery is at full charge. I want to replace the
battery with an adapter to run the magnet from an outlet. What I am
wondering is, what is the max current the battery is outputting when it
is new? If you have an ammeter, can you please test the output of a new
battery.

Thank you,
Chad

I've managed to get good results with a standard 250g coil of 24 swg wire
(0.56 mm) unwound from the bobbin, split in 3 equal lengths, and then
wound back on again, with the coils connected in parallel. The coil
resistance is around 1 ohm. With a 1.2Ah 12V lead acid battery, this gives
a peak current of about 10-11 amps. (The battery voltage drops to around
10.5 volts from about 12.5)

I'm using a piece of rebar (concrete reinforcing rod) as the core - this
works the best out of the metal objects I've tried. Bolts are no good.

With this setup, it's strong enough to push a neodymium magnet off the end
of the core, and lift the core against gravity. Guessing about 50-100
grams force when you try to pull the core out of the magnet with the
current on. To make a proper push/pull solenoid, you'd need a permanently
magnetised core, I think, which would be harder to find.

--
http://www.niftybits.ukfsn.org/

remove 'n-u-l-l' to email me. html mail or attachments will go in the spam
bin unless notified with

 or [attachment] in the subject line.

Try connecting the three windings in series; see if you can make a
meaningful comparison of the relative strengths (series VS parallel).

I think I can guess that one - 3 3.3 ohm coils in parallel makes one ohm,
so the current is around 12A. In series would make about 10 ohm, with a
current of around 1.2A. So the strength would be about 9 times less.

--
http://www.niftybits.ukfsn.org/

remove 'n-u-l-l' to email me. html mail or attachments will go in the spam
bin unless notified with [html] or [attachment] in the subject line.
[/QUOTE]
  Do *not* guess!
  Your "logic" is incomplete, and thus inaccurate.
  I suggest you make the measurement; you will find the series
configuration to be a lot stronger than your "estimate".

 

[Robert Baer]

John Larkin wrote:

On Fri, 20 Aug 2004 17:42:16 +0100, andy
news4@earthsong.free-online.co.uk> wrote:

Try connecting the three windings in series; see if you can make a
meaningful comparison of the relative strengths (series VS parallel).

I think I can guess that one - 3 3.3 ohm coils in parallel makes one ohm,
so the current is around 12A. In series would make about 10 ohm, with a
current of around 1.2A. So the strength would be about 9 times less.

Um, I think it's 3.3 times less.

But the big picture is that the amount of field you can sustain
longterm depends on how well you can cool the coil. So for a fixed
copper cross-section and surface area, there's some maximum number of
watts you can pump into the copper before you toast it, and those
watts set the field strength. So series/parallel or wire size doesn't
change the basic limit on field strength so long as the power supply
can be adjusted.

John

AT LAST!
You got it correct; ampere turns.
Parallel = if each coil has 100 turns, then the parallel combination has
100 turns (looks like fatter wire, folks), and one then has 1200
AmpereTurns.
Series = The turns add up (assuming the connection polarity is correct)
for 300 turns, and one then has 360 AmpereTurns.

 

[Clint Sharp]

In message <41267991$0$20249$cc9e4d1f@news-text.dial.pipex.com>, exxos
<exxos@home.com> writes

Big fat washers come to mind, ive got a few of um now, very large and
strong, im sure they will come in handy which I need a big fat washer for
something someday..........
Some of the platters are glass though. IIRC IBM have some glass platter

drives.

Chris

--
Clint Sharp

 

[John Fields]

On Sat, 21 Aug 2004 09:47:50 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

AT LAST!
You got it correct; ampere turns.
Parallel = if each coil has 100 turns, then the parallel combination has
100 turns (looks like fatter wire, folks), and one then has 1200
AmpereTurns.
Series = The turns add up (assuming the connection polarity is correct)
for 300 turns, and one then has 360 AmpereTurns.

---
Your logic (or your arithmetic) is incomplete and inaccurate.

1200AT/360AT = 3.333, but:



12V 12V
| |
+-----------+------------+ |
| | | [10T] 1R
[10t] 1R [10T] 1R [10T] 1R |
| | | [10T] 1R
+-----------+------------+ |
| [10T] 1R
0V |
0V



4pi N I
Since B = K ---------,
l

If we assume the same diameter and length and they're both wound over
the same core, then K, 4pi, and l drop out and we're left with


B = N I

Where N is the number of turns per winding and N is the current
flowing in the winding.

If we assume 1 ohm coils for convenience, then for each winding in the
parallel case:

E 12V
I = --- = ----- = 12 amperes
R 1R

and

Bp = N I = 10 turns * 12A = 120 AT

Since there are three windings with the same diameters and lengths and
they're wound over each other the fields will add, for a total of

Bp = 3 N I = 3 * 120AT = 360AT.


For the series case we'll still have the same length and diameter, but
the current through each of the coils will be

E 12V
I = --- = ----- = 4A
R 3R

Then, for each coil,


Bs = N I = 10 turns * 4A = 40AT

and for all the coils.

Bs = 3 N I = 3 * 40AT = 120 AT


So, since Bp = 360AT and Bs = 120AT, the magnetic induction for the
parallel case will three (not 3.333) times greater than for the
series case, just like Larkin said earlier.

--
John Fields

 

[John Fields]

On Sat, 21 Aug 2004 09:40:10 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

John Fields wrote:

On Fri, 20 Aug 2004 17:42:16 +0100, andy
news4@earthsong.free-online.co.uk> wrote:

On Fri, 20 Aug 2004 07:40:21 +0000, Robert Baer wrote:

Try connecting the three windings in series; see if you can make a
meaningful comparison of the relative strengths (series VS parallel).

I think I can guess that one - 3 3.3 ohm coils in parallel makes one ohm,
so the current is around 12A. In series would make about 10 ohm, with a
current of around 1.2A. So the strength would be about 9 times less.

---
Since it's Ampere-Turns that's doing the work and the number of turns
stays the same, if the current drops to one-tenth of what it was, so
will the strength of the field, so it's ten times less.

--
John Fields

Your logic is incomplete and inaccurate.

---
Yes, you're right. Thank you.

--
John Fields

 

[exxos]

"Clint Sharp" <clint@clintsmc.demon.co.uk> wrote in message
newsB0NE1ALTyJBFwyr@clintsmc.demon.co.uk...

In message <41267991$0$20249$cc9e4d1f@news-text.dial.pipex.com>, exxos
exxos@home.com> writes
Big fat washers come to mind, ive got a few of um now, very large and
strong, im sure they will come in handy which I need a big fat washer for
something someday..........
Some of the platters are glass though. IIRC IBM have some glass platter
drives.

Chris

--
Clint Sharp

Not seen any of those, only the metal types.

Chris

 

[Joe Soap]

In response to what Smokeyone <mailstarclipper@btopenworld.com> posted in
news:e264a9ed.0408220554.1b371b50@posting.google.com:

Could someone suggest a firm in the UK where I might be able to
purchase miniature rocker switches. They are going into a car dash
panel so they should look acceptable, some need to be two way, hole
cut out should be round, (trying to cut neat square holes would be
difficult) and hole must be less than 20mm diameter - not enough
clearance for 20mm. Rapid almost sell the right ones but the hole cuts
are too large. Any ideas please.

Thanks

Smokeyone

PS.. Unless somebody knows a clever way of making neat square holes in
which case Rapid have the switches.

RadioSpares (RS Components) have a selection of rectangular hole cutters.

--
Joe Soap.
JUNK is stuff that you keep for 20 years,
then throw away a week before you need it.

 

[CWatters]

http://uk.farnell.com/jsp/home/homepage.jsp

For info... many panel mounted switches have a flange to cover up the edge
of the hole - so a badly cut square hole probably wouldn't be seen.

 

[John Fields]

On 22 Aug 2004 06:54:20 -0700, mailstarclipper@btopenworld.com
(Smokeyone) wrote:

PS.. Unless somebody knows a clever way of making neat square holes in
which case Rapid have the switches.

---
http://uk.farnell.com/jsp/endecaSearch/searchPage2.jsp?x=18&Ntt=metal+nibbler&Nty=1&N=401&Ntk=gensearch&y=9

http://rswww.com/cgi-bin/bv/browse/Module.jsp?BV_SessionID=@@@@1584190115.1093188201@@@@&BV_EngineID=ccchadcmgdljhihcfngcfkmdgkldfhl.0&cacheID=ukie&3270641078=3270641078&stockNo=547789


--
John Fields

 

[Watson A.Name - \"Watt Su]

"K2" <godwin@austin.com> wrote in message
news:vteog0de0jvfcbbt2jub40lng4m4ukftc1@4ax.com...

Do battery-powered motion sensors draw any significant current when no
motion is present? This is a Heath-Zenith wireless system (about $40)
that sends a signal to an indoor AC powered receiver when it detects
motion. I'd like to know exactly how these things work. No current at
idle?

How long might the sensor's 2 AA batteries last with an anticipated 3
or 4 triggers per day? Most would be false alarms from local cats. The
packaging says 1 year, but doesn't specify at what trigger rate - or
does that really matter? Thanks.

The sensor may draw significant current, but the circuit is activated
for a very brief time every second or so. So on the average, the
current drain is very low. Also, 2 AA batteries can supply a decent
amount of current; to see them in action check out a wireless optical
mouse. The mouse is constantly glowing red, even when not moving, and
the batteries last for a few months.

> K2