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'[EE] disposable cameras'
2009\07\25@145314 by Al Shinn

picon face
To answer a couple of questions

About NiCds - when a NiCd battery dies due to whiskers shorting out the
cell, a common practice is to discharge a large high voltage cap into
the battery - blows out the whiskers and restores function.

Voltage-   about 300V with  about 100Mfd capacitor

I have used these with a voltage trippler to run a Geiger counter

Also for simpler high voltage experiments you can just wire several
unmodified cameras in series. CAUTION you may well be able to kill yourself.


solarwind wrote:
> > On Fri, Jul 24, 2009 at 12:43 PM, Al Shinn<spam_OUTalshinnTakeThisOuTspammindspring.com>
wrote:
> >
>> >> They also make pretty good Ni Cd short blasters for those of us
who only
>> >> have 5 and 12 V supplies. careful though, they WILL shock the
heck out
>> >> of you.
>> >>
> >
> > Please explain.
--

Looking forward,
Al Shinn


2009\07\25@155048 by olin piclist

face picon face
Al Shinn wrote:
> About NiCds - when a NiCd battery dies due to whiskers shorting out
> the cell, a common practice is to discharge a large high voltage cap
> into
> the battery - blows out the whiskers and restores function.
>
> Voltage-   about 300V with  about 100Mfd capacitor

That's obviously absurd!

1/2 (300V)**2 * 100MF = 4.5TJ = about 1 kiloton of TNT equivalent, or a
large fleet of B-52s fully loaded with conventional bombs, or about 1/15 the
energy that leveled Hiroshima in 1945.

Assuming you really meant millifarads instead of megafarads (additionally
assuming "fd" was supposed to mean Farads), that's 4.5KJ unleashed on the
battery in a fraction of a second.  That's still rediculous when you
consider that's enough energy to launch a normal 5 pound clay brick 300 feet
into the air.

Don't try this at home folks.  This is messed up advice on a number of
fronts and could get you seriously hurt.  This guy can't even get basic
units right, so anything else he says is best disregarded.  You don't want
the equivalent of a 5 pound brick falling 300 feet onto your battery, and
you don't want to be nearby if you did try it.

Even with a lower capacitance, there is no need for 300V.  A NiCd cell is
only 1.2V.  The point is to produce a short current pulse to blow out the
little whiskers, or dendrites, while minimizing any other damage.  It
doesn't take 10s of amps to do this.  Ideally the damaging high voltage is
gone just as the dendrites fuse open.  That's tricky to arrange since the
amount and strength of the dendrites is unknown.  It's best to start at
5-10V on 1mF and work your way to higher energies until the dendrites blow.
Increase the energy by 2x each time, but 15-20V is max.  Use a higher
capacitance if you get that far and they're still not blown.  If 20V and
10mF doesn't work there is little point trying to salvage the battery.


********************************************************************
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(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\25@190358 by Jinx

face picon face
> Use a higher capacitance if you get that far and they're still not blown.
> If 20V and 10mF doesn't work there is little point trying to salvage
> the battery

I've tried 10,000uF and 15V. Sometimes it revives a cell, sometimes
it doen't. I'm surmising that if a cell has grown multiple whiskers the
zap will take out the weakest. At the first go anyway

2009\07\25@195538 by Sean Breheny

face picon face
Olin,

I agree that it sounds suspicious that one would use 300V to restore
NiCd's, but I think that Al meant microfarads when he wrote Mfd.

You should know that it was once common for capacitors to use the
abbreviation Mfd for microfarad, even though it could cause
a lot of confusion (potentially - although one should use common sense
about the impossibility, given current technology, that Mfd could mean
either Megafarad
or even millifarad when one is talking about 100 millifarad at 300V in
a small package).

100 microfarad would only be 4.5 Joules when charged to 300V.

Sean


On Sat, Jul 25, 2009 at 3:51 PM, Olin Lathrop<.....olin_piclistKILLspamspam@spam@embedinc.com> wrote:
{Quote hidden}

>

2009\07\25@203012 by Spehro Pefhany

picon face
At 07:55 PM 7/25/2009, you wrote:
>Olin,
>
>I agree that it sounds suspicious that one would use 300V to restore
>NiCd's, but I think that Al meant microfarads when he wrote Mfd.
>
>You should know that it was once common for capacitors to use the
>abbreviation Mfd for microfarad, even though it could cause
>a lot of confusion (potentially - although one should use common sense
>about the impossibility, given current technology, that Mfd could mean
>either Megafarad

And mmfd (or mmf) was used to mean pF in the day.

http://blog.modernmechanix.com/mags/qf/c/PopularScience/5-1945/med_giant_capacitor.jpg

>or even millifarad when one is talking about 100 millifarad at 300V in
>a small package).

I don't think I've ever seen a capacitor marked in millifarads.

>100 microfarad would only be 4.5 Joules when charged to 300V.

A respectable amount of energy nonetheless.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2009\07\26@050135 by Joseph Bento

face
flavicon
face

On Jul 25, 2009, at 5:55 PM, Sean Breheny wrote:

> Olin,
>
> I agree that it sounds suspicious that one would use 300V to restore
> NiCd's, but I think that Al meant microfarads when he wrote Mfd.
>

The US electronics industry, especially several decades ago, was  
rather stupid when it came to using metric terminology.  They used  
Mfd, mfd, or ufd for microfarad, MMF, uuf, etc for picofarad.  And for  
some reason I never understood, American electronics never used the  
'nano' term.

Since I restore antique radios as one of my hobbies, these  
discrepancies seem less pronounced with prewar European electronics,  
while American manufactures seemed to have each invented their own  
terminology for classifying components.

Joe

2009\07\26@091313 by olin piclist

face picon face
Sean Breheny wrote:
> I agree that it sounds suspicious that one would use 300V to restore
> NiCd's, but I think that Al meant microfarads when he wrote Mfd.

Then he should learn to write it correctly.  "M" stands for mega, "K" for
kilo, "m" for milli, and the greek mu for micro although it's perfectly
acceptable and common to use "u" since it looks similar and is directly
available on many keyboards whereas mu isn't.

> You should know that it was once common for capacitors to use the
> abbreviation Mfd for microfarad,

Yes, but that was long long ago.  Back then you never saw millifarads or
nanofarads either, so anything with a M was unambiguous.  Sometimes even
values like 100pF were written as .0001 microfarads.  Fortunately those days
are gone.

There is enough confusion in the world, and sloppiness with units causes
real harm.  It needs to be stomped on and pointed out for the stupidity it
is whenever it comes up, especially considering that's it's no harder to get
it right.  In this case doing right would actually have been easier since
apparently this guy meant "uF" when he wrote "Mfd".


********************************************************************
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(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\26@140141 by Gerhard Fiedler

picon face
Olin Lathrop wrote:

> There is enough confusion in the world, and sloppiness with units
> causes real harm.  

Besides that, there is a beauty in the use of correct units. There is a
lot of thought that went into the SI system, and using it properly, you
kind of get a free ride to enjoy the beauty of these thoughts.

And, despite some rumors to the contrary (and the French original name),
the SI is neither anti-American nor anti-British :)

Gerhard

2009\07\26@150504 by Al Shinn

picon face
Hey, lighten up!!, we are talking about a disposable camera here (see
the Subject). The cap  fits INSIDE the camera, it's the size of my
pinkie! When was the last time you saw a 100 megaFarad cap, eh? - they
probably have them lying around at Livermore lab.
and no, not milliFarads either - microFarads . So I'm an old f@rt! So go
ahead, kick me around a bit. By the way, thanks for the correction
(update), I'll try to be more careful in the future, (but the intent was
to help folks repair batteries, not win a spelling bee). You could have
left it at a simple units convention correction without getting nasty.
Of course then you wouldn't have had all the fun of calculating how many
fission bomb equivalents there are in a disposable camera.

This is a common practice for restoring NiCds. I have merely suggested a
common source for a tool to restore NiCds - no need to be nasty.
By the way - it did work for me on a dead 9V Makita battery pack and
some other stuff. And yes, you probably don't want to use this on a
button cell.
And yes, you can get by with less voltage, but >100V is common - I had
thought that 300V would be OK cause the cap is EVER so much smaller than
my house.
And yes, it's true, you can use <100V but if you don't want to take the
battery pack apart, I would guess that you need quite a bit more than
the terminal voltage if only one cell is shorted.

I wonder though if someone who can't even spell ridiculous (you spelled
it "rediculous" should be listened to at all about anything that he is
ridiculing  :-)  I AM kidding here - wouldn't even have seen it, but my
spell checker found it.

PLEASE forgive any gramme errors or misspellings on my part!
--

Looking forward,
Al Shinn


>That's obviously absurd!

1/2 (300V)**2 * 100MF = 4.5TJ = about 1 kiloton of TNT equivalent, or a
large fleet of B-52s fully loaded with conventional bombs, or about 1/15 the
energy that leveled Hiroshima in 1945.

Assuming you really meant millifarads instead of megafarads (additionally
assuming "fd" was supposed to mean Farads), that's 4.5KJ unleashed on the
battery in a fraction of a second.  That's still rediculous when you
consider that's enough energy to launch a normal 5 pound clay brick 300 feet
into the air.

Don't try this at home folks.  This is messed up advice on a number of
fronts and could get you seriously hurt.  This guy can't even get basic
units right, so anything else he says is best disregarded.  You don't want
the equivalent of a 5 pound brick falling 300 feet onto your battery, and
you don't want to be nearby if you did try it.

Even with a lower capacitance, there is no need for 300V.  A NiCd cell is
only 1.2V.  The point is to produce a short current pulse to blow out the
little whiskers, or dendrites, while minimizing any other damage.  It
doesn't take 10s of amps to do this.  Ideally the damaging high voltage is
gone just as the dendrites fuse open.  That's tricky to arrange since the
amount and strength of the dendrites is unknown.  It's best to start at
5-10V on 1mF and work your way to higher energies until the dendrites blow.
Increase the energy by 2x each time, but 15-20V is max.  Use a higher
capacitance if you get that far and they're still not blown.  If 20V and
10mF doesn't work there is little point trying to salvage the battery.
>


2009\07\26@162747 by olin piclist

face picon face
Al Shinn wrote:
> Hey, lighten up!!, we are talking about a disposable camera here (see
> the Subject).

No, the part you are objecting to was about sloppy units.  And no, I'm not
going to lighten up about abuse of units since it can be so damaging and
there's so little excuse.  You were off by 12 orders of magnitude!  Anyone
can make a simple mistake, but that wasn't what was going on here.  People
who get sloppy with units, especially on a technical forum, deserve the
modern equivalent of being tarred and feathered, schackled in a stock or
pillary on the courthouse steps, or declared a witch and hung.

> The cap  fits INSIDE the camera, it's the size of my
> pinkie!

I didn't at all get that you meant to use a strobe cap from a camera to
"fix" your NiCd batteries.  It sounded like you were espousing a general
recipe to zap shorted NiCds back to life.

> and no, not milliFarads either - microFarads.

Maybe now you can see why we have standards for units?  Go look up something
called the "SI" units.  One of the key features is prefixes for powers of
1000.  Once again:

 M = mega = 10**6
 K = kilo = 10**3
 m = milli = 10**-3
 u = micro = 10**-6 (actually greek mu, but "u" is common for those
     of us without greek letters on the keyboard)
 n = nano = 10**-9
 p = pico = 10**-12

There are others, but those cover the vast majority of real world
electronics.

> This is a common practice for restoring NiCds.

Zapping them with a charged cap is, charging the cap to 300V isn't, and I
don't think 300V is a very good idea.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\26@164450 by Bob Blick

face
flavicon
face
Olin Lathrop wrote:

> No, the part you are objecting to was about sloppy units.  And no, I'm not
> going to lighten up about abuse of units since it can be so damaging and
> there's so little excuse.  You were off by 12 orders of magnitude!  Anyone
> can make a simple mistake, but that wasn't what was going on here.  People
> who get sloppy with units, especially on a technical forum, deserve the
> modern equivalent of being tarred and feathered, schackled in a stock or
> pillary on the courthouse steps, or declared a witch and hung.

I guess pick your battles. If anyone tried to get a 100 megafarad
capacitor to rejuvenate batteries they'd have a hard time finding one
and might ask for clarification.

It is a great idea to be clear about units. I specify things all the
time and always try to be very specific about numbers and units. Knowing
what the other party expects is not always enough. The most common one
is trying to specify resistors under 1 K and not having the "ohm" sign
available.

I'm not clear about the "pillary" thing you suggest. It doesn't seem to
be a valid word. You could really cause some dangerous confusion,
especially since this is a technical forum :)

Cheerful regards,

Bob

2009\07\26@165204 by Peter Onion

flavicon
face
On Sun, 2009-07-26 at 09:14 -0400, Olin Lathrop wrote:

> Yes, but that was long long ago.  Back then you never saw millifarads or
> nanofarads either, so anything with a M was unambiguous.  Sometimes even
> values like 100pF were written as .0001 microfarads.  Fortunately those days
> are gone.
>

I have some 100 uuF capacitors !

PeterO



2009\07\26@165911 by Joseph Bento

face
flavicon
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On Jul 26, 2009, at 2:45 PM, Bob Blick wrote:

> It is a great idea to be clear about units. I specify things all the
> time and always try to be very specific about numbers and units.  
> Knowing
> what the other party expects is not always enough. The most common one
> is trying to specify resistors under 1 K and not having the "ohm" sign
> available.

You could do it the Euro way and use R.  221R for 221 ohms.  Use the K  
or M rather than a decimal - 2K21 for 2.21K, for example.

As for the ohm sign, you could look up the ASCII code.  On the Mac,  
it's a keyboard shortcut - Ω  = "option Z"

Joe


2009\07\26@174759 by Spehro Pefhany

picon face
At 04:45 PM 7/26/2009, you wrote:


>I'm not clear about the "pillary" thing you suggest. It doesn't seem to
>be a valid word. You could really cause some dangerous confusion,
>especially since this is a technical forum :)

The OED defines it as "having the nature of a pillar". Google finds a number
of references to "pillary cloud", typically of a poetic nature.

There's also "pillery", which is the act of pillaging, although the word may
suggest a pharmacy.

>Cheerful regards,
Bob

Likewise.

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam.....interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2009\07\26@174838 by Marcel Birthelmer

picon face
> People who get sloppy with units, especially on a technical forum, deserve the
> modern equivalent of being ... declared a witch and hung.

Well, let's say the offender weighs 80kg = 80,000 g = 0.08 Mg.
Your average duck weighs, let's say, 3.5kg = 3500 g.

And clearly, 3500g > .08 mg (= 0.00008 g), so the person is indeed
lighter than a duck, and thus A WITCH!!!

( http://www.youtube.com/watch?v=yp_l5ntikaU )

2009\07\26@181050 by cdb

flavicon
face


:: M = mega = 10**6
::  K = kilo = 10**3
::  m = milli = 10**-3
::  u = micro = 10**-6 (actually greek mu, but "u" is common for those
::      of us without greek letters on the keyboard)
::  n = nano = 10**-9
::  p = pico = 10**-12

Slightly off topic - I had a project redactored by a US hobby magazine
because I used nF values rather than K's of pF.  I have found (about
10 years ago) that some EE's in the US and Australia didn't use the
nano descriptor, I was surprised when I was told it was a weird
descriptor used by the the UK and Europe only. In fact, apart from
Farnell and RS (for obvious reasons) no other supplier (at that time)
used nano - .It is only recently that Jaycar and Tricky Dickies have
listed capacitors in this way - Tandy (Radio Shack) never did.

I also prefer (though don't use) the older cycles per second for
frequency than Hertz. I think the original far more explanatory and is
more understandable a concept for beginners.

Colin
--
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2009\07\26@181340 by olin piclist

face picon face
Bob Blick wrote:
> I'm not clear about the "pillary" thing you suggest. It doesn't seem
> to be a valid word.

I just looked it up, and it's spelled "pillory".  It was a common punishment
in the early days of the new world.  There were usually a few in front of
courthouses or other public places.  People were even allowed to take a
whack at whoever was shackled in one, throw rotton fruit at them, etc.  In a
few cases the criminals were beaten to death by angry mobs.

They are usually on display at old colonial historic sites, like Plymouth
Plantation, Williamsburg, and (the artificially created) Old Sturbridge
Village.


********************************************************************
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(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\26@181549 by Jinx

face picon face
> I'm not clear about the "pillary" thing you suggest. It doesn't seem to
> be a valid word

Pillary - rather like a pillar

cf

Vanquish - rather like a vanqu

2009\07\26@181817 by Jinx

face picon face
> And clearly, 3500g > .08 mg (= 0.00008 g), so the person is
> indeed lighter than a duck, and thus A WITCH!!!

Got a match ?

2009\07\26@182010 by Jinx

face picon face
> some EE's in the US and Australia didn't use the nano descriptor

And yet "nanosecond" is common everywhere

2009\07\26@182651 by cdb

flavicon
face


:: Pillary - rather like a pillar
::
:: cf
::
:: Vanquish - rather like a vanqu

Pilloried from pillar to post - that about covers it! :)
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2009\07\26@183436 by peter green

flavicon
face

> It is a great idea to be clear about units. I specify things all the
> time and always try to be very specific about numbers and units. Knowing
>  what the other party expects is not always enough. The most common one
> is trying to specify resistors under 1 K and not having the "ohm" sign
> available.
>  
I always thought the convention there was to use R

The unit thing that I find most bother with is "mil". In the PCB
industry it means thousanth of an inch and is very widely used. However
others in the UK use mil means millimeter or milliliter depending on the
context (note: i'm talking about spoken english here, people do
generally seem to use the correct abbrivation for millemeter and
milliliter when writing)

2009\07\26@185736 by Al Shinn

picon face
Going more on the subject of ridiculous.
Given 300V and 100uF
300^2 X .5 X 100 x 10-6
I get 4.5J = 3.3 ftlb
Now. if you dropped a 3.3 lb object (brick like), 1 foot  onto one of
them teeny, tiny little flash tubes found in the disposable cameras It
would surely smash into smithereens!!

I guess we'll have to stop taking pictures.

Long ago, I was building a supply for the xenon tube flashlamp for a
fundus camera that I (and team) was designing - BIG caps, High volts -
tube not a whole lot bigger than the throw aways -
The stored energy numbers were indeed ridiculous sounding but we got
lotsa pictures anyway.
--

Looking forward,
Al Shinn


2009\07\26@190446 by cdb

flavicon
face


:: However
:: others in the UK use mil means millimeter

When I worked in for a certain hearing aid and heart pump
manufacturer, in the pick and place room or talking with the stencil
designers, you'd get 'that component placement is 3 mil off' , and I
would ask is that thou or millimetres - I'd either get blank looks or
occasionally - 'what's a thou?'

The P&P machines used metric for placement and interesting angles -
-920 degrees was the one that got me.

Colin
--
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Don't assume people do things you don't like just to hurt you





2009\07\26@192521 by John Ferrell

face
flavicon
face
FWIW:
mmf was pronounced "Mickey-mike" so I suppose you might say that
1 Mickey-mike = 1 puff

John Ferrell  W8CCW

"Extremism in defense of liberty is no vice, and moderation in pursuit of
justice is no virtue."
-Barry Goldwater
"You don't get harmony when everybody sings the same note."
-Doug Floyd

{Original Message removed}

2009\07\27@042307 by Alan B. Pearce

face picon face
> I'm not clear about the "pillary" thing you suggest. It doesn't seem to
> be a valid word

I believe the correct term in this context is 'pillory', generally used as
term of public abuse when a person was put in stocks on the village green,
and abused by the rest of the village for whatever wrong they had done.

2009\07\27@124009 by Eoin Ross

flavicon
face
With prescription drug pricing - the term seems to fit! :)

>>> Spehro Pefhany <KILLspamspeffKILLspamspaminterlog.com> 26 Jul 09 17:57:34 >>>
At 04:45 PM 7/26/2009, you wrote:

There's also "pillery", which is the act of pillaging, although the word may
suggest a pharmacy.


2009\07\27@162338 by Richard Benfield

flavicon
face
amazing !

maybe you meant k = kilo not K = kilo

Olin Lathrop wrote:
{Quote hidden}

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