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'Power from piezo?'
1998\11\30@233240 by MattBeck

picon face
I realize piezo elements produce relatively high potential but little current
if stress is applied, but is there any way, using natural body motion, to
produce enough power to supply 4 ma at 5V for about a .06% duty cycle on a 24
hour rotation using proper storage (low leakage cap). I want to build a super
small RF remote xmitter using a PIC, but the problem is the power source being
too large. This was my next brainstorm. Thanks for any help, opinions
(critical or otherwise), solutions
Matt


'Power from piezo?'
1998\12\01@091503 by wwl
picon face
On Mon, 30 Nov 1998 23:30:28 EST, you wrote:

>I realize piezo elements produce relatively high potential but little current
>if stress is applied, but is there any way, using natural body motion, to
>produce enough power to supply 4 ma at 5V for about a .06% duty cycle on a 24
>hour rotation using proper storage (low leakage cap). I want to build a super
>small RF remote xmitter using a PIC, but the problem is the power source being
>too large. This was my next brainstorm. Thanks for any help, opinions
>(critical or otherwise), solutions
>Matt
I doubt it, unless you can wiggle the piezo an awful  lot!
You may be able to use an electromagnetic generator, but size & weight
would be a problem - there is at least one watch on the market that
does this - you might like to take one apart and see how they do it!
What's wrong with coin cells ? your avarage drain is 2.4uA, call it
5uA to account for cpu leakage in sleep etc. a 1216 lithium cell
(1.6mm thick, 12mm dia) is rated 25maH, so that's 5000 hours from 2
cells (6V), or you could probably switch a capacitor to double a
1-cell 3V supply for the duration of the transmission.

1998\12\01@095912 by keithh

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MattBeck@AOL.COM wrote:
>
> piezo elements ...
> is there any way, using natural body motion, to
> produce ... 4 ma at 5V for about a .06% duty cycle on a 24
> hour rotation using proper storage (low leakage cap).

~12 uW overall, maybe. But transmitting for 52 seconds
your cap needs to be fairly big. Caps are not really
practical, a tiny nicad might be better.

> I want to build a super small RF remote xmitter using a PIC

Who/what are you bugging?
I heard the FBI already had one that fitted inside an olive
so they could bug a Mafia boss who insisted on meeting in
a sauna. Meeting naked, he could be sure people had no
wires on them. He didn't realise the olive in the agent's
Martini picked up everything!

1998\12\01@111423 by Peter L. Peres

picon face
If you can arrange for the piezo to be stepped onto when the person walks
you would have LARGE amounts of energy. A person weighing 50kg and walking
casually will apply these 50kg on each foot alternately. A piezo makes so
much voltage with 50kg on it that I'd start thinking about a MOV for
protection.

I think that an experiment is in order to try and find out just how much
can be had like this:

Take a lage 2" piexo, and affix it to the sole of a sports shoe (under the
heel), connect with 2 thin wires to a circuit that contains only an AAA
NiCd cell, empty, and a rectifier bridge made of four Shottky diodes.

One should walk with this special shoe doing usual things for a counted
number of hours (maybe on a Sunday when one is home), and then take the
NiCd connect it to a resistor discahrger with a DVM across it and find out
how much power was stored in it.

I for one, have used a number of piezo disks mounted with the rubber
dampers of a motor/compressor to obtain power for a simple CMOS automatic
circuit (that was used to monitor pressure with a contact pressostat).

Peter

1998\12\01@115157 by Sten Dahlgren

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"Peter L. Peres" wrote:
>
> If you can arrange for the piezo to be stepped onto when the person walks
> you would have LARGE amounts of energy. A person weighing 50kg and walking
> casually will apply these 50kg on each foot alternately. A piezo makes so
> much voltage with 50kg on it that I'd start thinking about a MOV for
> protection.
>
> I think that an experiment is in order to try and find out just how much
> can be had like this:
>
> Take a lage 2" piexo, and affix it to the sole of a sports shoe (under the

Who makes such big piezo's ? Any URL?

{Quote hidden}

--
Sten Dahlgren  ! I'd rather have 39 hp under my right arm than
Enea Data AB   ! one horse under my bottom !
Box 232        !
183 23 TŠby    !
Sweden         !
+46 8 6385038  !
spam_OUTstdaTakeThisOuTspamenea.se   !

1998\12\01@125203 by Peter L. Peres

picon face
On Tue, 1 Dec 1998, Sten Dahlgren wrote:

> Who makes such big piezo's ? Any URL?

For a sounder piezo ask at a local electronics shop. They are about 5 cm
across and used in every alarm system siren that I've ever seen, plus are
sold as is (bare disk) for about $1-2 each (here).

If you can't find one, try to buy a large type piezo sounder, and make
sure that it is he kind that can be taken apart (not glue/epoxy filled).

There are 3 tricks that you need to know if you prepare a bare disk:

1) The silvered face is not really silvered, and it should be soldered
very quickly with very little solder and the heat turned down on the iron,
else it will melt into the solder and leave the ceramic bare.

2) The ceramic face is fragile and needs to be covered with a semirigid
layer for compression purposes. A layer of quick-setting epoxy and a metal
plate equal to the diameter of the disk will do that, after you solder the
wire.

3) When you do 2) you must make sure that the epoxy does not build a
bridge with the metal disk of the piezo (it must push only on the
ceramic).  When I used to play with this, I used a ring of medium
stationery paper cut to fit around the ceramic on the piezo before
applying epoxy. The ring was left there afterwards.

The prepared piezo has a number of applications, among others, as a scale
and force sensor. For sensor applications the covering metal plate needs
to be connected to the piezo metal back, for shielding purposes.

In sensor mode this kind of device is pretty lousy mostly due to the
instability of the ceramic material and plasticity of the piezo backing
metal (it bends and stays bent, ruining any kind of zero calibartion).

Peter

1998\12\02@023326 by Sten Dahlgren

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"Peter L. Peres" wrote:
{Quote hidden}

Your tips is put in the "valuable knowledge folder" :-)

My application would be to build a "cleaning bath" with solvents thats
vibrates and
cleans carburators and such smaller things, do you have an idea of the
size of piezo's
required and power feeding them ?

regards
/Sten

1998\12\02@060537 by wwl

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On Tue, 1 Dec 1998 17:50:32 -0800, you wrote:

>"Peter L. Peres" wrote:
>>
>> If you can arrange for the piezo to be stepped onto when the person walks
>> you would have LARGE amounts of energy. A person weighing 50kg and walking
>> casually will apply these 50kg on each foot alternately. A piezo makes so
>> much voltage with 50kg on it that I'd start thinking about a MOV for
>> protection.
>>
>> I think that an experiment is in order to try and find out just how much
>> can be had like this:
>>
>> Take a lage 2" piexo, and affix it to the sole of a sports shoe (under the
>
>Who makes such big piezo's ? Any URL?
Maplin do a 50mm disc - code YU28D http://www.maplin.co.uk

1998\12\02@115102 by Peter L. Peres

picon face
> ultrasonic cleaning

Ah. That is a different matter. Depending on the size of what you clean,
you determine the required power, apply some over-engineering and then
look for a transducer that does this, then you match your generator to it
(which is critical, as it's a power switcher with HV output).

For energy density try to talk to cleaning chemicals makers about
chemicals for ultrasonic cleaning and they will tell you about how much
power is required and the freq. ranges. The W/cm^3 you multiply by the
volume of your vessel to hold the parts and over-engineer this, then start
looking for a transducer. Notice that lousy coupling can and will destroy
your transducer if not taken care of (i.e. run w/o liquid etc). Do not
expect miracles from ultrasonic cleaning, only a good tinnitus is assured
if you do not use hearing protection while experimenting.

You want over 50Watts, probably more like 100-400Watts for heavy duty
cleaning. The oscillators are surprisingly simple to make but the process
resembles designing switchers a lot if you do not take precautions (crack
! bang ! stink ! smoke !). A current limited PSU with shutdown on
overcurrent mode is highly recommended ;) (the generators run off
rectified 220V directly, so you need a supply that gives 400Vdc with
these characteristics).

A 50 Watt input cleaning vat takes about 2 liters of liquid for jewelry,
diamonds etc. cleaning (mild cleaning). For carbs you might want ten times
as much power.

hope this helps,

Peter

1998\12\02@121143 by Sten Dahlgren

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"Peter L. Peres" wrote:
>
> > ultrasonic cleaning
>
> Ah. That is a different matter. Depending on the size of what you clean,
> you determine the required power, apply some over-engineering and then
> look for a transducer that does this, then you match your generator to it
> (which is critical, as it's a power switcher with HV output).
>
> For energy density try to talk to cleaning chemicals makers about
> chemicals for ultrasonic cleaning and they will tell you about how much
> power is required and the freq. ranges. The W/cm^3 you multiply by the
> volume of your vessel to hold the parts and over-engineer this, then start
> looking for a transducer. Notice that lousy coupling can and will destroy
> your transducer if not taken care of (i.e. run w/o liquid etc). Do not
> expect miracles from ultrasonic cleaning, only a good tinnitus is assured
> if you do not use hearing protection while experimenting.
>

So much theory :-)

> You want over 50Watts, probably more like 100-400Watts for heavy duty
> cleaning. The oscillators are surprisingly simple to make but the process
> resembles designing switchers a lot if you do not take precautions (crack
> ! bang ! stink ! smoke !). A current limited PSU with shutdown on
> overcurrent mode is highly recommended ;) (the generators run off
> rectified 220V directly, so you need a supply that gives 400Vdc with
> these characteristics).
>
I suppose they don't like anything else than sine waves to.
> A 50 Watt input cleaning vat takes about 2 liters of liquid for jewelry,
> diamonds etc. cleaning (mild cleaning). For carbs you might want ten times
> as much power.
>
Up to 5 liters is what i have in mind. I don't think 50mm piezo's would
be enough
for this level of power.

Do you know what voltage levels is used ?
I think they need sinewaves to.

> hope this helps,
>
> Peter

This is on my todo pile, but since priority differs over time....
It is however nice to thinker about it.

regards
/Sten


--
Sten Dahlgren  ! I'd rather have 39 hp under my right arm than
Enea Data AB   ! one horse under my bottom !
Box 232        !
183 23 TŠby    !
Sweden         !
+46 8 6385038  !
.....stdaKILLspamspam@spam@enea.se   !

1998\12\03@102717 by Peter L. Peres

picon face
On Wed, 2 Dec 1998, Sten Dahlgren wrote:

> I suppose they don't like anything else than sine waves to.

The piezos are usually one of the capacitors in a LC resonant circuit,
whose L is the secondary of a transformer driven by the switcher.

> > A 50 Watt input cleaning vat takes about 2 liters of liquid for jewelry,
> > diamonds etc. cleaning (mild cleaning). For carbs you might want ten times
> > as much power.
> >
> Up to 5 liters is what i have in mind. I don't think 50mm piezo's would
> be enough
> for this level of power.

No. The 50mm piezos will drive up to about 10Watts iff loaded (else they
exfoliate earlier). I think that you can make a very small cleaning vat
with one of these. There was a project in a French Mag: Electronique
Pratique. It was not the real thing re: power imho. It used a 50mm disk
and a cup-sized vat with less than 2W input (imho). It had lots of
'educative' timers etc around the actual driver.

> Do you know what voltage levels is used ?
> I think they need sinewaves to.

The sine results from the resonance but it must not be sine. Noise is
better ;) The voltage can reach 3-4kV pk-pk unloaded in a 20Watt unit.

Notice that I keep saying 'loaded'. NOTICE that please. Unloaded drivers
die early unless you have some sort of power feedback. Also, none of these
operate at a constant frequency, they rather let themselves be 'dragged'
by the resonance of the vat, or are frequency or noise swept, which
results in a frequency modulation / noise that moves the nulls in the
standing waves produced in the vat all the time. It also makes an
incredibly unbearable noise (the neighbor is a jeweller and he has one of
these running all day long - I can hear it even through 2 walls).

One interesting thing to try out is to get one of those piezo sirens for
alarms (the kind that has a plastic nut screwed onto the body for panel
mount, and is water-proof), and mount it in the bottom of an empty
aluminium can (w/o lid), after removing the electronics to gain access to
the bare driver. It should withstand water well enough for a while,
especially if siliconed into the hole. I suppose that the water will raise
the resonant frequency from about 3-5 kHz nominal but I don't know how
high.

Basically an ultrasonic cleaner that does not achieve the energy density
required for cavitation to occur in the cleaning liquid will do nothing at
all except kill your ears slowly. Also the higher the frequency the better
it gets at the dirt (within reason), or so the books say.

Last: It seems that it is possible for hollow bodies (such as carbs ?) NOT
to be cleaned properly in a normal cleaner on account of the walls of the
body acting as lenses/shields for the acoustical waves. f.ex. hydraulical
lines are cleaned by 'shining' ultrasound directly into the tube, through
circulating liquid under pressure, instead of putting the tube in a
cleaning vat.

sorry for the long posting,

Peter

1998\12\03@220510 by Mark Willis

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On the same topic, IIRC the wear-hard list has something about using
'underfoot' piezo for power for wearable computers (I think that's on
http://wearcomp.org/ someplace, or Thad's pages perhaps.)  I can look if
anyone wants/needs <G>

 Mark, mwillisspamKILLspamnwlink.com

1998\12\04@050344 by Sten Dahlgren
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"Peter L. Peres" wrote:
>
> On Wed, 2 Dec 1998, Sten Dahlgren wrote:
>

>
> sorry for the long posting,
>

Saying "sorry" for knowledge is not necessary !!

> Peter

--
Sten Dahlgren  ! I'd rather have 39 hp under my right arm than
Enea Data AB   ! one horse under my bottom !
Box 232        !
183 23 TŠby    !
Sweden         !
+46 8 6385038  !
.....stdaKILLspamspam.....enea.se   !

1998\12\04@105008 by Danny Sulit

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Thursday's New York Times Circuits section had an article on snow skis that absorbed bumps using piezo tranducers to converting vibration to electricity and then dissipating the energy to heat.

Smart skis?

1998\12\04@122207 by Engineering Department

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<Danny Sulit observes>

> Thursday's New York Times Circuits section had an article on snow skis
> that absorbed bumps using piezo tranducers to converting vibration to
> electricity and then dissipating the energy to heat.

> Smart skis?


Hm, I thought that was how materials work in general.  Flex 'em and they
generate heat.

Good marketing?

Cheers,

Win Wiencke
Image Logic Corporation

1998\12\04@160625 by paulb

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Engineering Department wrote, quoting Danny Sulit:

>> Smart skis?
> Good marketing?

 Dumb skis (no CPU)!  *SMART* marketing.
--
 Cheers,
       Paul B.

1998\12\04@165720 by mwalsh

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There was an article on a similar application recently in Design News.  They

are putting piezo transducers into baseball aluminum baseball bats.  Some of

the shock and vibration that is normally transmitted to the batter's hands
is
now converted to electricity and dissipated as heat in a resistance in the
bat.

I don't know how effective it is, but anyone who has been stung by the
resonance set up in a bat when you nailed the ball may be a potential
customer.

Mark Walsh


Engineering Department wrote:

{Quote hidden}

1998\12\05@051552 by g.daniel.invent.design

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Danny Sulit wrote:
>
> Thursday's New York Times Circuits section had an article on snow skis that ab
sorbed bumps using piezo tranducers to converting vibration to electricity and t
hen dissipating the energy to heat.
>
> Smart skis?

CV joins on cars sometimes use a rubber disk/s along the shaft to absorb
vibration, kind of like ringing a bell and then damping the ring by
application of hand.   I am sure most of us could match piezos to much
more useful tasks.

regards,
Graham D.

1998\12\05@084018 by Peter L. Peres

picon face
On Fri, 4 Dec 1998, Engineering Department wrote:

> Hm, I thought that was how materials work in general.  Flex 'em and they
> generate heat.

Actually there is a little bit more to it. Magnetic and piezo dampers have
a ^2 characteristic which kills vibration faster than friction damping.
This is the good part.

> Good Marketing ?

definitely ;)

Peter

1998\12\05@084033 by Peter L. Peres

picon face
On Sat, 5 Dec 1998, Graham Daniel wrote:

> CV joins on cars sometimes use a rubber disk/s along the shaft to absorb
> vibration, kind of like ringing a bell and then damping the ring by
> application of hand.   I am sure most of us could match piezos to much
> more useful tasks.

The nice part about piezo dampers is, that they have no moving parts, and
no hollows volumes in them, which makes producing them so much easier. I
strongly suspect that the baseball damper is of the new polymer piezo
kind, and I believe that more of this will be seen soon in tennis roquets
and other sports inplements. I could also see it used in small yacht's
booms and even sails and in small aircarft's thin aerodynamic surfaces. I
think that the piezo polymer can be laminated together with conductive
plastic to form a vibration-killing coating/mat that can be applied to
anything.

imho this is a very high tech use for the piezo effect.

Peter

1998\12\05@204513 by Mark A Moss

picon face
Yeah, but these ski's have LED's that light up as you hit the bumps. (I
saw them in the local ski shop a year or two ago)

Mark Moss
Amateur Radio Operator, Technician, and General Tinkerer


On Fri, 4 Dec 1998 12:21:53 -0500 Engineering Department
<EraseMEimagelogicspam_OUTspamTakeThisOuTIBM.NET> writes:
{Quote hidden}

Mark Moss
Amateur Radio Operator, Technician, and General Tinkerer

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1998\12\06@114521 by Peter L. Peres

picon face
On Sun, 6 Dec 1998, Mark A Moss wrote:

> Yeah, but these ski's have LED's that light up as you hit the bumps. (I
> saw them in the local ski shop a year or two ago)

Now that you say that, I remember a lot of kids running about in sports
shoes with flashing toes (red).

Peter

1998\12\06@121628 by Dave VanHorn

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"Peter L. Peres" wrote:
>
> On Sun, 6 Dec 1998, Mark A Moss wrote:
>
> > Yeah, but these ski's have LED's that light up as you hit the bumps. (I
> > saw them in the local ski shop a year or two ago)

Believe it or not, the myth is that the energy that the piezo elements
take from the vibration is supposed to help you ski better by acting as
a shock absorber.. ($$$ absorber IMHO)

> Now that you say that, I remember a lot of kids running about in sports
> shoes with flashing toes (red).
>
> Peter

A lithium battery, LED, and I swear to god, a couple of mercury
switches! Your kid is standing on a pair of glass capsules filled with
mercury. Can we spell "product liability lawsuit"?

1998\12\06@123945 by Peter L. Peres

picon face
On Sun, 6 Dec 1998, Dave VanHorn wrote:

> Believe it or not, the myth is that the energy that the piezo elements
> take from the vibration is supposed to help you ski better by acting as
> a shock absorber.. ($$$ absorber IMHO)

I usually refrain to comment on such things before I see a credible study.
Having seen a couple of really cool tangible physics experiments done re:
movement and vibration damping using supermagnets and new piezo materials,
I'll keep mum until I see that study, however long that may take.

Peter

> A lithium battery, LED, and I swear to god, a couple of mercury
> switches! Your kid is standing on a pair of glass capsules filled with
> mercury. Can we spell "product liability lawsuit"?

Uh. I was under the impression that these last quite a while. In fact one
can step only so fast. Assuming a duty cycle of 1% and 4 steps per second
(f. ex. kid running from large dog) I assume that the Li battery will be
empty before the shoe warranty wears out... Anyone ? ;)

Peter

1998\12\06@130513 by Reginald Neale

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>"Peter L. Peres" wrote:
>>
>> On Sun, 6 Dec 1998, Mark A Moss wrote:
>>
>> > Yeah, but these ski's have LED's that light up as you hit the bumps. (I
>> > saw them in the local ski shop a year or two ago)
>
>Believe it or not, the myth is that the energy that the piezo elements
>take from the vibration is supposed to help you ski better by acting as
>a shock absorber.. ($$$ absorber IMHO)
>

Yeah, that's my opinion too. Seems to me that with common MAGNETIC field
generators, there can be real-world amounts of power to play with. Common
ELECTROSTATIC generators, no. Of course, there could be bleeding-edge
breakthroughs here that I don't know about.

And, as always, marketing can work miracles....

Reg Neale

1998\12\06@133031 by Dave VanHorn

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> I usually refrain to comment on such things before I see a credible study.
> Having seen a couple of really cool tangible physics experiments done re:
> movement and vibration damping using supermagnets and new piezo materials,
> I'll keep mum until I see that study, however long that may take.
>

I'm just giving my impression based on a thumbnail analysis of the
amount of energy involved. The flexing of a ski, during operation, has a
fair bit of energy behind it. If someone wants to convince me that a
piezo can convert an appreciable fraction, say 5-10% of that into
electrical energy, then I'll be more tractable. Otherwise, I'll get back
to greenlining my CDs :)

> Uh. I was under the impression that these last quite a while. In fact one
> can step only so fast. Assuming a duty cycle of 1% and 4 steps per second
> (f. ex. kid running from large dog) I assume that the Li battery will be
> empty before the shoe warranty wears out... Anyone ? ;)


I got a pair for my younger daughter, with the condition that when she
wore them out, I got to tear them apart to find out how they worked. The
module was potted in clear resin of some type, and it was very easy to
see the components. There was some sort of transistor circuit in there,
but no numbers were visible. I assume that converted the mercury switch
signals to LED pulses of short duration.

As to mercury dangers, thermometers are used under supervision for about
three minutes, rarely, and contain a very small amount of mercury. Shoes
are used over many hours, daily, with no supervision. The switches I saw
were about 3/8" x 1/4", and about half-full of dirty-looking mercury
(not shiny, very dull. Oxides or ???). I guess only my kids have ever
taken a nail through the shoe?  I have no trouble picturing a nail
carrying some amount of mercury into the puncture wound. I'll admit the
odds are very high against it, but it's not a risk I would have chosen
to take if I had known about it beforehand.

1998\12\06@134111 by Peter L. Peres

picon face
On Sun, 6 Dec 1998, Reginald Neale wrote:

> Yeah, that's my opinion too. Seems to me that with common MAGNETIC field
> generators, there can be real-world amounts of power to play with. Common
> ELECTROSTATIC generators, no. Of course, there could be bleeding-edge
> breakthroughs here that I don't know about.
>
> And, as always, marketing can work miracles....

For a small immediate miracle, attach a large piezo to a rim mount (can be
a medical locking tweezer) and ping it with 1 finger's nail, 1st time
unconnected, then again shorted. Do this in a quiet room. Tell me what
happens.

Peter

1998\12\06@140634 by Dave VanHorn

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> For a small immediate miracle, attach a large piezo to a rim mount (can be
> a medical locking tweezer) and ping it with 1 finger's nail, 1st time
> unconnected, then again shorted. Do this in a quiet room. Tell me what
> happens.
>
> Peter

Now picture the tweezer scaled up to a ski, and picture the size of the
piezo involved.

1998\12\07@001132 by Matthew Ballinger

picon face
       Wow, never thought this topic would go so far! Its much more interesting
than
my original question though. I found a company who designs these smart
structures out of piezo material. Very interesting, some of the stuff they've
built. http://www.acx.com/home.html
       Thanks for all the comments on the idea. Relevant or not. Matt.

1998\12\07@150717 by Russell McMahon

picon face
>As to mercury dangers, thermometers are used under supervision for
about
>three minutes, rarely, and contain a very small amount of mercury.

I bit a mercury in glass thermometer as a child and swallowed the
mercury, I'm told - I don't recall the event. Apparently it was all
passed through in due course - how they knew I don't know. Its done
me no harm <vbg> - those who know me well may question this :-).

       Russell McMahon

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