KLM wrote:

On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton
tim.auton@uton.[groupSexWithoutTheY] wrote:


Do you all think that tangos are dumb enough to trigger the bomb
with the ringer or would the detonator answer first and listen for a
DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just
as he's connecting the thing.

I very much doubt they bother with DTMF decoders. I mean, how often do
you get a wrong number? I've had about 4 in my life. They'll just
connect the ringer (or vibrate function) to the detonator (with
whatever minimal circuitry in between is required - I've never used a
detonator!) and then only turn the phone on at the last minute.

It's not dumb to design a remote detonation system that requires the
absolute minimum of specialist knowledge and equipment to construct.



To use the unique cellphone ID to detonate a remote bomb is actually
a very ingenious innovation. No timers to mess with. The terrorist
has full and instant control of the time and place to set off the
bomb.

As Tim says its relatively easy to connect the ringer wires to a
simple circuit to output enough juice to trigger the detonator. Frist
year student project - like using a battery to keep a capacitor
charged and the ringer closes the discharge switch. Boom.

I'm pretty sure that it won't work that simple. There are other
factors at play that make controlling things with a telephone a lot
harder to achieve than you think... For everyone's safety I'm not
going into the details.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

If you think it is that hard, it's obvious the reason you won't go into the
details. You don't know.
It is rather easily done.

"Nico Coesel" wrote in message
...
I'm pretty sure that it won't work that simple. There are other
factors at play that make controlling things with a telephone a lot
harder to achieve than you think... For everyone's safety I'm not
going into the details.

I read in sci.electronics.design that Jeff Liebermann
wrote (in c1tr509eqipks7lt08ttt5cvnpkumu
) about 'CB Radios, Cellphones and Gasoline Vapor
Ignition', on Sun, 21 Mar 2004:
I didn't know that it wasn't linear.


Google for Paschen's Law. For high voltages it is linear enough for
calibrated spark gaps to be used as voltmeters in the past. The high-
voltage terminals were open and accessible, giving a whole new meaning
to the phrase 'Paschen killers'.(;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

John Woodgate wrote in message ...
I read in sci.electronics.design that Bill Sloman
wrote (in ) about 'CB
Radios, Cellphones and Gasoline Vapor Ignition', on Sun, 21 Mar 2004:
For the difference between Dewar benzene and Kekule benzene see

http://www.chemsoc.org/exemplarchem/...enzenering.htm

Dewar benzene can actually be made? Do you know when it was discovered?
What about the prismatic form? I would have thought that was a lot
easier to make, if I didn't have a suspicion that that is where simple
bonding ideas break down.

IIRR all three Dewar benzenes can be made - with difficulty.

They've been available since before 1971 at least - which is when my
project fell apart - but they were newish then.

The three-carbon rings at either end of the prismatic version do have
a lot of steric strain, but they can be made - I think pyrethroid
insecticides include just such a cyclopropane ring.

----------
Bill Sloman, Nijmegen

(John Michael Williams) wrote in message om...
(Bill Sloman) wrote in message . com...
...

The controlling relationship is between the volume of the sphere in
which the reaction is first initiated, and the surface area of that
sphere - if the intial volume is too small, not enough energy is
released to heat the surrounding shell of gas to the ignition
temperature.

...
-------
Bill Sloman, Nijmegen

This makes sense. I think I can see a spark 0.1 mm in
radius, at say 4000 K. That's about 4 cubic picometers
in volume and about 0.1 square micron in surface area (assuming
sparks have smooth surfaces). But, I'm not sure how to relate
that to the threshold of flame propagation.

If energy is a factor, rather than power, the duration of
the spark would seem to be relevant, too.

Sparks are much faster than flame fronts - when I was involved in
instrinsic safety nobody paid any attention to spark duration, and for
all practical purposes the energy stored in the capacitance of a spark
gap is dumped into the gas much faster than it can be dissipated.

------
Bill Sloman, Nijmegen

CW says...

"Nico Coesel" wrote...

I'm pretty sure that it won't work that simple. There are other
factors at play that make controlling things with a telephone a lot
harder to achieve than you think... For everyone's safety I'm not
going into the details.

If you think it is that hard, it's obvious the reason you won't go into the
details. You don't know.
It is rather easily done.

Any electronics engineer or technician can do it.

(CW, please don't top post)


--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
have an "impossible" engineering project that only someone like
Doc Brown can solve? My resume is at http://www.guymacon.com/

In , Jeff Liebermann wrote
in part:

Neon lamp needs about 60 volts to light and 40 volts to stay lit. The
4 watt flourescent tube wants at least 90 volts to start, and I think
(i.e. guess) about 50 volts to stay lit.

Lower voltage neon lamps do indeed light at 60 volts RMS and stay lit at
40 volts RMS. But these are lowish figures.

4-watt fluorescents need more, except they stay lit at only about 30
volts at full current, and part of that reason is thermionic emission from
hot electrodes.

I would not worry about RF from a cellphone igniting anything. If a
cellphone is going to be found to ignite gasoline vapor, I think more
likely ways a

* Sparks in the vibration motor
* Sparks from failing wires/connections
* Sparks in speakers with voice coils with intermittent shorts
* Sparks in switches (in whatever few models having switches that
actually switch enough current to make a spark)

I have already seen the Snopes item months ago when I first heard of
cellphones supposedly causing gas station fires, and they make it sound
as if cellphone ignition of gasoline vapors may never have actually
occurred, evidence that this has indeed happened appears mainly anecdotal,
and that this is rare if it does happen.

When I refuel my car, I keep my cellphone either far or upwind from the
gas inlet of my car. (My cellphone has vibration on.) I also ground
myself by touching something far/upwind of the fuel inlet if I let go of
the nozzle and have to touch the nozzle or anything near the fuel inlet
again before leaving the gas station to avoid the greater danger of static
electricity.

- Don Klipstein )

In , Bill Sloman wrote
in part:

I had to work through the equations many years ago for an experiment
intended to monitor the process in which one of the "Dewar benzenes"
converted itself to normal - Kekule's - benzene, which is an
enormously energetic process, involving about an order of magnitude
more energy per molecule than you get out of TNT and PETN. I really
didn't want to blast my experimental apparatus to smithereens.

When I went through the calculations with my supervisor, he pulled a
very long face - the motivation for the experiment had been some
unexpected flashes of light seen when a dumb organic chemist had
released small drops of liquid "Dewar benzene" into a hot cell, and my
calculations made it clear that the flashes of light were just thermal
radiation from a hot plasma, rather than fluorsecence from from an
electronically excited state of Kekule benezene, which is what my
supervisor had been hoping for ...

For the difference between Dewar benzene and Kekule benzene see

http://www.chemsoc.org/exemplarchem/...enzenering.htm

If this produces anything near 10x the energy per weight of TNT or PETN,
then a version with controlled reaction rate would make one heck of a
rocket propellant.

I thought the ultimate energy per mass was magnesium and oxygen (or was
it beryllium and oxygen?), just a few times as much energy per mass as TNT
and not good like usual rocket propellants for producing gas to use as
rocket exhaust.

I am surely skeptical of changing one isomer of a molecule to another
producing even comparable energy to, let alone more energy than
decomposition of a similar or somewhat greater mass molecule of high
explosive.

- Don Klipstein )

In , Jeff Liebermann wrote:
On Sun, 21 Mar 2004 08:47:34 +0000, John Woodgate
wrote:

I read in sci.electronics.design that Jeff Liebermann
wrote (in mppp50ho4dr08ahkb3dlbqkcfkp0ih
) about 'CB Radios, Cellphones and Gasoline Vapor
Ignition', on Sun, 21 Mar 2004:
The gap necessary to create an arc with 22 volts is:
22V / 20,000V/in = 0.001 inches Kinda small, but given a microscope,
a 1 mil spark gap will arc.

But it takes about 350 V to do so. The relationship between voltage and
gap length is very non-linear below about 500 V.

I didn't know that it wasn't linear. I just assumed that it takes the
same amount of energy to peel electrons off of a single atom (ionize)
regardless of gap seperation.

It gets messy. You can see how messy it gets when you see what happens
in the cathode area of a "glow discharge".

A "glow discharge" is one of two common processes where positive ions of
the gas/vapor are accelerated by the cathode-adjacent electric field into
the cathode material, and where positive ions bombarding the cathode
dislodge electrons from the cathode to maintain the supply of free
electrons in the "discharge" (conductive path of glowing gas/vapor).
(The other of the two common discharge mechanisms where cathode
bombardment by positive ions dislodges electrons is the "cold cathode
arc". There is still another cathode process for a discharge known as the
"thermionic arc".)

The glow discharge cathode process has 5 layers, 3 dim/dark and 2
bright. There is some sort of 'natural spacing' and 'natural thickness'
of these layers, which varies with gas/vapor type and pressure and the
cathode material. There is also a characteristic voltage drop of the
cathode process known as the "cathode fall", and that is normally a few
times or several times the ionization potential of the gas/vapor.

There is such a thing as "normal glow", where the cathode process occurs
at its natural current density (for the gas/vapor type and pressure and
cathode material), and the first two dark layers and the two bright layers
and some minimal portion of the third dark layer have a tendency to occupy
some 'natural distance' (a function of gas/vapor type and pressure
and cathode material) between cathode and anode.

Then there is "abnormal glow", where the cathode process is forced into
a smaller space between electrodes and/or is conducting a current density
higher than 'natural' (for the gas/vapor type/pressure and cathode
material) due to more current flowing than is "natural" for the available
cross section of cathode process. When that happens, the "cathode fall"
is even higher than that of "nowmal glow".

There's also the minor detail of RF excitation versus DC. As I
vaguely remember from my 35 years ago college welding classes, TIG
welding uses RF to strike the arc because it takes less
power/energy/whatever to start the arc.

I don't know about that, but I have heard of RF glow discharges maybe
having the cathode process eliminating one bright layer and one dark layer
(for "electrodeless discharge" that occurs where insulation exists over
the cathode for example), and that may reduce the cathode fall.

We're allegedly talking about
striking an arc across 0.001" with a 5 watt, 27MHz transmitter
terminated with a 50 ohm load. If it's non-linear in the opposite
direction, the calcs are gonna be no fun.

at best!!!

I have everything it takes to test this. Microscope slide, with two
sewing pins glued with hotmelt goo and seperated by 0.001". Apply RF
and watch through the microscope. I'll see if I can throw something
together and post photos (time permitting).

Please do!!!

- Don Klipstein )

"S" wrote in message et...
the show on discovery channel, mythbusters. debunked that myth,


They also showed in the same episode that a good percentage of
fueling fires come from static sparks around the gas tank. Someone
mentioned it before, but ground yourself away from the tank before you
start fueling. Apparently women are more likely not to ground
themselves and have something 70% of all spark induced fires. It was
pretty cool to watch the show and see a firefighter deliberately
generate a static spark and light himself on fire at a gas pump.