"Peter Hucker" wrote in message
newsp.tmmhxayr4buhsv@fx62...
On Tue, 23 Jan 2007 00:53:27 -0000, colin
wrote:

"Peter Hucker" wrote in message
newsp.tmkkhkha4buhsv@fx62...
On Mon, 22 Jan 2007 14:18:49 -0000, colin
wrote:

"Peter Hucker" wrote in message
newsp.tme3s0ec4buhsv@fx62..
Is it really true that turning on a microwave with nothing in it
will
break it?

Even more worrying - will it catch fire or explode?

Don't they have a safety cutout? Can't it sense the Klystron
overheating,
or a build up of microwaves over a certain level?

I have purchased a new microwave which has an easier to grab
control.
I'm
concerned one of my pet parrots will switch it on! (Seriously, they
do
stuff like that)

When I designed some of the early mcu controllers for them eons ago
we used to give them a heck of a lot of abuse such
as running them empty to try and get the mcu to crash,
(wich with a piggy back eprom mcu was all too easy)
ofc always a microwave leakage meter nearby,
the most spectacular thing was to melt the glass tray,
the turntable mechanism was the first thing to melt usually.

If theres food inside it will eventually catch fire and the flames
will
come
out of the back,
this was a serious liability worry at the time I assume theyve added
some
safty things since I worked on them.

Some have water vapour detectors wich sense the peak and stop
cooking, I
assume they will stop if nothing is detected.

This is a £27 Tesco Value microwave - probably only has legal safety
requirements.

I've already turned it on momentarily with nothing in it, as I'm used
to
an electronic one. If my food has gone cold due to a phonecall etc, I
tend
to shove it in and just turn the timer round to get it to go, then open
the
door after 20 seconds. The electronic ones cancelled the timer when you
opened the door, but this one turns back on when you shut the door.

Well, we used to leave them on for 24 hours soak test, if you put
anything
in them it would be long incinerated by then,
so they were run empty,
they used to end up real hot but theres probably only about 600W of
microwave heating power plus losses ofc and theres a fan wich gets rid
of
most of the heat so total temp rise is limited, the only real danger
that I
can see is that it gets so hot the plastic/ferrite door seal melts,
this is serious becuase it is essential to form a safe seal from
microwave
energy leaking past the door,
if the electronics gets too hot and melts it should safely blow the fuse
and
so will no work again so should be safe.
if the magnetron blows up ofc this will probably also blow the fuse and
end
up safe.
If the fan vent gets blocked this would probably make a meltdown more
certain.
ofc we did this in a building with little risk of any fire spreading.

Sounds reassuring. But does this also apply to cheap ones?

Some of the ones we had were quite cheap, actually some were pretty awfull,
and some of the controllers we had to make had to be so cheap it was a
shame.
the basic magnetron/oven arangement was hardly any different from the cheap
to expensive ones.

but I assume theres a maximum limit on the timer ? polly would have to
keep
setting it to max to cuase a problem I would think.

Most likely they'd turn it slightly, about 5 minutes. When the thing
turned on they'd probably get a fright and fly off anyway.

I doubt it would go pop after 5 minutes just becuase it was empty, I would
be even more surprised if it became dengerous after 5 minutes on empty too,
either way the manafacturer would probably have a liability waiting to
happen.

If you do decide to try it empty despite what the manafacturer tells you its
on your own risk ofc, make sure the glass tray is still in as that does
absorb some microwave energy.

a CD makes an interesting display when you put it in the microwave.

I can't see them opening the door. The like to twist and chew stuff. The
door requires a hard pull (no button to push).

One of my cats managed to repeatedly get out of a locked cat flap. I couldnt
figure out how untill I watched once.
animals can surprise you sometimes.

Colin =^.^=