death by computer

[Tim Shoppa]

bigcat@meeow.co.uk (N. Thornton) wrote in message news:<a7076635.0405040157.267ac6b1@posting.google.com>...

The switches are not ordinary consumer grade switches, they are rated
specifically for interlocks.

I would claim that the majority of "broken" microwave ovens in the
US are because of failed door interlock switches.

The switches are indeed designed to fail into the "safe" position but
they fail the other way too. (especially the ones on the door latch
that trigger the light and fan.) The thing we rely on for safety is that they
don't fail simultaneously in the "dangerous" direction, but with hundreds
of millions of microwave ovens made over the years I'm sure it has happened.

I work in an industry that prides itself in vital relays that are
(supposedly) more reliable than those used to arm nuclear weapons, and
there are always freak failures if you look hard enough at a system that's
been operating for a good chunk of a century. Most of these failures
get investigated and written up by the FRA and/or DOT, and the root cause
is usually much more complex than a simple failed component or two.

Tim.

 

[John Miller]

Ken Taylor wrote:

The OP's description seems consistent with the switches being used as
inputs to a uP, which then decides whether to turn things on or not. If
correct this is not good, for the very reasons the OP has mentioned.

Why has nobody yet pointed out that the actual make and model of the
microwave have not been mentioned? That'd put the circuit configuration to
rest in about 30 seconds.

--
John Miller
Email address: domain, n4vu.com; username, jsm

Save energy: Drive a smaller shell.

 

[Ben Bradley]

On Tue, 04 May 2004 14:05:29 GMT, John Miller <me@privacy.net> wrote:

Ken Taylor wrote:
The OP's description seems consistent with the switches being used as
inputs to a uP, which then decides whether to turn things on or not. If
correct this is not good, for the very reasons the OP has mentioned.

Why has nobody yet pointed out that the actual make and model of the
microwave have not been mentioned?

I pointed this out indirectly by asking for it to be posted, and I
think someone else asked too. The OP's posting address is obviously
fake, OTOH google shows a few recent legit-looking posts from that
address, posted through rcn.com.
Of course, even the most legit poster could decide to have fun by
posting a "troll"...

That'd put the circuit configuration to
rest in about 30 seconds.

-----
http://mindspring.com/~benbradley

 

[Ken Taylor]

"Ben Bradley" <ben_nospam_bradley@mindspring.com> wrote in message
news:88cf90lsoeau44at5eu31gj5m6h9vmgisb@4ax.com...

On Tue, 04 May 2004 14:05:29 GMT, John Miller <me@privacy.net> wrote:

Ken Taylor wrote:
The OP's description seems consistent with the switches being used as
inputs to a uP, which then decides whether to turn things on or not. If
correct this is not good, for the very reasons the OP has mentioned.

Why has nobody yet pointed out that the actual make and model of the
microwave have not been mentioned?

I pointed this out indirectly by asking for it to be posted, and I
think someone else asked too. The OP's posting address is obviously
fake, OTOH google shows a few recent legit-looking posts from that
address, posted through rcn.com.
Of course, even the most legit poster could decide to have fun by
posting a "troll"...

That'd put the circuit configuration to
rest in about 30 seconds.

My suspicion too - even a clown in a Krusty-burger hat would feel some

indignation if their hand got warm when the microwave oven did funnies.
Still, if he posts more detail....

Ken