"Fail Safe" and Watchdogs!
Ever since the widespread use of machines in the nineteenth century, there
has a been a history of system failure. The most dramatic examples of these
failures were in railway systems. If a train driver fell asleep, the
consequences for the passengers were often disastrous. There has been a
long history of steady improvements over more than 100 years of train management
that resulted in "fail safe" systems. The core of this principle is that
if a system does stop working, then it must fall back to a safe level of
operation. If the brakes fail, for instance, then the vehicle stops
automatically by other means.
In electronics, a fail safe device can reset the circuit back to the normal
operation if it fails. If the circuit is not actually damaged, the
circuit will restart the progam
back to normal operation.
Tasks and Activities
- What does "fail safe" mean in your own words? ( please do
not copy or paste an Internet definition )
- What might happen to a train driver which would cause a train to
run "out of control"?
- How does a "Dead Man's Switch" work on a train? Why is it
regarded as a "fail safe" device.
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- How does a "Watchdog" circuit work? (
Hint - read the first
paragraph on this page )
Don't forget to email your choices/answers
to Mr. Widmer by the end of this week. Keep a copy of that email
in your Google Docs folder.
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