By Jim Sky
BUILD THE
For several years
now, I have
remotely managed
a small radio
observatory at a
school campus in
Hawaii. There are a
number of PCs that
run the
radiotelescope
receivers and make
the data available
online. When the
project began, it
seemed like we
constantly had to
call someone at the
school and have
them go over and reboot one or more
of the PCs. Things are better now that
Windows XP has matured. Still, there is
the occasional problem that requires a
person to manually push the power-reset button. This project is aimed at
replacing that human button pusher
with a bit of automation.
If you work with microcontrollers, you are probably aware that many of these chips have internal “watchdog
timers.” These consist basically of a virtual reset button
connected to a timer. If the watchdog timer is not reset
before a set time expires, the microcontroller reboots
itself. This can be helpful if by some chance the device
gets stuck in a loop waiting for an external stimulus that
never arrives. Watchdogs are also available for larger
computers. These devices may take the form of an internal
card or external device that monitors the PC for a regular
signal. If the signal fails to arrive within a predefined time,
it is assumed that things are awry in either software or
hardware, and a hardware reset is applied to the PC.
Often this reboot fixes the problem.
