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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Wednesday, June 02, 2021 03:48 AM
Hobby Circuits List
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More
Timer Circuits
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36 Hour Watchdog Timer
(April 11, 2010) |
| A watchdog timer is often
used in computer systems to detect when a computer is hung up and is no longer
running properly. If it does become locked up and is not able to supply a reset
pulse to the circuit within a defined time frame the timer times out and activates
some kind of alarm. Watchdog timers can also be used for humans. As in
the computer, if the human fails to press the reset button in the circuit below, an
alarm buzzer is activated. This hobby circuit uses two common logic ICs. The
CD4060 contains an oscillator and a number of logic dividers. The output of
the first counter is fed to the second timer. With the component values given,
the timer is set for a timeout after 36 hours. It is very easy to change the
oscillator frequency or the number of counter stages to program the circuit for
longer or shorter times. I have supplied the formulas for determining the
component values. |
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Click on Circuit Below to view PDF of Schematic |
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