Electronic Reminder

This easy-to-build electronic alarm will remind you of an impotant task after a preset time. It is particularly useful for housewives and busy professionals. All you have to do is set the time in minute swith the help of two thumbwheel switches (S3 and S4) -- Raj K. Gorkhali

3013
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The counters have been wired in count-down mode as only then the counter IC completes its count cycle in a number of clock cycles equal to the number set by thumbwheel switches.

The time can be set in steps of one minute. If the clock period is changed to, say, 2 minutes, time resolution becomes 2 minutes, whereas the maximum settable time delay increases from 99 to 198 minutes. In essence, the maximum time delay that is achievable with this circuit is 99 clock cycles with a time resolution equal to the duration of one clock cycle.


 

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