Alarm Clock With Day Selector


This circuit disables an
alarm clock on Saturdays and Sundays when people like to sleep in but
enables normal operation on Mondays to Fridays so that people rise in
time for work or school. The core of the circuit is a 4017 decade
counter which acts as the day counter and it is used in conjunction with
a desk clock which acts the alarm and a watch module with alarm
function which provides one clock pulse very day to the 4017. In
operation, the watch module feeds a day pulse via transistor Q3 to the
clock input of IC1. This has seven outputs connected via day switches
(S1-S7) and diodes D3-D9 to Q1 which disables the alarm signal to the
speaker via transistor Q2. LEDs1-7 indicate the actual day (if you
forget!).

Circuit diagram:

Alarm Clock With Day Selector Circuit

Alarm Clock With Day Selector Circuit Diagram

To set the system, set the desk clock for the correct time and for
the desired alarm time (eg, 6’o’clock). The watch module is set to the
correct time and its alarm set to midnight. The day counter, IC1, is set
to the correct day, as indicated by the LEDs, by pushing switch S12 and closing switch S8 or S9. S8 is normally left open to conserve the battery by leaving the LEDs
off. As shown on the circuit, switches S1-S7 are set to sound the alarm
on Mondays to Fridays and disable it on Saturday and Sunday. However,
you can change the days to suit your work habits.

Author: Rasim Kucalovic
Copyright: Silicon Chip Electronics


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