Specifications

194
CONSTRUCTION
circuit gets auto-
matically
switched off.
Though the
ringing of bell
and display of
periods dis-
continue, the
digital clock
continues to
work as
usual. Next
morning, the
above opera-
tion needs to
be repeated.
This sys-
tem was suc-
cessfully
demon-
strated by
the author in
a science and
technology
exhibition where it was appreciated and
liked by most of the visitors—especially
those from the educational institutes.
o
Fig. 6: Component layout
seconds after every 40 minutes. In the evening, after
the eleventh period is over and the institute is to be
closed, the power supply to parts II and III of the
the period display from 00 to 01 (indicat-
ing that the first period has started).
Hereafter, the circuit works auto-
matically, sounding the bell for a few
www.electronicsforu.com
a portal dedicated to electronics enthusiasts