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Circuits
This novel buzzer circuit uses a relay
in series with a small audio transformer and speaker.
When the switch is pressed, the relay will operate via
the transformer primary and closed relay contact. As
soon as the relay operates the normally closed contact
will open, removing power from the relay, the contacts
close and the sequence repeats, all very quickly...so
fast that the pulse of current causes fluctuations in
the transformer primary, and hence secondary. The
speakers tone is thus proportional to relay operating
frequency. The capacitor C can be used to "tune" the
note. The nominal value is 0.001uF, increasing
capacitance lowers the buzzers tone. |
