This circuit
is for an audible metronome, which is a device that indicates musical
tempo. The main component of this
circuit is the 555, a versatile timer IC. It is configured as an
astable multivibrator, i.e., a timing circuit whose output toggles
between 'low' and 'high' continuously, in effect generating a train of
pulses.
The train
of pulses generated by an astable multivibrator can be used to drive
either a speaker or a simple, non-self-oscillating piezoelectric
buzzer to generate sound. In the case of a metronome, the frequency
at which these sound producing elements are driven should be low,
e.g., 1 Hz to 10 Hz.
Since the
output frequency
f
of the
555 circuit above is defined by the equation
f
= 1.44/(C1(R1+2R2)),
lower frequencies can be achieved by using high values for C1 and
(R1+2R2). In the circuit above, R2 was fixed at 1 K, but a 1M-ohm
variable resistor was used as R1 in conjunction with a 1 microfarad
C1 to achieve the low frequency required for a practical metronome.
In the
circuit above, either the piezo buzzer or the speaker may be
omitted, depending on the quality of sound required.
See
also: 555 Astable
Multivibrator
Go
Back to the PROJECTS Menu
HOME
