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Touch-Sensitive
Musical Bell with Timer
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circuit is built around CMOS IC CD4011 and popular melody
generator IC UM66. When touch plates are bridged by hand
for a moment, the circuit starts to generate music. After
a few seconds the music automatically stops. Maximum supply
voltage for this circuit is 5 volts only because of IC
UM66. This IC cannot operate beyond this voltage. IC 7805
regulator based power supply can be used to power this
circuit. Time delay can be changed by changing values
of capacitor C1 and resistor R2. Two silicon diodes connected
in series between pin 2 of UM66 IC and positive 5-volt
rail keep voltage applied to pin 2 of UM66 below 3.8 volts
because of the drop of approximately 1.2 volts across
them |
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