Smart Vibration Sensor

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In this vibration sensor alarm circuit,
initially, when power switch
S1 is flipped to ‘on’ position, power
indicator LED1 lights up immediately.
IC LM555 (IC1), wired as a simple latch
circuit with control input, is powered
and R-C components R4 and C5 connected
at its reset pin 4 force the latch
to standby mode (with inactive low
output). The circuit is driven into sleep
mode.


As a result, control input
pins 2 and 6 of IC1 latch are grounded.
Output pin 3 of IC1 now goes high.
The positive supply from output pin 3
of IC1 is extended to three-tone siren
generator UM3561 (IC2) through R5,
D1 and R6. Components R6 and ZD1
stabilise the input power supply of IC2
to around 3.3V.


Reset switch S1 can be used to
switch off the alarm sound by resetting
the latch circuit. For safety, use key-lock
type switches for S1 and S2. A relay can
also be connected at the output socket
(SOC1) of the circuit to energise highpower
beacons, emergency sirens and
fence electrification units.
The circuit works off 9V DC. A
compact PP3-/6F22-type alkaline
battery can be used to power the
circuit.