Transcript Document
Vibration Detector
Indian Institute of Technology
Hyderabad
Basic Principle
The basic principle used in this setup is piezoelectricity.
It is a phenomenon of internal accumulation of charge
in crystals in response to external mechanical force
applied on it.
:source(Wikipedia)
Applications of piezoelectricity
oDetecting & producing of sounds
oGenerating voltage
oMicrobalance
oUltrafine focusing of optical assemblies
Material used:
The material used in piezoelectric element is lead zirconate
crystal.
These crystals generate measurable piezoelectricity when
they are deformed
about 0.1% of their original dimensions.
These crystals readily release the current when the orientation
of crystal is disturbed by mechanical vibrations.
These signals are in turn given to IC 741 (Op-Amp)
Material used
Op-Amp has two terminals
V+ (non-inverting) input &
V-(inverting) input
OpAmp is a difference amplifier so it amplifies
difference between the inputs
Even if the difference is small the output can
be as high as supply voltage(Vs)
Negative feedback is given to V- so as to make
it a non inverting amplifier
Open loop gain of OpAmp is very high (nearly
100000)
NPN transistor
NPN transistor is used as a switch in this circuit
When the base voltage is high the current in emitter and collector
increases
Collector voltage will drop because of load resistance
This will act as a switch to trigger signals to IC 555 (timer IC)
Mechanism:
These signals are in turn given to an Operational Amplifier(OpAmp).The Op-Amp amplifies the current signal which in turn
gives high output .
This high output from Op-Amp in turn will switch on NPN
transistor and it will start conducting.
Mechanism
When transistor conducts, it will trigger pin 2 of
IC555(monostable multivibrator).
IC555 will give high output to pin 3.
VR is used to adjust the sensitivity of the piezo
element.
This element is kept in a metal box which will be buried
inside the soil to detect seismeic vibrations.
Advantages
The piezo element can
detect slightest vibrations
to make it useful to
detect seismic waves
Useful, cheap and can
be used for many
applications
Disadvantage
It is difficult to monitor
such a detector
Piezoelement loses its
efficiency after certain
period of time
THANK YOU
Indian Institute of Technology
Hyderabad