- Piezo switch
A piezo switch is an electrical
switch based on thePiezoelectric Effect .The charge generated by the piezoelectric element in the switch is typically used to turn on an integrated
semiconductor device such as afield effect transistor (FET), causing the switch assembly's output to be active, or "on". [ [http://discovercircuits.com/DJ-Circuits/piezoswitch2.htm DiscoverCircuits] ] When the FET is on, current can flow through it as with a conventional metal contact-basedswitch . After the voltage pulse is dissipated in the gateresistor , the FET turns back "off", its normal high impedance state. ThePiezoelectric Effect uses the fact thatforce applied to certain materials causes stresses thatgenerate this electric charge. In the case of piezo switches, theforce could be compressivepressure that causes the (typically disc-shaped) piezo element to bend very slightly like adrumhead .Thus piezo switches produce a single, brief "on" pulse. This pulse can vary with the amount of pressure which is applied, since higher pressures generate higher voltages which take longer to dissipate. A capacitor may be used to store the charge in order to lengthen the
time constant of the gate circuit and therefore the width of the pulse. With additional circuitry this pulse can be extended further or used to change the state of an output from steady "Off" to steady "On" by toggling a flip-flop.
Piezo switches have some interesting advantages over their conventional mechanical counterparts. One is that there are nomoving parts necessary for them to do their job. This means the lifetime of such a switch can be ensured to be tens of millions of operations, since there is no wear involved. [ [http://www.epn-online.com/page/new57534/piezo-switches-with-seal-tight-protection-from-schurter.html Piezo switches with seal-tight protection from SCHURTER] ]
Another advantage is that they may easily be completely sealed from the environment and thus made weatherproof. They are often constructed withstainless steel housings such that they are resistant to damage by vandals or heavy use.ee also
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Piezoresistive
*Piezo ignition
*Piezoelectric sensor References
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