Piezo switch

Piezo switch

A piezo switch(sometimes referred to as Touch metal piezo switch) is an electrical switch based on the piezoelectric effect, designed to be installed in a location (or device) and application where they may be subject to vandalism or tampering, as in the case of pedestrian crossing switches, or fraudulent or unauthorized use, as in the case of vending machine switches. Anti vandal switch that are located on devices that are accessible to the public or which are located outside also have to be able to withstand dust, rain, snow, and frequent operation.

The charge generated by the piezoelectric element in the switch is typically used to turn on an integrated semiconductor device such as a field effect transistor (FET), causing the switch assembly’s output to be active, or “on”. When the FET is on, current can flow through it as with a conventional metal contact-based switch. After the voltage pulse is dissipated in the gate resistor, the FET turns back “off”, its normal high impedance state. The piezoelectric effect is the generation of electric charge when certain materials are under stress. In the case of piezo switches, the force could be compressive pressure that causes the (typically disc-shaped) piezo element to bend very slightly like a drumhead.

Thus piezo switch 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 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 switch have some interesting advantages over their conventional mechanical counterparts. One is that there are no moving parts, just the small deformation on the front plate and the piezo element (typically a few micrometers). This means the lifetime of such a switch can be ensured to be tens of millions of operations, since there is no wear involved. Another advantage is that they may easily be completely sealed from the environment and thus made weatherproof. They are often constructed with stainless steel housings such that they are resistant to damage by vandals or heavy use.

Conventional electromechanical switches have moving parts that inevitably wear out
The reliability of the electromechanical switches can be reduced by contaminants such as moisture and dust that will foul contact points
The solution is a Piezo Switch with no moving parts

How a piezo switch working?

Piezo-switch-wiring-schemes-2wire

  • Finger pressure is applied to the surface of the switch-housing which deflects about 2 microns.
  • This pressure activates the piezo crystal that converts this pressure to an electrical signal that is amplified by electronics imbedded within the housing.

LANGIR Piezo Technology

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The LANGIR® technology is based on a single VPM (Versatile Piezo Module) mechanically assembled without the use of adhesives nor soldering. The VPM is encapsulated in a metal, one piece construction housing, custom designed or as per industry standard, creating the most reliable and durable switch and keypad.
The LANGIR® product line spans from single switches via a variety of keypads and control panels to full size keyboards. Virtually indestructible the LANGIR product line is rugged, sealed, tamper and vandal proof, with metal housing and solid state electronics featuring unprecedented durability and reliability.

LANGIR Piezo Technology Applications

We manufacture over 4000 custom made products covering a full spectrum of applications: Food Processing • Petroleum Dispensing • Clean Room Interfaces • Internet Kiosks • Access Control • Fluid Dispensing • Mining Equipment • Emergency Call Systems • Dairy Equipment • High-End White Appliances • Oceanographic Instruments • Elevators • Conveyers • Car wash • Weighing Devices • Military applications and many more.

Technical Characteristics:

Electrical Specifications

  • Voltage:
    Standard 200mA 24VAC/DC – option 1A 24VAC/DC
    NC functions max. 600mA 24VAC/DC
  • LEDs Voltage: 5VDC, 12V DC and 24V Standard or per customer specifications
  • Contact Resistance: None
  • Contact Bounce: None
  • EMI/RFI: No Effect

Functional Operation Specifications

  • Momentary / Latching
  • Normally Open / Normally Closed
  • Impact: 1kg Shock Test
  • Make / Break via Transistor

Mechanical Specifications

  • Water Resistance: Up through IP68
  • Connection: Wireleads PVC wires 30cm 24AWG
  • Materials: Aluminum & Stainless Steel
  • Minimum Actuation Force: 5 – 15N+ (Typical)
  • Mechanism: 100% Solid-state, No Moving Parts
  • Operational Life: +20mm cycle, -40C to 70C (Typical)
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