CN117129021A - A PVDF piezoelectric sensor device that can achieve pressing and holding - Google Patents

Abstract

The invention discloses a PVDF piezoelectric sensor device capable of realizing pressing and holding, which comprises a PVDF piezoelectric sensor for sensing pressing actions and a pressing detection and holding circuit for detecting the pressing and holding actions, wherein the PVDF piezoelectric sensor adopts a PVDF film sensor, is adhered to a surface to be detected, and is connected with and outputs sensing signals to the pressing detection and holding circuit. The invention performs slotting treatment on the operational amplifier and the pressing detection circuit so as to replace a feedback resistor and a pull-up resistor, and can avoid loss of electric charge converted from force, thereby realizing the pressing and holding functions. The problem that the piezoelectric sensor cannot realize signal detection of long-term pressing action for a long time is solved, so that the application field of the piezoelectric sensor, particularly the PVDF piezoelectric sensor, is greatly expanded.

Description

A PVDF piezoelectric sensor device that can achieve pressing and holding

Technical field

The present invention relates to the field of piezoelectric sensors, and in particular, to a PVDF piezoelectric sensor device that can achieve pressing and holding.

Background technique

PVDF piezoelectric sensor is a thin-film piezoelectric sensor with good flexibility. Piezoelectric crystal can convert input physical quantities such as force, displacement, acceleration, etc. into charge output. Piezoelectric crystal sensors designed with this characteristic have a wide range of applications. Applications, such as measuring acceleration, vibration, object deformation, pressure, etc.

When the PVDF piezoelectric film sensor is subjected to an external force in the vertical direction and bends, it will output a corresponding strain voltage. At the same time, PVDF piezoelectric sensors also have some shortcomings, such as: the effective output comes from a part of the measured energy, the internal resistance of the sensor is high, and the output energy is relatively small; at zero frequency, it is required to maintain a weak electrostatic charge for a long time difficult, so its low-frequency characteristics are poor and can usually only be used for dynamic or approximately dynamic measurements; due to the polarization characteristics of piezoelectric materials, the piezoelectric system can only satisfy approximate linearity within a certain range and is susceptible to various external influences. environmental impact.

Therefore, the charge generated by the PVDF piezoelectric sensor must be converted into a voltage signal through a charge amplifier before it can be collected. However, the signal generated by the PVDF piezoelectric sensor cannot be held by the traditional charge amplifier, so the traditional charge amplifier needs to be modified and needs to be able to It avoids the loss of force converted into electric charge, thereby realizing the function of pressing and holding.

Contents of the invention

The technical problem to be solved by the present invention is to realize a modification of the traditional charge amplifier, slotting the operational amplifier and the press detection circuit to replace the feedback resistor and the pull-up resistor, thereby avoiding the loss of force converted into charge, and thus PVDF piezoelectric sensor device that implements press hold function.

In order to achieve the above object, the technical solution adopted by the present invention is: a PVDF piezoelectric sensor device that can realize pressing and holding, including a PVDF piezoelectric sensor for sensing the pressing action, and a pressing detection and holding circuit for detecting the pressing and holding action. , the PVDF piezoelectric sensor uses a PVDF film sensor, the PVDF piezoelectric sensor is bonded to the surface to be detected, and the PVDF piezoelectric sensor is connected and outputs a sensing signal to the press detection and holding circuit.

The PVDF piezoelectric sensor is bonded to the touch layer through an adhesive layer, and the non-touch pressed surface of the touch layer is bonded to the adhesive layer.

The press detection and holding circuit is composed of an operational amplifier unit U1 fixed on the PCB circuit board, a feedback capacitor C1, and a bias capacitor C2. Both ends of the feedback capacitor C1 are connected to the inverting input terminal 4 and the output of the operational amplifier unit U1 respectively. Terminal 1, one end of the bias capacitor C2 is connected to the non-inverting input terminal 3 of the operational amplifier unit U1, and the other end is connected to Vref.

The input and output terminals of the operational amplifier unit U1 are respectively on both sides of the package module.

The PCB circuit board is provided with a first through-type slot, and the position of the first through-type slot is between the inverting input terminal 4 and the output terminal 1 of the operational amplifier unit U1. The operational amplifier unit U1 is fixed on the PCB circuit board across the first through-type slot.

The PCB circuit board is provided with a second penetrating slot and a third penetrating slot, and the parameters of the first penetrating slot, the second penetrating slot and the third penetrating slot are They are all 13mm long and 1.5mm wide, and the three slots are parallel to each other;

The two ends of the bias capacitor C2 are fixed on the PCB circuit board across the second penetrating slot; the two ends of the feedback capacitor C1 are fixed on the PCB circuit board across the third penetrating slot.

The parameters of the feedback capacitor C1 are determined by the size of the piezoelectric sensor surface area S and satisfy the formula C1=S·K, where

The parameter of the bias capacitor C2 is equal to the maximum value of the feedback capacitor C1.

The Vref parameter is equal to half the maximum output voltage of operational amplifier unit U1.

The present invention performs slot processing on the operational amplifier and the press detection circuit to replace the feedback resistor and the pull-up resistor, thereby avoiding the loss of force converted into charge, thereby realizing the press hold function. It solves the long-standing signal detection problem of piezoelectric sensors that cannot achieve long-term pressing action, thus greatly expanding the application fields of piezoelectric sensors, especially PVDF piezoelectric sensors.

Description of the drawings

The following is a brief description of the content expressed in each drawing in the specification of the present invention:

Figure 1 is a schematic diagram of the bonding of PVDF piezoelectric sensors;

Figure 2 is a schematic diagram of the circuit principle;

Figure 3 is a schematic diagram of the circuit board slotting process;

Figure 4 is a schematic diagram of the long press signal waveform;

Figure 5 is a schematic diagram of the continuous short press signal waveform.

Detailed ways

The following describes the embodiments with reference to the accompanying drawings, and the specific implementation methods of the present invention include the shape and structure of each component involved, the mutual position and connection relationship between each part, the function and working principle of each part, and the manufacturing process. and operation and usage methods, etc., are further described in detail to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concepts and technical solutions of the present invention.

PVDF piezoelectric sensor for sensing the pressing action and a pressing detection and holding circuit for detecting the pressing and holding action. Through the specially designed press detection and holding circuit, the signal detection of long-term press actions is realized, while still maintaining the function of rapid press detection. The sensor used to sense the pressing action uses a PVDF film sensor. The sensor needs to be firmly bonded to the surface to be detected. As shown in Figure 1, one side of the pressing contact surface is used for touch pressing, and the other side is a non-touch pressing surface. , PVDF film sensor is bonded to the non-touch pressing surface.

The PVDF piezoelectric sensor has two electrodes, one of which serves as the positive electrode and the other as the negative electrode, used to receive and transmit the charge signal generated by the piezoelectric effect. When the sensor is subjected to pressure or force, a charge signal will be generated between the positive and negative electrodes. These electrodes can be connected to the press detection holding circuit through wires. One end of the wire is connected to the electrode of the PVDF piezoelectric sensor, and the other end is connected to the press detection Hold the input to the circuit so that the charge signal generated by the sensor can be transferred into the circuit for further processing.

The press detection and hold circuit consists of an operational amplifier unit U1, a feedback capacitor C1 and a bias capacitor C2. A typical circuit schematic is shown in Figure 2. In particular, this circuit differs from common circuits in that there is no feedback resistor R1 and pull-up resistor R2.

The selected feedback capacitance C1 is determined by the surface area S of the PVDF piezoelectric sensor, that is, it satisfies the formula C1=S·K, where For example, if the area of the PVDF piezoelectric sensor is S = 280mm ² , the selected feedback capacitor C1 range can be calculated and rounded according to the above formula to be 120pF ~ 340pF.

Within this value range, selecting a smaller feedback capacitor C1 value can obtain a larger signal amplification factor. For the bias capacitor C2, its value is equal to the maximum value of the feedback capacitor C1, which is 340PF in this example. Figure 2Vref whose value is equal to half of the maximum output voltage of the op amp.

The feedback resistor R1 canceled in Figure 2 is replaced by a through-type slot on the PCB circuit board. The slot area is located between the inverting input terminal 4 of U1 in Figure 1 and the output terminal 1 of the operational amplifier unit U1, and Feedback capacitor C1 should span this trench. The canceled pull-up resistor R2 is replaced by a through-groove on the PCB circuit board. The groove area is between Vref and the non-inverting input terminal 3 of the operational amplifier unit U1, and the bias capacitor C2 should span the trench. above. Furthermore, for the selection of the operational amplifier unit U1, an operational amplifier whose input and output terminals are on both sides of the package module should be selected. The PCB circuit board is provided with a first through-type slot, and the position of the first through-type slot is between the inverting input terminal 4 and the output terminal 1 of the operational amplifier unit U1. The operational amplifier unit U1 is fixed on the PCB circuit board across the first through-type slot.

Specifically, there are three slots, namely the first penetrating slotting, the second penetrating slotting, and the third penetrating slotting. The three slotting parameters are all 13mm long and 1.5mm wide, and The three slots are parallel to each other, and the two ends of the bias capacitor C2 are fixed on the PCB circuit board across the second penetrating slot; the two ends of the feedback capacitor C1 are fixed on the PCB circuit board across the third penetrating slot. Both ends of the operational amplifier unit U1 are fixed on the PCB circuit board across the first through-type slot. The PCB board slot processing method realizes the impedance matching properties, functions as a feedback resistor and a pull-up resistor, and can reduce noise. interference, thereby improving the performance of the charge amplifier.

This detection circuit can keep the signal unchanged when pressed for a long time (one minute). Its typical characteristics are shown in Figure 4, and the signal that changes when pressed quickly (ten times per second) can also be detected in real time. A typical feature is shown in Figure 5.

The present invention has been exemplarily described above in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited by the above-mentioned manner, as long as various non-substantive improvements are made using the method concepts and technical solutions of the present invention, or without improvement. Direct application of the concepts and technical solutions of the present invention to other situations shall fall within the protection scope of the present invention.

Claims (9)

1. The PVDF piezoelectric sensor device capable of realizing pressing and holding is characterized by comprising a PVDF piezoelectric sensor for sensing pressing action and a pressing detection holding circuit for detecting the pressing and holding action, wherein the PVDF piezoelectric sensor adopts a PVDF film sensor, the PVDF piezoelectric sensor is adhered to a surface to be detected, and the PVDF piezoelectric sensor is connected with and outputs an induction signal to the pressing detection holding circuit.

2. The pressure retention PVDF piezoelectric sensor device of claim 1, wherein the PVDF piezoelectric sensor is bonded to the touch layer by an adhesive layer, the non-touch pressed surface of the touch layer being bonded to the adhesive layer.

3. The PVDF piezoelectric sensor device according to claim 1 or 2, wherein the pressing detection holding circuit is composed of an operational amplifier unit U1 fixed on a PCB, a feedback capacitor C1, and a bias capacitor C2, wherein both ends of the feedback capacitor C1 are respectively connected to the inverting input terminal 4 and the output terminal 1 of the operational amplifier unit U1, and one end of the bias capacitor C2 is connected to the non-inverting input terminal 3 of the operational amplifier unit U1, and the other end is connected to Vref.

4. A PVDF piezoelectric sensor device according to claim 3, wherein the input and output terminals of the operational amplifier unit U1 are on both sides of the package module, respectively.

5. The PVDF piezoelectric sensor device according to claim 4, wherein the PCB is provided with a first through slot, the first through slot being located between the inverting input 4 and the output 1 of the op amp unit U1, the op amp unit U1 being fixed to the PCB across the first through slot.

6. The PVDF piezoelectric sensor device of claim 5, wherein the PCB is provided with a second through slot and a third through slot, the first through slot, the second through slot, and the third through slot are each 13mm long and 1.5mm wide, and the three slots are parallel to each other;

two ends of the bias capacitor C2 are fixed on the PCB in a crossing way through the second penetrating slot; and two ends of the feedback capacitor C1 are fixed on the PCB in a crossing way through the third penetrating slot.

7. The PVDF piezoelectric sensor device according to claim 1 or 6, characterized in that the feedback capacitance C1 parameter is determined by the size of the piezoelectric sensor surface area S, satisfying the formula c1=s·k, wherein

8. The pressure retention PVDF piezoelectric sensor assembly of claim 7, wherein the bias capacitance C2 parameter is equal to the maximum value of the feedback capacitance C1.

9. The pressure-retention-enabled PVDF piezoelectric sensor device according to claim 1, characterized in that the Vref parameter is equal to half the maximum output voltage of the operational amplifier unit U1.