JP2014203772A - Mat sensor device using conductive cloth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mat sensor device using a conductive cloth which can be a sensor having flexibility over a wide area and with which a touched state and a loaded state can be identified by one sensor without adverse influences caused by noise.SOLUTION: The mat sensor device comprises a mat sensor 6 which is configured in a three-layer structure from an insulator cloth 2 which is provided as an insulator with a non-conductive cloth, and front-side and rear side conductive clothes 1 and 3 laminated on front and rear sides of the insulator cloth 2, and which is provided in a mat shape, carpet shape or a sheet shape of cloth by adding electric wires to the front-side and rear-side conductive clothes 1 and 3, respectively, and making them functional as a capacitor. The front-side conductive cloth 1 is connected to a CPU 13 of a sensor detection circuit, and the rear-side conductive cloth 3 is connected to a ground side of a sensor detection substrate 7.

Description

  The present invention provides a mat-like, carpet-like, or sheet-like shape having a function of a capacitor by an insulator cloth provided by a non-conductive cloth as an insulator and a conductive cloth laminated on the insulator cloth. The present invention relates to a mat sensor device using a conductive cloth constructed as described above.

Many hospitals and nursing homes use mat sensors on the bedside floor to monitor the bed leaving patients who need care such as dementia and Alzheimer's.
However, since most mat sensors use mechanical switches, there are disadvantages that they are thick and do not operate unless a certain load is applied. For this reason, the detection of the sensor is delayed, the patient is trying to get up, the accident is seriously injured, and the mat is stumbled on the edge and falls. For this reason, there is a demand for a mat sensor that can detect a mat just by touching it without applying a load to the mat and that is as thin as a bath mat.

On the other hand, touch sensors currently used in smartphones and the like detect a change in capacitance by detecting a change in capacitance by simply touching a hand without applying a strong force. It is conceivable to apply this method to a mat sensor.
A touch sensor such as a smartphone has a small sensor unit and a small capacity, and therefore, even if a person touches it, a large capacity is added. For this reason, there is a feature that the change in electrostatic capacitance is very large and the detection of touch is easy. In contrast to this touch sensor, when the size of the mat sensor is, for example, one third of the size of a tatami mat, the area thereof is about one hundred times that of a smartphone. For this reason, even if the conventional touch sensor device is applied to a mat sensor device that uses the entire mat as a sensor, in addition to the wide detection range of the capacitance, the capacitance of the mat itself is large. Detection is difficult with a slight change in capacitance when touched. Further, for example, because it is used on the floor, all noises including a 100V AC power supply for home use get on, making it very difficult to use as a sensor. Furthermore, from the viewpoint of procurement of commercially available materials, a large area could not be made.

  In contrast, a capacitive touch sensor comprising a conductive fabric using conductive fibers and a cloth covering the surface of the conductive fabric is first provided at the end of the bed where the person requiring care is lying, and care is required. A touch detection circuit that detects a change in capacitance of a capacitor composed of a capacitive touch electrode and a human body dielectric when a person touches or approaches the capacitive touch sensor and outputs a detection signal. A bed leaving condition detection device (see Patent Document 1) that generates a detection signal indicating a bed leaving situation of a care recipient is proposed when a change in capacitance is detected.

  Although this bedside detection device can use a recently developed conductive cloth, it is only a touch sensor and its area is small. Even if this device configuration is applied to a mat sensor with a large area, In addition to the wide detection range of capacitance, the mat itself has a large capacitance, so that it is difficult to detect even a slight change in capacitance when touched by a person and is not suitable for practical use. Moreover, this bed leaving condition detection apparatus is the structure which covered the sheet of conductive cloth with cloth, and there is a possibility that it is not suitable for practical use because of a large noise.

JP2007-213845 (first page)

The problem to be solved with respect to the mat sensor device using the conductive cloth is that the conventional touch sensor configuration for detecting a change in the electrostatic capacitance is not suitable for a sheet-like sensor having a large area such as a mat. It is not suitable for practical use because it is difficult to detect with a slight change in capacitance when touched, and is easily affected by noise.
Therefore, an object of the present invention is to provide a flexible sensor with a large area, and with one sensor, a conductive sensor that can distinguish between a touched state and a loaded state without being adversely affected by noise. An object of the present invention is to provide a mat sensor device using a cloth.

The present invention has the following configuration in order to achieve the above object.
According to one embodiment of the mat sensor device using the conductive cloth according to the present invention, the insulating cloth provided by the non-conductive cloth as the insulator and the front and back surfaces of the insulating cloth are laminated. The front side conductive cloth and the back side conductive cloth have a three-layer structure. Electric wires are attached to each of the front side and back side conductive cloths, and the function of a capacitor is given to form a mat, carpet, A mat sensor provided in a sheet shape, the conductive cloth on the front side is connected to a sensor detection circuit, the conductive cloth on the back side is connected to the ground side of the sensor detection board, and the conductive cloth on the front side is And the use of the fact that the capacitance of the electrode increases by increasing the area of the electrode when touched by a part of the body and / or an object including the foot, and the conductive cloth on the front side and the back side corresponding to the electrode part of the capacitor And the table And by applying a load on a part of the body including hands and feet and / or an object in the laminating direction of the laminated structure constituted by the insulating cloth between the conductive cloth on the back side and the insulating cloth, It is characterized in that it is used as a sensor by utilizing the fact that the capacitance increases due to the distance between the front and back conductive cloths being reduced by the flexibility of the cloth used.

  Also, according to one embodiment of the mat sensor device using the conductive cloth according to the present invention, a rectangular wave voltage pulse is output at regular intervals from the output port of the CPU connected to the conductive cloth on the front side. The time required for the voltage on the front side conductive cloth to rise to the set voltage and the time required for the voltage to fall to the set voltage from the voltage corresponding to the maximum voltage of the rectangular wave are connected to the front side conductive cloth via the input terminal. By measuring with the connected CPU, a change in electrostatic capacitance of the conductive cloth on the front side can be detected.

  According to the mat sensor device using the conductive cloth of the present invention, it is possible to make a flexible sensor with a wide area. With one sensor, a touched state and a loaded state are caused by noise. It has a particularly advantageous effect that it can be identified without being adversely affected.

It is a perspective view which shows typically the example of the form of the mat | matte sensor apparatus which uses the electroconductive cloth which concerns on this invention. It is a circuit diagram used for the mat | matte sensor of the form example of FIG. FIG. 3 is a time chart executed by the circuit of the embodiment of FIG. 2.

Hereinafter, the form example of the mat | matte sensor apparatus which uses the electroconductive cloth which concerns on this invention is demonstrated in detail based on an accompanying drawing (FIGS. 1-3).
The mat sensor device using the conductive cloth according to the present invention includes an insulator cloth 2 provided by a non-conductive cloth as an insulator, and the front-side conductivity laminated on the front and back of the insulator cloth. The cloth 1 and the back side conductive cloth 3 are formed into a three-layer structure, and electric wires are attached to the front side and back side conductive cloths 1 and 3 respectively, and the function of a capacitor is given to form a mat or carpet. And a mat sensor provided in a sheet form. In this embodiment, it is provided in a mat shape so that the conductive cloth 3 on the back surface is placed on the lower side.

  The conductive cloth 1 on the front side is connected to a sensor detection circuit (a circuit including the central processing unit CPU 13), and the conductive cloth 3 on the back side is connected to the ground (GND) side of the sensor detection board (CPU board) 7. It is equivalent to the electrode part of the capacitor while utilizing the fact that the area of the electrode increases when a part of the body including hands and feet and / or an object touches the conductive cloth 1 on the front side and the capacitance increases. Of the body including hands and feet in the laminating direction of the laminated structure composed of the conductive cloths 1 and 3 on the front and back sides and the insulating cloth 2 between the conductive cloths 1 and 3 on the front and back sides. By applying a load on the part and / or the object, the capacitance between the conductive cloths 1 and 3 on the front side and the back side is reduced due to the flexibility of the cloth used for the insulator cloth 2. Configured to use and use as sensor That.

  Further, a rectangular wave voltage pulse is output from the output port A of the CPU 13 connected to the front side conductive cloth 1 at regular intervals, and the time until the voltage of the front side conductive cloth 1 rises to the set voltage is rectangular. The time until the voltage drops from the voltage corresponding to the maximum voltage of the wave to the set voltage is measured by the CPU 13 connected to the conductive cloth 1 on the front side via the input terminal 8, so that the conductive cloth 1 on the front side is measured. It is configured to detect a change in capacitance.

  According to the mat sensor device using the conductive cloth having the above-described configuration, it is detected that the electrostatic capacity of the conductive cloth 1 on the front side has increased, and a person or an object has got on or a person or an object has touched it. Can be determined. If you only touch the mat, it is only a change in capacity due to the increase in the area of the electrode, but if a load is applied, in addition to the area of the part of the touched body, the distance between the electrodes will be closer. The capacitance increases. By utilizing this fact, it was possible to determine whether it was touched or on board by detecting the increased value of the capacitance when it was just touched on the mat and when it was on board. Thus, there has never been an inexpensive and thin sensor that can distinguish between a touched state and a loaded state with a single sensor. Although the present invention works in the same way as a capacitor, a general capacitor does not change its capacity. In the present invention, the capacitance of the capacitor is proportional to the size of the electrodes and has a characteristic inversely proportional to the distance between the electrodes, and the principle is suitably used.

Next, specific examples will be described in detail with reference to FIGS.
With 1 or 3 conductive cloths, 2 general cloths (insulating cloths) are sandwiched so that the structure shown in FIG. 1 is sandwiched, and 3 mats are stitched together to create one mat, which is as thin as a bath mat. 6 mat sensors were devised. The general cloth 2 is for insulation. Conductive threads and fabrics are already on the market. The conductive cloth of 1 is used as a sensor, and the noise entering the sensor also enters the conductive cloth of 3 as well, and it is connected to the GND side of the CPU board of 7 so as to cancel the noise. It was possible to have a capacitance and to stabilize it.

  FIG. 2 shows the overall configuration, and 6 is a mat sensor in which the three fabrics created in FIG. 1 are stitched together. The CPU is composed of 13 one-chip microcomputer type CPUs, one ADC input and four output ports of the 13 CPUs.

  Connect 4 terminals connected to 1 conductive cloth and 8 input terminals. 9 is connected to the output port A via a resistor 100 kΩ, and a pulse of 5 V is output from the output port A at a constant interval, and the capacitance time until the voltage rises to the set voltage and from 5 V to the set voltage The method of detecting the change was performed. As a result, the change in the capacitance of one conductive cloth directly connected to the ADC input of 13 CPUs can be measured.

  Next, in the present embodiment, the details of the produced substrate and the measuring method will be described. The time until the output port A is raised from 0V to 5V and the ADC input is changed from 0V to 3.2V, and then the output port A is raised from 5V to 0V until the ADC input is changed from 5V to 1.8V. The electrostatic capacity is calculated by the method of integrating the time of the above, and the average value of the normal electrostatic capacity values is determined. If the capacitance increased by 10% or more based on that, the output port D was set to 5V, the 12 digitra (digital transistor) was turned ON, and the detection signal of the 6 mat sensor was output to the 14 output terminals. .

  The 10 digitra is for rapidly setting the sensor potential to 5V after the ADC input is detected at 3.2V, and the 11th digita is for rapidly setting the ADC input to 1.8V after the ADC input is detected at 1.8V. However, in the case of a one-chip microcomputer that can switch the ADC input port to the output port, 10 digitra and 11 digitra are unnecessary. Furthermore, when using a CPU without ADC input, it is also possible to detect changes in capacitance by using a normal input port and measuring the time from 0V to 2.5V, and further from 5V to 2.5V. It is.

  In this embodiment, when the produced 6 mat sensors are connected to the 8 input terminals mounted on the 7 CPU boards, the time from the rise time of the output port A to the set voltage of the ADC input is the same. The fall time is about 150 μs each, and when the hand or foot comes into contact, it is about 200 μs, and there is a change of 30% or more. Therefore, even if there is a variation due to noise, it can be detected sufficiently. there were.

  By the way, the voltage change time due to the capacitance can be calculated from the following formula using the time constant of the capacitor (C) and the resistance (R) to change to about 3.2 V (64%) at a voltage of 5 V: .

Since the resistance R is 100 kΩ and the time for the ADC input voltage to rise from 0 V to 3.2 V is about 150 μsec, from the formula of T = CR, C = T ÷ R, C = 150 μsec ÷ 100 kΩ, C = It is 1500 pF, and it can be seen that the produced 6 mat sensors (60 cm × 100 cm) have a capacitance of about 1500 pF.
Moreover, since it was about 200 microseconds when the hand and the foot contacted, it is understood that it is about 2000 pF when calculated from the above formula.

As a result, they can be used as a reliable mat sensor device.
In addition, when a sensor with a large sensing area is required, it may be hard to fold and be packed and stored when it is made of metal, and it may be bent when thin metal is used, making it impossible to use. By using a highly flexible conductive cloth, a product without such a problem could be created.

  As described above, the present invention has been described in various ways with preferred embodiments. However, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. That is.

1 Conductive cloth 2 Insulator cloth (general cloth)
3 Conductive cloth 4 Conductive terminal 5 Conductive terminal 6 Mat sensor (mat made by stacking 3 cloths)
7 Sensor detection board (CPU board)
8 Input terminal 9 Resistance 10 Digitra (digital transistor)
11 Digitra (digital transistor)
12 Digitra (digital transistor)
13 CPU
14 Output terminal

Claims (2)

An insulator cloth provided by a non-conductive cloth as an insulator, and a front-side conductive cloth and a back-side conductive cloth laminated on each of the front and back sides of the insulator cloth are configured in a three-layer structure, A wire sensor is attached to each of the conductive cloth on the front side and back side, and a mat sensor is provided in the form of a cloth mat, carpet or sheet with the function of a capacitor.
The front-side conductive cloth is connected to a sensor detection circuit, the back-side conductive cloth is connected to the ground side of the sensor detection board, and the front-side conductive cloth includes a part of a body including hands and feet and / or Utilizing the fact that the area of the electrode increases when the object touches and the capacitance increases, and between the conductive cloth on the front side and the back side corresponding to the electrode part of the capacitor and the conductive cloth on the front side and the back side Depending on the flexibility of the cloth used for the insulator cloth, a load is applied to a part of the body including hands and feet and / or an object in the laminating direction of the laminated structure composed of the insulator cloth. A mat sensor device using a conductive cloth, which is used as a sensor by utilizing the fact that the capacitance increases as the distance between the conductive cloths on the front side and the back side decreases.   A rectangular wave voltage pulse is output at regular intervals from an output port of the CPU connected to the front side conductive cloth, and the time until the voltage on the front side conductive cloth rises to the set voltage and the maximum voltage of the rectangular wave The time required for the voltage to fall to the set voltage from the voltage corresponding to the above is measured by the CPU connected to the front side conductive cloth via the input terminal, thereby changing the capacitance of the front side conductive cloth. The mat sensor device using the conductive cloth according to claim 1, wherein

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