RU2507563C1 - Design of capacitance button - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: design of a capacitance button comprises the following components serially arranged along the height and in contact with each other: an upper transparent conducting metal coating 1 on a protective glass 2, a lower transparent conducting metal coating 3 on the glass 2, a ring 4 with vertical slots from conducting rubber resting against a plastic ring 5, under which there is an electronic circuit board 6 with a sensitive electrode 7 on its upper side. At the same time coatings 1 and 3 are made in the form of sectors separated between each other by gaps, and the lower coating 3 is pressed at the bottom without a gap along the perimeter of the protective glass 2 by the ring 4 from conducting rubber to provide contact with the sensitive electrode 7 of the electronic circuit board 6.

EFFECT: higher sensitivity of a button.

3 dwg

Description

The invention relates to proximity switches (triggered when approaching), made using capacitive detectors, and can be used in measuring technique, for example, in pressure sensors, flow sensors, etc.

Known design capacitive buttons, described in p. RF №238071 class. H03K 17/955, s.22.08.07, op. 09/20/09.

A well-known capacitive touch device button includes sensitive electrodes, one of which is located under the external dashboard of a button made of non-conductive material and connected to an AC voltage source, and the other sensitive electrode located below the above sensitive electrode is connected to a capacitance to digital code converter and differs the fact that it further comprises at least one, for example, a laser LED, an external control device, the output of which is connected connected to the LED control circuit, the output of which is connected to the LED located in the rectangular cut-out of both sensitive electrodes, under the external instrument panel of the button made of non-conductive material, and the output of the capacitor into a digital code is connected to the input of an external control device.

The design provides visualization of the state of the button, which leads to the complexity of the electronic part of the device.

The known design of the capacitive button, presented in the article "Microchip Technology Solutions for the implementation of touch control on capacitive sensors" on the site (see the appendix to the application) and selected as a prototype.

The known button contains a printed circuit board with a sensitive conductive coating deposited on top of it - an electrode that is grounded, and a protective plate (nameplate) made of a dielectric located on top.

The main element necessary for the implementation of such a button is a variable capacitor. It has a simple design and sensitivity to touch. Since the sensitive element is constructed as an “open” capacitor, the electric field can interact with an external capacitive object, in this case, a finger.

The value of the introduced capacitance C is proportional to:

- dielectric constant of vacuum ε _0;

- relative dielectric constant ε of the material between the conductive coating and, for example, a finger:

- the area of overlap S;

- inversely proportional to the distance d between the conductive coating and the sensitive electrode:

C = ε × ε0 × S / d

The sensitivity of the button depends on the distance between the conductive and ground layer. Recommended distance = 0.5 mm. In addition, the overall sensitivity of the button depends on the thickness of the protective dielectric plate: sensitivity decreases with decreasing thickness. Recommended plate thickness 1 ... 1.5 mm.

The capacity of the sensor without the capacity of the finger is about 5 ... 10 pF.

The ground layer below the button shields it from other electronic components of the system. It also helps to maintain a constant base capacity, which is required as a reference for each measurement.

A disadvantage of the known design is its low sensitivity due to the use of a thick protective plate, which is often required by operating conditions, the presence of air gaps between the elements of the button, and the small area of contact between the finger and the button.

In particular, when using such a button in a measuring device, for example a pressure sensor, a protective plate of glass 10 mm thick is used, which critically reduces the sensitivity of the button. In addition, air gaps between the different layers worsen sensitivity, as air has a low dielectric constant ε≈1.

In this case, the contact area when pressed with a finger is small, which reduces the overlap area for the inserted capacity (S≈1cm ² )

The presence of a display in the sensor limits the area of the capacitive buttons in the version with the placement of buttons on the board.

The objective is to increase the sensitivity of the button.

The problem is solved in that in the design of the capacitive button containing a protective glass sequentially arranged in height and in contact with each other and a sensitive electrode located on top of the electronic circuit board, according to the invention, transparent conductive metal coatings are applied to the protective glass from above and below, under the coating on the bottom the side of the glass is placed in contact with a ring of conductive rubber, made with vertical slots and resting on a plastic ring, under which Position the electronic card with a sensing electrode, wherein the coating made in the form of sectors separated by a gap, and the lower cover without clearance pressed against the bottom perimeter of the glass of the conductive rubber ring for contacting the sensing electrode with the electronic board.

The presence of transparent metal coatings on the upper and lower surfaces of the protective glass provides an increase in the contact area, which, together with the placement of a ring of conductive rubber pressing it around the perimeter of the lower transparent metal coating, removing the air gap between the protective glass and the sensitive electrode on the electronic board, increases the sensitivity buttons when touching its surface.

The technical result is an increase in capacity when touching the surface above the conductive electrode.

The inventive design of the capacitive button has a novelty in comparison with the prototype, differing from it by such significant features as the presence of transparent conductive metal coatings on the protective glass on top and bottom, placement of a contacting ring of conductive rubber made with vertical slots under the coating on the underside of the glass and resting on a plastic ring, under which there is an electronic board with a sensitive electrode, making coatings in the form of sectors divided between oh gap preload dense undercoating below without gap on window perimeter of the conductive rubber ring for contacting the sensing electrode with the electronic board providing a plurality of achieving the desired result.

The applicant is not aware of technical solutions that have the indicated distinguishing features, which together provide the desired result, so he believes that the claimed design of the capacitive button meets the criterion of "inventive step".

The inventive design of a capacitive button can be widely used in measurement technology, and therefore meets the criterion of "industrial applicability". The invention is illustrated by drawings, which are presented in:

- figure 1 is a side view in section of the design of a capacitive button;

- figure 2 is a view of the design of a capacitive button during assembly;

- figure 3 is a view of a transparent metal coating on the surfaces of the protective glass.

The inventive design of the capacitive button (1, 2) contains sequentially arranged in height and in contact with each other the upper transparent conductive metal coating 1 on the protective glass 2, the lower transparent conductive metal coating 3 on the glass 2, ring 4 with vertical slots of conductive rubber, based on a plastic ring 5, under which there is an electronic board 6 with a sensitive electrode 7 on its upper side. At the same time, coatings 1 and 3 (Fig. 3) are made in the form of sectors 8, separated by gaps 9, and the lower coating 3 is pressed from below without a gap around the perimeter of the protective glass 2 by a ring 4 of conductive rubber to ensure contact with the sensitive electrode 7 of the electronic board 6.

Structurally, coatings 1 and 3 can be made by sputtering or gluing a film with ITO. The ring of conductive rubber is, in particular, Zebra strip.

When the operator touches the coating 1 with a finger on the protective glass 2 due to the above-described button design, the capacitance increases significantly, which increases the sensitivity of the button, and it reliably works.

Compared with the prototype, the inventive design of the capacitive film has a higher sensitivity.

Claims (1)

The design of the capacitive button, containing a protective glass sequentially arranged in height and in contact with each other and a sensitive electrode located on top of the electronic circuit board, characterized in that transparent conductive metal coatings are applied to the protective glass from above and below, under contact with the glass a ring of conductive rubber, made with vertical slots and resting on a plastic ring, under which there is an electronic board with an electrode, while the coatings are made in the form of sectors separated by a gap, and the lower coating is pressed from below without a gap around the glass perimeter by a ring of conductive rubber to ensure contact with the sensitive electrode of the electronic board.

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