JP2010204769A - Electrostatic capacity type coordinate input device - Google Patents

Abstract

In a capacitive coordinate input device, a panel for detecting coordinates has a structure of two ITO transparent electrode sheets, and bonding to the two sheets causes problems such as positional misalignment and scratches during bonding work, resulting in high costs. turn into. Provided is a capacitive coordinate input device having a function equivalent to that of a matrix system with a single ITO transparent electrode sheet.
A panel unit is formed by connecting switch electrodes with a bridge resistor to form a single panel switch in which connection electrodes are formed, and attaching the panel switch to an acrylic plate or the like. The control board has a built-in counter with an input capture function that can measure the width of a nonvolatile memory waveform for storing threshold data, and a connection electrode switching circuit, a C / F conversion circuit that converts capacitance changes to frequency using an oscillation circuit The CPU is configured.
[Selection] Figure 4

Description

  The present invention relates to a capacitance-type coordinate input device that employs a capacitance method as an input method.

The conventional capacitive coordinate input device shown in FIG. 1 includes a panel switch and a control board. The panel switch is composed of a plurality of X-line electrodes and a plurality of Y-line electrodes (Japanese Patent Laid-Open No. 2008-05279-FIG. 2, Japanese Patent Laid-Open No. 2007-141817) shown in FIG. 2, and is bonded to an acrylic plate or a transparent ABS resin plate. It's a thing. When a finger (conducting member) approaches the front panel, a parallel plate capacitor with a dielectric (insulator such as plastic, ceramic, glass, etc.) sandwiched between the line electrode (multiple X-line electrodes and multiple Y-line electrodes) and the finger As a result, the capacitance increases. Conversely, when the finger is removed from the front panel, the capacitance decreases.
The control board converts the capacitance change of the X line electrode and the Y line electrode into a voltage by a C / V (capacitance voltage) conversion circuit, and replaces it with digital data by a CPU ADC (A / D converter). The general operation principle of the capacitive coordinate input device is that the coordinate position is specified by detecting the intersection of the X line electrode and the Y line electrode from the calculation program.

JP2008-052729 JP2007-141817A

  In the capacitive coordinate input device, since the matrix is composed of the X line electrode and the Y line electrode, it is necessary to form a two-layer structure with two electrode sheets of the X line electrode sheet and the Y line electrode sheet. is there. There are two methods for constructing a two-layer structure: a method of bonding two X-line electrode sheets and a Y-line electrode sheet shown in FIG. 2-1, and an X-line electrode on the surface shown in FIG. There is a method of vapor-depositing an ITO transparent electrode having a Y line electrode on the back surface.

Ideally, ITO transparent electrodes are vapor-deposited on both sides, and the X-line electrode and Y-line electrode are composed of a single film, but the current technology has a poor yield (it is difficult to keep the resistance value constant). It is impossible to achieve without riding the base. Also, the method of bonding the ITO transparent electrode to the two sheets also causes problems such as misalignment and scratches during the bonding operation, resulting in high costs.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a capacitive coordinate input device with a single ITO transparent electrode sheet in order to solve the above problems.

  A capacitive coordinate input device having a control board comprising a panel switch, a CPU, a C / F conversion circuit, a nonvolatile memory, and a connection switching circuit, wherein the panel switch is formed by an ITO transparent pattern A plurality of connection electrodes in which a plurality of bridge resistors and switch electrodes are alternately connected are provided in parallel, and the capacitance of the connection electrodes in a non-contact state is registered in a nonvolatile memory, and the connection electrodes are connected in a contact state. The position of the switch electrode is calculated by comparing the difference between the capacitance of the connection electrode, which is measured by sequentially switching both ends of each connection electrode by the switching circuit, and the capacitance of the non-contact state registered in the nonvolatile memory. An electrostatic capacitance type coordinate input device to be specified is proposed.

  According to the present invention, when a capacitive coordinate input device is configured, it can be configured with one ITO transparent electrode sheet, and a low-cost capacitive coordinate input device can be configured without bonding work.

Configuration diagram of conventional capacitive coordinate input device Matrix type panel switch Structure of connected electrode type panel switch Configuration diagram of capacitive coordinate input device System configuration diagram of capacitive coordinate input device Coordinate identification mechanism 1 Coordinate identification mechanism 2 Coordinate detection circuit

The present invention comprises a connection electrode type panel switch and a control board as shown in FIG. As shown in FIG. 3, the connection electrode type panel switch has a structure in which the switch electrodes are connected by a bridge resistor to form a connection electrode and is attached to a transparent plate such as acrylic.
The control board sequentially switches the connection electrodes of the panel switch, a C / F conversion circuit that converts the capacitance change using the oscillation circuit into a frequency change, a non-volatile memory for storing the frequency change, and a waveform width It consists of a CPU with a built-in counter with an input capture function that can be measured.

Hereinafter, the coordinate specifying mechanism of the present invention will be described with reference to FIG.
The oscillation frequency of the LMC 555 used in the oscillation circuit of FIG. 5 is determined by the time constant of C1 and R1. The calculation formula of the frequency is presented as f = 1.4C × R (Application Information 7 for LMC555 CMOSTimer) from the LMC555 data sheet manufactured by National Semiconductor. When the oscillation frequency is applied to the calculation formula based on the LMC555 data sheet, the following calculation formula is obtained.
In the connection electrode switching circuit, the non-contact state and the contact state at the connection electrode are applied to the calculation formula.
1-1) Connect L1A with the connection electrode switching circuit shown in FIG. 6 and measure the frequency.
・ Calculation formula of frequency in non-contact state F1A = 1.4C1 × R1
・ Calculation formula of frequency in contact state f1A = 1.4 (C1 × R1 + C2 × mR)
・ Change amount Δ1A = F1A−f1A = −1.4C2 × R
1-2) Connect L1B in the connection electrode switching circuit shown in FIG. 7 and measure the frequency. Formula for calculating frequency in non-contact state F1B = 1.4C1 × R1
・ Calculation formula of frequency in contact state f1B = 1.4 (C1 × R1 + C2 × nR)
・ Change amount Δ1B = F1B−f1B = −1.4C2 × nR
(Where m and n are the number of bridge resistors, m + n = 6, and R is a bridge resistor of about 2KΩ)
1-3) Rate of change relative to the amount of change in L1A and L1B Change rate Δ1A / Δ1B = (− 1.4C2 × mR) / (− 1.4C2 × nR)
= M / n
1-4) Specify a switch from the relationship of m + n = 6 When SW01 is in a contact state, since m = 1 and n = 5, m: n = 1: 5
When SW02 is in contact, m = 2 and n = 4, so m: n = 1: 2.
When SW03 is in contact, m: 3 n = 3 m: n = 1: 1
When SW04 is in contact, m: 4 n = 2, so m: n = 2: 1
When SW05 is in contact, m = 1, n = 5, m: n = 5: 1
Based on the above theory, the switch in the contact state can be specified by measuring the frequencies at both ends (L1A and L1B) of the connecting electrode. Similarly, it is possible to specify which switch is in contact by measuring the frequencies of L2A, L2B, L3A, L3B, L4A, and L4B at both ends of the connection electrode.

First, in order to measure the non-contact state of the panel switch shown in FIG. 8, a control signal is output from the I / O terminal 2 of the CPU to the connection electrode switching circuit so that the L1A line is connected, and C / The frequency output from the F conversion circuit is measured by the input capture function of the CPU, and the measured frequency data is registered in the nonvolatile memory connected to the I / O terminal 1 of the CPU. Similarly, the frequency is measured in order of L1B, L2A, L2B, L3A, L3B, L4A, and L4B from the I / O terminal 2 of the CPU to the connection electrode switching circuit, and is registered in the nonvolatile memory. The values at that time are assumed to be F1A, F1B, F2A, F2B, F3A, F3B, F4A, and F4B.
Next, when the contact state is measured, L1A measures SW01, L1B measures SW05, L2A switches SW06, L2B switches SW10, L3A switches SW11, L3B switches SW15, L4A switches SW16, and L4B switches SW20 to measure the frequency. Register in the memory. At that time, the value obtained by subtracting the contact state frequency from the non-contact state frequency stored in the non-volatile memory is used as the change amount, and 70% of the change amount is registered in the non-volatile memory as the contact state threshold data in consideration of variations and errors. To do.

Next, a method for specifying that SW07 is in a contact state will be described with reference to FIG. From the connection electrode switching circuit, it is measured in order from L1A to L4B whether the frequency change amount exceeds the threshold data registered in the nonvolatile memory. Since L2A and L2B exceed the threshold data, it can be confirmed that any one of the switches SW06 to SW10 is in contact. The connection electrode switching circuit connects to L2A and measures the change amount Δ2A. Next, the connection electrode switching circuit is connected to L2B, and the change amount Δ2B is measured.
Based on the above theory, since the change rate Δ2A / Δ2B = 0.5, it can be determined that SW07 is in a contact state.

Claims (1)

A capacitive coordinate input device having a control board comprising a panel switch, a CPU, a C / F conversion circuit, a nonvolatile memory, and a connection switching circuit, wherein the panel switch is formed by an ITO transparent pattern A plurality of connection electrodes in which a plurality of bridge resistors and switch electrodes are alternately connected are provided in parallel, and the capacitance of the connection electrodes in a non-contact state is registered in a non-volatile memory, and the connection electrodes are connected in a contact state. The position of the switch electrode is calculated by comparing the difference between the capacitance of the connection electrode that is sequentially measured by switching the both ends of each connection electrode and the non-contact state capacitance registered in the nonvolatile memory. A capacitance type coordinate input device characterized by specifying.