JPH06332603A - Wireless coordinate reader - Google Patents

Abstract

PURPOSE:To constitute the reader so that the variance of parts precision can be allowed, and also, many (four pieces or more) switch states can be detected easily by a small number of switches by providing a coordinate indicator to which a coil, a capacitor circuit and a resistance circuit are connected in series. CONSTITUTION:An energizing scanning circuit 20 applies in order an AC signal VDS supplied from a variable oscillating circuit 21 to an energizing line 2 of a tablet 1. A control circuit 22 finds a coordinate value of a position in which a coordinate indicator 23 is placed from an amplitude signal AS and a position difference signal PS, and also, discriminates an operated switch. The coordinate indicator 23 is provided with an LCR resonance circuit to which a coil 24, a capacitor circuit 25 to which plural capacitors and switches are connected, and a resistance circuit 26 to which plural resistances and switches are connected in series and parallel are connected in seiries. Accordingly, the coordinate indicator 23 can vary singly a resonance frequency and a loss, respectively, and can set the resonance frequency and the loss in which the variance of parts precision of the coil and the capacitor is taken into consideration.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a wireless coordinate reader.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 4-44116 discloses a technology of a wireless coordinate reading device capable of discriminating a switch operated by a coordinate indicator. Hereinafter, description will be given with reference to the drawings. ◆ Fig. 7 is a block diagram of the coordinate reading device.
FIG. 8 is a circuit configuration diagram of the coordinate indicator. In the figure, 1 is a tablet in which two excitation lines and three sense lines are laid. An excitation scanning circuit 4 is composed of a plurality of electronic switch elements such as analog switches, and is designed to excite the AC signal DS supplied from the excitation circuit 5 according to an excitation selection signal DA from a control circuit 9 described later. Apply to line 2. The AC signal DS is obtained by converting the digital signal DC of the reference frequency supplied from the control circuit 9 into a predetermined AC signal by the exciting circuit 5. Reference numeral 6 denotes a sense scanning circuit, which is composed of an electronic switch element, selects the sense line 3 designated by the sense selection signal SA from the control circuit 9, and is a signal induced on the sense line 3 (hereinafter, detection signal). IS) is output to the phase detection circuit 7 and the amplification detection circuit 8. The phase detection circuit 7 detects the detection signal I
The phase of S and the digital signal DC are compared and the phase difference signal PS is output to the control circuit 9. The amplification detection circuit 8 detects the detection signal IS
Is amplified and detected, and the amplitude signal AS of the detection signal is output to the control circuit 9. The control circuit 9 is composed of a microprocessor and outputs the signals such as DA, DC, and SA described above. The control circuit 9 also controls the amplitude signal AS and the phase difference signal PS.
The coordinate value is calculated from the above, and which switch of the coordinate indicator 10 has been operated is determined by the method described later. That is, the circuit of the coordinate indicator 10 is an LC resonance circuit in which a switch and a resistor (S ₁₁ , R _11, etc.) connected in series, a coil L ₁₁ and capacitors C ₁₁ , C ₁₂ are connected. Now, the resonance frequency when all the switches are off is f _A (where f _A = 1 / {2π√ (L ₁₁ ·
C ₁₁ )}), the resonance frequency becomes f _B (where f _B = 1 /) by turning on at least one switch.
[2π√ {(L ₁₁ · (C ₁₁ + C ₁₂ )}]).
Also, depending on the value of the resistor connected in series with the switch, L
The loss of the C resonance circuit (that is, the phase of the detection signal) also changes. Therefore, the change in the phase of the detection signal IS is detected to determine which switch is on.

[0003]

However, the parts precision of the coil and the capacitor vary widely, and the characteristics greatly change due to temperature fluctuations, so that the phase of the detection signal IS greatly changes in the LC resonant circuit. For example, the switches in FIG. 8 are S ₁₁ , S ₁₂ , and S ₁₃ , the inductance of the coil L ₁₁ is L ₁₁ = 0.6 mH, and the capacitance of the capacitors C ₁₁ and C ₁₂ is C ₁₁ = 400 pF, C ₁₂ = 80
pF, resistance values of the resistors R _{11 to} R ₁₃ are R ₁₁ = 13.2 kΩ,
When R ₁₂ = 5 kΩ and R ₁₃ = 2 kΩ, the frequency response corresponding to switch off, S ₁₃ only, S ₁₂ only, and S ₁₁ only is P _0L , P _1L , P _2L shown by the solid _{lines in} FIG. 9. ,
It becomes P _3L . Now, the frequency f ₁ (about 3
AC signal of 10 KHz) is applied, and L of the coordinate indicator 10 is applied.
When the phase of the detection signal IS due to the electromagnetic coupling between the C resonance circuit and the sense line 3 is measured, A
The phase angle at point D is obtained. If the values of C ₁₁ and C ₁₂ are decreased by 5% or the value of L ₁₁ is decreased by 5% due to temperature fluctuations, the phase characteristics are indicated by dotted lines P _0H , P _1H ,
Since it changes like P _2H and P _3H , it becomes impossible to determine which of the switches S ₁₂ and S ₁₁ is turned on for the phase angle at the point C. As is apparent from FIG. 9, in the above case, if the frequency of the AC signal DS applied to the excitation line 2 group is set to, for example, 315 KHz, even if the values of C ₁₁ and C ₁₂ or L ₁₁ fluctuate by 5%, the switch is switched. The condition can be detected correctly. However, if not only variations in component accuracy but also changes in characteristics due to temperature fluctuations are included, the appropriate frequency range is narrow, and the work of optimizing circuit constants is extremely difficult. Furthermore, in order to increase the number of switches to four or more, it is necessary to reduce the variation in component accuracy of the coil and the capacitor to 1% or less. An object of the present invention is to allow variations in parts precision of coils and capacitors and to detect a large number (four or more) of switch states easily and with a small number of switches.

[0004]

SUMMARY OF THE INVENTION The above-mentioned problems are solved by the following: a coordinate indicator, a coil, a capacitor circuit in which a plurality of capacitors and switches are connected in series and parallel, and a resistor circuit in which a plurality of resistors and switches are connected in series and parallel. And a coil, a capacitor circuit, and a resistor circuit are connected in series, and the resonance frequency and loss of the circuit can be independently varied. This is solved by making it possible to supply an AC signal to the excitation line group.

[0005]

The circuit of the coordinate indicator is a series circuit of a capacitor circuit in which a coil, a plurality of capacitors and switches are connected in series and parallel, and a resistor circuit in which a plurality of resistors and switches are connected in series and parallel. Therefore, the resonance frequency and the loss can be individually changed, and the resonance frequency and the loss can be set in consideration of the variation in the component accuracy of the coil and the capacitor. Therefore, the switches can be pushed multiple times, and the number of switches can be reduced. Furthermore, the output of the phase detection circuit when the frequency is set to a value lower than the resonance frequency of the LC resonance circuit determined by the capacitor circuit of the coordinate indicator and the output of the phase detection circuit when the frequency is set to a higher value than the resonance frequency of the LC resonance circuit. The state of the switch can be reliably discriminated from the difference.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is a block diagram of the coordinate reading device, and FIG. 2 is a circuit block diagram of the coordinate indicator. The same parts as those in FIGS. 7 to 8 are designated by the same reference numerals. Reference numeral 20 denotes an excitation scanning circuit, which is composed of a plurality of electronic switch elements such as analog switches, and the AC signal VDS supplied from the variable oscillation circuit 21 is designated according to an excitation selection signal DA from a control circuit 22 described later. It is applied to the excitation line 2. The AC signal VDS is a frequency designation signal FS which is a digital signal DC of a reference frequency input from the control circuit 22.
Is a signal converted into an alternating current of a frequency corresponding to. Reference numeral 6 denotes a sense scanning circuit, which is a sense selection signal S from the control circuit 22.
The sense line 3 designated by A is selected, and the detection signal IS is output to the phase detection circuit 7 and the amplification detection circuit 8. The phase detection circuit 7 compares the phases of the detection signal IS and the AC signal VDS and outputs the phase difference signal PS to the control circuit 22. The amplification detection circuit 8 outputs the amplitude signal AS of the detection signal IS subjected to amplification detection to the control circuit 22 and provides information for calculating coordinate values. The control circuit 22 is composed of a microprocessor and outputs the signals such as DA, FS, and SA described above. Further, the control circuit 22 calculates the coordinate value from the amplitude signal AS and the phase difference signal PS and determines the operated switch. Reference numeral 23 is a coordinate indicator in which a coil 24 (inductance L ₁ ), a capacitor circuit 25 in which a plurality of capacitors and switches are connected in series and parallel, and a resistance circuit 26 in which a plurality of resistors and switches are connected in series and parallel are connected in series. It has an LCR resonant circuit.

Before explaining the operation below, it should be noted that the resonance frequency and the loss of the resonance circuit (that is, the phase of the detection signal) can be switched in four ways respectively (a),
It will be described below with reference to (b) that the variation in component accuracy of the coil and the capacitor can be tolerated. ◆ (a): Example of switching the resonance frequency to four frequencies having the same interval ◆ The resonance frequency is switched by the capacitor circuit 25 shown in FIG. ◆ constituting the capacitor circuit 25 with four capacitors C ₁ -C ₄ and the two switches S _3, S _4.
Now, assuming that the inductance L _{1 of the} coil 24 is 0.6 mH, C ₁ = 130 PF, C ₂ = 180 PF, C ₃ = 75 P
When F and C ₄ = 91PF, the resonance frequency of the coordinate indicator becomes as follows by turning on and off the switches S ₃ and S ₄ . ◆ (1) When switches S ₃ and S ₄ are both off: 507 KHz
◆ (2) When switch S _{3 is} on and S _{4 is} off: 437 KHz
◆ (3) When switch S _{3 is} off and S _{4 is} on: 368 KHz
◆ (4) When switches S ₃ and S ₄ are both on: 298 KHz
◆ The capacitance C _AB between terminals A and B is 164P each.
F, 221PF, 311PF and 477PF.

(B): Loss of the resonance circuit is separated by 4
Example of switching as follows ◆ The switching of the loss is performed by the resistance circuit 26 shown in FIG. The resistance circuit 26 is composed of three resistors R _{1 to} R ₃ and two switches S ₁ and S ₂ . Now, R ₁ = 267Ω, R ₂
= 100Ω and R ₃ = 30Ω, switches S ₁ and S ₂
The combined resistance value R _BC between the terminals B and C, that is, the loss of the resonance circuit of the coordinate indicator becomes as follows by turning on and off. ◆ (5) When switches S ₁ and S ₂ are both off: 100Ω ◆ (6) When switches S _{1 are} on and S _{2 are} off: 57Ω ◆ (7) When switches S _{1 are} off and S _{2 is} on: 27Ω ◆ ( 8) When switches S ₁ and S ₂ are both on: 0 Ω ◆ That is, the loss of the resonant circuit is 100 Ω with an almost equal interval.
It can be switched to 4 types of 57Ω, 27Ω, and 0Ω. ◆ (c): An example of allowing variation in component accuracy of coils and capacitors. ◆ The component constants of the coordinate indicator 23 are the same as those in (a) and (b) above, and the switches S ₃ and S ₄ are turned on. Then, the inductance L _{1 of the} coil 24 is set to 0.57 mH to 0.6 mH
In the range of 0.01 mH. In addition, the frequency of the AC signal applied to the excitation line 2 group is L ₁ = 0.5
315 KHz (f ₂ ), which is 10 KHz higher than the resonance frequency 305 KHz obtained by calculation with 7 mH, and L ₁ =
The resonance frequency is 288 KHz (f ₁ ) which is 10 KHz lower than the resonance frequency at 0.6 mH. ◆ Under the above conditions,
The phase of the current flowing through the coil when the switches S ₁ and S ₂ are turned on / off in combination is shown in FIG.
In the figure, subscripts 0 to 3 in the curve P are switch states (0: S ₁ and S ₂ are both on, 1: S ₁ off, S ₂
On, 2: S ₁ on, S ₂ off, 3: S ₁ , S ₂ off)
And the subscripts A to D are the differences in the inductance of the coil (A: 0.60 mH, B: 0.59 mH, C: 0.58).
mH, D: 0.57 mH). Also, 0-3
, The phase difference corresponding to the switch state, that is, the frequency f ₁
And the phase P (f ₁ at the frequency f ₂
Is the difference between the _{2) (P (f 1)} -P (f 2)) of the calculation results are shown in Table 1. In addition, in the same table, in order to clarify the difference between the present invention and the conventional technique, the calculation result of the conventional technique (the frequency of the AC signal applied to the excitation line 2 group is f ₃ (= 270K
Hz) and the P when (f ₃₎₎ are also shown.

[0009]

[Table 1]

The comparison between the present invention and the prior art based on the table is as follows. (A) In the present invention, the phase difference in each switch state is 2 to
It is 4 °, and the fluctuation range is small as compared with the phase difference of 2 ° to 6 ° of the conventional technique. (B) In the present invention, the range of the phase for judging the switch state is as wide as 14 to 16 ° corresponding to each switch state, and the phase margin is greatly improved as compared to the conventional technique of 2 to 3 °. . ◆ From the above (a) and (b), in the present invention, the switch state can be easily discriminated and variations in the coil inductance can be tolerated. ◆ In the case of the above-mentioned conventional technique, the fluctuation of the coil inductance is allowed and the switch state can be correctly detected in the range where the phase angle difference is clear and does not intersect. In FIG. 5, the above condition is satisfied only in the frequency range of about 270 KHz ± 5 KHz, and the phase difference between the switch states (hereinafter referred to as the phase margin) is small. Considering this, it is difficult to stably determine the switch state.

The operation will be described below with reference to FIG.
◆ The states of the switches S _{1 to} S ₄ are identified by the steps (A) to (C). As described in (a) and (b) above, two switches each can be switched in four ways, so that by pressing switches S _{1 to} S ₄ multiple times, 16
The switch status of the street can be detected. When the circuit constants are the same as those in (a) and (b) above, the frequency characteristic is as shown in FIG.
become that way. That is, the combination of the switches S ₃ and S ₄ makes the resonance frequency 4 groups, and the switch S ₁
There are four phases depending on the combination of S ₂ and S ₂ (P ₀₀ ~
P ₀₃ , P _{10 to} P ₁₃ , P ₂₀ to ₂₃ , P ₃₀ to ₃₃ ), and coil current (I _{00 to} I ₀₃ , I ₁₀ to ₁₃ , I ₂₀ to ₂₃ , I ₃₀ to ₃₃ )
Characteristics are divided into 4 groups. (A) From the control circuit 22 to the variable oscillation circuit 21, see FIG.
The frequency designation signal FS corresponding to f _L is output, and the excitation selection signal DA is further output to select one of the excitation lines. In this state, the sense selection signal SA is output and it is determined whether or not the amplitude signal AS of the detection signal is above a certain level (a threshold value for distinguishing when the coordinate indicator 23 is on the excitation line and when it is not). When the amplitude signal is below a certain level (hereinafter referred to as AS off), the sense selection signal SA is switched to scan all sense lines. Next, the procedure of switching the excitation selection signal DA and scanning all the sense lines (hereinafter referred to as line scanning) is repeated until all the excitation lines have reached a certain level (hereinafter referred to as AS ON). Line scanning is performed by switching (hereinafter referred to as area scanning). If the AS is not turned on even after the area scan is completed, the area scan is performed by outputting the frequency corresponding to f _H in FIG. 6 as the frequency designation signal FS (hereinafter referred to as F scan). If the AS is not turned on even after the F scan is completed, the F scan is repeated while alternately switching the frequency designation signal FS to f _L and f _H. It should be noted that in the present embodiment, by determining whether the phase is positive or negative, two _values of f _L and f _H can be obtained.
It makes four kinds of discrimination in one. (B) When AS ON is detected during the F scan, the phase difference signal PS is measured to determine whether the phase is positive or negative. Depending on the combination of the positive / negative of the phase and the frequency designation signal (f _L / f _H ), it is possible to determine which of the four resonance frequencies (the combination of switches S ₃ and S ₄ is 0 to 3). Become. (C) When AS is detected, in addition to the resonance frequency determination in (B) above, the excitation selection signal DA and the sense selection signal S are added.
When the frequency designation signal FS is switched from the resonance frequency determined in the above (B) to a frequency lower by a certain frequency (the frequency corresponding to f _{1 in} FIG. 5) while keeping A as it is when AS is detected. The phase difference signal PS1 and the frequency difference signal PS2 when the frequency designation signal FS is switched from the resonance frequency to a frequency higher than the resonance frequency by a constant frequency (the frequency corresponding to f _{2 in} FIG. 5), and the difference between PS1 and PS2 is measured. And the states (0 to 3) of the switches S ₁ and S ₂ are determined based on P (f ₁ ) −P (f ₂ ) in Table 1.

In the present embodiment, the frequencies f ₁ and f ₂ for detecting the switch state are set to ± 10 KHz with respect to the resonance frequency, but the upper and lower widths may be different. Further, although the method of pressing the switches multiple times is not specifically described, for example, the switches 1, 2, 3, 4 are associated with the weighting codes 1, 2, 4, 8 respectively, and the switches 1 and 3 are pressed. Sometimes code 5 (= 1 +
4) may be output. And, "1", "2", on the surface of the switch button of the coordinate indicator,
Operability is marked with "4" and "8", for example, when inputting the switch code 6, pressing "2" and "4" (the added value of the pressed key becomes the input code). Can be improved.

[0013]

As described above, according to the present invention, it is possible to tolerate variations in the precision of parts of coils and capacitors, and to easily switch a large number (4 or more) of switches, and to switch a large number of switches with a small number of switches. The effect is that the state can be detected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a coordinate reading device according to the present invention.

FIG. 2 is a circuit configuration diagram of a coordinate indicator according to the present invention.

FIG. 3 is a circuit example of a capacitor circuit.

FIG. 4 is a circuit example of a resistance circuit.

FIG. 5 shows the relationship between frequency and phase in the present invention.

FIG. 6 shows the relationship between the resonance frequency and the phase angle in the present invention.

FIG. 7 is a configuration diagram of a conventional coordinate reading device.

FIG. 8 is a circuit configuration diagram of a conventional coordinate indicator.

FIG. 9 shows a conventional relationship between frequency and phase.

[Explanation of symbols]

 1 tablet 2 excitation line 3 sense line 7 phase detection circuit 21 variable oscillation circuit 23 coordinate indicator 24 coil 25 capacitor circuit 26 resistance circuit

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Seiichi Nakano 2100 Kamiimazumi, Ebina City, Kanagawa Prefecture, Hitachi Seiko Co., Ltd.

Claims (2)

[Claims] 1. A coil, a capacitor circuit in which a plurality of capacitors and switches are connected in series and parallel, and a resistance circuit in which a plurality of resistors and switches are connected in series and parallel, wherein the coil, the capacitor circuit, and the resistance circuit are connected in series. A tablet which is connected to the magnetic resonance indicator and is configured to be able to independently change the resonance frequency and loss of the circuit, and a tablet which is provided with a variable oscillation circuit and is capable of supplying AC signals of a plurality of frequencies to the excitation line group. And sequentially supplies AC signals of a plurality of frequencies to the excitation line group, and the coordinate value of the position where the coordinate indicator is placed and the coordinate indicator switch from the supplied AC signal and the induction signal induced to the sense line group. The wireless coordinate reading device is characterized in that 2. The output of the phase detection circuit when the frequency of the AC signal applied to the excitation line group is set to a frequency lower by a constant value than the resonance frequency of the LC resonance circuit determined by the capacitor circuit of the coordinate indicator, and a high value by a constant value. 2. The wireless coordinate reading device according to claim 1, wherein the switch state of the coordinate indicator is determined from the difference between the output of the phase detection circuit when the frequency is set.