JP2004201175A - Input means having electrostatic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an input means having an electrostatic sensor which is miniaturized yet can surely detect an input and output the detected result and is excellent in responsiveness and reliability. <P>SOLUTION: The input means has a clock signal generating means 2 for generating a clock signal, a delay means 6 for generating a delay signal by imparting delay of rising to the clock signal in accordance with electrostatic capacitance that is detected when a human body approaches or touches an electrostatic sensor 5, an AND means 3 for outputting an output signal with the clock signal and the delay signal as its input signals, an analog switch 9 for switching and outputting the output of the AND means 3 according to the clock signal, and a smoothing means 10 for smoothing and outputting the output of the analog switch 9. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an input unit having an electrostatic sensor, and more particularly to an input unit having an electrostatic sensor that outputs an electric signal when a part of a human body such as a hand or a finger approaches or comes into contact with the human body.
[0002]
[Prior art]
Generally, electrostatic sensors are widely used as input means in various applications. For example, mobile phones that have become widespread in recent years are used as information input means for numbers and characters.
[0003]
This electrostatic sensor has an electrode provided inside a predetermined position which is an input portion of a housing serving as a case of a mobile phone. An output is generated by detecting a change in capacitance of a housing interposed therebetween.
[0004]
[Problems to be solved by the invention]
In the conventional electrostatic sensor, the size of the electrode was large and the thickness of the housing was thin, so that the capacitance of the electrostatic sensor greatly changed when a finger was touched, and the response was high. .
[0005]
However, with the demand for miniaturization and multi-functionality of mobile phones, there is a demand for miniaturization of electrodes and increase in the thickness of the housing in electrostatic sensors. It is becoming difficult to detect an input due to contact or the like.
[0006]
The present invention has been made in view of these points, and an input means having an electrostatic sensor excellent in responsiveness and reliability, which can reliably detect and output an input of a miniaturized electrostatic sensor. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the input means having the electrostatic sensor of the present invention comprises a clock signal generating means for generating a clock signal, and a capacitance detected when a human body approaches or contacts the electrostatic sensor. Delay means for giving a rise delay to the clock signal to generate a delay signal; AND means for outputting an output signal using the clock signal and the delay signal as input signals; and switching an output of the AND means by the clock signal. And an analog switch for smoothing and outputting the output of the analog switch.
[0008]
With this configuration, the input of the miniaturized electrostatic sensor can be reliably detected and output, resulting in excellent responsiveness and reliability.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0010]
FIG. 1 shows an embodiment in which input means having the electrostatic sensor of the present invention is applied to a mobile phone.
[0011]
As shown in FIG. 1, a clock signal generating means 2 of a microcomputer 1 built in a mobile phone outputs a clock signal serving as a drive wave as one input signal of an AND circuit 3 serving as an AND means. The input side of the AND circuit 3 is connected to a delay unit 6 including a resistor 4 and an electrostatic sensor 5 connected in series from the clock signal generation unit 2 side. The delay means 6 outputs a delayed signal obtained by adding a rising delay to the clock signal in accordance with the capacitance detected when a human body approaches or contacts the electrostatic sensor 4 as another input signal of the AND circuit 3. I do. As illustrated in FIG. 2, the electrostatic sensor 4 is formed by attaching an electrode 8 to an inner surface of a housing 7 of a mobile phone. An analog switch 9 that switches the output of the AND circuit 3 by a clock signal and outputs the output is connected to the output side of the AND circuit 3. The analog switch 9 may be of any known type. The output side of the analog switch 9 is connected to a resistor 11 and a capacitor 12 as a smoothing means 10 for smoothing and outputting the output. The output of the smoothing means 10 is connected to be output to an AD converter 13 provided in the microcomputer 1.
[0012]
Next, the operation of the present embodiment will be described.
[0013]
A clock signal CK composed of a regular pulse signal (one cycle length is T1 and half cycle length is T2) of a predetermined frequency as shown in FIG. Output to the circuit 3.
[0014]
When the human body is not touching the electrostatic sensor 5, while the clock signal CK passes through the delay means 6, based on the time constant CR determined by the resistance value R of the resistor 4 and the capacitance C of the electrostatic sensor 5. An analog output as shown in FIG. 3B is input to the AND circuit 3.
[0015]
The capacitance C of the electrostatic sensor 5 can be generally expressed by Expression 1.
[0016]
C = ε (S / d) (Equation 1)
Here, ε is the dielectric constant of the housing, S is the facing area between the counter electrode and the human body, and d is the facing distance between the electrodes. Here, the dielectric constant ε is constant.
[0017]
When the threshold SL between the H level and the L level of the AND circuit 3 is set as shown in FIG. 3B, the logical product of the AND circuit 3 becomes a pulse of T3 time as shown in FIG. It becomes.
[0018]
On the other hand, when the human body 14 is in contact with the electrostatic sensor 5, the clock signal CK is determined by the resistance value R of the resistor 4 and the capacitance C of the electrostatic sensor 5 while passing through the delay unit 6. An analog output as shown in FIG. 3D is input to the AND circuit 3 based on the constant CR.
[0019]
When the threshold SL between the H level and the L level of the AND circuit 3 is set to the same as that shown in FIG. 3D as shown in FIG. 3D, the logical product of the AND circuit 3 becomes As shown in FIG.
[0020]
Each output of the AND circuit 3 shown in FIGS. 3C and 3E is switched by the clock signal CK in the analog switch 9 and output to the smoothing means 10. After that, the smoothing means 10 smoothes the signal based on a time constant C1 · R1 determined by the resistance value R1 of the resistor 11 and the capacitance C1 of the capacitor 12, outputs the smoothed signal to the AD converter 13, and then outputs the signal to the AD converter 13. , For example, are converted into digital values of d0 to d7.
[0021]
In the present embodiment, since the analog switch 9 is used, the amount of change in the output voltage of the smoothing means 10 when the human body is in contact with the electrostatic sensor 5 and when the human body is not in contact with the electrostatic sensor 5 is expressed by the following equation (2). It becomes street.
[0022]
V = {(T3-T4) / T2} VDD (Equation 2)
On the other hand, in the conventional example in which the analog switch 9 in FIG. 1 is not provided, the amount of change in the output voltage of the smoothing means 10 when the human body is in contact with the electrostatic sensor 5 and when the human body is not in contact with the electrostatic sensor 5 is expressed by the following equation. 3
[0023]
V = {(T3-T4) / T1} VDD (Equation 3)
Comparing Equations 2 and 3, the voltage change in the present embodiment is larger by (T1 / T2) than in the conventional example.
[0024]
Therefore, according to the present embodiment, even if the capacitance of the electrostatic sensor 5 is limited to a small value, the contact / non-contact state of the human body can be reliably and accurately detected, and the response can be improved. It is excellent in performance and reliability.
[0025]
Note that the present invention is not limited to the above-described embodiment, and can be changed as needed.
[0026]
【The invention's effect】
As described above, since the input means having the electrostatic sensor of the present invention is configured and operates, the input of the miniaturized electrostatic sensor can be reliably detected and output, and the responsiveness and reliability are improved. It has effects such as being excellent.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing one embodiment of input means having an electrostatic sensor according to the present invention; FIG. 2 is a side view showing one embodiment of the electrostatic sensor; FIG. 3 is a signal in each part of the circuit of FIG. Time chart showing [Description of code]
2 clock signal generating means 3 AND means (AND circuit)
5 electrostatic sensor 6 delay means 9 analog switch 10 smoothing means

Claims (1)

Clock signal generating means for generating a clock signal, and delay means for generating a delay signal by giving a rise delay to the clock signal in accordance with the capacitance detected when a human body approaches or touches the electrostatic sensor. AND means for outputting an output signal using the clock signal and the delay signal as input signals, an analog switch for switching the output of the AND means by the clock signal and outputting the output signal, and a smoothing means for smoothing and outputting the output of the analog switch And an input means having an electrostatic sensor.

Images