JPS624806B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a touch switch that detects a touch by a person and outputs a detection signal.

FIG. 1 shows an example of a conventional touch switch circuit. This includes a touch plate 10 that is touched by a person, an input capacitor 11, a bias resistor 12, input overvoltage protection diodes 13 and 14, a sensitivity adjustment volume 15, an operational amplifier 16, and a bias transformer 17. In such a configuration, when a person touches the touch plate 10, the voltage induced in the human body by surrounding electrical equipment etc. is input to the touch plate 10, and the voltage is transferred to the operational amplifier 16.
Since the input resistance of is very high, input capacitor 1
1 and the bias resistor 12, and is inputted to the inverting input terminal of the operational amplifier 16 as the input voltage _Vb . The input voltage V _b is the sensitivity adjustment volume 15
Therefore, when the comparator voltage V _p becomes higher than the preset comparator voltage V p , the output voltage V _p of the operational amplifier 16 becomes the potential of the negative bus N rather than the positive bus P by the inverting comparison circuit constituted by the operational amplifier 16 , and is output as a detection signal. It is output to a control device (not shown). The relationship between the input voltage V _b and the comparator voltage V _p is as shown in FIG. Note that R indicates a registration signal and COM indicates a common bus (zero bus).

However, the induced voltage around the touch switch may be weak, or the touch plate 1 may be inserted through an insulating material such as a glove.
In order to fully function as a touch switch even if the touch switch touches
COM is AC biased by a bias transformer 17 connected to an AC power supply 18.
The AC bias voltage output from the bias transformer 17 causes a bias current to flow through the bias resistor 12, the input capacitor 11, the human body capacitance 19, and the ground. This bias current causes a positive bias voltage V _b to appear across bias resistor 12 during the negative half cycle. Therefore, similarly to the above, when the bias voltage V _b exceeds the comparator voltage V _p as shown in FIG.
The output voltage V _p of No. 6 becomes the potential of the negative bus line N, and becomes a detection signal. As mentioned above, since the AC bias circuit is added, the detection signal which is the output signal of the operational amplifier 16 cannot be directly connected to other directly grounded control circuits, and must be separated from the power source. Therefore, the power supply system becomes complicated. Also, if a short circuit failure occurs in the input capacitor 11, it is natural for a person to touch the touch plate 1.
When you touch zero, a large amount of current flows through your body due to the AC bias, and you will feel an electric shock, which is extremely dangerous. Furthermore, when installing the touch switch or adjusting the sensitivity using the sensitivity adjustment volume 15, if the adjuster accidentally touches a part other than the touch plate 10, a large amount of current will be applied to the human body due to the AC bias as described above. The flow is dangerous. Furthermore, when the distance between the touch switch and the control device is long, that is, when the wiring distance becomes long, the load impedance of the AC bias becomes small due to stray capacitance between the wirings, and the capacity of the bias transformer 17 becomes large, which becomes very uneconomical. Become.

SUMMARY OF THE INVENTION An object of the present invention is to provide a touch switch that can solve the problems of conventional touch switches and has a push button function.

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 4 shows a circuit of an embodiment of a touch switch according to the present invention, and parts having the same functions as those in the circuit of FIG. 1 are given the same numbers.

The circuit of this touch switch includes a touch plate 10, an input resistor 20, a bias resistor 12, input overvoltage protection diodes 13 and 14, an input sensitivity adjustment volume 15, an operational amplifier 16 forming an inverting comparison circuit,
It is composed of a switch 21. Note that the input resistor 20 uses an internal resistance formed by the outer part (conductive part) of the switch 21.

FIG. 5 shows an example of the structure of such a touch switch. A button 22 made of an insulating material such as acrylic, a metal touch plate 10 that can be touched with a finger, a substrate 23 forming the touch switch circuit described above, a pattern printed on this substrate 23, and a touch plate 1 described above.
A switch 24 (corresponding to the resistor 20 and switch 21 in FIG. 4) made of conductive rubber connects 0, a bolt 27 welded in advance to the surface plate 26, and a hole formed in which the button 22 can move forward and backward. It is composed of a spacer 28 for fixing the surface plate 26 and the substrate 23 provided, a nut 29, and an indicator light 30 formed on the substrate 23.

The switches 24 used in this invention are all made of conductive rubber, and the outside always connects the pattern of the touch plate 10 and the substrate 23. Also, when the inner protrusion is pressed, it shorts the pattern on the substrate 23. Its stroke is usually 0.2-0.3mm.

When a person touches the touch plate 10, the commercial frequency alternating current voltage that has been induced therein passes through the outer part of the switch 24 and is transmitted to the pattern on the board 23. In other words, in FIG. 4, when a person touches the touch plate 10, the AC voltage induced in the person is input to the inverting input terminal of the operational amplifier 16 due to the voltage division ratio of the input resistor 20 and the bias resistor 12. The voltage V _b is the voltage V _p set by the sensitivity adjustment volume 15,
When it exceeds the voltage, the inverting comparison circuit by the operational amplifier 16 operates, and the output voltage V _p becomes the same potential as the negative bus line N, and is output as a detection signal. In this case, since the switch 21 operates by its own mechanical deformation, the energization can be opened and closed reliably.

On the other hand, when a person not only touches but also presses the button 22, the conductive rubber switch 24 is pressed, and the protrusion on the inside of the switch 24 shorts the pattern on the board 23, resulting in a so-called push button switch. work. In other words, in FIG. 4, switch 21 corresponds to this, and when a person presses button 22,
The switch 21 is short-circuited, and the potential of the positive bus P is input to the inverting input of the operational amplifier 16. This potential is naturally the voltage V _p set by the volume 15.
Since it is larger, the inverting comparison circuit formed by the operational amplifier 16 operates, and the output voltage V _p becomes the potential of the negative bus line N, and is output as a detection signal.

Note that the present invention is not limited to the above-mentioned embodiment; for example, as shown in FIG. good. In addition, various modifications can be made without changing the gist of the invention.

Since the touch switch according to the present invention described above does not use an alternating current bias, there is no electric shock and is very safe. If no voltage is induced in the human body or if you touch it through an insulating material such as gloves,
There is no need to unnecessarily increase the sensitivity of the touch switch in order to detect it as a push button, so there are fewer malfunctions.Furthermore, if you use a low stroke switch made of conductive rubber, it will be almost as easy as a conventional touch switch with no stroke. Indistinguishable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional touch switch circuit, FIG. 2 is an input/output waveform diagram of the same example, FIG. 3 is a diagram showing the AC bias principle of the same example, and FIG. 4 is a diagram of a touch switch circuit according to the present invention. A diagram showing one embodiment, FIG. 5 is a partial sectional view showing the structure of the same embodiment,
FIG. 6 is a partial sectional view showing a modification of the touch switch according to the present invention. 10... Touch plate, 11... Input capacitor, 12... Bias resistor, 13, 14... Input overvoltage protection diode, 15... Sensitivity adjustment volume, 16... Operational amplifier, 17... Bias transformer, 18... AC power supply, 20... Input resistance, 21, 24... switch, 22... button, 23... board, 26... surface plate,
27...Bolt, 28...Spacer, 29...Nut, 30...Indicator light.

Claims (1)

[Claims] 1. A touch plate made of a conductive member that is provided in a hole formed in a surface plate so that it can move forward and backward, a detection board that has a built-in circuit that outputs a detection signal when a signal of a predetermined level or higher is input, and this detection It is interposed between the conductive part of the board and the touch plate, and when a person touches the touch plate, an induced voltage is applied as an input signal to the detection board through the outer part, which is the conductive part. A touch switch comprising a switch made of conductive rubber that is deformed and operates as a mechanical switch and applies an external voltage introduced to the detection board to the detection board as corresponding to the input signal.