JPH05151856A - Proximity switch drive apparatus - Google Patents

Abstract

PURPOSE:To enable automatic apt adjustment of the sensitivity of a proximity switch by controlling the capacitance value of a variable capacitance circuit through operation of a control circuit in response to the proximity switch. CONSTITUTION:The sensitivity of each proximity switch 10... at the time of a power source rise is compared, from a maximal initial state, with a threshold value A in a detection circuit 26 and a decision circuit 46 to function as means for increasing the capacity of a variable capacitance circuit 52 via a control circuit 51, resulting in that all the sensitivities become equal to or lower than the threshold value A to a normal condition. During normal operation, not only each proximity switch 10... but also a reference proximity switch RSW for correcting the detection signal level makes its detection operation. The reference proximity switch RSW sends a control signal to a mechanical drive circuit 53 via the control circuit 51 when it is decided in the decision circuit 46 that a human finger touches on a sensor electrode 11 and the signal exceeds an on point threshold value B. Simultaneously, the detection signal of the reference proximity switch RSW is made stable within a specified range of level by the variable capacitance circuit 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proximity switch drive device for inducing sneak noise of a commercial power source and driving an inductive proximity switch for detecting switch operation by capacitively coupling with the ground through a human body. ..

[0002]

2. Description of the Related Art Regarding the proximity switch used in various automatic vending machines, the applicant of the present application has already proposed some technical proposals in Japanese Patent Application Nos. 1-182995 and 3-16712.
No.

The proximity switch, which is the core of the technology proposed by the above application, basically induces sneak noise of the commercial power source and detects the switch operation by capacitively coupling with the ground through the human body. It is the one.

[0004]

By the way, since the above-mentioned proximity switch is an inductive type, in the process until it is actually installed in the vending machine, the sensitivity is greatly changed due to various factors, so that it can be put to practical use. There is a problem that it is difficult to set the operating point.

The influences on the sensor sensitivity of the proximity switch are (1) the positional relationship with the sensor surface of the metal part connected to the ground, and (2) the sensor surface and the DC G.
Positional relationship with ND, (3) electrical characteristics of a member inserted between the sensor surface and the near-side conducting object (human finger),
(4) Power supply capability, (5) Electronic component variation, (6)
The environment of the installation location (temperature, humidity, noise situation) can be mentioned.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a novel proximity switch driving device capable of automatically and appropriately adjusting the sensor sensitivity of the proximity switch.

[0007]

In order to achieve the above object, the present invention provides one or more proximity switches, a detection circuit for detecting the output of the proximity switches, and a power supply circuit for driving the proximity switches. Controlling the variable capacitance circuit according to the output of the detection circuit and the variable capacitance circuit connected between the primary side and the secondary side of the power supply circuit, between the secondary side and the ground, or between the primary side and the ground The proximity switch drive circuit is configured with a control circuit for controlling.

[0008]

The capacitance of the variable capacitance circuit can be controlled by the control circuit according to the output of the proximity switch, and the sensitivity of the proximity switch can be changed by the capacitance of the variable capacitance circuit.

Therefore, it is possible to automatically control the sensitivity of the proximity switch to an appropriate value.

That is, the research of the present invention revealed that the sensitivity of the proximity switch is basically determined by the coupling capacitance between the primary side and the secondary side of the transformer and the coupling capacitance between the secondary side and the ground. Specifically, if the coupling capacitance between the primary side and the secondary side of the transformer increases, the impedance decreases, the sneak noise of the commercial power source increases, and the sensitivity of the proximity switch increases. Also, if the coupling capacitance between the secondary side of the transformer and ground increases, the impedance between the secondary side of the transformer and ground decreases, and noise leaks from this path, reducing the sensitivity of the proximity switch. is there. Therefore, the sensitivity of the proximity switch can be controlled by controlling the variable capacitance circuit.When the output of the proximity switch is too large, the sensitivity is lowered, and when the output of the proximity switch is too small, the sensitivity is increased so that the sensitivity is always appropriate. It becomes possible to set it in the range.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings show an embodiment of the present invention. First, the structure of a proximity switch will be described. In FIGS. 1 to 4, reference numeral 1 denotes a front panel of various vending machines, for example. A frame 2 made of sheet metal having a boat shape is fixedly attached to the plate by mounting screws 4 via cushions 3 and 3. The frame 2 is connected to the ground by a member (not shown). The frame 2 is not limited in shape, and may be attached to a portion other than the front panel 1 such as an inner door. Rather, it may be preferable in terms of processing the front panel 1 and assembling the switch, or preventing rainwater from entering. On the back side of the front panel 1, a sheet-shaped name plate 5 having a symbol and a letter indicating that the sheet is on sale or sold out is attached.

A part of the proximity switch is provided on the back side of the name plate 5, 6 is a sub board, and 7 is a main board. The sub-boards 6 are smaller than the main board 7, and a plurality of sub-boards 6 are arranged at a predetermined interval in the parallel direction to the main board 7. It The child board 6 has two rectangular large and small Ls.
Windows 8 and 9 for ED are provided, and the circuit 4 of the proximity switch 10 as shown in FIG.
The sensor electrode 11 that constitutes a part of 1 is formed of a conductive plate. A resistor 1 is provided on the back side of the child board 6.
2, high resistance 13, inverter 14, and capacitor 1
Electronic components that constitute another circuit portion of the switch 10 composed of 5 and the like are mounted in the arrangement as shown in FIG. The high resistance 13 is usually about 10 megohm, but 700 megohm was used in the examples. Of course, this resistance is not absolute,
You may use the thing from about 0 megohm. As shown in FIGS. 1 and 4, elongated holes 6a are provided between the lands connecting the high resistances 13. From the child board 6, connecting pins 16 and 18 connected to the positive side and the negative side of the power source and a connecting pin 17 for output are drawn out, and these connecting pins 16, 17 and 18 are electrically connected to the parent board 7, respectively. And mechanically connected.

At a portion of the surface of the parent board 7 facing the child board 6 side, a conductive plate 19 constituting a shield portion is provided with a DC plate.
A connecting pin 18 which is formed as a GND and is connected to the negative side of the power source for driving the switch circuit 10 of the child board 6 is electrically connected to the conductive plate 19. The conductive plate 19 that constitutes the shield part
Although not shown, it may be provided on the back surface of the child board 6 or may be interposed as an independent member between the parent board 7 and the child board 6. When the independent member is formed, it may be formed in a box shape and the child board 6 may be housed with only the sensor surface thereof exposed. This configuration has the advantage that the shield is more complete. When the shield part is provided on the back surface of the sub-board 6, the other electronic components constituting the switch part 10 may be installed on the front surface of the sub-board 6 or at another place.

Between the child board 6 and the parent board 7, large and small L
Insulating bottom plate 22a provided corresponding to the ED windows 8 and 9
A plurality of reflect cases 22 having large and small reflecting mirrors 20 and 21 are provided corresponding to each child board 6, and the light emitting diodes 23, 24 and 25 housed in the reflecting mirrors 20 and 21 are installed. Each lead terminal 23a, 23a
.Bottom plate 22a by 24a, 24a, 25a, 25a
The shield portion is fixed to the parent board 7 through the via in a state of being electrically insulated. Among the light emitting diodes, the one with the indicator symbol 23 indicates that it is on sale, and the one with the indicator symbols 24 and 25 indicates that it is sold out.

Resistors 27, 28, diodes 29, capacitors 30, MOSFETs 31, etc., which are various electronic parts constituting a part of the detection circuit 26 as shown in FIG. 5, are mounted on the rear surface side of the main board 7. ing. Of the above-mentioned connecting pins, the one with the remaining indicator code 16 is a MOSFET.
The drain side of 31 and the power source are connected to the gate side of the MOSFET 31 via the resistor 27, respectively. The parent board 7 is fixed to the frame 2 via a plurality of spacers 32, 32 ... In a state of being electrically insulated by screws 33, 34, and 35 is installed in another part of the vending machine. It is a connector that is connected to the power supply circuit and the drive circuit of the machine section. Also, 3
Reference numeral 6 is a light emitting diode for reaction that indicates the approach of a human finger, 37 is its MOSFET, 38 is a Zener diode, and 39 is a resistor. Further, 23 and 24 are light-emitting diodes that indicate discontinuation of sales, 25 is a light-emitting diode that indicates that they are on sale, 40 and 41 are diodes that block reverse currents, and 42 and 43 are resistors.

Next, the overall circuit configuration and drive device of the proximity switch according to the present invention will be described. According to the drawings, FIG. 5 shows a proximity switch and a detection circuit, FIG. 6 shows the entire circuit configuration, FIG. 7 shows a judgment circuit, and FIG. 8 shows a power supply circuit and a variable capacitance circuit, respectively.

6, a switch group 44 includes a plurality of proximity switches 10, 10, ... And a sensor electrode 11,
11 ... etc. As shown in FIG. 5, each proximity switch 10 amplifies the potential change of the sensor electrode 11 by the CMOS inverter 14 and sends it to the detection circuit 26. Incidentally, RSW is a reference proximity switch, which has the same configuration as the proximity switches 10, 10 ... And is connected to the detection circuit 26 in the same manner, but the power circuit 45
It is different in that it is connected to the ground side of with a certain capacity. This reference proximity switch RSW is each proximity switch 1
It is provided to obtain a reference value for sensitivity adjustment of 0, 10 ...

Further, each proximity switch 10, 10, ...
Although not shown in FIG. 6, the RSW is configured to receive a current voltage from the scan + 5V terminal and send an output signal to the detection circuit 26, as shown in FIG.

Reference numeral 46 denotes each proximity switch 10, 10, ...
And a determination circuit for determining the proximity detection signal received from the reference proximity switch RSW via the detection circuit 26.
As shown in FIG. 7, the comparison circuit (A) 47 and the correction circuit 4
8, an adder / subtractor circuit 49, and a comparison circuit (B) 50.

The comparison circuit (A) 47 is a circuit for comparing the preset first threshold value A with the proximity detection signals from the proximity switches 10, 10 ... When all of the detection signals of 10 ..., That is, when none of them remains below the threshold value A, the correction circuit 48
Output signal to.

The correction circuit 48 stores the detection signal from the reference proximity switch RSW when it receives a signal from the comparison circuit (A) 47 as a correction reference value, and then detects the reference value and the reference proximity switch RSW. The difference from the signal is output as a correction value.

The adder / subtractor circuit 49 includes the proximity switches 10, 1
The detection signal from 0 ... is output after subtracting the reference value of the correction circuit 48.

The comparison circuit (B) 50 includes each addition / subtraction circuit 49.
The proximity switches 10, 10 ...
Is compared with a preset threshold value B, and this threshold value B is an on-point threshold value for judging the proximity of a human finger.

Reference numeral 51 is a control circuit which is controlled by the determination circuit 46 and controls the capacity of the variable capacity circuit 52 connected to the power supply circuit 45. Specifically, as shown in FIG. 8, the switching means S1, S2, S of the variable capacitance circuit 52.
The capacitance is controlled by sending a capacitance control signal for switching between S3 and S4 to the variable capacitance circuit 52.

The power supply circuit 45 transforms the commercial power supply by the transformer T as shown in FIG.
3 is full-wave rectified, smoothed, and stabilized in the power supply voltage, but the variable capacitance circuit 52 is connected between the primary side of the transformer T and the ground via capacitors 54, 55, 56. There is.

The variable capacitance circuit 52 includes capacitors C1 to C.
4 and the switching means S1 to S4 are connected in parallel to form a plurality of series circuits. In this example, there are four series circuits of which the first capacitor C1 is 330 pF and the second capacitor C2 is 680 pF.
The capacitance of F and the third capacitor C3 is set to 1330 pF.

Therefore, the switching means S1 to S4
Is selectively controlled by the control circuit 51 to change the capacitance value of the variable capacitance circuit 52 in the range of 0 to 5020 pF. The switching means S1
A photocoupler is used as S4.

Next, the operation will be described.

The proximity switch driving device is set to the initial state in which the sensitivities of the proximity switches 10, 10 ... Are maximized when the power is turned on. Specifically, the initial state is a state in which all the switching means S1 to S4 are off and the on-point is maximum.

From this initial state, the comparison circuit (A) 47 detects the detection signals of the plurality of proximity switches 10, 10 ...
The comparison with the threshold value A is sequentially performed. On the other hand, the proximity switch 1
The detection signals of 0, 10 ... Are supplied to the comparison circuit (B) 50 via the addition / subtraction circuit 49, and the comparison circuit (B) 5
An output signal of 0 is sent to the control circuit 51.

Then, the control circuit 51 outputs a capacitance control signal for increasing the capacitance of the variable capacitance circuit 52. As a result, the sensitivities of the proximity switches 10, 10 ...
The detection signal output from ... is reduced.

In this way, the sensitivity is gradually reduced. Such a decrease in sensitivity is caused by a plurality of proximity switches 1.
Even if one of 0, 10 ... Detected signal is larger than the threshold value A, it continues.

Then, all proximity switches 10, 10 ...
When the sensitivity decreases until the detection signal becomes smaller than the threshold value A, the normal state is reached.

In the normal state, the comparison circuit (A) 47 sends a signal to the correction circuit 48. Then, the correction circuit 48
Captures the detection signal of the reference proximity switch RSW at that time and stores it as a correction reference value.

In the normal state, the detection signals of all the proximity switches 10, 10 ... Are always compared with the on-point threshold value B by the comparison circuit (B) 50.

Then, one of the proximity switches 10 and 1
When the human body touches the sensor electrode 11 of 0 ... And the detection signal exceeds the on-point threshold value B, the control circuit 51 generates a control signal corresponding to the proximity switch 10.
It is sent to the machine unit drive circuit 53.

By the way, in the normal state, the reference proximity switch RSW also performs the detection operation similarly to the normal proximity switches 10, 10, ... And continues to output the signal to the correction circuit 48. Then, the value is compared with the correction reference value, and when a difference occurs, the difference component is substantially added to the on-point threshold value B, so that the finger of the human body is always in contact with the sensor electrode 11. The on-point is made constant.

Then, it is judged whether or not the detection signal of the reference proximity switch RSW is stable within a predetermined range, and when the detected signal deviates from the predetermined range, the switching means S1 of the variable capacitance circuit 52, depending on the deviation direction, S2, S3 and S4 are switched to keep the sensitivity within a predetermined range.

The operation of the proximity switch driving device according to the present application is summarized as follows. The sensitivity of the proximity switch is intentionally set to be high in the first initial state, and the sensitivity is adjusted so as to decrease the sensitivity. The point which became lower than the threshold value B was set as the optimum sensitivity.

Secondly, the reference proximity switch is provided with the same conditions as the other proximity switches, and the level of the detection signal of the other proximity switch is corrected according to the variation of the detection signal, so that the detection signal of the proximity switch is large. If there is a change, the installation capacity is changed to adjust the sensitivity.

Therefore, the problem that the sensitivity of the proximity switch fluctuates due to various factors and the operating point cannot be fixed stably can be solved.

Although the variable capacitance circuit 52 may be connected between the primary side and the ground as shown in FIG. 8, the variable capacitance circuit 52 is not necessarily limited to this. For example, as shown in FIGS. 9 (A) to 9 (C). As shown in the figure, various variations are conceivable in connection points.

The connection point of the variable capacitance circuit 52 may be before or after the rectifying bridge or regulator. In short, it suffices if the variable capacitance circuit can be connected between the primary side and the secondary side, between the secondary side and the ground, or between the primary side and the ground.

[0044]

As described above, according to the present invention,
Since the sensitivity of the proximity switch is adjusted by controlling the capacitance value of the variable capacitance circuit according to the output of the proximity switch by the control circuit, it is difficult to ensure normal operation because the sensitivity of the proximity switch fluctuates due to various factors. Can solve the problem.

[Brief description of drawings]

FIG. 1 is a partial front view of a proximity switch according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a side sectional view for explaining the structure of the proximity switch according to the present invention.

FIG. 4 is a partially exploded perspective view showing a main part of the proximity switch according to the present invention.

FIG. 5 is a partial circuit diagram of a proximity switch according to the present invention.

FIG. 6 is an overall circuit configuration diagram of a proximity switch driving device according to the present invention.

FIG. 7 is a detailed diagram of the determination circuit diagram of FIG.

FIG. 8 is a detailed view of the power supply circuit and the variable capacitance circuit of FIG.

9A and 9B are diagrams showing different variations of connection points of the variable capacitance circuit of FIG.

[Explanation of symbols]

 1 Front Panel 6 Sub Board 7 Parent Board 10 Proximity Switch 11 Sensor Electrodes 16, 17, 18 Connecting Pins 19, 19a Conductive Plate (Shield) 23, 24, 25, 36 Light Emitting Diode 26 Detection Circuit 41 Switch Group 44 Power Supply Circuit 45 Judgment circuit 46 Comparison circuit (A) 47 Correction circuit 48 Addition / subtraction circuit 49 Comparison circuit (B) 50 Control circuit 51 Variable capacitance circuit 52 Machine part drive circuit SW Proximity switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Matsubara 27-11 Oyamakanaicho, Itabashi-ku, Tokyo Inside Mini Pyro Electric Co., Ltd.

Claims (2)

[Claims] 1. One or more proximity switches, a detection circuit for detecting the output of the proximity switch, a power supply circuit for driving the proximity switch, a primary side / secondary side of the power supply circuit, and a secondary side. A proximity switch characterized by comprising a variable capacitance circuit connected between the grounds or between the primary side and the ground, and a control circuit for receiving the output of the detection circuit and controlling the capacitance value of the variable capacitance circuit. Drive. 2. The reaction circuit is provided with a reaction lamp for indicating the approach of fingers of a human body.
The proximity switch drive device according to claim 2.