JP4737527B2 - Infrared touch switch - Google Patents

Description

  The present invention relates to an improvement of an infrared touch switch provided in a process device or the like for setting parameters from the outside.

FIG. 3 shows a circuit configuration showing an example of a conventional infrared touch switch. The drive circuit 1 including the rectangular wave generation unit 2 causes the rectangular wave drive current IF to flow through the light emitting element 3 to emit infrared light.
The emitted infrared light is reflected by the reflector 10 in contact with the operation panel 11 via the operation panel 11 and received by the light receiving element 4, whereby a photocurrent IL flows through the light receiving element 4. In the absence of the reflector 10, the photocurrent IL does not flow because infrared rays cannot be received.

  When there is the reflector 10, the photocurrent IL is converted into the voltage VL 1 by the resistor 5 and input to the comparator 6. The comparator 6 outputs a determination signal having information indicating whether the voltage VL1 is larger or smaller than the determination voltage 7 to the determination circuit 9. Accordingly, the determination circuit 9 determines the presence or absence of the reflector 10 and turns the switch on (ON) and off (OFF).

  When there is no reflector 10, that is, when the switch is off, the photocurrent IL does not flow at all. When the reflector 10 is present, that is, when the photocurrent IL flows only when the switch is on, only the presence or absence of the photocurrent IL is present. Can be used to determine whether the switch is on or off.

  However, in reality, the photocurrent IL does not become zero when the switch is off. This is because the infrared rays are reflected by the components of the case housing the infrared switch and are input to the light receiving element 4. The photocurrent at this time is IL (off).

  If the photocurrent when the switch is on is IL (on), the relationship IL (on)> IL (off) is established. Therefore, as shown in FIG. 4, the determination voltage 7 is set to IL (on) and IL (off). ) Corresponding to the voltage VL1 (on) and VL1 (off).

  However, the light transmission characteristics of the light emitting element 3 and the light receiving element 4 vary by several tens of times, and the photocurrent IL does not become constant even if the drive current IF is constant. For example, the voltage VL1 (on) may be 1V or 20V depending on the situation, and VL1 (on)> the determination voltage 7> VL1 (off) may not be satisfied. Therefore, it is necessary to individually adjust the determination level so that VL1 (on)> determination voltage 7> VL1 (off). Specifically, the sensitivity is adjusted by making the resistor 5 a variable resistor.

  In addition, when performing this sensitivity adjustment, it is necessary to consider an operational feeling. The voltage VL1 (on) increases as the reflector 10 is closer to the operation panel 11, and the switch is turned off when the reflector 10 is away from the operation panel 11. If the switch is turned on only when the reflector 10 touches the operation panel 11, a good operational feeling can be obtained. Therefore, sensitivity adjustment is performed so that the voltage when the reflecting object 10 touches the operation panel 11 is slightly larger than the determination voltage 7.

  The following Patent Document 1 describes an infrared touch switch that is provided in a process device or the like in order to set parameters from the outside.

JP 2003-273721 A

  Usually, since a plurality of infrared switches are used as operation switches, manual sensitivity adjustment is required by that number. For this reason, many man-hours are required, and there is a problem that it hinders cost reduction.

  In addition, sensitivity adjustment is performed in consideration of changes over time (characteristic deterioration) of components such as light emitting elements and light receiving elements, characteristic changes due to the usage environment such as ambient temperature, individual differences in reflectivity of reflective objects, etc. When these fluctuations are large, there is a problem that the switch cannot be operated or the operability is deteriorated.

  FIG. 5 shows an example of variation factors. Here, as an example of the variation factor, the photovoltage VL1 when a reflector having a different reflectance touches the operation panel is shown. A, B, C, D, and E show the difference in reflectance, and the reflectance increases in the order of A <B <C <D <E.

  In the case of A having the smallest reflectivity, it is impossible to determine on or off, that is, the switch cannot be operated. In the case of B, C, and D, the operation is possible. However, in the case of D having the highest reflectance, the operability is deteriorated. That is, since the switch is determined to be on even if the reflector 10 is away from the operation panel 11, the user's operation feeling does not match the actual setting operation, and the operation feeling is poor, leading to an incorrect setting. There is a problem that it ends up.

  Therefore, an object of the present invention is to eliminate manual sensitivity adjustment, thereby realizing cost reduction (reduction in manufacturing man-hours) and automatically adjusting sensitivity every time it is used. This is to prevent deterioration of the operational feeling due to the difference.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In the infrared touch switch that receives the light of the infrared light emitting element reflected by the reflective object touching the operation panel with the light receiving element, and determines the presence or absence of the reflective object,
A variable gain amplifier that is controlled by an error output so that a voltage converted by the light receiving element is input and a predetermined output voltage is set as a display mode;
An error amplifier that compares the output voltage of the variable gain amplifier with a reference voltage, amplifies the deviation, and outputs the error output;
A comparator that compares the output voltage from the variable gain amplifier with a determination voltage and outputs a determination signal;
A sample and hold circuit that holds an error output from the error amplifier and outputs it as a sample and hold signal;
The error output and the determination signal are input, the first specific operation is recognized by the error output, and the amplification factor of the variable gain amplifier is fixed by the sample hold signal from the sample hold circuit and then operates as a setting mode. And a control circuit that outputs the determination signal as a switch signal corresponding to the reflector, and controls to return to the display mode when a second specific operation is recognized,
Is provided.

  According to a second aspect of the present invention, in the first aspect of the invention, the first specific operation is such that the error output is constantly monitored and recognized when the error output has decreased for a predetermined time. .

  According to a third aspect of the present invention, in the first aspect of the invention, the second specific operation is recognized by an operation end signal input from an operator.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the error amplifier compares the output voltage of the variable gain amplifier with a reference voltage set slightly larger than the determination voltage. Is output.

As is apparent from the above description, the present invention has the following effects.
According to the first, second, third and fourth aspects of the present invention, the control circuit recognizes the first specific operation from the error output, and determines the amplification degree of the variable gain amplifier immediately before entering the setting mode. Since the determination signal is output as a switch signal corresponding to the reflecting object after being fixed by the hold value of the output mode, the sensitivity adjustment can be automatically performed and the cost can be reduced (manufacturing). This reduces the man-hours) and automatically prevents deterioration of the operational feeling due to changes over time, usage environments, individual differences in reflectors, and the like.

Hereinafter, the present invention will be described in detail with reference to the drawings.
First, an outline of a display setter using an infrared touch switch equipped in a process device such as an electromagnetic flow meter will be described.

This display setting device has a display device such as an LCD (Liquid Crystal Display Device) and a plurality of switches SW1, SW2, SW3 for setting parameters and the like from the outside. An infrared touch switch is used in combination with this display. These SW1, SW2, and SW3 correspond to infrared touch switches.

The display is displayed in two types of modes, a display mode and a setting mode. The display mode is a state in which a measurement result (flow rate value) or the like is normally displayed on a display setting device such as an electromagnetic flow meter. In addition, information such as warnings and error occurrences may be displayed. The point is that the user is informed of the state of the device.

The setting mode refers to a state in which a switch that can read / write the internal data of the device using the infrared touch switch is valid. In this setting mode, the internal data is checked or the data is changed by looking at the display.

  Next, the infrared touch switch will be specifically described. FIG. 1 is a block diagram showing an embodiment of an infrared touch switch according to the present invention. Parts having the same functions as those of the conventional infrared touch switch shown in FIG.

  In FIG. 1, a photocurrent IL is converted into a voltage VL2 by a fixed resistor 20, and the converted voltage VL2 is input to a variable gain amplifier 21. The variable gain amplifier 21 controls the gain of the voltage VL2 and outputs an output voltage at its output terminal. Output as SO.

  The error amplifier 22 compares the output voltage SO input to the inverting input terminal (−) with the reference voltage ES input to the non-inverting input terminal (+), amplifies the deviation, and generates an error at the output terminal. Output as output EO.

  The error output EO is applied to the a terminal of the switch 23 and also to the sample pole circuit 24 and the control circuit 25.

  The sample pole circuit 24 applies the sample hold signal SH sampled and held by the control signal CS from the control circuit 25 to the b terminal of the switch 23. The switch 23 switches between the a terminal and the b terminal while being controlled by the control signal CS, and applies the voltage applied to each terminal to the gain control terminal T of the variable gain amplifier 21 via the c terminal.

  On the other hand, in the comparator 26, the output voltage SO of the variable gain amplifier 21 is applied to the non-inverting input terminal (+), the determination voltage JE is applied to the inverting input terminal (-), and the magnitude of the determination voltage JE is determined. Then, the determination signal SJ is output from the output terminal. The determination voltage JE is set to a value slightly smaller than the reference voltage ES.

Further, the control circuit 25 receives the determination signal SJ and the error output EO, and further receives the second specific operation signal SA by the operation of the plurality of switches SW1, SW2, SW3, etc. of the display, and processes them. Then, the control signal CS is output to the switch 23 and the sample pole circuit 24, and the switch signal SS is output.

  Next, the operation of the infrared touch switch configured as described above will be described with reference to the waveform diagram shown in FIG.

In FIG. 2, the photocurrent IL is actually a rectangular wave like the drive current IF as shown in the waveform details of FIG. 2A, and the high level is ILH and the low level is ILL with respect to 0V. Although the current is a rectangular wave, it is indicated by a dotted envelope for easy understanding of the outline of the operation.

This is not limited to the photocurrent IL of FIG. 2C, but the output voltage SO (FIG. 2D) that is the output of the variable gain amplifier 21 and the error output EO that is the output of the error amplifier 22 (FIG. 2E). The same applies to the determination signal SJ of the comparator 26.

Therefore, when the control circuit 25 reads the output voltage SO, the error output EO, and the determination signal SJ, although not shown in FIG. 1, a signal synchronized with the rectangular-wave drive current IF is read. . The reason why the drive current IF is rectangular wave is that if the current is always supplied to the light emitting element 3, the life is insufficient.

  Display setters for process equipment such as electromagnetic flowmeters normally maintain a display mode that displays flow rate output values, etc., and only when the operator operates internal data To do. The following description is based on these two modes.

  First, the operation in the display mode will be described. The switch 23 is set to the a terminal side by the control circuit 25. Then, the output voltage SO at the output terminal of the variable gain amplifier 21 is controlled by the error amplifier 22 to be the same as the reference voltage ES, and becomes a constant value regardless of the photocurrent IL (FIG. 2D).

  Since the reference voltage ES is set to a voltage slightly higher than the determination voltage JE, the determination signal SJ, which is the output of the comparator 26, is always an ON signal in the display mode (FIG. 2 (F)). Since the control circuit 25 detects the continuation of the ON signal and invalidates it and does not output the switch signal SS (FIG. 2 (G)), it is not displayed on the display unit. Is displayed.

  Next, the transition from the display mode to the setting mode will be described. The error output EO that is the output of the error amplifier 22 changes according to the magnitude of the photocurrent IL. Therefore, the error output EO is constantly monitored by the control circuit 25, and when the error output EO decreases (FIG. 2E), the control circuit 25 touches the operation panel 10 with the reflector 10 (FIG. 2B). ) And shift to the setting mode (FIG. 2F).

  Normally, when an operator performs an operation (first specific operation) such as maintaining a specific switch, for example, SW1 in an ON state for a relatively long period of time, the error output EO (FIG. 2E) decreases during this period. Therefore, the control circuit 25 detects this, outputs the control signal CS to the switch 23, switches the c terminal to the b terminal, and outputs the error output held in the sample hold circuit 24 immediately before switching the variable gain amplifier 21. The gain corresponding to EO (FIG. 2E) is fixed (FIG. 2D).

  Next, the setting mode will be described. After shifting to the setting mode (FIG. 2F), the error output EO is held by the sample hold circuit 24 and the switch 23 is fixed to the b side. For this reason, since the gain of the variable gain amplifier 21 is fixed (FIG. 2D), the gain is reduced only when the reflector 10 touches the operation panel 10, that is, with a good operational feeling, the rectangular shape is output from the comparator 26. A wavy determination signal SJ is output, and the control circuit 25 outputs it as a switch signal SS.

  When the setting mode ends, the control circuit 25 recognizes that the second specific operation signal SA has been input to the control circuit 25 by the operator performing a second specific operation such as simultaneously pressing a plurality of switches SW1 and SW3, for example. Then, the control circuit 25 switches the switch 23 to the a terminal side and returns to the display mode.

It is a block diagram which shows one Example of this invention. It is a wave form diagram for demonstrating operation | movement of one Example of this invention. It is a block diagram which shows the conventional infrared touch switch. It is explanatory drawing explaining the setting of the determination voltage of the conventional infrared touch switch. It is explanatory drawing explaining the example of the fluctuation | variation factor of the conventional infrared touch switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive circuit 2 Rectangular wave generation part 3 Light emitting element 4 Light receiving element 5 Resistance 6, 26 Comparator 7 Judgment voltage 9 Judgment circuit 10 Reflector 11 Operation panel 20 Fixed resistance 21 Variable gain amplifier 22 Error amplifier 23 Switcher 24 Sample hold circuit 25 Control Circuit 26 Comparator SO Output Voltage EO Error Output SJ Judgment Signal SH Sample Hold Signal SS Switch Signal SA Second Operation Signal CS Control Signal SJ Judgment Signal ES Reference Voltage JE Judgment Voltage

Claims (4)

In the infrared touch switch that receives the light of the infrared light emitting element reflected by the reflective object touching the operation panel with the light receiving element, and determines the presence or absence of the reflective object,
A variable gain amplifier that is controlled by an error output so that a voltage converted by the light receiving element is input and a predetermined output voltage is set as a display mode;
An error amplifier that compares the output voltage of the variable gain amplifier with a reference voltage, amplifies the deviation, and outputs the error output;
A comparator that compares the output voltage from the variable gain amplifier with a determination voltage and outputs a determination signal;
A sample and hold circuit that holds an error output from the error amplifier and outputs it as a sample and hold signal;
The error output and the determination signal are input, the first specific operation is recognized by the error output, and the amplification factor of the variable gain amplifier is fixed by the sample hold signal from the sample hold circuit and then operates as a setting mode. And a control circuit that outputs the determination signal as a switch signal corresponding to the reflector, and controls to return to the display mode when a second specific operation is recognized,
An infrared touch switch comprising:   2. The infrared touch switch according to claim 1, wherein the first specific operation is continuously monitored by the error output and recognized when the error output has decreased for a predetermined time.   The infrared touch switch according to claim 1, wherein the second specific operation is recognized by an operation end signal input from an operator. The infrared touch switch according to claim 1, wherein the error amplifier compares the output voltage of the variable gain amplifier with a reference voltage set slightly higher than the determination voltage and outputs the error output.

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