JPS62146011A - Detecting switch - Google Patents

Abstract

PURPOSE:To make the operation easy and set detection levels of many detecting switches on a uniform condition by storing the output of a signal receiving circuit for the absence of an object to be detected and that for the presence of the object and setting a threshold level of a comparing circuit automatically on a basis of stored outputs. CONSTITUTION:In the threshold setting operation of, for example, of a photoelectric switch, an output Vs of an amplifying circuit 6 is given to a comparing circuit 7, and a switch SW 1 is closed at this time to hold its voltage V1 in a peak holding circuit 10. The light between light projecting and receiving parts 1 and 4 is intercepted by an object 15, and a switch SW 2 is closed without giving the light from a light emitting diode 2 to a photo transistor 5. A voltage V2 of the output of the amplifying circuit 6 is held in a peak holding circuit 11, and the switch SW 2 is opened thereafter. The divider of a dividing circuit 13 is set to N larger than one (for example, 2), and its output Vf is given by Vf=(V1-V2)/N through a subtracting circuit 12. Thus, the level higher than the held value V2 by the voltage Vf is set to a comparing circuit 7 as a threshold level V0. A ratio of voltages V1 and V2 is calculated by a dividing circuit 15 and is compared with a prescribed value by a comparing circuit 16, and the state of detection is discriminated in accordance with the comparison result.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a detection switch for detecting an object, such as a photoelectric switch or a proximity switch, and particularly relates to a detection switch having a feature in a threshold level setting section of a comparison circuit thereof. .

[Summary of the invention]

The detection switch according to the present invention holds the outputs obtained from the signal receiving circuit when an object is present and when the object is absent, and automatically sets the threshold level of the comparison circuit based on the output difference, and also outputs an output depending on the presence or absence of the object. This method determines whether an object can be detected stably based on the level ratio.

[Prior art and its problems]

2. Description of the Related Art In conventional detection switches such as photoelectric switches and proximity switches, objects are detected by discriminating the output from a signal receiving circuit at a predetermined level. FIGS. 3 and 4 are block diagrams showing an example of such a conventional photoelectric switch. In these figures, a light projecting section 1 has a light emitting diode 2 as a light emitting element and a light projecting circuit 3 for driving the light emitting diode 2, and a light receiving section 4 is provided opposite to the light projecting section 1. The light receiving section 4 includes a phototransistor 5 that receives light from the light emitting diode 2 and converts it into an electric signal, an amplifier circuit 6 and a comparison circuit 7 that amplify the output thereof. Since the received light output changes depending on the object between the light emitting and receiving parts,
An object can be detected by discriminating the amplified output using a comparison circuit 7 at a predetermined threshold level.

Here, when the threshold level of the comparator circuit 7 is fixed as shown in Fig. 3, the amplification factor of the amplifier circuit 6 is changed by the variable resistor ■R1 based on the installation condition of the photoelectric switch, etc., to obtain an appropriate level. It needs to be adjusted to detect the object when the signal is obtained. Alternatively, as shown in FIG. 4, the amplification factor of the amplifier circuit 6 may be kept constant, and the threshold level of the comparator circuit 7 may be adjusted to an appropriate level by adjusting the variable resistor VR2. In this way, conventional detection switches require precise adjustment of the variable resistor according to the usage environment in order to detect the detected object at the appropriate level, which takes time and effort, and the detection level may vary depending on the operator. There was a problem in that there was a risk that variations would occur.

[Purpose of the invention]

The present invention was made in view of the problems of conventional detection switches, and it is possible to adjust the threshold value extremely easily and with the same accuracy, and to detect objects stably. It is an object of the present invention to provide a detection switch that can determine.

[Structure and effects of the invention]

The present invention is a detection switch having a first comparison circuit that provides a detection output of a detected object by discriminating the output of a signal receiving circuit using a predetermined threshold value, and the switch has a first comparison circuit that provides a detection output of a detected object. The first one holds the output of the signal receiving circuit when present. a second peak hold circuit; a first peak hold circuit; A subtraction circuit receives the output of the second peak hold circuit and calculates the difference, and a first subtraction circuit divides the subtracted value of the subtraction circuit by a predetermined value.
and the division output of the first division circuit and the first and second division circuits.
an arithmetic circuit that calculates an intermediate level by addition or subtraction with the output of either one of the peak hold circuits of the first and second peak hold circuits, and uses the calculated output as a reference input of a first comparison circuit; Second
a second division circuit that calculates the output ratio of the peak hold circuit; and a second comparison circuit that compares the output of the second division circuit with a predetermined value to determine the detection state of the detection switch. It is characterized by this.

According to the present invention having such characteristics, the outputs of the signal receiving circuit when the detected object is absent and present are stored respectively, and the threshold level of the comparison circuit is automatically set based on the outputs. I try to do that.

Therefore, it is no longer necessary to adjust the amplification factor of the amplifier circuit in the signal receiving circuit and the threshold level of the comparator circuit one by one using a variable resistor, and the threshold level can be set easily. Unlike when adjusting using a variable resistor or the like, it is possible to set the detection level under uniform conditions for many detection switches. Also, it is determined whether the object can be detected stably based on the stored output ratio of the signal receiving circuit when the object is absent and when the object is present. Therefore, the user can recognize the state of object detection based on this determination output.

[Explanation of Examples]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a transmission type photoelectric switch. In this figure, the same parts as in the conventional example are given the same reference numerals. In this embodiment as well, the light emitting diode 2 is driven by the light emitting circuit 3 of the light emitting part l, and the light is given to the phototransistor 5 of the light receiving part 4 and amplified by the amplifier circuit 6, which is the same as the conventional example described above. The same is true. In this embodiment, the output of the amplifier circuit 6, which is a signal receiving circuit, is applied to two peak hold circuits 10 and 11 via a comparator circuit 7 and switches SWI and SW2. The switch SWI is closed when an object does not block the light emitting/receiving section 1.4, and the output of the amplifier circuit 6 is applied to the peak hold circuit 10 to hold it.
is closed when an object blocks light, and supplies the output of the amplifier circuit 6 to the peak hold circuit 11 to hold it there.

The outputs of these peak hold circuits 10 and 11 are provided to subtraction circuits 12, respectively. The subtraction circuit 12 subtracts the output of the peak hold circuit 11 from the output of the peak hold circuit 10 and provides the resulting output to the division circuit 13. The division circuit 13 divides the difference between the peak values by a divisor N of 1 or more, for example, a value such as 2 or 3, and provides its output to the addition circuit 14. The output of one of the peak hold circuits 11 is supplied to the adder circuit 14, and the outputs are added together and the result is supplied to the comparator circuit 7 as a comparison output. The outputs of the peak hold circuits 10 and 11 are also provided to the divider circuit 15, respectively. The division circuit 15 calculates the ratio by dividing the value held by the peak hold circuit 10 by the value held by the peak hold circuit 11, and the output is sent to the comparison circuit 16.
give to This ratio is the output ratio of the amplifier circuit 6 depending on the presence or absence of an object, that is, the S/N ratio, and it can be said that the larger this ratio is, the better the detection state is. The comparison circuit 16 sets this ratio to a predetermined value, for example 1.5.
In this case, the display device 17, such as a light emitting diode, is driven.

Next, the threshold value setting operation of the photoelectric switch of this embodiment will be explained. First, the light emitting diode 2 of the light emitting section 1 is turned on and the light emitting/receiving section 1. An optical signal obtained when there is no object between the two amplifying circuits 6 is amplified by a predetermined amplification factor.

The output VS of the amplifier circuit 6 is given to the comparator circuit 7, but at this time, the switch SWI is closed and the peak hold circuit 1
Hold that voltage at 0. Next, after opening the switch SWI, the object 18 blocks light between the light emitting and receiving parts 1.4 so that the light from the light emitting diode 2 is not applied to the phototransistor 5, and the switch SW2 is closed. After holding the output of the amplifier circuit 6 in the peak hold circuit 11, the switch SW2 is opened. Here, the voltages held in the peak hold circuits to and 11 are V, respectively.

V2, these held values are given to the subtraction circuit 12. Then, the subtraction circuit 12 subtracts the subtracted value V3 (=VI V2) and provides the division circuit 13 with the subtracted value V3 (=VI V2). If the divisor of the division circuit 13 is N, then the division circuit 13
The output Vf of is given by the following equation.

Vf =V3/N= (Vl-V2)/N where divisor N
For example, let it be 2. Then, this division output Vf and the hold value V2 of the peak hold circuit 11 are added by the adder circuit 14 and applied to the reference input terminal of the comparator circuit 7. Therefore, as shown in FIG. 2, a level higher than the hold value 2 held in the peak hold circuit 11 by the voltage Vf can be set in the comparator circuit 7 as the threshold level Vo.

Here, if the ratio of the voltages V, . . . V2 held in the peak hold circuit 10.11 is small, the threshold level set in the comparison circuit 7 will be in the middle, but a sufficient SN ratio cannot be obtained. Therefore, the division circuit 15 calculates this ratio, and the comparison circuit 16 compares it with a predetermined value, 1.5 in this embodiment. If this ratio exceeds 1.5, the ratio of voltages V, V2 is large enough to stably detect an object, and the display 17
will be displayed. If this ratio is small, the display 17 will not light up, so it can be determined that the signal to noise ratio is poor and the detection condition is poor.

As described above, according to the present invention, an appropriate threshold level can be set for the detection switch with an extremely simple operation. Therefore, even if the usage status changes, the threshold value can be set according to the environment at that time. Also, stable object detection power 1
It is also possible to clearly identify whether or not the operation can be performed, thereby making it possible to prevent erroneous operations.

In this embodiment, when the output 2 of the amplifier circuit when the light emitting and receiving parts are blocked by an object is at a level lower than the output Vl of the amplifier circuit when no object exists, the adding circuit 14 calculates the peak value to the divided value Vf. The output v2 of the hold circuit 11 is added to the reference level of the comparison circuit 7, but if the detection switch has a high output from the signal receiving circuit when an object is present, the output from the signal receiving circuit when the object is not present is the same. It is necessary to set the reference level of the comparator circuit 7 by adding the output from the comparator circuit 7 to the division value. Alternatively, instead of the adding circuit 14, the reference level may be set by subtracting the division value from the output of the signal receiving circuit with the higher signal level when the object is present or absent.

Furthermore, although this embodiment has been described with reference to a transmission type photoelectric switch, the present invention is applicable not only to various other types of photoelectric switches but also to magnetic type,
It goes without saying that the invention can be applied to various detection switches such as ultrasonic type.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a photoelectric switch according to the present invention, FIG. 2 is a diagram showing its threshold level, and FIGS. 3 and 4 are block diagrams showing examples of conventional photoelectric switches, respectively. . l--...Light emitter 2---Light emitting diode
3.----Light emitter circuit 4-----1.Light receiving section 5
-・-Phototransistor 6・-1~---Amplification circuit 7,16・---Comparison circuit 10.11-
...-Peak hold circuit 12----Subtraction circuit
13.15−・−・−・Division circuit 14・−・・・・−
Adding circuit 17-...- Display 18-...-
·object

Claims (2)

[Claims] (1) In a detection switch having a first comparison circuit that provides a detection output of a detected object by discriminating the output of a signal receiving circuit using a predetermined threshold value, when the detected object is absent and when the detected object is present. first and second peak hold circuits that hold the outputs of the signal receiving circuit, respectively; a subtraction circuit that receives the outputs of the first and second peak hold circuits and calculates the difference therebetween; and the subtraction circuit. a first division circuit that divides the subtracted value of by a predetermined value; and an addition of the division output of the first division circuit and the output of either the first or second peak hold circuit; The intermediate level is calculated by subtraction, and the calculation output is used as the first
a calculation circuit that serves as a reference input for the comparison circuit; a second division circuit that calculates the output ratio of the first and second peak hold circuits; and a comparison circuit that compares the output of the second division circuit with a predetermined value. and a second comparison circuit that determines the detection state of the detection switch. (2) The first division circuit divides the subtraction output of the subtraction circuit into 1
2. The detection switch according to claim 1, wherein the detection switch is a dividing circuit that divides the output voltage by 2.