JPH0330165B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] In an input circuit that converts a contact signal into a voltage signal, the on/off of the contact is handled by the connection method between the contact and the current limiting resistor, power supply, and ground. Since the polarity change of the voltage signal output is different,
By detecting the mismatch between the output voltage signal level and the voltage level at the other end of the current limiting resistor connected to the voltage signal output terminal and generating an output, the contact It is possible to obtain a voltage signal output that changes the same polarity depending on the on/off state. However, when a large number of such circuits are used, the number of mismatch detection circuits increases.

In the method of the present invention, a mismatch detection circuit is provided corresponding to one group obtained by dividing a large number of input circuits, and the voltage signal output of the input circuit of each group is switched and applied to the mismatch detection circuit. , the circuit size is reduced and the number of circuit components is reduced.

[Industrial application field]

The present invention relates to a circuit system for converting an interface signal from a controlled object into a voltage signal, and particularly relates to an input circuit system for converting an interface signal consisting of a contact signal or a signal equivalent thereto into a voltage signal. It is.

Generally, in numerical control devices (NC) and programmable controllers (PC), signals different from those of the internal control logic are used as interface signals with controlled objects such as machine tools, so these devices requires an input circuit to convert the interface signals into signals for the internal control logic.

In such an input circuit, if the interface signal is a contact signal, it is necessary to generate a voltage signal change of the same polarity when the contact turns on/off, regardless of the configuration of the contact signal generation circuit. In addition, even when there are a large number of contact signal generation circuits, it is desired that the configuration be as simple as possible.

[Conventional technology]

Figure 3 shows a conventional input circuit, and there are two types depending on the connection method in the conversion circuit that converts a contact signal into a voltage signal. The case where the contact 2 is connected between the terminals is shown, and b shows the case where the contact 2 is connected between the electric terminal of the conversion circuit 1 and the input terminal.

In FIG. 3a, a low level or high level output is produced at the terminal connected to the resistor 3 in accordance with the on/off change of the contact 2. This output is input to the comparator 5 via the filter circuit 4, and is compared with the reference voltage Vref.
A high-level or low-level output is generated in response to whether contact 2 is turned on or off. On the other hand, the output of the voltage level detection circuit 6 that detects the voltage level of the terminal connected to the other end of the resistor 3 is always at a low level. The exclusive OR circuit 7 detects a mismatch between the output of the comparator 5 and the output of the voltage level detection circuit 6, and outputs a high-level or low-level voltage signal depending on whether the contact 2 is on or off. Occur. In other words, the voltage signal output in this case is
There is a non-inverting relationship with respect to the voltage output level of comparator 5.

In Figure 3b, the output levels of the terminal and comparator 5 that occur in response to the on/off changes of contact 2, and the output level of the voltage level detection circuit are all in a reverse relationship compared to the case of Figure 3a. Therefore, the voltage signal output of the exclusive OR circuit 7 becomes a high level or a low level corresponding to whether the contact 2 is turned on or off. That is, the voltage signal output in this case is the voltage output level of the comparator 5 inverted.

Whether to connect the other end of contact 2 connected to the input terminal to the ground terminal or to the power supply terminal is determined by
Generally, it is determined by safety standards and the circumstances of the contacts on the machine tool side, but according to the circuit shown in Figure 3, no matter which connection method is used, a voltage signal is output as the on/off status of contact 2 changes. The same polarity change is obtained.

[Problem that the invention seeks to solve]

The input circuit shown in FIG. 3 requires a voltage level detection circuit and an exclusive OR circuit for each interface signal, and therefore, when there are many interface signals, the circuit scale becomes large. There is a problem that miniaturization is hindered and it is not economical.

[Means for solving problems]

In order to solve the above-mentioned problems, the input circuit system of the present invention has the basic configuration shown in FIG. 1. That is, groups 101 _-1 , 1 each have a plurality of input circuits 10 that are the same as shown in FIG. 3, and have different contact connection methods in the conversion circuits.
For 01 _-2 , groups 102 _-1 and 102 _-2 each consisting of a plurality of gate circuits that turn on/off the output of the respective voltage level detection circuits are provided, and the gate circuits of either group are selectively turned on. At the same time, voltage level detection circuits 103 _-1 and 103 _-2 are provided to detect the voltage level of the commonly connected second terminals in each input circuit group, and the output is sent to the gate circuit group 102 _-1 via the multiplexer 104. , 102 _-2 , and commonly applies the output of the selected gate circuit to the other input of each of the plurality of mismatch detection circuits 105, which are applied to one input of each. By doing so, a desired voltage signal output is obtained at the output of each mismatch detection circuit.

[Effect]

In the input circuit system of the present invention, the method of connecting the contacts in the conversion circuit is different, and therefore each input circuit group 101 _-1 , 101 _-2 accompanies the on/off of the contacts.
Even if the change in polarity of the voltage signal output is reversed, the output selected by the gate circuit groups 102 _-1 and 102 _-2 is transferred to the selected voltage level detection circuit 103 _-1 in synchronization with this selection. , 103 _-2 is sent to the mismatch detection circuit group 105 and multiplexed in two systems to obtain a voltage signal output that is an inverted or non-inverted version of the output of the mismatch circuit. Regardless of the connection method, the same change in polarity of the voltage signal output can be obtained as the contacts are turned on and off.

〔Example〕

FIG. 2 shows _the configuration of an embodiment _of the input circuit system of the present invention.
_-5 to 10 _-8 are input circuit groups each consisting of the same four input circuits as the input circuit ₁₀ shown in _FIG . The ground side terminal is common, contact 2 is the terminal, and the terminal connected between
There is a short circuit between them. In addition, input circuit 10 _-5 ~1
In 0 _-8 , the power supply side terminal is common, and the contact 2 is connected between the terminals and the terminals are short-circuited. Each input circuit 10 _-1 to 10 _-4 , 10 _-5
Gate circuits 11 _-1 to 11 _-4 , 11 _-5 to 11 _-8 are provided corresponding to the outputs of -10 _-8 , respectively, and each input circuit 10 _-1 to 10 _-4 , 10 _-5 is provided.
The respective terminals of ~10 _-8 are connected in common and connected to the voltage level detection circuits 12 _-1 and 12 _-2 , respectively, and the signals of the voltage level detection circuits 12 _-1 and 12 _-2 are selected by the multiplexer 13. and output.
The corresponding outputs of the input circuits 10 _-1 to 10 _-4 and 10 ^-5 _to 10 _-8 are connected in parallel, and each is added to one input of the exclusive OR circuits 15 _-1 to 15 _-4 . At the same time, the output selected by the multiplexer 13 is commonly applied to the other input of each exclusive OR circuit.

Now one of the input circuit groups, for example 10 _-1 ~
When trying to extract a voltage signal output with a changed contact signal from _10-4 , the voltage level detection circuit 1 is output in the multiplexer 13 according to the address signal.
2 _-1 is selected, and gate circuit 1 is selected via decoder 14 in synchronization with the same address signal.
Turn on 1 _-1 to 11 _-4 .

As a result, exclusive OR circuits 15 _-1 to 15 _-4
, the voltage outputs of the input circuits 10 _-1 to 10 _-4 and the output of the voltage level detection circuit 12 _-1 are added, but the input circuits 10 _-1 to 10 _-4 are as described in FIG. 3a. Similarly, the voltage level detection circuit 12 -1 produces a high level or low level output depending on the on/off change of the contact 2, and the voltage level detection circuit 12 _-1 always produces a low level output, so the exclusive OR circuits 15 _-1 to 1
5 _-4 is by detecting the mismatch between both inputs,
A high level or low level voltage signal output is generated depending on whether the contact 2 is turned on or off.

Furthermore, when attempting to extract a voltage signal output with a changed contact signal from the input circuit groups 10 _-5 to _{10 -8} , the output of the voltage level detection circuit 12 ^- ₂ is selected in the multiplexer 13 using the address signal as well. , turns on the gate circuits 11 _-5 to 11 _-5 via the decoder 14.

As a result, the exclusive OR circuits 15 _-1 to 15
_-4 has the voltage output ^of input circuits _10-5 to _10-8 ,
The output of the voltage level detection circuit 12 _-2 is applied to the input circuits 10 _-5 to 10 -8, but the input circuits 10 -5 to 10 _-8 are set to low level or high level according to the on/off change of the contact 2, as explained with reference to FIG. 3b. produces a level output,
Since the voltage level detection circuit 12 _-2 always produces a high level output, the exclusive OR circuits 15 _-1 to 15
_-4 generates a high-level or low-level voltage signal output depending on whether contact 2 is turned on or off.

As described above, in the input circuit system of the present invention, the output from the input circuit, which has a different polarity depending on the connection method in the conversion circuit, is inverted or non-inverted by the mismatch detection circuit, thereby turning on the contact. It is possible to obtain a voltage signal output that produces the same polarity change depending on /off.

In this example, an example of two input circuit groups each consisting of four input circuits has been described, but the input circuit system of the present invention becomes more effective when the number of input signals is large. For example, when the number of input signals is 64, the voltage level detection circuits 12 _-1 can be reduced to 1/8 by configuring eight input circuit groups each consisting of eight input circuits.

〔Effect of the invention〕

As explained above, according to the input circuit system of the present invention, there is a resistor whose one end is connected to a power supply or ground, a contact connected between the other end of this resistor and the ground or the power supply, and a contact between this contact and the resistor. and a voltage level detection circuit for detecting the voltage level at the connection point.
In a system that includes many input circuits that change the polarity of the voltage signal output depending on the connection method depending on the on/off state of the contact, the same voltage signal will be output depending on the on/off state of the contact regardless of the connection method. It is possible to cause a change in the polarity of the output, selectively apply the output of each input circuit group to a mismatch detection circuit, and install a voltage level detection circuit for each input circuit group to detect the voltage at the other end of the resistor. Since the inconsistency detection circuit output is inverted or non-inverted depending on the output thereof, the circuit configuration is simplified, the number of parts used is reduced, and it is economically advantageous.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the system of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment of the system of the present invention, and FIG. 3 is a diagram showing the configuration of a conventional input circuit. 1...Conversion circuit, 2...Contact, 3...Resistance, 4
...Filter circuit, 5...Comparator, 6,1
2 _-1 , 12 _-2 ... Voltage level detection circuit, 7, 15
_-1 ~15 _-4 ...Exclusive OR circuit, 10,10 _-1
~ _10-8 ...Input circuit, _11-1 ~ _11-8 ...Gate circuit, 13...Multiplexer, 14...Decoder.

Claims (1)

[Claims] 1. A plurality of input circuits having first and second terminals connected to each other via a resistor and a voltage level detection circuit that detects the voltage level of the second terminals;
A third terminal connected to the power supply and a fourth terminal connected to ground.
These input circuits are divided into a plurality of groups, and within each group, the output of each voltage level detection circuit is selectively turned on/off in a circuit formed by connecting the first terminal in common. a plurality of gate circuits to be turned off; voltage level detection means for detecting the voltage level of commonly connected first terminals of each of the groups; a multiplexer for selecting the output of each of the voltage level detection means; The outputs of each gate circuit of the group are sequentially connected to one input of each in parallel, and the output of the multiplexer is commonly connected to the other input of each, and a mismatch between both inputs is detected to generate an output. a plurality of mismatch detection means, wherein the selective on/off output of the gate circuit and the selection of the output of the voltage level detection means are output in synchronization with an address signal applied to the multiplexer. An input circuit method characterized by the following.