JPH03253901A - External contact input device - Google Patents

Abstract

PURPOSE:To surely output a contact signal without causing an erroneous judgement even if a noise goes in by considering width of a noise predicted in advance, and setting a threshold level to a high side and a low side so that the threshold level can be switched to the side which is not influenced by the noise in accordance with a contact state. CONSTITUTION:The device is provided with a threshold level switching means which inputs an analog voltage signal corresponding to a state of contacts m1, m2, has a comparing means 71 for comparing that which is converted by an analog-to-digital converter 4, and a threshold level, and switches the threshold level in accordance with a result of the comparing means 71, and an output means 9 for deciding a contact signal to be ON or OFF, based on a result of comparison of the comparing means 71, and outputs it. That is, the threshold level switching means switches the threshold level from a low side to a high side, when the contact signal is varied from OFF to ON, and switches the level from the high side to the low side, when the signal is varied from ON to OFF. In such a way, even if a noise gets on the contact signal, ON/OFF can be judged appropriately.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an external contact input device used in a temperature controller switch, etc., and more specifically, to measures to prevent misjudgment regarding temperature controller input signals. be.

<Prior Art> FIGS. 4 and 5 are circuit configuration diagrams of a conventional external contact input device. In Fig. 4, m 1 and m 2 are contact input terminals, one end of R is contact input terminal m1, and the other end has a potential of VC.
1 is a Luasub resistor held at C, and 1 is a microprocessor that introduces a voltage signal at point A according to a contact signal from a contact input terminal.

In this device, contact signals from contact input terminals m and m2 are input, and a microprocessor compares an analog voltage signal at point a corresponding to this signal with a threshold level to determine whether it is on or off.

In FIG. 5, R2 and R3 are resistors, and Trl is a transistor fPNP type for protecting the digital IC2.
In this device, when the contact input terminals m1 and m2 are off, the potential at point b is maintained at Vcc, so the transistor Tr1 is off.

At this time, since no current flows through the resistor R3, the 0 point becomes a low level. When the contact input terminals m 1 and m 2 are turned on, a current flows between the emitter and collector of the transistor Tr1, and the transistor Tr1 is turned on. Therefore, 0 point is a high level. This on/off signal is input to the digital IC 2, which sends an interrupt signal and an on/off signal to the microprocessor.

<Problems to be Solved by the Invention> In the external contact input device shown in Fig. 4, when the contact resistance is not 0 or when noise is present at the contact input terminal, the signal turns on/off near the threshold level. There is a problem of misjudgment. An example is shown in FIG.

Figure 6 (a) is a waveform diagram showing the potential change at point a due to the on/off switch of the external contact input device in Figure 4, and Figure 6 (b) is a waveform diagram showing the change in potential at point a due to the on/off switch of the external contact input device in Figure 4. FIG. 3 is a waveform diagram showing a contact signal. In FIG. 6(a), Cb8 is a preset threshold level, usually set at the midpoint of the voltage signal, in this case Cba=Vcc/2. T is the sampling period, which is usually about 500 m5 for a temperature controller. In Figure 0, at point e, the threshold level Cb
Since the input voltage signal is greater than a, the microprocessor determines that the contact state is off. However, if noise occurs between e- and the width of the noise exceeds the threshold level Cba, it will be determined that the contact is on at point f even though it is not closed. It is judged that the signal is off again at a point, but if noise like the one shown in the figure appears again between h and i, it is incorrectly judged that the signal is off again at a point.
If noise enters when the contact state is stable in this way and exceeds the threshold level, there is a problem of erroneous judgment.

In addition, in the external contact input device shown in Figure 5, even if the contact resistance is O, voltage remains between the emitter and collector of the transistor, and depending on the threshold level of the digital IC, erroneous on/off judgments may occur. There is sex.

The present invention was made to solve such problems, and is an external contact input device that can appropriately determine on/off even when contact resistance exists or when noise is added to the contact signal. The purpose is to provide

Means for Solving the Problems> The present invention provides an external contact input device that inputs a contact signal from the outside, compares it with a threshold level, determines whether the contact signal is on or off according to the comparison result, and outputs the result. an analog-to-digital converter that takes in an analog voltage signal according to the state of the contact and converts it into a digital signal; and a comparison means for comparing the converted signal by the analog-to-digital converter with the threshold level; a threshold level switching means for switching the threshold level to a high side or a low side by an amount corresponding to the noise level according to the result of the comparison means; and a threshold level switching means for turning on the contact signal based on the comparison result of the comparison means or output means for determining that the contact signal is off and outputting the output; the threshold level switching means switches the threshold level from the low side to the high side when the contact signal changes from off to on; 1. This external contact input device is characterized by switching from a high side to a low side when changing from on to off.

<Effect> The present invention operates as follows.

The comparison means detects whether the current contact state is on or off, and operates differently depending on whether it is on or off.

If it is on, input an analog voltage according to the contact state at the timing of the sampling cycle, perform A/D conversion, and then compare it with the high-side threshold level by the comparison means, and check that the input signal is greater than the threshold level. At this time, it is recognized as an off signal, the threshold level switching means switches the threshold level to the low side, and the output means outputs an off signal.

If it is off, input an analog voltage, perform A/D conversion, and then compare it with the low-side threshold level using a comparing means. If the input signal is smaller than the threshold level, it is recognized as an on signal and the threshold is The hold level switching means switches the threshold level to a high side, and the output means outputs an on signal.

<Example> The present invention will be described in detail below using the drawings.

FIG. 1 shows an example of an external contact input device according to the present invention.
FIG. Note that the same components as in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

3 is a microprocessor, 4 is contact input terminal m1, m2
An A/D converter that converts an analog voltage signal according to a contact input signal from a converter into a digital value. For example, if the resolution is 8 bits and Vcc = 5 V, the count is 0 when the analog voltage signal is 0. , converts to 255 counts at 5V. 5 is an input port that takes in the input signal converted into a digital value, and 6 is a memory, which has a high-side threshold level Chigh, a low-side threshold level C1o8, the current contact state V, and the current threshold ut hold level. Data such as value CX is stored. Here, the threshold level High, Cl
ow is set in consideration of the noise width of the input signal.

7 is a CPU that receives input signals from input board 5;
Comparing means 71, data rewriting means 72, and output change detecting means 73 are provided. Comparison means 71 is a comparison means that compares the A/D converted input signal with a threshold level, and outputs a change signal when the current state changes. Further, the comparison means 71 detects whether the current contact state is on or off. The data rewriting means 72 accesses the memory 6, reads the required threshold level value and the current state of the contact signal,
Further, the current value of the threshold level C and the current contact state V are determined according to the output result of the comparing means 73. , t as needed, sends a rewriting signal to the data rewriting means 72 when a change signal is detected from the output result of the comparing means 71. Reference numeral 8 denotes a clock generator that provides the timing of the sampling period, and reference numeral 9 denotes an output means that receives the contact signal recognized by the comparison means 71 from the CPU 7 and outputs it.

Next, the present invention will be explained in detail using FIGS. 1, 2, and 3. Fig. 2 is a flowchart of the operation of the external contact input device according to the present invention, Fig. 3 (a>(c) is a waveform diagram of the input analog signal according to the input contact signal, and points k to 7 are sampling points vertically The axes indicate the digitally converted values. Figures 3(b) and 3(d) are waveform diagrams of the contact signals determined by the microprocessor. First, the contact input terminals m1,
Consider the case where the m2 switch is closed from an open state.

When the switch is open, point d in Figure 1 is maintained at 5V, so before point k, the contact state is low level,
Memory 6 V. An off signal is stored in ut.

When sampling at k in Fig. 3, first, the memory 6
V stored in The data rewriting means 72 reads ut, and the comparing means 71 compares whether it is an on signal. Since it is in the off state at point d, memory 6
The threshold level C contains the value of the low side threshold level × Claw. The input signal at the point A/
The data is converted by the D conversion 4 and read through the input port 5. Here, the data rewriting means 72 reads the current threshold level Cx of the memory 6, and the comparing means 71 compares C8 with the read value. When the read value is larger than C, data is written to V in the memory 6 by the data rewriting means 72. , t, and the output means 9 outputs the off signal. When the read value is smaller than 08, an output change signal is sent from the comparing means 71 to the output change detecting means 73,
The output change detection means 73 receives this signal and sends a rewriting signal to the data rewriting means 72.
and the contact signal V of memory 6. , 1 is rewritten to an on signal, and the threshold level C is rewritten to a high-side threshold level Chigh. By the way, in this case, since the input signal is larger than Clow at point k, the CPU 9 recognizes the contact signal as OFF. (Hereinafter, explanations of the operation of sending and receiving signals within the microprocessor 3 and accessing the memory 6 will be omitted.) Hereafter, at points 1 and n,
The read value is still at the threshold level C1
Since it is larger than ow, the output means 9 contains a large noise at the 0m point where it outputs the off signal, but this value is also C8□
Since it is larger, an off signal is output. Co on the vertical axis in FIG. 3 is the conventional threshold level, and in the conventional case, the output would be inverted.

(Steps A to F in Figure 2) Next, since the read value becomes smaller than C8W for the first time at point 0, set the threshold level to the high side Chlgh.
, and the output means 9 outputs an on signal. (Steps A to D, GH) Here, the threshold level is set in advance to a value that cannot be exceeded even when a large amount of noise enters when the signal is stable.

This time, the read value is at the threshold level Chi
Comparison means 71 compares whether it is larger than gh, and if smaller, outputs an on signal, and if larger, outputs an off signal. Here, at the 9th point, the read value is smaller than High, so the output means 9 outputs an on signal. Thereafter, since the read values at points q, r, and 5 are also smaller than the threshold level High, ON signals are output. (Steps A, T~M) At the point, the read value is at the threshold level Ch
Since the contact signal exceeds ``high'', the microprocessor 3 again recognizes the contact signal as an OFF signal, outputs the OFF signal, and switches the threshold level to CLOW on the low side. (Steps A, I~, N~O> After that, when the read value is stable on the high side, that is, when the contact state is off, it is compared with the low side threshold level C, and the low When the read value exceeds Clow (when it becomes smaller than C), it outputs an on signal and switches the threshold level to High.On the other hand, when the read value When it is stable on the low side, that is, when the contact state is on, compare it with the high side threshold level C, and
Outputs an on-high signal while it does not exceed high, and outputs an on-high signal when it exceeds high.
(when the threshold level becomes higher), an off signal is output and the threshold level is again switched to the low side Clow.

<Effects of the Invention> As described above in detail, in the present invention, in the external contact input device, the threshold level is set to the high side and the low side, taking into consideration the expected noise width, Since the threshold level can be switched to the side that is not affected by noise depending on the contact status, there will be no misjudgment even if there is noise while the contact signal is stable, and the contact signal will be output reliably. can do.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of an embodiment of an external contact input device according to the present invention, and FIG. 2 is an operation flowchart of the present invention.
Figure 3 is a waveform diagram of an input analog signal according to the contact state and a waveform diagram of a contact signal determined by a microprocessor; Figures 4 and 5 are diagrams showing an example of a conventional external contact input device; The figure shows an analog signal waveform diagram of the device shown in FIG. 4 and a waveform diagram of a contact signal determined by a microprocessor. 3... Microprocessor 4... A/D converter 5... Input port controller... Memory 7... CPU 71... Comparison means 72... Data rewriting means 73... Output change Detection means 8...Clock generator 9...Output means m, m2...Contact input terminal R1...Pull-up resistor

Claims (1)

[Claims] An external contact input device that inputs a contact signal from the outside, compares it with a threshold level, determines whether the contact signal is on or off according to the comparison result, and outputs the contact signal according to the state of the contact. an analog-to-digital converter that takes in an analog voltage signal and converts it into a digital signal; a comparing means for comparing the converted signal by the analog-to-digital converter with the threshold level; threshold level switching means for switching the threshold level to a high side or a low side by an amount corresponding to the noise level, and determining that the contact signal is on or off based on the comparison result of the comparing means, and outputting the resultant signal. and output means for switching the threshold level from the low side to the high side when the contact signal changes from off to on, and from the high side to the high side when the contact signal changes from on to off. An external contact input device characterized by switching to the low side.