JPH03188713A - Contact input circuit - Google Patents

Abstract

PURPOSE:To back up lots of input points of a contact input circuit over a long time without preparation of a larger voltage source of a battery by connecting a diode and a 1st resistor suppressing a current in series with an output of a 2nd voltage source of a battery lower than a 1st voltage source and connecting a series circuit comprising a 2nd resistor and a capacitor across an external contact. CONSTITUTION:With an external contact 1 closed, a current (Va-VD1Vp)/(R4+R5) flows from a voltage source Va to a diode D1, the external contact 1, resistors 4,5 and an LED 2a side (primary side) of a photocoupler 2 in the normal state, and a current (Vb-VD2Vp)/(R3+R4+R5) flows from a voltage source Vb to a diode D2, a resistor R3, the external contact 1, the resistors 4, 5 and the LED 2a side (primary side) of the photocoupler 2 at a power failure, and a photo transistor 2b (secondary side) of the photocoupler 2 is conductive in both the cases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a contact input circuit that takes in contact signals to a computer or the like for industrial xFA.

[Prior Art] FIG. 7 is a circuit diagram showing a conventional contact input circuit. In the figure, l is an external contact, 2 is a photocoupler consisting of an LED (light emitting diode) 2a (negative side) and a phototransistor 2b (secondary side), and R+ determines the current flowing to the external contact 1 and the photocoupler 2 on the LED 2a side. A resistor, Vl is a voltage source that applies a voltage to the external contact l, R2 is a pull-up resistor for converting the output of the phototransistor 2b of the photocoupler 2 into a digital signal, and 3 is a pull-up resistor for shaping the waveform of the digital signal. Schmitt trigger gate, 4
, 5 are the respective terminals of the external contact l, 6 is the manual power of the Schmitt trigger gate 3, and 7 is the output of the Schmitt trigger gate 3.

FIG. 8 is a timing chart of each part for explaining the operation of the contact input circuit of FIG. 7.

Next, the operation of the above-described conventional contact input circuit will be explained. When external contact 1 is off, voltage source VI and resistor R
No current flows through the circuit consisting of + and the L E D 2 a side (− side) of the photocoupler 2, and as a result, the phototransistor 2b (secondary side) of the photocoupler 2 is turned off. Therefore, since the human power 6 of the Schmitt trigger gate 3 becomes rHJ due to the pull-up resistor R2, the output cuff of the Schmitt trigger gate 8 becomes "■7".

On the other hand, when external contact 1 is on, voltage l! iVI.

l of resistor R1 and photocoupler 2, E D 2 a
A current 8 flows through the circuit consisting of the two sides, and as a result, the phototransistor 2b of the photocoupler 2 is turned on.

So, the point where the pull-up resistor R2 is connected, i.e. Schmidts)) Hemlock gate 30 input 6, is r L J
Therefore, the output cuff of the Schmitt trigger gate 3 becomes "H". Here, ■ is the voltage between each terminal 4 and 5 of the external contact l.

The timing of each part in the series of operations of the conventional contact input circuit shown in FIG. 7 as described above is clearly illustrated by the timing chart shown in FIG.

In addition, in the conventional contact input circuit described above, in order to operate the circuit even during a power outage of the normal voltage source (1), a separate battery voltage source is provided to back up the circuit. It is necessary to switch the voltage source (1) to a battery voltage source and use the voltage source (2) without interruption.

[Problems to be Solved by the Invention] Since the conventional contact input circuit described above is configured as described above, in order to continue the operation of the circuit even in the event of a power outage of the normal voltage source V1, it is necessary to back up the circuit. A battery voltage source is provided, and in the event of a power outage, the normal voltage source Vl is switched to the battery voltage source.

However, when backing up the circuit, the battery voltage source also requires the same power as the normal voltage source V1. Therefore, in order to back up the circuit for a long time with a large number of input points of the contact input circuit, it is necessary to use the battery. The problem is that four large batteries must be provided as voltage sources for the voltage source, which requires a relatively expensive circuit configuration and is not economical.

This invention was made to solve the above problems, and it is possible to back up a large number of input points of a contact input circuit for a long time without preparing a large battery voltage source. The purpose is to obtain a contact input circuit.

[Means for Solving the Problems] A contact input circuit according to the present invention has two systems: a normal first voltage source and a battery second voltage source having a lower voltage than the first voltage source. A voltage source is provided, a first voltage R, a second voltage
A first diode and a second diode are connected to the output of the voltage source, respectively, and in the event of a power outage, the reverse characteristic of the diode is used to automatically switch the first voltage source to the second voltage source. The current supplied from the second voltage source to the external contact is suppressed to a steady current by a first resistor connected to the output of the second voltage source, and a second resistor is connected in series with both terminals of the external contact. Using the discharge current of the connected capacitor,
This is designed to ensure stable contact when the external contact is in the on state.

Further, a contact input circuit according to another aspect of the present invention uses two voltage sources: a normal first voltage source and a battery second voltage source having a lower voltage than the first voltage source. A first diode and a second diode are connected to the outputs of the first voltage source and the second voltage source, respectively, and in the event of a power outage, the reverse characteristic of the diode is used to switch the first voltage source to the second voltage source. At the same time, the resistor is also automatically switched from the second resistor to the first resistor, and the current supplied from the second voltage source to the external contact is changed to the voltage source of the first voltage source. The current is set to be maintained at approximately the same level as when the external contact is turned on to ensure stable contact when the external contact is in the on state.

[Function] In the contact input circuit of the present invention, a first diode is connected to the output of a normal first voltage source, and the contact input circuit connects the first diode to the output of a second voltage source of a battery whose voltage is lower than that of the first voltage source. Second
By connecting a diode in series with a first resistor that suppresses the current, and roughly connecting a series circuit of a second resistor and a capacitor to both terminals of the external contact, the second voltage source is without current flowing from to external contacts.
Further, during a power outage, almost the same current as in normal times can be supplied from the second voltage source to the external contact without momentary interruption.

Further, in a contact input circuit according to another aspect of the present invention, a first diode and a second resistor are connected in series to the output of a normal first voltage source, and a voltage lower than that of the first voltage source is connected. A second diode is connected to the output of the second voltage source of the battery, and an external contact and the first resistor are connected in series to the connection point between the cathode of the second diode and one side of the second resistor. By connecting to the external contact, the current will not flow from the second voltage source to the external contact during normal times, and during a power outage,
Almost the same current as in normal times can be supplied from the second voltage source to the external contact without momentary interruption.

Embodiment FIG. 1 is a circuit diagram showing a contact input circuit according to an embodiment of the present invention. In the figure, l is an external contact, 2 is an LED
A photocoupler consisting of (light emitting diode) 2a (-next side) and phototransistor 2b (secondary side), R3, Ra,
Rs is a resistor that determines the current flowing to the external contact l and the LED 2a side of the photocoupler 2, ■ is a normal voltage source, and Vb
is the voltage source ■. A battery voltage source with a voltage lower than D+
is a diode connected to the output of voltage source V, D2 is a diode connected to the output of voltage source Vb, C1 is a capacitor, and R2 is a pull-up resistor for converting the output of phototransistor 2b of photocoupler 2 into a digital signal. ,
3 is a Schmitt trigger gate for waveform shaping the digital signal, 4 and 5 are each terminal of external contact 1, 6 is the human power of Schmitt trigger gate 3, 7 is the output of Schmitt trigger gate 3, and 8 is the cathode of diode D1. This is the connection point between the side and one side of the resistor R3.

FIG. 2 is a timing chart of each part for explaining the operation of the contact input circuit of FIG. 1.

Next, the operation of the contact input circuit according to the embodiment of the invention described above will be explained. When the external contact l is off, no current flows to the LED 2a side (-next side) of the photocoupler 2, and as a result, the phototransistor 2b of the photocoupler 2 (
secondary side) is turned off. The connection point 8 during normal operation is connected to the voltage source V via the diode D1 (V,
The voltage (V, -VDI) is applied between both ends of the capacitor C1 and each terminal 4 and 5 of the external contact 1 (VDI is the forward voltage of the diode D1). Diode D2 is reverse biased and cut off). In addition, during a power outage, the voltage of the voltage source V8 becomes O, so the connection point 8 is connected to the voltage (vb - VO2) from the voltage source Vb via the diode D2 and the resistor R3 (VO2 is connected to the diode D2 (7 ) forward voltage), and the voltage V between each terminal 4°5 of external contact 1 is (Vb
-Vb2), and its current I8 is O (diode D1 is cut off by reverse bias).

On the other hand, when external contact 1 is on, under normal conditions, voltage #V, diode D+, external contact 1°, resistors 4 and 5. Current (V −V n I−V p ) / (Ra+R
5) flows (vI is the forward voltage of LED2a), and if there is a power outage, the voltage source Vb is connected to the diode D2゜resistor R.
3. External contact 1. Each resistor 4 and 5. Current (Vb VD2Vp)/(R3
+Ra+Rs) flows, and both phototransistors 2b (secondary side) of the photocoupler 2 are turned on. Note that the current flowing during a power outage can be freely set by the value of the resistor 3, but the CTR (Cur
It is necessary to set an appropriate value in consideration of the transfer ratio (rentTransfer Ratio). Also, since the current flowing during a power outage is small, the discharge current of the capacitor CI is used to obtain a stable contact signal at the external contact 1.
The peak value of the discharge current is determined by the value of resistor R4. That is, the smaller the value of the resistor R4, the larger the discharge current, but it is set to about several hundred mA (milliamperes) or less, taking into account the characteristics of the external contact l.

Here, the timing of each part in the operation of the contact input circuit as shown in FIG. 1 is clearly shown by the timing chart shown in FIG. 2.

Note that the embodiment shown in FIG. 1 above uses the photocoupler 2, but as another embodiment that does not use the photocoupler 2, a contact input circuit having the circuit configuration shown in FIG. Good, the same effects as in the above embodiment can be achieved. Here, R6 is a resistor connected by the Schmitt trigger gate between the human power 6 of the gate 3 and ground.

FIG. 4 is a circuit diagram showing a contact input circuit according to another embodiment of the present invention. In the figure, 1 is an external contact, 2
Ra is a photocoupler consisting of an LED (light emitting diode) 2a (negative side) and a phototransistor 2b (secondary side).
, RJ is external contact 1 and LED 2 of photocoupler 2
The resistor that determines the current flowing to the a side, ■ is a normal voltage source,
■ is the voltage source V.

The voltage source of the battery with a voltage lower than , Dl is the voltage source v8
D2 is a diode connected to the output of voltage source Vb, R2 is a pull-up resistor for converting the output of phototransistor 2b of photocoupler 2 into a digital signal, and 3 is a waveform shaping device for the digital signal. 4 and 5 are the respective terminals of external contact 1, 6 is the input of Schmitt trigger gate 3,
7 is the output of the Schmitt trigger gate 3, and 8 is the connection point between the cathode side of the diode D2 and one side of the resistor R4.

FIG. 5 is a timing chart of each part for explaining the operation of the contact input circuit of FIG. 4.

Next, the operation of the contact input circuit which is another embodiment of the invention described above will be explained. When the external contact l is off, no current flows to the LED 2a side (-secondary side) of the photocoupler 2, and as a result, the phototransistor 2b (secondary side) of the photocoupler 20 is turned off. The connection point 8 during normal operation is connected from the voltage source V to the diode DI,
The voltage (V-Vow) (V o+
is the forward voltage of diode D+), and the voltage V between each terminal 4 and 5 of external contact 1 is (V-Vow) (
7) voltage, and its current (8) is 0 (diode D2 is reverse biased and cut off). In addition, at the time of a power outage, the voltage of the voltage source v8 becomes O, so the connection point 8 is connected to the voltage source Vb via the diode D2.
VD2) (7) Voltage (VD2 is the forward voltage of diode D2), and the voltage ■8 between each terminal 4 and 5 of external contact 1 becomes the voltage (Vb - VD2), and the current ■8 is (Diode D1 is reverse biased and cut off).

On the other hand, when external contact 1 is on, under normal conditions, voltage source V8 is connected to diode DI, and each resistor R4 and R3
, external contact l, current (V-VDI VD) / (R3+ Ra
)' flows (v p is the forward voltage of LED2a),
If there is a power outage, the diode D2.
Resistor R3, external contact l, photocoupler 2 LED2a
A current (Vb VD2 VD)/R3 flows, and both transistors 2b (secondary side) of the photocoupler 2 are turned on. At this time, the voltage at the connection point 8 must normally be (V-VD2 R4.I x) > Vb (diode D2 is cut off by reverse bias).

Here, during a power outage, the voltage at 80 connection points is (Vb-V
D2) Therefore, in order to make almost the same current 8 flow through the connection point 8 during normal times and during a power outage, the voltage must be (Va-Vow Ra・Ix) (Vb VD
2) It is necessary to set =a (α is a small value).

Now, if we insert specific values into the above equation and consider it, for example, V, = 48v (volts) t Vo+ = 0°8v,
l, = Q, 11A (7 amps 7), Vb = 12v,
VO2:=0. If it is 8V, (4B-0, 8-0
,01・R4) −(12−0°8)=36−0.
01 ・R4=α, and judging from this, R4”
It can be calculated that 3.3Ω to 3°5Ω (ohm) is optimal.

Here, the timing of each part in the operation of the contact input circuit as shown in FIG. 4 is clearly shown by the timing chart shown in FIG.

The embodiment shown in FIG. 4 above uses the photocoupler 2, but as another embodiment that does not use the photocoupler 2, a contact input circuit having the circuit configuration shown in FIG. 6 may be used. , the same effect as the above embodiment is achieved.

[Effects of the Invention] As described above, according to the contact input circuit of the present invention, the two voltage sources are a normal first voltage source and a battery second voltage source having a lower voltage than the first voltage source. A system voltage source is provided, and a first diode and a second diode are connected to the outputs of the first voltage source and the second voltage source, respectively, and in the event of a power outage, the reverse characteristics of the diode are used to switch the first The first voltage source automatically switches the voltage source to a second voltage source and the supply current from the second voltage source to the external contact is connected to the output of this second voltage source.
The resistor suppresses the current to a steady state, and the discharge current of the capacitor connected in series with the second resistor to both terminals of the external contact is used to ensure stable contact when the external contact is in the ON state. By using the second voltage source of the battery and the capacitor, it is possible to back up a large number of input points in a contact input circuit for a long time, and it is also possible to obtain a contact input circuit having an inexpensive and compact circuit configuration. It has excellent effects such as

According to another aspect of the present invention, the contact input circuit has two voltage sources: a normal first voltage source and a battery second voltage source having a lower voltage than the first voltage source. established,
A first diode and a second diode are connected to the outputs of the first voltage source and the second voltage source, respectively, and in the event of a power outage, the reverse characteristics of the diode are used to switch the first voltage source to the second voltage. At the same time, the resistor is also automatically switched from the second resistor to the first resistor, and the current supplied from the second voltage source to the external contact is changed from that of the first voltage source. By setting the current to be approximately the same and ensuring stable contact when the external contact is in the ON state, a small battery second voltage source can be used to operate a large number of human input points in the contact input circuit over a long period of time. This provides excellent effects such as being able to back up the circuit and providing a contact input circuit with an inexpensive and compact circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a contact input circuit according to an embodiment of the present invention, FIG. 2 is a timing chart of each part to explain the operation of the contact input circuit of FIG. 1, and FIG. FIG. 4 is a circuit diagram showing a modified example of the contact input circuit according to another embodiment of the present invention. FIG. 5 is a circuit diagram showing a modification of the contact input circuit according to another embodiment of the present invention. Timing chart of each part for explaining the operation of the circuit, Figure 6,
4 is a circuit diagram showing a modified example of the contact input circuit of FIG. 4, and FIG. 7 is a circuit diagram showing a conventional contact input circuit.
FIG. 8 is a timing chart of each part for explaining the operation of the contact input circuit of FIG. 7. In the figure, 1... external contact, 2... photocoupler, 2a... LED (light emitting diode), 2b...
Phototransistor, 3...Schmitt trigger gate,
4゜5...terminal, 6...input, 7...output,
8... Connection point, Rs, R3, R4, Rs,
Re...Resistor, R2...Pull-up resistor, DI
, D2...diode, V, , Vb... voltage source, C1... capacitor. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Two voltage sources, a normal first voltage source and a battery second voltage source having a lower voltage than the first voltage source, are provided, and the first voltage source is The output of the second voltage source is connected to the anode of the first diode and the second diode, respectively, and the cathode of the second diode connected to the output of the second voltage source is connected to the anode of the second diode. The circuit is connected to the cathode of the first diode on the first voltage source side via the first resistor, the connection point is connected to an external contact, and the circuit has a circuit configuration for supplying voltage to the external contact. A contact input circuit further comprising a circuit configuration in which both terminals of the external contact are connected to a series circuit of a second resistor and a capacitor. 2. Two voltage sources are provided, a normal first voltage source and a second voltage source of a battery having a lower voltage than this first voltage source, and the first voltage source and the second voltage source are provided. The outputs of the voltage sources are connected to the anodes of a first diode and a second diode, respectively, and the cathode of the first diode connected to the output of the first voltage source is connected through a second resistor. and connected to the cathode of the second diode on the side of the second voltage source, the connection point of which is connected to an external contact via a first resistor, and a circuit that supplies voltage to the external contact. A contact input circuit characterized by comprising: