JPS59165117A - Digital input device - Google Patents

Abstract

PURPOSE:To reduce the heat generation of an input current limiting resistance and to realize high-density packaging by providing a storage circuit which is stored with the logical information of a digital signal output source in the feeding period of an impulsive input current. CONSTITUTION:A pulse generating circuit 21 generates a pulse signal 22 with a period tau, which is inputted to a switching circuit 24 through a photocoupler 23 for insulation. A voltage supplied from an external DC power source 2 at the timing of this signal 22 is outputted to input circuits 11-14 by turning on the circuit 24 for a period (t). At this time, the input current i2 flows through a photocoupler 7 and the input current limiting resistance 9 for the period (t). Therefore, a logical level signal 3A after the level conversion by the photocoupler 7 is latched by the storage circuit 25 at a rise of the signal 22 and outputted as a digital signal 3B. The signal 22 falls with slight- time delay, and consequently the circuit 25 latches the signal 3A. Other input circuits 12-14 operate similarly.

Description

Detailed Description of the Invention [Description of the Technical Field] The invention relates to a digital input device; Improved digital human-powered equipment for two reasons @1=
related.

[Technical background of the invention and its problems]

Statistical signals handled by process control systems (
The second is the output source of various digital signals, and the output source of those signals (the second is the on/off output by switches and relays, and the magnetic on/off output by semiconductor switches such as transistors). There is an output.Since the voltage repeats of these digital 1g are different from the valley digital system R (=therefore, each ma'c), it is necessary to change the input resistance etc. of the digital input device for each voltage level. Therefore, there is a problem in that the number of input points handled by the process control system (in addition to the number of input points handled by the process control system) and the number of digital input devices for each voltage level increases.

Figure '#J1 is a circuit diagram showing an external digital input section of a conventional general digital input device. The same figure (in 2, 1 is a digital input device, 2 is an external DC source, 3-
6 is a contact and a switch of a digital signal output source.

The digital human power device 1 is an input circuit 11 consisting of a photocoupler 7 for signal isolation, a reverse voltage +X, a protection diode 8, an input magnetic current limiting resistor 9, and a level converting resistor 10.
It consists of 14.

The above configuration (1 in 1, valley digital signal output sources 3 to 6 on/off (2) corresponding to the outputs of each input circuit 11 to 14 (
The second is the digital signal 3A converted to logic level.
6A is obtained.

When the valley digital signal output sources 3 to 60 are on, an input current 11 flows through the valley input circuits 11 to 141m, which is filled with the magnetic pressure of the external direct current source 2 and the input current 1tI' and the resistance value of the resistor 9. This input 4 (Iff, it) must be set to a value necessary to detect the on/off state of the digital signal output sources 3 to 4.

However, the magnetic pressure of the external direct coil 2 becomes weak (the power loss consumed by the input magnetic current limiting resistor 9 for setting the input magnetic current is large, and the heat generation increases. , this will lead to a temperature rise 2 in the digital input device 1.

In addition, the resistance value of the limiting resistor 9 (two-person power current city 1) is also external DC source 20 tonne pressure (2 installations are required, and the large resistance of the power capacitor for heat generation is required) , there is a problem that the packaging density becomes low.

(Object of the Invention) The present invention has been made in view of the above-mentioned reason (1). The purpose is to provide a memory circuit for storing the logic information of the digital signal output source during the energization period of the pulsed input Km, and to obtain a digital input device that reduces the heat generation of the input current limiting resistor of the digital signal input circuit. is.

[Summary of the invention]

The present invention converts the fiber information caused by the opening and closing of various switches into an electrical logic level digital signal (tt2) into a disgusting logic level when each of the switches is closed. An input circuit (1 flowing input 444) periodically (=pulse-like) switching circuit, and the above-mentioned pulse-like (2) period of energization (holding the self-converted logic level signal) to output the digital signal. The device is a digital input device that reduces heat generation by reducing input voltage limiting resistance and power loss.

[Embodiments of the invention]

FIG. 2 is a block diagram of a digital input device showing one embodiment of the present invention.

In this figure, the same reference numerals as in FIG. 1 indicate the same functions.

A pulse generating circuit 21 generates a pulse signal 22 having a constant pulse width at a constant cycle. The output is the insulating photo coupler of the pulse No. 16 n, and the switching circuit is used to convert the voltage of the external DC voltage source 2 into the pulse signal 2.
2 (Two synchronously chopped and output. 5 is a storage circuit that temporarily stores the logic level signals 38 to 6A output from the input ports N111 to 14 and outputs the digital signal 3B.
~ Output as 6B.

FIG. 3 is a time chart for explaining in detail the present invention shown in FIG. 2. A pulse signal nk with a predetermined period τ as shown in FIG. 3 is generated from the pulse generation circuit 21, and the switching circuit Nr2/i (
Two people work together. At the timing of this pulse signal ρ, the voltage supplied from the external DC power supply 2 is turned on for a period t shown in FIG.
Outputs two. At this time, for example, if the digital signal output source 3 outputs ON and OFF signal power at the regular timing shown in FIG. 3, the 7 automatic couplers 7 and the 9 input current limiting resistors miss, and the input current 12 flows for a period of t. Therefore, the logic level signal 3A after level conversion becomes a signal with the same waveform as the input current 12.This logic level signal 3A is input to the memory circuit 2 at the timing t1 of the rising edge of the pulse No. 16n. Digital signal 3
It is output/output as B. The falling time of the logic level signal 3A is slightly delayed from the rising time of the pulse No. 16 ρ, so that the memory circuit 5 can latch the logic level signal 3A't'.

K (two latch operations are performed and the digital signal 3B is generated at time tsl2 when the period τ elapses due to the pulse signal n. At time t2, the digital signal output source 3 is still in the ON state, so latch production is performed. The digital signal 3B does not change even if the other digital signal 1g output sources 4~
6 (even if there are two, the same operation is performed and the latched digital signals 4B to 6B are output from the memory circuit 5.

As described above (2) In the digital input device of the present invention (2), even if the digital signal output sources 3 to 6 are always on, the input current 12 has a period of A pulse-like current flows, that is, the effective value of the input current 12 is 1. Jt/τ 9. If t/τ is reduced, the magnetic loss and heat generated by the input current limiting resistor 9 are reduced. The number of layers of the input current limiting resistor 9 can be constant regardless of the external DC voltage or the voltage of the power source 2.

[Efficacy of invention]

According to the digital input device (2) of the present invention, the heat generation of the input current limiting resistor is small, so high-density packaging of supplies is possible.Also, the digital signal output source (2) has different pressure levels of the outside gun source used. Therefore, it is possible to use a digital input device with improved measuring performance.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional digital input device.
The figure is a block diagram showing one embodiment of the present invention, and FIG. 3 is a time chart for explaining its operation. 1... Digital input device 3A to 6A... Word of mouth 2... External DC source 21... Pulse generation circuit 3 to 6... Digital signal output source Ru...
Photocoupler 7... Photocoupler Sae... Switching circuit 8... Reverse voltage holding diode 5... Memory circuit 9... Input current limiting resistor 3B-6B... Digital signal 11-14...・Input circuit

Claims (1)

[Claims] When the various switches are closed, a digital signal at a magnetic logic level, which is logic information, flows into an input circuit that converts it into a magnetic logic level when the various switches are closed. A switching circuit that generates a human-powered current in a periodic (double-pulse) manner,
The digital input device is provided with a +1iL8 arm circuit that holds the converted logic level 1d and outputs it as a FitJ digital number 1B during the pulse-like (=iljl) period (-).