JPS6277655A - Substrate trouble diagnosing circuit for programmable controller - Google Patents

Abstract

PURPOSE:To diagnose an input and an output substrate periodically in substrate units during the operation of a trouble diagnosing device by indicating trouble if a pulse signal inputted to the input substrate changes in state. CONSTITUTION:A pulse train 13 having a constant period is inputted as an output 8 to the bits 6 of input substrates 1A-1C for control from the bit 7 of an output substrate 4 dedicated to an input substrate trouble diagnosis and inputted to a state change detecting circuit 14 for the input substrates. When none of the input substrates is abnormal, the pulse train signal 13 is supplied to the input 6 of a state change detecting circuit 14 as it is and its output 23 is also a pulse train, but if opening or closing trouble occurs, the input 6 becomes 1 or 0 and the output 23 also becomes 1 or 0; and a timer 15 operates, and an output 12 becomes 1, and a pilot lamp 16 illuminates to make a display. An input substrate 2 dedicated to output the substrate trouble diagnosis operates similarly to diagnose output substrates 3A-3C for control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a board failure diagnosis circuit for a programmable controller that diagnoses failures of input boards and output boards of a programmable controller on a board-by-board basis.

[Technical background of the invention and its problems]

In general, fault diagnosis for programmable controllers only involves diagnosing faults in the control device itself, such as watchdog timer, parity error, CPU stop, sequence command verification, checking the mounting of input boards and output boards, and collectively displaying analog input boards. , failure diagnosis for each input and output board is not performed.

Therefore, when a failure occurs in the input board or output board, even if the failure can be detected, it may take time to determine which board is at fault, or the control unit must be stopped to replace the faulty board. There is a problem in that this may cause malfunctions in plant operation.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a board failure diagnosis circuit for a programmable controller that periodically performs failure diagnosis of an input board and an output board on a board-by-board basis during operation of the device.

[Summary of the invention]

The present invention provides an output board for fault diagnosis of an input board that generates a pulse signal of a constant period and inputs it to a predetermined bit of each input board, and an output board for fault diagnosis of an output board that inputs a pulse signal of a constant period from each output board. It includes a state change detection circuit that detects a change in the state of the input board and the pulse signal input to each input board, and a display circuit that indicates a failure when the above state change occurs. This is a circuit board failure diagnosis circuit for a programmable controller that can periodically diagnose failures on a board-by-board basis while the device is operating.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

In Fig. 1, IA, IB, and IC are input boards for control, 2 is an input board dedicated to output board failure diagnosis, 3A,
3B and 3C are output boards for control, 4 is an output board dedicated to input board fault diagnosis, and 5 is a fault display board.

One bit 6 for each input board IA, IB, IC and 2
The output 8 of each bit 7 of the output board 4 dedicated to input board failure diagnosis is input to each of the input boards.

In addition, each output board 3A, 3B, 3G and 4-1
Outputs 10 from the two bits 9 are input to each bit 11 of the input board 2 dedicated to output board failure diagnosis.

When a failure occurs, a failure signal is input to the corresponding bit 12 of the failure display board 5, thereby indicating a failure on a board-by-board basis.

FIG. 2 is a block diagram showing the operation of the fault diagnosis circuit.
FIG. 2(A) shows the input board diagnosis, and FIG. 2(8) shows the output board diagnosis.

That is, in FIG. 2(A), from the four bits 7 of the output board 4 dedicated to input board failure diagnosis, a pulse train 13 of a constant period is inputted as an output 8 to one bit 6 of the corresponding input board, and the pulse train 13 of the input board It becomes an input to the state change detection circuit 14.

If there is no abnormality in the input board, the pulse train signal 13 becomes input 6 of the state change detection circuit 14, and its output 23 also becomes a pulse train. However, if an open or close failure occurs in the input board, input 6 becomes 11. ' or 110', and the output 23 also becomes either 11' or %O', and the state does not change even after a certain period of time has elapsed.

FIG. 3 is a diagram showing the logic sequence of the state change detection circuit 14, and the operation waveforms of each part thereof are as shown in FIG. 4, for example. In FIG. 4, (A) shows the normal state, (B) shows the faulty state, and To is the scan time.

That is, under normal conditions, the output 23 of the state change detection circuit 14 becomes a pulse train with a period T1, as shown in FIG.
□The timer 15 having a longer time limit T2 does not operate, so its output 12 remains at "0" and no display appears on the indicator light 16.

When a failure occurs at time t1, the pulse train of output 23 stops as shown in Fig. 4 (B), and the pulse train stops.
2 (T, > T1), timer 15 operates and output 12 becomes 1.
1', a display appears on the 1 indicator light 16 to indicate the occurrence of a failure, so that fault diagnosis of the board can be periodically and continuously carried out.

In addition, in FIG. 2(A), the negation 18 of the output board abnormality signal 17 dedicated for input board failure diagnosis and the state change detection circuit 14
The reason why the logical product 19 of the outputs of is input to the timer 15 is as follows.
This is to check that the cause of the state change is not due to an abnormality in the output board 4 dedicated to input board failure diagnosis.

Although FIG. 2 (II) is for fault diagnosis of the output board, its operation is the same as that in FIG. 2 (A), and its explanation will be omitted.

〔Effect of the invention〕

As explained above, according to the present invention, it becomes possible to periodically diagnose and display the failure between the input board and the output board or the failure on a board-by-board basis, making it easier to find and repair the faulty board. It becomes possible to improve the reliability of the entire system.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a board showing an embodiment of the present invention, and Figure 2 (
A) and (B) are block diagrams showing the failure diagnosis circuits of the input board and output board, respectively, and Fig. 3 is the block diagram shown in Fig. 2 (A).
Logic diagram of the state change detection circuit in (B), 4th
Figures (A) and (B) are signal waveform diagrams of various parts showing the operation of Figure 3 in a normal state and in a failure state, respectively. ■A~IC...Input board 2...Output board fault diagnosis dedicated input board 3A~3C...
・Output board 4... Output board dedicated to input board failure diagnosis 5... Fault display board 14... Status change check circuit 15... Timer 16... Indicator light agent Patent attorney Yoshiaki Inomata ( (and 1 other person) Figure 1 (A) (B) Figure 2

Claims (1)

[Claims] An output board for input board fault diagnosis that generates a pulse signal of a constant period and inputs it to a predetermined bit of each input board in a board fault diagnosis circuit of a programmable controller that diagnoses the fault of the input board or output board of a programmable controller on a board-by-board basis. , an input board for output board failure diagnosis that inputs pulse signals of a constant period from each output board, a state change detection circuit that detects changes in the state of the pulse signals input to each of the input boards, and a state change detection circuit that detects changes in the state of the pulse signals input to each of the input boards. A circuit board fault diagnosis circuit for a programmable controller, characterized by comprising a display circuit that indicates a fault when a fault occurs.