JPH0264708A - Programmable controller - Google Patents

Abstract

PURPOSE:To identify the condition of a service power by a user program and to prevent the malfunction of the lowering of the power by providing a detecting means to detect the voltage lowering of the service power and an output means to output an output lowering condition to the outside. CONSTITUTION:At a certain time, an overload is connected to a service power terminals 11a and 11b, a protecting circuit functions and a terminal voltage lowers. In this case, a comparator 26 detects the voltage lowering, and when a power status is '1', an FF 28 is set through an interface 27. Consequently, a relay X turns on, an abnormal condition is outputted to the outside and a light emitting diode D2 is turned on by a Q output. When the power status is not set, it is regarded that there is not an abnormality in the service power, the relay X turns off, the FF 28 is reset and the diode D2 is turned off. Thus, the power status area can be accessed and the condition of the service power can be identified by the user program if necessary and therefore, the malfunction by the lowering of the power can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a programmable controller, and particularly to a programmable controller that is characterized by measures against abnormalities in power supplied from the programmable controller to external equipment.

[Prior art]

Conventionally, the power supply circuit of a programmable controller includes an internal power supply that supplies internal circuits and input/output circuits of the programmable controller itself, and a service power supply for input/output devices used by users. The service power supply is not used within the programmable controller and is entirely open to the user. A power supply protection circuit is provided to protect the power supply when the user uses the service power supply in an overloaded state.

[Problem to be solved by the invention]

However, in such conventional programmable controllers, if a user uses the service power supply in an overloaded state, the protection circuit is activated, which may cause the voltage of the service power supply to drop or cut off the power supply. However, a voltage drop or interruption of the service power supply cannot be detected by the user program used in the programmable controller. Therefore, there is a problem in that the input/output load may cause a malfunction of the resequence control which does not operate normally.

The present invention has been made in view of the problems with the conventional service power supply, and a technical problem is to detect a voltage drop or cutoff of the service power supply and make the state available for use in a user program. shall be.

[Means to solve the problem]

The present invention is a programmable controller having an internal power supply supplied to each internal block, a service power supply connected to an external device and having a protection circuit, and comprising: a detection means for detecting a voltage drop in the service power supply; and output means for outputting to the outside an output reduction state caused by the output reduction.

[Effect]

According to the present invention having such characteristics, a voltage drop in the service power supply is constantly checked by the detection means,
If the service power supply is overloaded or short-circuited, the protection circuit operates and detects the voltage drop. Then, the abnormal state of the power supply is outputted to the outside by the output means.

〔Effect of the invention〕

Therefore, according to the present invention, once the voltage of the service power supply drops, this state is identified within the programmable controller and an output can be provided to the outside. Therefore, the state of the power supply can be identified by determining it using a user program. Therefore, it is possible to prevent malfunctions in sequence control.

[Explanation of Examples]

FIG. 2 is a block diagram showing the overall configuration of a programmable controller in which the present invention is implemented.

In the figure, the programmable controller has a central processing unit (hereinafter referred to as CPU) 1, and a main memory 3 that stores a control program is connected to the CPU via a path line 2. The CPU 1 also has an I10 that holds the status of the input/output devices connected to the user memory 4 and the programmable controller, and the power status signal of the service power supply.
Memory 5 is connected. The pass line 2 also includes an input circuit 7 that temporarily holds input from a switch 6 such as a proximity switch or a photoelectric switch, and an output circuit 7 that controls an output device such as a relay 8 based on the input state and user program. A circuit 9 is connected to the programmable controller.A power supply circuit 10 is connected to the programmable controller to supply power to each block and also to supply service power to devices outside the programmable controller that can be set arbitrarily by the user. Provided.Terminal 1
1a and llb are output terminals of the service power supply.

In the present invention, the power supply circuit 10 is provided with a detection means A for detecting a drop in the voltage of the service power supply, and an output means B for providing the detection output to the outside.

FIG. 1 is a diagram showing a detailed configuration of a power supply circuit 10 according to this embodiment. This embodiment shows an example of a power supply using a switching regulator, and both ends of a commercial AC power supply are connected to a main switching circuit 22 via a noise filter 21. The main switching circuit 22 cuts off the power at a predetermined high frequency, and has a transformer 2 at its output end.
The two primaries of 3 are connected. The transformer 23 converts the input voltage into a predetermined voltage, and has secondary windings for the internal block power supply and the service power supply.

Rectifier/smoothing circuits 24 and 25 for rectifying and smoothing the AC output are connected to these windings, respectively. The output of the rectifier/smoothing circuit 25 is supplied to each block shown in FIG.

Now, the rectifier/smoothing circuit 24 has a predetermined voltage, for example, DC 24V.
It outputs a voltage of 1, and includes a protection circuit to protect the power supply when the load current exceeds a predetermined value. Further, the output end of the rectifying/smoothing circuit 24 is directly connected to the power supply output terminals 11a and 11b, and at the same time is connected to the detection means A for detecting the voltage state thereof. In this embodiment, a comparator 26 is provided as a detection means, and a common connection terminal of a resistor R1 and a Zener diode ZD connected to both ends of the internal power supply is connected to a reference input terminal of the comparator 26. Further, the service power source is voltage-divided by resistors R2 and R3, and the midpoint thereof is connected to the other end of the comparator 26. Comparator 2
6 detects an abnormal state and outputs an output when the reference voltage reaches a threshold value Vrefl set below the normal voltage of the service power source by appropriately setting the reference voltage. A resistor R4 for providing hysteresis is connected to the input/output terminal of the comparator 26, and a load resistor R5 is connected to the output terminal and the power supply terminal. Now, the output of the comparator 26 is connected to the pass line 2 via an interface circuit 27. The interface circuit 27 transmits power status (referred to as PS status) information obtained as the output of the comparator 26 to the CPU 1 via the path line 2, and sets and resets the flip-flop 28 using a control signal from the CPUI. . A transistor Tri is connected to the Q output terminal of the flip-flop 28, and when the flip-flop 28 is set, the transistor Tri is turned on and the relay X is energized. Relay X outputs a contact signal indicating the cutoff state of the service power source to the outside as a contact output. A light emitting diode D2 serving as an indicator is connected to the Q output terminal of the flip-flop 28. On the other hand, the interface circuit 27 connects the output of the comparator 26 to the pass line 2.
The flip-flop 27 is reset based on a reset signal obtained from the CPU 1. Here, flip-flop 28.
The relay X and the light emitting diode D2 constitute an output means B that holds the power status information of the comparator 26 and outputs it to the outside.

Next, FIG. 3 is a flowchart showing the operation of this embodiment. When the operation starts, first, in step 31, initial processing such as recognizing the RAM area of the main memory 3 and the states of the input/output cover sofa circuits 7 and 9 is performed. and step 32
The on/off states of input switches and the like are read from the manual buffer circuit 7 and the output buffer circuit 9 and stored in the I10 memory 5. Furthermore, in step 33, the program counter of the user memory 4 is set to "0", and the process proceeds to step 3.
4, the commands in the user memory 4 are sequentially read out. Then, it is checked whether the command is an end command, and if it is not an end command, the process advances to step 36, executes the command, and returns to step 34. In this way, the user programs held in the user memory 3 are executed sequentially, and when the end command is reached, the process proceeds from step 35 to step 3.
7, the execution result of the instruction is given to the output sofa circuit 9, and the input data is read from the input sofa circuit 7. Then, the process advances to step 38 and the PS status information of the service power supply is read out from the interface circuit 27.

This status information is used to detect whether the voltage of the service power supply has decreased below the dark value based on the output state of the comparator 26. The process then proceeds to step 39 and stores the data in the PS status area of the I10 memory 5. Now, as shown in FIG. 4, when an overload is connected to the service power supply terminals 11a and 11b at time t1 and the protection circuit operates and the terminal voltage drops, the voltage drop is detected by the comparator 26. At this time, the PS status is detected in step 40 and if the PS status is 1, the process proceeds to step 41 and the flip-flop 28 is set via the interface circuit 27. Then, relay X is turned on and the abnormal state can be outputted to the outside by its output.

Furthermore, the Q output of the flip-flop 28 lights up the light emitting diode D2, which is an indicator. and step 33
Return to , reset the program counter, and repeat the same process. If the PS status is not set, it is determined that there is no abnormality in the service power supply, so the process proceeds to step 42, where relay X is turned off and flip-flop 28 is reset. Then, the light emitting diode D2 serving as the indicator will be turned off. Then, the process returns to step 33 and repeats the same process.

In this way, the power status of the service power supply can be monitored every time the user program is executed, and when the voltage of the service power supply falls below a predetermined value, the abnormal state is retained in memory and output to the outside by a relay. Ru.

Therefore, the state of the service source can be identified by the user program accessing the PS status area of the I10 memory 5 as necessary. Therefore, it is possible to prevent malfunctions due to a drop in service power.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power supply circuit and its peripheral circuits of a programmable controller according to an embodiment of the present invention, FIG. 2 is a block diagram showing the overall configuration of a programmable controller according to this embodiment, and FIG. 3 is a circuit diagram showing the entire configuration of a programmable controller according to this embodiment. FIG. 4 is a flowchart showing the operation of the programmable controller according to the method shown in FIG. A ------- Detection means B... Output means l - CPU 2 - Pass line 3 - Main memory 4 -... -User memory 5...--I10 memory 10...
−・Power supply circuit 24.25−・−・・・・Rectification/smoothing circuit 26・−・−・Comparator 27・−・−
Interface circuit 28-...-Flip-flop X------Relay

Claims (1)

[Claims] (1) In a programmable controller having an internal power supply supplied to each internal block and a service power supply connected to an external device and having a protection circuit, a detection means for detecting a voltage drop in the service power supply, and the detection means A programmable controller characterized by having an output means for outputting an output reduction state due to the output to the outside.