JP3663606B2 - Time management method using fixed period type PLC - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention can be used to control an external device by generating a time that can be freely managed by a user using a user command during a fixed cycle control of a fixed cycle PLC device (programmable logic controller). About how to make.
[0002]
[Prior art]
In the prior art, when using arbitrary time management during the control period of the PLC, a counter with a preset function is provided on the system side of the PLC device as an I / O device, and the time value is determined by an IN / OUT instruction of the CPU. It is possible to manage an arbitrary time by presetting and generating an interrupt signal for notification of the arrival time or reading and monitoring the count value of the counter by an IN command.
[0003]
[Problems to be solved by the invention]
However, the conventional technique has a problem in that the burden on the CPU side is increased according to the interrupt signal generation method. In addition, a PLC device that is not provided with an I / O for interrupt cannot manage arbitrary time.
Therefore, the present invention does not use interrupt signal generation, and outputs a timed signal according to the set time for the user to set an arbitrary time during the fixed-cycle control of the PLC, which is used for control of the external device. It provides a way to use it.
[0004]
[Means for Solving the Problems]
To solve the above problems, the present invention is the periodic type PLC, said the time management counter for counting the reference pulse having a constant period shorter period than the cycle time of the time management in IN command of the user program of the PLC A reading gate for reading the count value of the counter into the PLC;
1) When the periodic processing of the PLC is started, the current value T of the time management counter is read by the IN instruction of the user program and stored _in Tin .
2) Add the target time ΔT _n and the current value T _in to set the target time T _sn .
3) Output signal A for external control equipment,
4) The current value T of the time management counter is read by the IN instruction of the user program and stored in T _inx .
5) Compare the current value T _inx with the target time T _sn ,
6) If the current value T _inx is equal to or greater than the target time T _sn , the signal A for the external control device is turned off,
7) A time management method using a fixed period type PLC, wherein the steps from 4) are repeated if the current value T _inx is smaller than the target time T _sn .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
By the above means, a signal having an arbitrary time width can be output to the outside using the user program during the control period of the fixed-cycle PLC.
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. 1 is a PLC, that is, a programmable logic controller, 2 is a CPU, 3 is a hard counter for time management, and counts 1 MHz pulses unconditionally. Reference numeral 4 denotes a reading gate, from which the count contents of the time management counter 3 can be arbitrarily read from the user program side by an IN command.
FIG. 2 is a flowchart showing a user program for arbitrary time management. FIG. 3 is a diagram for explaining the operation of FIG. The operation of this user program will be described below with reference to FIGS.
In the middle of the PLC system area process, one period of the fixed period PLC is started (K), and when the system area process is completed, the fixed period process is started (A). T is read with an IN command (B).
Next, the count value T is stored in T _in (C), and after setting the target time T _sn from the target time ΔT _n and the current value T _in (D), a signal A for external device control is output ( E).
Thereafter, user programs F to H for counting the duration of the external device control signal A are executed. That is, the count value T of the time management counter 1 is read by an IN command (F), the current time value T is stored in T _inx (G), and then the stored current time value T _inx and the target time T _{sn are} stored. If the target time has not been reached, the process returns to step (F). If the target time has been reached, the process proceeds to the next step (I) (H).
In step I, the signal A is turned OFF, and in the next step J, calculation, transmission, etc. are executed as other tasks.
Accordingly, since the time signal output to the outside can be arbitrarily adjusted by selecting the set value of the target time ΔT _n , it is possible to control the external device using this. Examples of external device control include pulse width modulation by controlling the gate signal of a transistor, interrupting the PLC itself with a generated periodic pulse, and executing periodic processing.
[0006]
【The invention's effect】
As described above, according to the present invention, an arbitrary time signal can be generated without imposing a burden on the system side of the PLC device, and this signal can be used as a signal for controlling an external device of the PLC.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of the present invention. FIG. 2 is a processing flow of an embodiment of the present invention. FIG. 3 is an operation explanatory diagram of the present invention.
1 PLC
2 CPU
3 Time management counter 4 Reading gate

Claims (1)

A time management counter that counts a reference pulse having a period shorter than the cycle time of the fixed period to the fixed period type PLC, and reading for reading the count value of the time management counter into the PLC by an IN instruction of the user program of the PLC With a gate,
1) When the periodic processing of the PLC is started, the current value T of the time management counter is read by the IN instruction of the user program and stored _in Tin .
2) Add the target time ΔT _n and the current value T _in to set the target time T _sn .
3) Output signal A for external control equipment,
4) The current value T of the time management counter is read by the IN instruction of the user program and stored in T _inx .
5) Compare the current value T _inx with the target time T _sn ,
6) If the current value T _inx is equal to or greater than the target time T _sn , turn off the signal A for the external control device,
7) A time management method using a fixed period type PLC, wherein the steps from 4) are repeated if the current value T _inx is smaller than the target time T _sn .

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