Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

Shunluo Inductance Power Inductor SWPA Series First Class Agent

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In the current industrial production process control, the plc control system is generally adopted, and the interlock control between the control devices is realized by the software program, that is, the automatic control, the factory machinery equipment driven by the control device completes the production process that satisfies the process requirements. . Here, the operation of the device is divided into two modes: single manual operation and automatic control operation. In the manual operation of the unit, the equipment is generally operated in situ (on the side of the machine). PLC program control is mainly for automatic control, but it also includes single manual operation, the completed function is the same as the local (machine side) operation, the difference is that it is realized by program, and Generally, it is performed by clicking the mouse in the monitoring screen of the upper computer, that is, in the machine room or control room instead of the local (machine side). The main difference between manual operation (including manual single operation in the program) and automatic control program is that the automatic control program is run after the equipment is officially put into operation and there is no fault in the normal operation. Manual operation is used during the debugging process for the commonly used "doping", or when there is a device failure during normal operation. For example, when the water level of a water supply tank is controlled, when the water level is high, the water supply of the water pump is started. When the water level is low, the pump water supply is stopped. If the water level sensor of the water tank fails, automatic control cannot be performed, so in order to continue to maintain production, it is necessary The operator manually operates on site, manually starting and stopping the operation of the outlet pump and the corresponding valve according to the liquid level indicator of the water tank. It should be pointed out that the equipment referred to in this paper is a switching device controlled by PLC output, and the analog equipment is not discussed in this paper.

Manual and automatic switching of devices

In this context, equipment refers to factory machinery and its control equipment. Control equipment refers to motors, valves, etc., while the manual and automatic operation of the equipment is mainly reflected in the manual and automatic operation of the control equipment. For example, the control of the motor is generally carried out by the MCC (Motor Control Center) electrical control system. The remote and local signals of the motor, ie the automatic and manual switching signals, as well as the start, stop, fault and other signals are provided by the MCC. And connected to the PLC hardware system. When the remote local switch on the MCC cabinet is hit to the ground, the local manual operation is performed; when the remote is reached, the PLC program is automatically controlled, or the mouse-type manual operation is performed on the upper computer screen. We can understand the relationship between PLC control system, local electrical control system, control equipment and factory machinery, that is, automatic control (including manual operation in PLC program) is controlled by PLC control system through electrical control system, by electrical The control system controls the control equipment like a motor, and finally the control equipment drives the operation of the plant machinery. The electrical control system, like the MCC cabinet itself, can be directly operated manually.

For the control of the motor, in normal operation, the first is the automatic control of the PLC program. At this time, the remote local conversion switch is in the remote position, and then if there is a problem or fault that the PLC cannot handle, it needs to be in the screen of the upper computer. In this case, the operation of the single device is manually performed to maintain production or perform a safety interlock operation. Finally, if you still can't solve the problem, you need to operate at the local (next to the machine), usually the motor stops.

For valves, there is also a corresponding electrical control system. Just like the MCC, it is usually a local on-site solenoid valve control cabinet (box), which generally has a remote local switch for manual and automatic operation. Switch. As with the motor control, in normal operation, the PLC is automatically controlled first. At this time, the remote local switch is in the remote position. If there is a problem or fault that the PLC cannot handle, it needs to be on the screen of the host computer. Manual operation of individual equipment to maintain production or perform safety interlock operations. Finally, if the problem still cannot be solved, the remote local switch will hit the local position and perform local control on site. If the problem cannot be solved, then only manual valves can be used for safe operation.

Obviously, manual and remote automatic operation on site is achieved by a transfer switch on the local control cabinet (box). The manual and automatic switching functions in the PLC program can also be done, and it is no problem to implement an operation similar to the changeover switch in the program.

Program implementation method for manual and automatic switching of devices 1

When the remote local signal is 1, it means that the switch on the control cabinet (box) in the field hits the remote position, and the automatic control of the PLC can be performed; when it is 0, it means the manual operation on site. In order to realize the manual automatic switching inside the program, just like the remote local signal, an intermediate variable is set. This intermediate variable is used as the flag of the manual manual device operation, and is assigned by the host computer monitoring program. When the value is 1 , the manual operation of the single device of the program; automatic control of the PLC program when 0. It can be seen that each device in automatic control operates under these two conditions.

Where (L) is the set instruction and (U) is the reset instruction. The reason for setting and resetting the command here is mainly to consider that the start (open) condition and the stop (off) condition may be pulse type (for example, rising edge pulse), and need to be maintained (Note: if the control loop in the MCC is used "Start-hold-stop" mode, then the pulse output is more suitable, just like the self-reset button. Here is not done to simplify the ladder program. Interested readers may wish to try). The motor start or stop condition is an interlock condition during automatic control. When the host computer performs manual operation, the automatic control program cannot be executed. When the local operation is performed, the PLC program control cannot be executed. The program can reset the motor start and stop control signals at this time as needed. The control of the valve is the same. In this way, each device can be operated automatically or manually according to the situation.

Program implementation method for manual and automatic switching of devices 2

The above method considers various situations when the opponent automatically switches. When the program is designed, it is necessary to pay attention to the automatic hand switching problem at all times, and the program amount is also increased compared with the automatic switching without the hand. If you separate the manual program from the automatic program, the program will become more clear, and you will not have to pay attention to the automatic switching problem when designing the automatic program. Is this feasible? We may wish to transform the above ladder program into Figure 2.

Obviously, this is possible because the manual execution of the manual program, the start, stop or opening or closing of the motor or valve is determined by the manual procedure. That is to say, when the automatic control program is running, if there is manual operation of the upper computer, the manual operation of the upper computer takes precedence. For example, when the automatic program requires the motor to stop, if the upper computer is manually operated to start it, the motor starts. The reason for this is that the program evaluates to the same variable or IO tag, and the last executed program is valid.