[Introduction] As the new year comes to a close, it’s time to press for project payment again. If we really encounter a problem, we might as well try the PLC scheduled shutdown method.
Preface
Due to many practical reasons, it is common for automation projects to use scheduled shutdowns. However, this is a double-edged sword. When collecting payment, you also face the risk of irritating customers or causing potential harm to equipment and people, which will involve some legal procedures. In fact, this is a situation that neither party wants to see. Therefore, how to design a scheduled shutdown is also very particular. It can give customers a little warning without causing major damage. In addition, it should not add too much workload to yourself. This editor is deeply aware of this. Timing program The more complex the design, the greater the potential risks, and the more frightened you become! Recommended scheduled shutdown methodsNO.1 For some small relay control equipment , because there is no PLC control program, a combination circuit of timer and intermediate relay to achieve scheduled shutdown. NO.2 Select the reference time of the timing program, for example, read the system time of the CPU, the system time of the host PC or the CPU hardware pulse accumulation time, etc. Generally speaking, it is more reliable to select the CPU system time. If necessary, you can use the host PC time or CPU hardware pulse accumulation time to verify whether the CPU system time is invalid.

NO.3
The timing program should not be too rigid. Do not lock the program as soon as the timing is up. This may cause damage to on-site equipment or injure on-site staff. You can choose some parts that do not involve life safety or equipment safety to stop first and set the position. Alarm sign, while warning the operator with text or sound on the host computer. You can also prohibit the display or error display of some non-critical data to attract the operator's attention.
NO.4
The timing program must be released appropriately. You can choose a free DI point as the release point or use a special combination operation on site to release it. Of course, it is best to use the host computer authorization code or combination code.

NO.5
Please also pay attention to the authorization code. Your authorization can be authorized in multiple time tags. For example, if some users cannot pay you all the fees as agreed, you can use the authorization to extend the operating period by 1 month, 3 months, or half a year, so that users are always protected. Your conditioning.
NO.6
The scheduled shutdown of the PLC can also be used in conjunction with the host computer program. When the PLC reaches the warning point at the scheduled time, some auxiliary functions of the host computer will be disabled. When the PLC reaches the stop point, the host computer screen will be automatically deleted, causing the operator to lose control.

NO.7
The highest level of timing - program bombing. The timing program has been executed. If you encounter a stubborn user who refuses to pay the fee, you will no longer be polite to him. Use the program bombing method to delete the main sections of the program to prevent the program from being interfered by other people. Modification, this method requires a special PLC to support, or use program copy to fill the space, etc., or send a command to the host computer to directly delete the program.
NO.8
Mastering the stick, but aiming for the yard. No matter how clever the design is, there is always a way to crack it. Once the other party cracks the PLC hardware password, the timing program can be canceled. This involves how to select and set the system's hardware protection and the CPU hardware password cracking problem; and One thing is that reading hardware information as a system running flag can prevent direct replacement of hardware operations.
Summarize
Finally, I still hope that everyone will never have to use these methods, and the world is still beautiful. I wish all my industrial control friends good luck in their work!