frnds....help me to solve this question

sudheeralla

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Jun 2013
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A machine is being designed for a foreign parts supplier. As part of the contractual agreement the logic will
run until February 26, 2015. However, after that date the machine will enable a ‘contract_expired’ value and
no longer run. Write the ladder logic
frnds give some idea .....either in siemens or ab plc
 
Welcome to the Forum !

Writing the ladder logic is your job, as a programmer.

If you want advice on how to secure that ladder logic, post which models of PLC controller from Siemens or Allen-Bradley you want to use. The different controller types have different features with regard to security.
 
I agree with Ken's recommendation, but to also point you in the right direction, usually most PLC's have a Date & Time clock. Make sure that the time is synchronized to the actual time and date. Then write logic so when that specific date and time has elapsed disable your corresponding logic.
 
Last edited:
Interesting, is this common practice? You buy a machine, and can only use it for a year? I understand you can lose support after a year, but to disable the code?
Just wondering.
 
I have a large OEM who does exactly this using CompactLogix, because they explicitly lease their machines for a given number of running hours.

Customers don't have to lay out the cash to buy the machines outright, so it's a win-win if everybody observes the rules of the lease.

The runtime counter enforcement of the terms of the lease is explained up front and is just another technical term of the lease agreement.
 
Ken Roach said:
I have a large OEM who does exactly this using CompactLogix, because they explicitly lease their machines for a given number of running hours.

Customers don't have to lay out the cash to buy the machines outright, so it's a win-win if everybody observes the rules of the lease.

The runtime counter enforcement of the terms of the lease is explained up front and is just another technical term of the lease agreement.
Click to expand...


Yes, it makes sense for an OEM lease system.
 
One thing not mentioned is that the machine or process should be left in a safe condition prior to the shutdown. You really wouldn't want a dangerous condition that couldn't be controlled because the plc was blocked. Of course it goes without saying, the plc program shouldn't be designed to allow dangerous conditions to exist with any failures of the plc or even a simple power failure.
 
This practice is not rare one. On Modicon M340 you even have "Halt" command for that purpose, after which you need to connect cable and rerun the PLC. Unfortunately many companies mix the purpose of suppliers and banks.
 
lots of software need service contract so the question is valid.
You will have to make a separate program (hidden) to check for the current date and compare it to your date.
As extra count the days to run and display them.
 
Make sure you code it so that the date can not be reset and let them go back in time if they are unscrupulous and want to cheat on the lease agreement.
 
Thank you friends......
i gained some knowledge with these discussion.... present i am pursuing my plc course ..so , guide me to solve this question......in our lab we are using slc 5/03 in ab and s7-300 (cpu 312c)....

THANK U IN ADVANCE
 
Ken Roach said:
Welcome to the Forum !

Writing the ladder logic is your job, as a programmer.

If you want advice on how to secure that ladder logic, post which models of PLC controller from Siemens or Allen-Bradley you want to use. The different controller types have different features with regard to security.
Click to expand...
Thank you friends......
i gained some knowledge with these discussion.... present i am pursuing my plc course ..so , guide me to solve this question......in our lab we are using slc 5/03 in ab and s7-300 (cpu 312c)....

THANK U IN ADVANCE
 
In the future, please disclose that you are working in a lab or classroom environment in your initial post.

The degree of rigor required to implement this feature in the "real world" is higher than it would be in the classroom.

Have you made any progress in your own research that you would like to post as an example of your understanding of the technologies and principles involved ?
 

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