Turn off a PLC but the other takes control

[amancini]

Hi,
I have a 1500 that controls a station with diferents warehouses, but i also have a 1200 that controls one of those warehouses, i have been told to if the 1200 is turned off the 1500 have to take control of that warehouse as well, the only solution i can come across is to duplicate the inputs and outputs of the 1200, or using a relay... i dont know, because if there is no other solution it doesnt make sense.
Thank you.

 

[tdoa]

Replace the 1200 with an ET200SP remote IO rack, add an UPS, now they cant power off the 1200..

 

[amancini]

Nice idea, but the point i have been told is to turn off on purpose the 1200 so the 1500 takes control

 

[Puddle]

I'm struggling to see the end goal here. As you said, you'd need to duplicate the IO to achieve this. ET200SP seems like the obvious way to go, but you'll end up with the 1200 serving no purpose. Are they trying to achieve a redundancy setup where either PLC can be turned off where required?

 

[amancini]

I dont understand the end goal either to be honest, they gave me a FESTO station, i wired it up, programmed with a 1200 and now they gave me a 1500 which is supposed to control the whole station, but the 1200 has to only control one warehouse in the station, but if this 1200 is turned off, the 1500 will take control of the warehouse, i dont know if its a real end goal or something but i cant see it, from my point of view the 1200 here is completely useless.

 

[Chris_M]

Might be worthwhile to ask whoever is in charge of the project. "I don't know what your end goal is, if you tell me I might be able to do it cheaper/better..."

 

[amancini]

He is my college teacher, i dont think the price is the problem

 

[Chris_M]

As a class assignment this makes more sense, there may not be any/much real world application but it will get you to think.
The two solutions you mentioned (duplicate inputs or relays) should work, just figure out how you will have the 1500 detect a failover state.
Good Luck!

 

[James Mcquade]

Program the 1200 with an unconditional output. the output has feedback wires to the 1500 input.
at long as the 1500 sees the input from the 1200, the logic sits there. when the output is off, turn on the logic.
OR
if there is a comms interface between the 2 units, create a heartbeat signal. when the 1200 heartbeat stops after x seconds, the 1500 takes over.
i may be missing something.
james

 

[I_Automation]

i have been told to if the 1200 is turned off the 1500 have to take control of that warehouse as well,....

There are many times when I have to tell a client, and bosses when I worked at shops, that what they wanted me to do was impossible (or impossible to do with no budget as that would cost $2 million)

I have also admitted that while it might be possible to do, it's not something I would be able to do and they would need to call in an engineering and controls company at a nice cost.