Logic help - shifts

[NoamC 1]

Hey,

(Programming a M224 with Machine Expert Basic)

I'd like to get some input from you guys about a logical task:

I have 8 contactors controlled by my PLC outputs, they heat a water boiler.

throughout my operation, I require a different amount of heaters (I could move between 1-8 heaters in a single operation)

I would like to scramble what contactors I put in use every time I start an operation, in order to not constantly use the same heating elements and wear specific ones out.

For example, in the first stage of heating I will use contactor #1, next time I start the operation I would like to use contactor #2 and so on..

How would you approach this problem? SBR? Timers?

Thanks

[Dhris 0]

Hey 

This is a intresting challenge and idea I like it ,

How much time can you alot to it?  is it posisble to keep a timer for how long each element has been run ?

I might go in the direction of making a array of timers and then sorting the timers and using x amount from the unused side

 

Cheers

 

[NoamC 1]

I also went for the timers - what I did was time each contactor, then sort the array of TMx values, stored the sorted array in more memory words and then back-compared the sorted memory word to every timer. this way I could choose the group of contactors that had worked the least (or most).

But in the automation system I am working on I do not want to equalize all the timers - since they are heating elements I want them to work for different lengths of time so they do burn out all together.

I was thinking in the direction of a shift bit every time the system goes on/off - an arbitrary shift with no regard to how long the heating elements have been used, but I am having trouble implementing this.

 

 

[Dhris 0]

Have you moved forward with this issue , what wast the development?