How to manage Consecutive shifts constrains?

Question

I'm trying to build an optimization scheduling program but I'm having troubles defining constrains for consecutive lunch time. It is easy to define a constrain setting that in a day of 8 hours, every worker must have at least 3 hours for lunch. With hrs being the model binary options for each hour, it would be something like Sum(hrs) >= 3

But for defining that those 3 hours must be consecutive I cant think of a way to set the constrain. I am starting to use disjuncts and so, but I dont know if it is the best way. Right now I am trying all of this with pyomo.

Answer 1

 startlunch[t] >= lunch[t]-lunch[t-1]
 sum(startlunch) <= 1
 sum(lunch) >= 3
 lunch, startlunch: binary variables

Intuition: startlunch[t]=1 is when we start lunch. We go from lunch[t-1]=0 to lunch[t]=1.

1. You probably can assume lunch[-1]=0.
2. You can add a worker index to the variables.