OK, flushed with my previous success I am now going to have a bash at using the comparator. What I am going to do is check the voltage of the supply batteries compare them against a known value and if they are OK do nothing but if they are below the appropriate level then flash an LED a couple of times (now that I can do it!!).
As far as I can see I am going to have to learn about A-D conversion and using the comparator.
Is there anything in particular that I should be aware of before I start?
Cheers
Stu