I recommend plotting your data on a graph on paper. Take a look at the data, and determine what is unique about the point you are looking for. Look for how you can teach your program to look for this point.
I have written several algorithms that do similar, one in fact being for a power supply, the other being for RPM. Neither algorithm used any advanced analysis tools. They are just a matter of determining, mathematically, when you achieve what you are looking for. Just sit down with your graph (I recommend multiple copies) and draw horizontal and vertical lines that determine when you get to the point you are looking for. You are probably going to have to reverse the array and start from the end, so think in those terms.
If you have trouble, emai
l me a bitmap of the graph, and what you are looking for and I will try to be of further assistance. Don't do that however; until you you have given this a few tries. Your solution should be involve a lot of logic on analog levels.
Good luck
