Can somebody give a push to get it done.
Come here. Stand right on the edge. I'll give you a push. 8)
You must have some code that collects sensor data now. We need to see that code.
If the Mega is the central collection point, what is it sending to the Unos? What does it need from them?
How will you know that exactly one minute, or two minutes, has gone by? Why do the Mega and Uno need to be in sync?