how to sense distance
How can I make use of microcontroller to check to distance between the two objects?
I want to use a transmitter and a receiver to monitor the distance between two objects. If there distance is too large, such as 10 meters away, my microcontroller to alarm me.
How can I achieve this? I am thinking about calculate the time delay, but not sure is it feasible or not.
By the way, which kind of receiver and transmitter shall I choose?
Thanks in advance =)