I want to be able to determine the location of an object that will be moving around in a rectangle about 15" X 10"
The location must be accurate to within about 1/4" and be measured at least 100 times per second.
The first idea I had for accomplishing this is to have the object transmit a pulse signal every 10ms and have a receiver in each corner wired to a micro controller and measure the difference in time between when each receiver gets the signal to triangulate it's source.
My first thought was to use IR receivers and transmitters, but I would have no idea how to do the triangulation with signals that move so fast.
So then my second thought was to use sound. I would want to transmit at a frequency above the human hearing range. And it seems to me that higher hertz = greater accuracy. The speed of sound is about 13,400 inches per second. So that means to get 1/4" resolution, I would need 56kHz or higher.
First off, I've never dealt with sounds above the human hearing range. This will probably be on for periods of about an hour, and may be just a few feet away from ears. As long as I use low power, is there any way that this could be a hazard?
Secondly, what kind of speakers are capable of transmitting 56kHz? And similarly, what kind of microphones could pick up 56kHz?
Other methods of triangulation would also be appreciated.
Best Answer
About RF:
The idea is to cast let's say 100Mhz signal and measure phase shift between received signals in different points. Then you'll be able to calculate the location.
Measuring time difference directly could be tricky, as you will need 0.1ns or better accuracy (1ns = 30cm in air).
Piezo-emitters are very capable going into sub-Mhz sound range. Nearly any mic(probably except coal one) can receive 50-100Khz sound with proper amplification. Safety is usually not a problem as long as you are under-1W range, and I doubt you would need more than 0.01 :-)
RF way is way harder to implement but I belive more reliable.