Im trying to build a LVDT transformer where copper windings have to be winded over a pipe with radii of 7mm... It must be winded upto 14mm.. Length of pipe is 500mm... Input is 12v AC 50hz... Can any one say how many turns required to do it and what copper wire is needed..

 

Hi and welcome.

HERE is a webpage on how to build an LVDT transformer.
Perhaps it will get you started with your project.