A carpet with presence detector consists of a big capacitor manufactured with usual materials inside the textile fabrication process, instead of metal sheet and dielectric plastics, ceramics, etc. It is a challenge to build a robust capacitor for an environment subject to frequent deformations. Moreover, we must add the difficulty of detecting small changes in the capacity of considerably big surfaces, to which 50/60 Hz noise is easily joined up. Besides, detector electronics must communicate with a central system by the means of a wireless link, since this electronics must be built in inside the textile and it has to maintain hermetically protected. For this reason, a charging battery system based on inductive connection has been added. This system is protected by a European patent with reference EP20060725828.