Probably most keen do-it-yourself enthusiasts are aware of the dangers of drilling into the walls of practically any building, and use some form of pipe/cable detector to check that it is safe prior to doing any work of this type. Such precautions should ensure that there are no nasty surprises, but some types of cable can be difficult to detect.

Most pipe and cable locators are actually metal locators that are optimized for this application. They are quite good at finding things like nails in doors and plasterwork, locating metal pipes, and finding cables in metal conduits. However, they tend to be less effective at finding electric cables that are in plastic conduits.

The problem seems to be that there is simply not that much metal in an electric cable, especially a lighting type that is only designed to carry modest currents. This makes such cables difficult to detect unless they are close to the surface of a wall.

The Simple Starter project featured here uses an alternative approach to finding cables, which is to pick up the 50-Hertz mains "hum" signal produced by the cable. This signal seems to be relatively easy to locate, even with a small cable that is buried deep in a wall.