To come up against an electric cable while drilling a hole in a wall can have catastrophic consequences. Likewise, drilling into gas, water or central heating pipes can be extremely hazardous. With a handy metal detector it can now be determined beforehand whether there are metal objects to be found in a wall, ceiling or floor.

An LED indicates if a metal object is in the vicinity. If an audio signal is also desired, space has been provided on the PCB for a buzzer ( type like SV4/12-S ) to be connected (not included).

The PCB has been specially constructed to fit entirely into to the separately available box.

If you experience difficulties with the calibration of the unit (I.E. if the LED doesn't turn off, when there isn't any metal present ), replace C1 with a ceramic 1.2nF (122) capacitor. This behaviour is due to a spread on the component values and differences created when winding the coils.