Installation of parts

The parts are mounted on a piece of single-sided breadboard according to the diagram. The board size is selected based on the case size. The leads from the case of the R8 resistor are significantly larger than the holes in the board, the holes need to be drilled to the required size. The leads of some trimmer resistors are slightly larger than the holes in the board, in this case the leads can be slightly filed.

Due to the large spread of component parameters, the sensitivity unit often does not work correctly; maximum sensitivity is not achieved in the extreme position of R8. To fix this, you can select R3 in the direction of increasing the nominal value. First set 1.3 kOhm, then 1.6, then 2 kOhm, and so on, until the detection distance stops increasing. It is advisable to use C3 with zero TKE, otherwise the sensitivity setting may “float away” when the temperature increases or decreases.

I would like to note that the BOX-G01B case has (in my opinion) a significant drawback – the battery compartment is too small, the battery barely fits in and is difficult to remove without a screwdriver. There is also a problem with opening the battery compartment cover, you have to pry it off with a screwdriver.

Assembling a metal detector

The metal detector rod is made of plumbing pipes with a diameter of 25 mm, the upper part is made of a metal-plastic pipe, the lower part is made of polypropylene. At the end of the lower part of the rod, a hole is drilled for attaching the sensor. The sensor is attached to the rod with a plastic screw (the toilet lid mounting screw is used). The armrest is made of a sewer pipe.