Variable Frequency Metal Detector
Tom Goff’s wife and son enjoy the hobby of metal detecting, and in order to join in on the fun – rather than simply following in a very slow walk–he decided to make his own detecting device. His project is based on the Matchless metal locator, and uses a pair of 555 timers and other discreet electronics for operation – with no microcontroller to be found.
The unique thing about this build from an electronics standpoint is that it not only includes adjustment potentiometers for coarse and fine thresholds, but adds a third pot to dictate its magnetic frequency oscillation.
The design employs a transmitter coil, along with a receiver that picks up on these signals. These signals are affected by metal objects to make a corresponding sound, and the ability to change this frequency gives another adjustment to tweak when finding treasure, trash, or something in-between.
Mechanically, the device is built with non-metallic elements so as not to interfere with the signal, including: PVC pipe, laser cut acrylic, 3D-printed parts, and even nylon bolts/nuts. You can see a bench test of the device in the video below, and more info and clips are available via Goff's write-up.
The build looks great, and Goff will certainly have a great time using it with his family. Maybe he'll even find some valuable items in the process!