Metal Detection (Not Really Possible)

The miserable search results have led me to document this otherwise easy going DIY soldering project. It is a "Metal Detector Kit" with around 14 parts to be soldered on an exemplary document PCB, which has the breadth of a modern smartphone.

What you get

The small bag contains different ceramic condensations (2x 2A222J with 2200 pF, 100 Volt and 2x 104 with 0, 10 uF), 1x electrolyte condensation (100 nF, 50 Volts) 1x potentiometer 104, 2x resistors (220K, 2.2K), 1x buzzer and 3 transistors (2x PNP: 1x S9012 H331 and 1x S9015 C118; 1x NPN: 1x S9018 H331) and of course the red PCB.

Following the link to ucreatefun.com I could not find useful information for me. Also I could not overcome a language barrier on a site.

Test

After the quick soldering I connected both 2 AA batteries and switcht to a 3.7V LiPo: the buzzer immediately gave a signal and could also be calibrated with the potentiometer. So far so good.

Problems

Neither my coins nor matallic objects with paper separated from the bottom of the PCB could be successfully detected. It worked only on a small knife from the kitchen and only in direct contact.

A use for finding fallen screws in DIY projects (that was my intended use) or even the finding of metallic objects on the beach or in the garden are not possible with this product.

On Youtube there are similar video projects: one works just fine, the other does not.

What was your experience with this kit and how do you find your dropped screws?