Metal detector kit (k7102)

please, can someone explain me how does this kit work? i thought metal detectors need AC to work, but this kit works with a 9V battery. so, how does the coil work? how can this kit detect metals without any V or I variation (sorry, i’m spanish and i have some troubles to write in english)? why does it have a diode (not the LED, but another one)? the LED is on without moving the metal, only because of its presence. there is a push button to close the circuit, but the LED stays on without pushing it repeatedly, only holding the button.

you can see the circuit in google easily if you don’t know how it is, i just tried.

there is an oscillator built around a transistor/coil/capacitor…
Do not understand your question about the led.

thank you. if you could explain how does that oscillator work it would be great. thank you anyway for your help

Explaining how an oscillator works is not possible in a few words. There are even books written about it. Please do some research yourself. At first sight this seems a tuned collector oscillator to me. So your friend Google will help you out.

thank you :wink:

This is a really interesting question