View Full Version : metal detector

12-29-2009, 05:09 PM
i am trying to build a bot which can detect metal... basically iron....can anyone please help..

12-29-2009, 06:12 PM
what depth ? more description would help.

12-29-2009, 06:51 PM
metal slab will be on the surface

12-29-2009, 09:44 PM
A metal detector can be an inductive field sensing circuit or a beat-balance detector using 2 oscillators with a difference detector.

Any LC oscillator resonant at the center frequency has a specific current I . This current is a function of the LC ratio and the Q of the oscillator. The L or C can be varied externally to offset the Resonant Current. A simple current level detector will output the change in current.

Look at it this way: if you have fooled around with a Radio, you will see the received station grow strong or weak when you touch the antenna, turn the radio etc., This happens because your hand or any stray object wil vary the resonance & or the Q of the LC circuit inside the radio. It will result in a change in the gain which can be > or < .
Most radios nowadays have a signal strength indicator (RSSI) in the form of a 'tuning LED' or an analog meter. These indicators are current driven - more current more bright / more meter deflection.

So, all you need is a LC oscillator, a radio or a receiver and a current level detector to have a Metal detector. The change in current can be used to derive a voltage drop across a Resistance to switch on or off a transistor with a buzzer in the collector.
A Diode tuned frequency detector can replace the bulky radio.

12-29-2009, 11:14 PM
Try this


Maybe this helps

Regards Akshay,