Suggest a metal detector sensor

[Nauman]

Hello.
I am searching a lot for metal detectors which can be use with Arduino UNO. Kindly tell me any sensor, which can be interface able with Arduino UNO. OR you can help me by telling the simple circuit diagram of the sensor so that i can make it and then attach it to the Arduino UNO. 
The module will work on simple rule, The sensor will detect , Arduino will get the output of the sensor and will perform further tasks.
Also i will need your help on How to read the output of the sensor you suggest / tell!
Its my second post guys and i am confused about asking the questions  and also i am not good in English, so sorry for this 
Hope i will get appreciable help from you guys.
Thanks

[cjdelphi]

I've never made one, but it seems it's not all that difficult, basically you have a ring of copper wire, the circuit produces a magnetic field, which is fed into the IC,  if something
interrupts/disturbs that magnetic field, your circuit will detect it..

how? no idea, but if someone can make a metal detector from a 555, how difficult can it be?

This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes.

[Nauman]

Thanks for the reply.
Sir, any idea about how Arduino UNO will read this sensor... the one with 555 timer!

[Grumpy_Mike]

Thanks for the reply.
Sir, any idea about how Arduino UNO will read this sensor... the one with 555 timer!

Just feed the arduino with the output from pin 3. If you run it off 5V then connect it directly otherwise use a potential divider. Then use the pulse in function to test the frequency on this pin, it will change when the 10mH coil is close to metal because this alters it's inductance.

[dc42]

How sensitive do you need the metal detector to be? Metal detectors that rely on the change of inductance of the search coil are long obsolete due to their poor sensitivity - although the principle is still usable for proximity detectors. There are two metal detector technologies in common use now: the VLF induction balance technique (which requires 2 coils and a lot of analog electronics or a DSP), and the pulse induction technique. There is a design for a pulse induction detector using two attinys at http://www.miymd.com/index.php/projects/tpimd/. Unfortunately, it doesn't work well using an Arduino instead of attiny for the receiver, because the Arduino doesn't have the 64MHz fast i/o clock needed for accurate timing.