Beginner would like to build Sandbanks PI Metal Detector

Cornelius, I wired the switch to the 0V, but when I turn the switch OFF, and the audio goes to a very high pitch and dosen't seem to turn OFF. I have to unplug the power for it to stop??

Aliman
 

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Cornelius, I have enclosed a pic of the connection to the switch. It is inbetween 0V and power connection. Is this right, because it still won't turn OFF until I unplug the power?

Aliman

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Thanks Cornelius. I used a DPST switch, connected it the way you specified, works perfectly.

Aliman

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Ali , do as Xavier told you . Make a second coil . A smaller diameter coil will detect very small objects sooner than a larger coil . A larger coil will go deeper but will not detect the smaller objects .  Measure the circumferense of the coil  ( in your case   2 x PI x R ) and multiply that by the amount of windings  ( in your case  20  )  . That will give you the total length of the Cu wire you used  . Use this same length to wind a coil with a  smaller  or larger  coil . Try it  , you will like to work with the new material you built yourself .  Cornelius

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Hey that's ok, it gives you the time to study the functionality of the whole thing like what is IC1 555 and what is it used for, how come is there a pulse and why is there a TIP 31A and not a BC 184 you can go very deep in to the study of the design and you will have a totally new perception of the whole thing.

Xavier


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Ali , I made those changes already  ( the two blue capacitors adde on to the PCB ) . You have to learn the settings of VR1 and VR2 .   Cornelius

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Ali.  No metal close to the coil. Settings are found by holding  Gold close to the coil and set the detector so that you hear a sound .  The settings are than for gold only ( and maybe silver .  For iron you find a different setting . Put  a dial under the knob and make some marks for the different settings .  Cornelius

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