simulation problem about metal detector coil

[DJSUOL]

Thanks for your reply, sir. Could you please tell me the performance of this circuit? For example, can this circuit detect a small object and I want to build a small prototype so if I reduce the coil size to 10-12 cm will it work effectively? In addition, where can I find the introduction of this product that I can learn the working principle of it? I am looking forward to your reply.

[waltr]

Typical detection distance is proportional to and about equal to coil radius (lot here in forum about this).
Then the smaller the object and the less conduction the object's metal the shorter is it TC of the eddy current decay so shorter first sample delay is required (also much info on this forum).

[DJSUOL]

Thanks, could you please tell me if all kinds of PI metal detector have a similar circuit design or not? Is it possible for a beginner to design his own circuit?

[waltr]

Very generally all PI Detectors have common circuit elements.
This is very easy to see by studying the many PI Detector circuits published in this forum.

Beginner?? In electronics? or detector design?

I did a re-design of the Hammer Head PI detector and it works very well.
I was a beginner in detector design but have 40 years experience with electronic and embedded microprocessor design.

See my thread detailing the design here:
http://www.geotech1.com/forums/showt...ake-on-the-HH2

[DJSUOL]

Thanks. so you re-design the whole circuit with microcontrollers. can I use two coils as transmitter and receiver for a PI metal detector

[waltr]

Yes and yes.
I replaced all the timing with a PIC16F88 processor which allows easy changing of timing parameters.
If you read my thread you will see that I also added GEB without any circuit changes which also gives discrimination of Low verse High conductors.

Any PI detector can use separate TX & RX coils. I also do this and the details include O'scope pictures and coil build details are in my thread.

[DJSUOL]

actually I also have the problem about the matchless metal locator design. As shown in the graph, the first 555 timer is used to produce the square wave. But how does the second 555 timer work? According to my test, it will produce a high voltage if there is no metal and a square wave while there is a metal. is it based on the threshold voltage2/3 Vcc?