I made a Metal detector circuit

neptune said:

yes i have seen that link and i will be going to make it.
i made a AND gate comparator to detect a magnetic field. but i have now a bigger problem.
How do i stop cross coupling between two coils ? as alec_T has questioned me in post #2

Click to expand...

hi,
I did suggest Mumetal screening as an option.

Will run your Sim.

EDIT:
If the output is from Q1 collector, its always the same Vdc ~ +5V.??? what ever the phase shift is.

it was not phase detection i was simple amplitude detector.
i am working on phase detector.

so i built a theoritical Comparator. this compares two AC signals.
when two signals are in phase and same amplitude then output is plain DC signal of 4V
and when the two signals are out of phase or of different amplitude or of different freq. then the output of comparator is square wave.
so this comparator only gives DC signal when two AC signals are exactly same.
(Coneect wire which i have cutted to see how it works when there is disturbance)

I am posting my metal detector version 2 block diagram as first is failure (Because we cant stop Mutual inductance of coils)

In case you haven't come across the term before, what you now have is a 'synchronous detector'. If you Google for that you may pick up some useful tips.

In case you haven't come across the term before, what you now have is a 'synchronous detector'. If you Google for that you may pick up some useful tips.

Click to expand...

i have figured how to detect Square wave myself. But my Comparator section is to much sensitive to 0.9999Hz of frequency
the two thing stopping me to build this is i cant find an good sine wave oscillator and comparator
I am thinking of using Pre manufactured Crystal oscillator

I came made a therotical metal detector , have a check if this will possibly work !