PI metal detector problem in my circuit board

[lou0908]

hello everyone I have in the trouble with my PI metal detector which made by myself. My circuit board related information and my problems are described in a picture and you can get is in the attachment. My problem is that when i supply the power to my board, i found that the falling signal transforms to MOSFET drive chip（TC4420） by the micro-controller disturbed by unknown signal form my board and the flyback signal generated by the board is not right.
I am very looking forward to your help，thank you！

[lou0908]

How can i insert my image？？

[kt315]

after you have wrote your first post you may insert image in following.

[lou0908]

after you have wrote your first post you may insert image in following.

Can you tell me in details，can give me some step or others，thank you very much

[kt315]

http://www.geotech1.com/forums/faq.p...b3_attachments

[lou0908]

problem of PI metal detector.pdf I have post my problem in the attachment, I am honestly looking forwarding to your help, thank you very much!

[Mechanic]

Hi Lou,

You will need to amplify the signal before you will see anything on the oscilloscope. Try with a gain of about 50. You might get a signal that has a peak of about 1v.

Cheers Mick

[lou0908]

Hi Lou,

You will need to amplify the signal before you will see anything on the oscilloscope. Try with a gain of about 50. You might get a signal that has a peak of about 1v.

Cheers Mick

Thank you for your reply， I will test it with an amplifier to amplify the signal. but i still confused that the signal produced by my circuit board whether ii right or not.
I have refer to the circuit diagram, in his diagram there is no amplifier come consequently after the signal produced by the coil. And I found the video the signal is very good generate by his circuit board. This is a link to the paper described how to make a PI metal detector http://www.miymd.com/index.php/projects/tpimd/ , and video link is http://www.miymd.com/files/3113/0305...1_0820_776.mp4. The circuit diagram is