Walk Through Metal detector Circuit digaram

[jamil_tech]

Hi Everybody,

I am a Undergraduate student of Electronics and Communication engineering. My final year project is Walk through metal detector. I allready try to build some Induction balance metal detector as walkthrough. But It is full of false alarm. I need a good circuit for this. Is there anybody wants to help me please. If need I will pay for this. Please help me out, my time is very limited.

Thanks
Jamil
Hongkong

[Qiaozhi]

Hi Everybody,

I am a Undergraduate student of Electronics and Communication engineering. My final year project is Walk through metal detector. I allready try to build some Induction balance metal detector as walkthrough. But It is full of false alarm. I need a good circuit for this. Is there anybody wants to help me please. If need I will pay for this. Please help me out, my time is very limited.

Thanks
Jamil
Hongkong

Hi Jamil,

There are 16 patents related to walk-through detectors here ->
http://geotech.thunting.com/cgi-bin/...le=patents.dat
Hopefully this will help.
You could also try contacting Garrett - http://www.garrett.com/security/home.htm
They may be able to assist you with your project.
Good luck.

[jamil_tech]

I allready made this circuit, But facing some problem

Thanks, I allready made a circuit , it is working but produce very much noise. It is induction balance type. Its have two coil and it is big loop type which sorrunds total walkthrough structure.

I got it from a portable walkthrough metal detector. I need a good desgin PI or transmit receive type. Could I use Delta Pulse for walk through ?

[jamil_tech]

I allready made a circuit , it is working but produce very much noise. It is induction balance type. Its have two coil and it is big loop type which sorrunds total walkthrough structure.

Here i attach my circuit. Please help me out and tell me what is the problem in this circuit, why it is produce noise. Speacially what other type FET transintor I can use Instead of BFW11.

I found this type of metal detector use Papaer type Booster capacitor with Coil. Is it necessary, If I use polyster or myler type capacitor, what is the difference ?

[Unregistered]

Any senior member can help you

Hi jamil,

I hope Any senior member can help you.


Maria

[Unregistered]

T/R locator

For walk through type , balanace induction is not a good chioce, you can try transmitt receive type metal detector. I have a link for this but i am not sure about its quality.

http://sevzirfo.narod.ru/trlocatorver1.gif

[Qiaozhi]

I allready made a circuit , it is working but produce very much noise. It is induction balance type. Its have two coil and it is big loop type which sorrunds total walkthrough structure.

Here i attach my circuit. Please help me out and tell me what is the problem in this circuit, why it is produce noise. Speacially what other type FET transintor I can use Instead of BFW11.

I found this type of metal detector use Papaer type Booster capacitor with Coil. Is it necessary, If I use polyster or myler type capacitor, what is the difference ?

The link to the image is broken.
Please can you repost the schematic.

[Limon]

T/R cannot use ???????????????????????

T/R use One vertical postion and one Horizontal , so how it is use as Walk Through ??

[jamil_tech]

Here is the schematic

Thanks Qiaozhi,

Hope you can help me. Here I attach the schematic again.

Thanks
Jamil

[jamil_tech]

Here is the schematic

Here is the schematic

[jamil_tech]

sorry for uploading problem

sorry for uploading problem, here is shematic.

[Qiaozhi]

sorry for uploading problem, here is shematic.

Hi Jamil,

This looks like a concentric coil arrangement. Is that true?
If so - how have you nulled the coil?

You would probably get better results with a P.I rather than I.B. Also, the coil would be a lot simpler and wouldn't need to be nulled.

[jamil_tech]

my walk through

Thanks for your answer me and also thanks for want help me. That is really a great thing in this forum for helping mind with every member.

For null the circuit I use 1 K preset with transistor BFW11. I made the circuit already and its works, but its main problem is very much un-stability. Suppose its works 2 mints good and after 2 minutes continue false alarm 5 to 10 minutes if I increase sensitivity a little. This is absulateyly not tolerable for Walkthrough type. Here I attach my circuit picture and my coil picture.

Which PI circuit you suggest for me, if possible please give me the link for schematic. And if it is PIC microcontroller base then it will more better for me.

Thanks

[Qiaozhi]

Thanks for your answer me and also thanks for want help me. That is really a great thing in this forum for helping mind with every member.

For null the circuit I use 1 K preset with transistor BFW11. I made the circuit already and its works, but its main problem is very much un-stability. Suppose its works 2 mints good and after 2 minutes continue false alarm 5 to 10 minutes if I increase sensitivity a little. This is absulateyly not tolerable for Walkthrough type. Here I attach my circuit picture and my coil picture.

Which PI circuit you suggest for me, if possible please give me the link for schematic. And if it is PIC microcontroller base then it will more better for me.

Thanks

Hi Jamil,

Have you looked at the Hammerhead design? -> http://geotech.thunting.com/cgi-bin/...head/index.dat
There is also Gary's P.I. here -> http://www3.telus.net/chemelec/Projects/Metal/Metal.htm
But - if you're looking a PIC-based design, then this may be more suitable -> http://geotech.thunting.com/cgi-bin/...dpic/index.dat

[Qiaozhi]

Thanks for your answer me and also thanks for want help me. That is really a great thing in this forum for helping mind with every member.

For null the circuit I use 1 K preset with transistor BFW11. I made the circuit already and its works, but its main problem is very much un-stability. Suppose its works 2 mints good and after 2 minutes continue false alarm 5 to 10 minutes if I increase sensitivity a little. This is absulateyly not tolerable for Walkthrough type. Here I attach my circuit picture and my coil picture.

Which PI circuit you suggest for me, if possible please give me the link for schematic. And if it is PIC microcontroller base then it will more better for me.

Thanks

It appears that your coil has both the TX and RX coils wound together. This will cause huge problems with nulling the coil. Also it's difficult to tell from the schematic, but it looks like you are using a non-motion mode of operation. If instability is occuring after a couple of minutes, this may be indicative of thermal instability. i.e. voltage levels are drifting with temperature.

Here's a couple of suggestions:
1. Rewind the coils with the RX coil in the middle, but with the TX coil split in two sections, but spaced equally either side of the RX coil. This is a co-planar arrangement. Nulling is achieved by changing the relative placement of the coils. See very rough sketch below.
2. Use a 2-box setup with the TX and RX coils placed at 90 degrees to each other.

The P.I would probably still be a better solution.