sheet steel strip detection

[kalectro]

Hi everyone,
for my bachelor thesis I need to build a detection of a sheet steel strip which is about 5cm (2 inch) wide and up to 4cm (almost 2 inch) under the surface.
It is supposed to be used as a robot navigation aid. My question is which type of metal detector is best to use if I want to analyse the results with a microcontroller?
It should be a simple and cheap schematic because I need at least 5 sensors.
thanks a lot for your help
Kai

[dfbowers]

Hi everyone,
for my bachelor thesis I need to build a detection of a sheet steel strip which is about 5cm (2 inch) wide and up to 4cm (almost 2 inch) under the surface.
It is supposed to be used as a robot navigation aid. My question is which type of metal detector is best to use if I want to analyse the results with a microcontroller?
It should be a simple and cheap schematic because I need at least 5 sensors.
thanks a lot for your help
Kai

You can accomplish this using a simple ferrous motion detector. I can e-mail you a schematic from an old book that I have for starters. One coil, an LM324, a battery and a handful of passive components. Might be good for starters.

Can anyone tell me if it is permissable to post material from books here?

Don

[Cyclonite]

Hi @kalectro,

You can use regular Stud Detection Metal Detectors with Signal Strength Indicator, that can be found in any hardware store. The only problem is, that the more expensive models will be able to detect to the depth that you require, and you may be working in a fairly Noisy Environment. You have models with LCD readout, and also ones with a LED VU Meter. The LED VU Meter ones are by far the easiest to modify for your application. It's only a pity that the metal strip lies so deep, for things would be simpler if it where more to the surface.

Stud Detector Images:
http://www.google.nl/images?client=f...ed=0CC8QsAQwAw

But if you insist in building it yourself to impress your teacher with, then you can go for Pinpointers!

Pinpointers TOPIC:
http://www.geotech1.com/forums/showt...ght=pinpointer

My motto is; Just keep things as stupid simple as possible, and you're least likely to run into Murphy

Regards, and I wish you lots of success with your Thesis!

Robert

[Qiaozhi]

You can accomplish this using a simple ferrous motion detector. I can e-mail you a schematic from an old book that I have for starters. One coil, an LM324, a battery and a handful of passive components. Might be good for starters.

Can anyone tell me if it is permissable to post material from books here?

Don

Which book is the schematic from?

[dfbowers]

Which book is the schematic from?

'Building Metal Locators - A Treasure hunter's Project Book" By Charles Rakes

[kalectro]

i guess the Pinpointer would be the right way to go.
The thing is that I need at least 5 detectors on my sensor bar and the bar should be ready for mass production when I am done.
I think it would be best to edit the schematics for digital use, so I can read the results with a microcontroller.

On the other hand..... how about a pulse detector? Would that be a more stable circuit or would it be easier to differ the signal of a crown cap inside the floating screed to a metal strip?

[kalectro]

I did some tests with a pulse detector and I think this will work best.
I will post some pictures later

[Qiaozhi]

'Building Metal Locators - A Treasure hunter's Project Book" By Charles Rakes

Yes - I also have that book.

I seem to remember that Charles gave permission to publish any of his older projects here, but I'm not sure what the position is with Tab Books.

Maybe Carl knows the answer?

[kalectro]

as promised... the pictures I took

this is the pulse response of a huge coil without metal around


and now with a huge metal block next to it


after using Schottky diodes and an RC filter, it looked like this without metal around


and now with a huge metal block next to it


I know that the results are not comparable to the real coil and the metal strip but I get a good idea on what I need to detect.
I ordered a LM158 to amplify the results and I'm planning on reading the output of the LM158 with the ADC of the microcontroller.