PI detector

[Karl]

First of all let me say what a great forum you have. I really enjoy it and have learned a lot.


Have always loved metal detecting in all it forms, got my first experience on the beach in Ocean City, NJ. Used an Whites unit back in the early 70's. Been out of metal detecting for the last 25 years so things have changed a little. Just got a used ML XS-2 pro
and am reverse engineering it in the evenings,
will draw it on Orcad.


I have been looking at the designs for PI units and am thinking of building one up. Was thinking of using some Burr-Brown parts in the front end and switching the pulse into it with a 74HCT4066 when appropriate. Use real good voltage references and pay close attention to detail. Then to a 16-24 bit A/D then have a controller do the rest.


There is a guy named Trevor in South Africa that has a very similar design.


What I was wondering is if a multiple coil setup would be interesting with maybe 4 or 5 different size drive coils and switch the excitation. This may give a better idea of size of the object? Or better pin
pointing ability? Or just fun???


Also I read somewhere that different pulse frequencies work better for different types of metals. This might allow for some sort of ID? I guess the conductivity problem is large.


A friend of mine works at Zong Engineering here in Tucson were they make geophysics units based on the theory of complex resistivity. He has told me for along time that he always wanted to make a small
unit for the metal detecting hobby??? Maybe I should concentrate in this area???


I have only recently got back into this hobby so please excuse my ignorance.


Look forward to reading any feedback. Thanks,


Karl


--
Senior Electrical Engineer
Multiple Mirror Telescope Observatory


http://sculptor.as.arizona.edu/foltz/www/mmt.html

[zedlav dyolf]

hi-
pi type metal detectors are the primary md issue at
http://www.insidetheweb.com/messageboard/mbs.cgi/mb122618
there has been communications here at times---and
several of the guys have built them--perhaps they
might respond--at the sight above you will find
several posts/responces on prr and discrimination.


reg-rick


>First of all let me say what a great forum you have. I really enjoy it and have learned a lot.


>Have always loved metal detecting in all it forms, got my first experience on the beach in Ocean City, NJ. Used an Whites unit back in the early 70's. Been out of metal detecting for the last 25 years so things have changed a little. Just got a used ML XS-2 pro
>and am reverse engineering it in the evenings,
>will draw it on Orcad.


>I have been looking at the designs for PI units and am thinking of building one up. Was thinking of using some Burr-Brown parts in the front end and switching the pulse into it with a 74HCT4066 when appropriate. Use real good voltage references and pay close attention to detail. Then to a 16-24 bit A/D then have a controller do the rest.


>There is a guy named Trevor in South Africa that has a very similar design.


>What I was wondering is if a multiple coil setup would be interesting with maybe 4 or 5 different size drive coils and switch the excitation. This may give a better idea of size of the object? Or better pin
>pointing ability? Or just fun???


>Also I read somewhere that different pulse frequencies work better for different types of metals. This might allow for some sort of ID? I guess the conductivity problem is large.


>A friend of mine works at Zong Engineering here in Tucson were they make geophysics units based on the theory of complex resistivity. He has told me for along time that he always wanted to make a small
>unit for the metal detecting hobby??? Maybe I should concentrate in this area???


>I have only recently got back into this hobby so please excuse my ignorance.


>Look forward to reading any feedback. Thanks,


>Karl


>--
>Senior Electrical Engineer
>Multiple Mirror Telescope Observatory


>http://sculptor.as.arizona.edu/foltz/www/mmt.html

[Paul]

Hi Karl,


I also was thinking along the very same lines. An added feature that would be nice, would be to add a


DAC to auto zero the amp. One added part and some


code is all it takes. Let us all know how the project


turns out.


HH


Paul

[Carl]

>Just got a used ML XS-2 pro


>and am reverse engineering it in the evenings,


>will draw it on Orcad.


Could I talk you into posting the schematic on Geotech when you're done?


>I have been looking at the designs for PI units and am thinking of building one up. Was thinking of using some Burr-Brown parts


No No! You want to use Analog Devices! :-)


> in the front end and switching the pulse into it with a 74HCT4066 when appropriate. Use real good voltage references and pay close attention to detail. Then to a 16-24 bit A/D then have a controller do the rest.


Take a look at ADI's ADuC812 microcontroller - has an 8051 plus 2 12-bit DACs and an 8-channel 12-bit ADC.


- Carl

[Steve]

I agree that this forum is very good and should be whole heartedly supported. I am aware of Eric Fosters


forum and this...both provide a very useful service in allowing the techies amongst us to share information and ideas concerning metal detecting.


A request for Karl ..I think he will find many of us


eagerly waiting for your reverse engineered schematic of the ML XS-2. Please do circulate it.


I too use Orcad so if I can be of assistance in anyway in bringing together the circuit please let me know. Hard to do but if you have a line drawing then email/fax and I could perhaps help in getting this task complete.


Bye for now


Steve


BEng(Hons) Electronics

[zedlav dyolf]

hi carl--


"Take a look at ADI's ADuC812 microcontroller - has an 8051 plus 2 12-bit DACs and an 8-channel 12-bit ADC."


about time a product like this--would (at this point
not sure tomorrow)prefer a z80 core---this looks
at brief to be a real cuteie...


do you know of any editor/assembler download package
for us poor folk ??????? still have to dnld the
data sheet---and look more to make to program--app.
notes...


reg-rick

[Carl]

>do you know of any editor/assembler download package


>for us poor folk ??????? still have to dnld the


>data sheet---and look more to make to program--app.


>notes...


Haven't looked into the software yet. However, I just got the preliminary data sheet for the ADuC824... same 8051 core plus 24-bit ADC + 16-bit ADC + 12-bit DAC... supposed to have a good Windows-based compiler/debugger.


- Carl

[zedlav dyolf]

thanks responce-


downloaded everything here-have yet to look close.


~~includes gerber files for pcb programmer..been


waiting for somthn' like this for a long time but


have to learn 8051-----24bit incredable..12 is


plenty for me generally---


reg-rick