New Member

[Stevedbk]

Hello all
I have been looking through many of the PI designs as I intend to build one. It seems there are many variations of the same idea with different designs for different localities and search intentions.
I have had an interest in basic electronics for many years and have built superhet and regen radios, DX crystal sets and various amplifiers. Many years ago I built the Magnum designed by Andy Flind which I enjoyed using on the beach, also the ETI 549.
This is an interesting site, many thanks to Carl and other contributors.(most anyway, some just waffle).
I wish to build a "fast" detector for small gold in Western Australia so I will have a challenge. Any suggestions welcome.
Stevedbk

[SkyeHi]

Hello all
I have been looking through many of the PI designs as I intend to build one. It seems there are many variations of the same idea with different designs for different localities and search intentions.
I have had an interest in basic electronics for many years and have built superhet and regen radios, DX crystal sets and various amplifiers. Many years ago I built the Magnum designed by Andy Flind which I enjoyed using on the beach, also the ETI 549.
This is an interesting site, many thanks to Carl and other contributors.(most anyway, some just waffle).
I wish to build a "fast" detector for small gold in Western Australia so I will have a challenge. Any suggestions welcome.
Stevedbk

Welcome Stevedbk to this fantastic site.
I have been looking around for my next build project. A build that took my interest, having read throught the thread, was the MiniPulse Plus and the thread on coil building to achieve a fast response, the 3DSS coil.
Others may suggest different.
Alan

[waltr]

Welcome Steve.
You mention Australia so good if you put that in your profile.
This helps us when recommending parts purchase, etc.

[Altra]

Welcome,

You might want to try this project He has circuit boards with instructions and is from AU. It does not ground balance but would be a good start to understanding.

https://www.geotech1.com/forums/show...630#post293630

[Carl-NC]

Hi Steve, for WA you're probably going to have to go with a ground-balance PI design. There have been discussions of GB-PI and some people have successfully modified std PI to add GB. What's been lacking is a fully vetted complete design. Maybe it's time to start one.

[ArchibaldSTM]

Welcome,

You might want to ...

You gave a link to a commercial project, but the person wants to do it himself

[Stevedbk]

Thanks for all the replies.
Skyhi, I have been trying to find a link to the 3DSS coil. No luck.
Carl, I believe I will need a ground balance due to the iron content where gold is found in WA. I have been looking at what you did with the hammerhead. I will keep you posted on my progress but no guarantees on the results.
Altra, I will go down the ground balance track.
ArchibaldSTM, yes I wish to do this as a learning project. I think I have the necessary test gear to help me.(and Geotech -) ))
Waltr, I have amended my profile to identify me as a Westralian.

I think my approach will be to make a motherboard and have plug-in modules made vero or manhattan style. This will give me the flexibility to change as ideas don't work....
Steve

[waltr]

Yes, the HammerHead is a good project and one I did mods to which added GB.
Check my thread here:
https://www.geotech1.com/forums/show...ake-on-the-HH2

[Stevedbk]

Yes, the HammerHead is a good project and one I did mods to which added GB.
Check my thread here:
https://www.geotech1.com/forums/show...ake-on-the-HH2

waltr, that's a huge amount of work you have done, a lot of information. I'll stay with the analog version while I play with it.
Thanks for the link.
Steve

[Stevedbk]

My progress so far
As I am new to PI detectors I went for the basic Hammerhead. I built it on a unit/ bus platform.




So far all seems to work except the VCO audio. I have a voltage rise on TP9 when a target comes to the coil but only smoke from Q7...
I will go through the cct again to see where I am going wrong. Overall a good result from my first build.
Steve

[MartinB]

Hello all
I have been looking through many of the PI designs as I intend to build one. It seems there are many variations of the same idea with different designs for different localities and search intentions.
I have had an interest in basic electronics for many years and have built superhet and regen radios, DX crystal sets and various amplifiers. Many years ago I built the Magnum designed by Andy Flind which I enjoyed using on the beach, also the ETI 549.
This is an interesting site, many thanks to Carl and other contributors.(most anyway, some just waffle).
I wish to build a "fast" detector for small gold in Western Australia so I will have a challenge. Any suggestions welcome.
Stevedbk

Hi,
Welcome to the forum.

I suggest that you look at this thread Updated Mirage PI (Ex Hammerhead)- Mono Coil, DD Coil or Super D Coil Options

Elliot lives in in Australia and is a great guy

[Stevedbk]

Hi,
Welcome to the forum.

I suggest that you look at this thread Updated Mirage PI (Ex Hammerhead)- Mono Coil, DD Coil or Super D Coil Options

Elliot lives in in Australia and is a great guy

Thanks for the reply.
I have been reading Elliot's forum and have learnt a lot from it, very informative.
A question: I am able to increase the IRF840 gate time to about 65uS to get 700v. More than this the flyback "flat-tops". Is this avalanche breakdown?
Thanks
Steve

[Carl-NC]

Yes, the IRF840 is rated for 500V which means it will avalanche somewhere higher. I'm a little surprised it made it to 700V.