Carl-Corbyn's PI?

[Randy Seden]

Have you or anyone on this forum built this PI? Would like to know your thoughts Carl as the Hammerhead doesn't seem to be based on Corbyn's. Needlessly to say, the guy really did his homework and makes me wonder if it isn't worth a second look. But the patchwork schematic is a mess, would have to sit down and piece it together. I can't believe it took so many parts either. Did this guy over engineer it perhaps?

Randy Seden

[Brian King]

Re: Carl-Corbyn's PI?

Hi Randy,
I built his design going back quite some time ago and as I recall he used an analog simulation for ground exclusion and a few bits of CMOS logic for timing. Simple to construct though.I took the unit for run aroun Bendigo goldfields here in Aus and although a little heavy on the old back after an hour or so, it non the less produced a nugget or two on that trip. I had a ML VLF unit with me and basically anytime I had a target, I would pinpoint with the VLF. It was extremely good for it's time and still is really but of course component counts can be reduced as in most designs.
At the end of the day different designers will use what works for them and there will always be different approaches to achieve the same goal. Corbyn's work was extremely important at a time when many people were scoffing at PI.....as I recall it anyway.
It is still worthy of further interpretation into the digital realm, I believe.

[Randy Seden]

Re: Carl-Corbyn's PI?

Brian,

Thank you for replying and congratulations on successfully building such a heavy component system.
That makes sense from what you say that at that time PI's weren't recognized for their abilities.
I would like to try a 2-box antenna system with the Hammerhead and have the receiving antenna shielded to cut down on the ground interference.
Lots of room for experimentation here.

Randy Seden

[Carl-NC]

Re: Carl-Corbyn's PI?

I vaguely recall that there was a bit of criticism over the Corbyn article, but don't remember what it was all about. In fact, somewhere I think I have a reader's letter published in a later Wireless World criticizing something about the design, and Corbyn's reply. I'll have to dig it out.

Until Brian's reply, I did not know of anyone who had ever built a working Corbyn design.

- Carl

[Tim]

Re: Carl-Corbyn's PI?

Hello! Carl is right about the Wireless World method of electronics hobby journalism - projects at that time were interactive, with a final "word" sometimes appearing from the author several years after the first article was published. The audio designs of J. L. Lindsley Hood come to mind. Sounds like something fun to investigate at the local library... Tim

[proscan]

I think, it was an argument on Macario's metal detector

Again, I can send it to anyone interested (if I find it).

proscan

[Kev]

Re: Carl-Corbyn's PI?

Hi Randy,
It’s interesting what Candy said about Corbyn’s detector in US patent 5576624 available here on Carl’s site, refer page 15, column 18, starting line 57 through column 19, line 25

http://www.thunting.com/geotech/pages/metdet/patents/US5576624.pdf

It is also interesting that Candy hasn’t got it 100% right either, despite pointing out the inadequacies of Corbyn’s design and postulates. There are still nuggets that hide in the ground mineral signal exclusion system of the Minelabs, and are now referred to as invisible nuggets. Some though, are even invisible without the surrounding ground matrix, and in this case, it appears that their invisibility is more the result of accretionary and precipitative processes involved in the nuggets formation, as opposed to holes in the detection system through which these gleamers continue to elude the Minelab PI user.

I think the answer is kicking around somewhere near here.
Cheers
Kev.

[Tim Johnston]

Re: Carl-Corbyn's PI?

Back from the library. Found a photo in Wireless World (May '80, p. 49) of Andrew Corbyn showing his prototype MD to the chairperson of Pulse Induction Ltd. of Yateley, Surrey, a division of the Kay Organisation, who had an interest in the patent(!) I couldn't find any reader letters or corrections as far as Dec. '85. Also, Sir John's name is spelled Linsley - my apologies. Tim

[Randy Seden]

Re: Carl-Corbyn's PI?

Good work Tim! Will have to sit down and piece together the schematic and figure out what he's done and see if modern IC's simplify things a bit.
Thanks for your hard work,

Randy Seden

[Brian King]

Re: Carl-Corbyn's PI?

Hi Carl,
From memory the Corbyn PI design was over 2 or maybe even 3 issues of Wireless World which down here in Aus were about 4 months apart!
I had to tweak a few values here and there and substitute some CMOS. I ended up using a 2716 Eprom and a counter for timing which gave me a few options....now that WAS a while ago!
There was a mini gold rush on in Aus at the time and Garret VLFs were kings and ML was the Aus alternative. PI was seen as an under-water machine only and was not taken seriously by main stream markets (in Aus anyway). It took a while to get my head around the design and a few months to actually finish building it.
It was a reasonably stable design, high gain stages caused no issues and everthing was built on matrix or Vero board. The coils were about 12 inches and I substituted the Bipolar transistors on the output for some Mosfets which were ok but not brilliant. All in all it was a good learning curve for me on PI since all my work before this was on VLF designs.

Cheers
Brian King

[Brian King]

2 box system

Hi Randy,
With your proposed 2 box system,have you decided on coil size and construction?
Would be an interesting project. Good luck with it. I would be interested in hearing how you go.
Cheers
Brian King

[Carl-NC]

Re: I think, it was an argument on Macario's metal detector

You're right, Piotr... I found the rather long reader's letter on Macario's article, I suppose I should scan it and add it to the web site.

I have no other info on Corbyn's design, beyond the two-part article.

- Carl

[Randy Seden]

Re: 2 box system

Brian,

Not yet as I haven't gotten serious enough to do an analysis and design. But the receive coil is definately going to be a faraday shielded loop. Will post info on this forum when I start heating up the soldering iron.

Randy Seden

[proscan]

Cobryn has patented his detector

At least he tried to. I must look up my files as I misplaced the material.

I will send it to you Carl, when I find it.
Then, you could make it available for all.

proscan

[proscan]

More info on Cobryn's design

Cobryn has applied for a patent:

GB2071327 Improvements in Electromagnetic Induction Systems for Geophysical Exploration and Conductor Location

Basically it consists of the same info as in the WW articles, but it is rearranged with new pictures. I do recommend this reading. The idea is easier to understand now.

Not clear for me if the patent was granted or not.

I have sent the pdf to Carl.

proscan