WELCOME!!

[ivconic]

Which parts are unobtainable? I can source all in that design from Mouser or Avnet.

What is wrong with a 4 layer board for $8.40?

WM6 already explained. Nothing much to add except maybe to emphasize the difference between conditions in UK, EU and other countries, respecting the availability of some newer material on market.
Some of those components are not possible to obtain in local shops. Ordering them from abroad will seriously affect overall costs, than we can't talk any more about hobby and diy project here.
Eventually it will end up with reduced number of participants, therefore the feedback too will be reduced. It can not be called "diy" project any more. It's just a modern kind of trading and making small niche business.
It's already seen on these forums. Not my intention to start debate here; but everyday more and more topics and threads here are polluted with "references" and appeals made by one moderator here, reminding and asking people to order and buy "this and that " from one and the same source, quite coincidently directly related to his own and personal wallet. How about that? The one is not able to start own MD industry; instead, the one is misusing public forum to spread own small niche business protected and secured by the fact he is moderator and nobody can't do nothing against.
I expected this to remain strictly diy&hobby place for us; the plain and honest enthusiasts. The way it was in recent past. Sorry if i lost my compass. My mistake!
Whatever... your effort is still respected from my side, i salute it. But at the same time i deeply regret because i can't participate.
Cheers!

[Qiaozhi]

It's already seen on these forums. Not my intention to start debate here; but everyday more and more topics and threads here are polluted with "references" and appeals made by one moderator here, reminding and asking people to order and buy "this and that " from one and the same source, quite coincidently directly related to his own and personal wallet. How about that? The one is not able to start own MD industry; instead, the one is misusing public forum to spread own small niche business protected and secured by the fact he is moderator and nobody can't do nothing against

Just to put the record straight, and to stop any misunderstandings ...

The PCBs and kits that Silverdog sells are supplied as a service to the Geotech community, and to support several of the most popular projects. I personally receive no money whatsoever from this enterprise, and Silverdog himself makes only a minimal profit, considering the effort required to put these kits together. The Minipulse Plus (MPP) project was completely funded out of my own pocket, and I have made absolutely no money from it. I purchased the original Minipulse via eBay (in a non-working state) and returned it to full working condition, prior to completing the back-engineering exercise. After that I decided to improve the design and make it available to Geotech members, since there were a number of advantages over the existing Surf-PI and Baracuda projects. Even though this took many hours of my own time, I did this without any regard to personal gain.

Also, I would like to remind everyone that Carl pays for this site out of his own pocket, and you will note that there is no funding from advertisers. Nor is there any annual fee to join, unlike many other metal detector forums.

And, with regard to the book "Inside the METAL DETECTOR", this took both Carl and I many many months of experimentation, writing, and re-writing, to produce the final result. If anyone thinks that writing such a book is a quick route to riches, then think again. ITMD came from a desire by both of us to create something that was missing from the market. That is, a book on metal detector technology. If such a book had already existed, then we both would have bought a copy. Since it didn't exist, we decided to create it. If we had to survive from the small profit made on this book, we would have starved to death by now.

Finally, I would like to remind Ivconic that I (again, out of my own pocket) sent him a FREE copy of ITMD, when we released Edition 1, as a personal thank you for the contribution he had made to the forum. Obviously there is no pleasing some people.

[soverey]

Thank you for publishing this project , I have succesfully build the surf pi from silverdog, and l'm interested to buy a pcb ,when they become available.

[ivconic]

Just to put the record straight, and to stop any misunderstandings ...

The PCBs and kits that Silverdog sells are supplied as a service to the Geotech community, and to support several of the most popular projects. I personally receive no money whatsoever from this enterprise, and Silverdog himself makes only a minimal profit, considering the effort required to put these kits together. The Minipulse Plus (MPP) project was completely funded out of my own pocket, and I have made absolutely no money from it. I purchased the original Minipulse via eBay (in a non-working state) and returned it to full working condition, prior to completing the back-engineering exercise. After that I decided to improve the design and make it available to Geotech members, since there were a number of advantages over the existing Surf-PI and Baracuda projects. Even though this took many hours of my own time, I did this without any regard to personal gain.

Also, I would like to remind everyone that Carl pays for this site out of his own pocket, and you will note that there is no funding from advertisers. Nor is there any annual fee to join, unlike many other metal detector forums.

And, with regard to the book "Inside the METAL DETECTOR", this took both Carl and I many many months of experimentation, writing, and re-writing, to produce the final result. If anyone thinks that writing such a book is a quick route to riches, then think again. ITMD came from a desire by both of us to create something that was missing from the market. That is, a book on metal detector technology. If such a book had already existed, then we both would have bought a copy. Since it didn't exist, we decided to create it. If we had to survive from the small profit made on this book, we would have starved to death by now.

Finally, I would like to remind Ivconic that I (again, out of my own pocket) sent him a FREE copy of ITMD, when we released Edition 1, as a personal thank you for the contribution he had made to the forum. Obviously there is no pleasing some people.

Yes that's all alright. Correct and true.
ITMD book is excellent. Thanks again!
Congrats to both authors again! Splendid job, my hat down!
However... all those true facts you mentioned doesn't give you right to pollute majority of threads and topics with subliminal appeals to buy "this and that" all the time.
It's kind annoying, don't you agree?
Sometimes reminds me on "modern" tv channel. You sit and start watching the movie... and than they interrupt you with numerous idiotic commercials on every 15 minutes!
One can get impression (though could be wrong too) that you misusing position of being moderator with privileges.
I would like not to repeat very true arguments mentioned by WM6, relating to this subject. That's what is the problem here.

[kt315]

Pozor dlia Serbija - you are. you have NO right to criticize the politics of forum.
NO RIGHTS! while George is VERY tolerating to you and all.
WHERE is SERBIAN forum, on serbian, with similar matter like Geotech?
WHERE???

I did two russian forums. TWO! you did NOTHING! all you do is only NOISE and bare claims.

[Sean_Goddard]

Well, I take on board ALL the points people have raised and I have to admit, I never thought of them as an issue, BUT, the input is all valid, especially from those who are more experienced in this field (pun intended) than myself.

I must admit, at first I thought Ivconic's comments a little harsh, but when you realise he is writing in a language which is foreign to him, sometimes the grammatical context gets distorted but I fully agree with his synopsis. Yes a four layer board is going to be harder to work with BUT, it is eaiser to design a low noise multi layer board with planes for supplies etc rather than a simple two layer board. Now I'm NOT stating it is impossible to design a super low noise board using only two layers.

Let's take the MiniPulse, there is a DC-DC converter switching pulse which leaks onto the signal line adding to the noise. Nothing can be done about this as it stands it would require a whole re-design and the design is great anyway. Yes, could be better, but how much extra do you want to spend? Don't forget we are AMATEURS, we don't have millions in R&D budgets or the luxury of a dozen prototypes which we can scrap or keep depending on how well different areas work.

The PCB's I have put up are the thirds go at this design. The CAD package I was using keeps telling me there are breaks in the +4V supply when I lay it out as tracks so I went with a plane instead of a track. Noticce I have also stitched the two GND planes together top and bottom. I've not seen anyone else do this on a detector design, not even a commercial one.

Regarding the amplifiers, yes they are fast current amp and I was thinking about chopper stabilised, but I know that the ones I have used are being used in a new design quite successfully. I can't give any details or hints but the machine in question is DEEEEEEEP (like 18" in ground on a cut quarter) and I've seen the prototypes working close up and personal so I know the designer has got something right. Quite why he used these I have no idea, but when I spoke to him, he said no one sle was doing things the way he does and he is seeing very real benefits.

Perhaps someone with more knowlege can shed some light on this for us.

At the risk of seeming to give in, I will TRY to lay out a 2 layer board but it may take a long time maybe osone else whould like to have a go at it (HINT, HINT)!

A thought occurs to me that maybe I jumped too far ahead with the improvements and I'll look at that as constructive criticism rather than someone "having a go" and so, I'll scale the design back to a simple more accessible one using easier components, though some people will always have the "Can't get that here" problem, more so as these politicians seemingly try to drag us into a third world war. And so as far as I'm concerened, if you need something to complete the project and you can't get it, let me know I'll get it for you. Stuff ITAR, like the world is going to end because I sell some Iranian experimenter an LM339, I mean, seriously??? Oh well there goes the security clearance!

Oh, just had a thought, on the vein of designing stuff, how about LEGO metal detectors? WTF you say? I mean blocks that work which can be put together. How about if EACH of us picked an area and worked on it until it was perfect, then laid out a small area of PCB which was ALSO perfect (low noise etc) so that when we wanted to make a new design we could just pick and choose which BLOCKS we needed and cut an paste onto a PCB? Voila, LEGO metal detectors.

I have this idea but doing it electronically under the host of an operating system called MetalOS(TM) this would work like NI Labview and allow a user to take blocks with common interfaces which they would put together on a PC (oscillator, amplifiers, filters, controls etc) then upload it to the metal detector which would then interpret the functionality in real time (Just watch Bruce Candy steal that and say ML has been woking on it for the last 5 years). Well TOUGH because that idea is at LEAST 20 years old and I have the documents to prove it . Imagine a LCD touch screen which could emulate the front panel of ANY machine on the market. Well this idea is that but done in analogue blocks .

[WM6]

Preferences of multilayer boards design are really great, by its possibilities to keep vias very short, by great separating possibilities of different stages and noise suppress capabilities.

I would be glad to buy such one 4-layer board (even more likely, if I can get it SMD populated and tested already), despite I am not feeling relaxed in DIY finalizing and error-managing such board.

Why? The only boards in my life which status get worse after my repair service intervention was multilayer boards. I "repair" its to dead status by desoldering and soldering again some parts. Evidently I destroy some contacts of inside layers and boards (about two PC motherboards and one uni-bus board) gone quickly to waste bin. This is my genetic fear of such hi-tech boards.

No doubt, single layer boards remained as amateur boards only today. But, highly reparable circuits, easy traceable vias according schematic, very suitable for homemade design, make it very popular till today. Even unwanted noise is not unsolved issue in case of single layer boards, if we know and use design approaches of earlier pre-multilayer engineers.

So, for me, it would be ideal, if someone of good PCB designer's here (with ivconic in mind) are ready to go with parallel design of single layer board alongside and based on Sean's main Surf PI II circuit development in 4-layer design.

[Old cart]

I too was thinking of the idea of a modular detector but at an even simpler level. Rather just define common input/ output interfaces and then let each specialist go at his thing. For example the blocks might be:

Power supply/ transmitter/ timing
Receiver/ signal processing/ audio.
In this case it would be a two board detector. They could be joined by a ribbon cable or perhaps even a high quality connectors like this:

This would also allow modules to be built and tested so troubleshooting would be simplified.

As I mentioned I have lurked on this forum for some time. I have noticed that some individuals have criticized others. Some contribute some do not. I know for a fact that Carl and George have poured a huge amount of there time and money into it. I also have recently been in communication with Ivconic. He is really a good man and while sometimes he seems a bit harsh I know he means no Ill will by it.
We must recognize that here are vastly varying skill levels, economic circumstances, languages and cultural differences present here.
Yet we ALL SHARE the love of constructing detectors for whatever reason.
One difference that seems to come up frequently is the difference in the style of communication. Some cultures are very direct and some will never criticize. Add to this the complexity of language translation and you have makings of disaster. I can only suggest that a PM with the individual you are having issues with can do wonders to help to understand each other and can keep the " noise" out of the signal! Before you dismiss this try it! I think you will be amazed at how much you have in common with the individual!

Ultimately this forum and each of us has to choose. Do we want conflict or do we want this forum to be our sanctuary from the bad things that go on in the world every day?

I for one can do without the conflict and just want to learn and to share. Please join me in trying to make this forum the pleasant and useful place it was intended to be.

[ivconic]

Old cart and other guys; thanks for understanding.
Such attitude simply disarms me completely and i give up from making noise here.
Let's back to topic.
Ok Sean, i understand your wish to move things on higher level. Why not if you have conditions, quite understandable.
But let me suggest something.
For other people, people like me, pure amateurs; can you just propose another version of schematic, but with conventional (maybe not a proper term) material?
Instead ones you named on your schematic to suggest closest substitutions, from older series with closest specs.
That's how we can follow your main idea and participate.
We can even try to compete, one "the modern" version on 4-layer pcb against "old school" version on single layer pcb.
Electronics is not born just yesterday, speaking of low noise technology, solutions and techniques.
30-40 years ago people also made ultra low noise projects, without fancy components and 4-layer boards.
I bet it can be done on classic way and provide good performances.
I can draw single layer board. I can't draw multi layer board, nor i want to use smt.
Nor i want to buy anything from abroad.
If you provide complete list of substitutions i will participate.
Cheers.

[Qiaozhi]

OK guys. You may have noticed that I have removed several abusive posts.

Please stop slinging mud at each other. Let's bury the hatchet and get back on topic.

[Davor]

Darn! I missed the good stuff. Again.

[Old cart]

No you didn't��!

[greylourie]

I like the schematic, especially attention to supply filtering/bypass. And shift towards using 4066 or similar instead of fets for gating. And the I also like the thoughts on a "LEGO" type concept. Have thought about the idea too, as it would be easier to experiment with changes to a particular section or "block". And it would become very easy to create a model following the pattern of any older or well known design using generic "blocks" or modules. You can find on places like thingyverse, generic opamp layouts/modules etc. Could be a useful way to learn about practical layout placement, and mixing manhattan and ugly style construction too.

[ivconic]

I also missed to see latest "noise" here!?
Luckily i was not involved this time!
...
Making modular design is SPLENDID idea.
For example, the way they did with Arduino and various shields for it is very good way to do things.
Earlier i was thinking to do something similar. To project several "universal" modules for metal detectors.
But it is not new and original idea; Wilhelm Herbst Verlag and Wolfgang Friese did similar project in their book "Der Selbstbau von LF-/VLF-Ortungsgeraten".
They projected series of modules which can be put together in various setups, depending on users needs.
For hobby and diy purposes i think it is the best possible approach.

[Sean_Goddard]

EXCELLENT POINTS ALL!!

I've NEVer yconsidered you an "amateur" Ivconic, quite the opposite in fact. I greatly value your input on all parts of this forum. Same with the other who are on this thread.

OK lets make THIS the first modular project.

Who wants what part to play with? I'm thinking a TX with blanking on the output to stop front end saturation for a start. The best part is the power supply, too many switching PSU's in existing designs, ssynchronous or not they generate NOISE (shouts) so lets put a whisper on those supply rails.

Of copurse no point in havinga silent PSU if the other stages chuck out a load of guff instead so each person who takes up will have the rsponsibility of making sure THEIR stage stage shtum (quiet) too. Ah you thought you were going to get off lightly? NO chance! ;-P.

Right, according to Dave (Guess who) the supplies can be as lowe as +/- 2V5 but I prefer +/- 4V so can we work from that?

I'll take the Tx stage, who wants the front end amp and first stage buffer amp?

This is going to be FUN ;-))