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Why don't we make a free pi design on this forum?

Bill, your post anticipated the philosophical content of this post, so I have edited it to be a response to both of you.
There's no reason why the electrical parameters of the searchcoil couldn't be specified right up front, to be the same as those of the searchcoil of an existing manufacturer, unless the design were so innovative that no existing standard searchcoil would suffice. Basing it on a standard searchcoil would make a wider variety of searchcoils available, and the present manufacturer's product could be used as a reference design to guage the effectiveness of the new electrical design.
Which manufacturer's coil? A first consideration would be suitability of its electrical characteristics. I believe someone mentioned in another post the availability of connectors.
There is a broader question that ought to also be addressed: what are the effects of linking a manufacturer to a process they do not control? Some manufacturers would resent this, and so everyone (including that manufacturer) would be deprived of the benefits of such a linkage. Therefore it is to everyone's advantage that the manufacturer so linked is one which grasps the benefits of being linked to such an uncontrolled process.
Benefit #1: The loop compatibility inherent in this, makes the "public design" immediately accessible to the in-house engineers to see what they can spin off of it. There is no presumption that they would disclose everything they would be doing with it: they would be contribute just enough to the uncontrolled process to remain effective collaborators.
Benefit #2: The whole process will produce personal links between collaborators which will facilitate exchange of information which needs to remain out of public view-- links which otherwise won't exist.
Benefit #3: The opportunity for divvying up major portions of the process to collaborators who have special expertise or resources, will make everything go more quickly and minimize duplication of resources. For example, one company could focus on regulatory issues whereas another could focus on software.
Benefit #4: The potential for a product which is basically an "industry-certified" design, which could then become a method of branding the product esp. for introduction into new markets.
None of the above implies a merger between companies, publication of all information, etc. It is necessary for the fractal nature of business (and everything which is analogous to business, for instance biological speciation) that boundaries exist. The whole semi-public collaboration effort would normally be just one part of the overall operation; which, however, would have ripple effects through the rest of the company.
OK, now a peek past the surface to the philosophical-psychological underpinnings of this approach.
It is human nature to want to remain in control, and that is the primary psychological barrier to this whole scheme. In order to see the potential benefits, even the ones I have already put into plain view above, a person will first have to ask, "Is it possible that it would be OK to be part of something uncontrollable?" If their internal personal answer is negative, it will be possible to explain everything to them in detail and they will have no idea what you're talking about.
Admitting to loss of control is a difficult thing. But once one looks reality square in the face and realizes that one was never, is not now, and never will be in control, conscious and deliberate loss of control becomes a powerful tool for dealing with reality.
It is arguably the most powerful tool available to humanity, because those who strive to do wrong are unable to forfeit control, and therefore unable to use the tool. This is different from (for instance) atomic power, which can be used equally for good or evil.
If you can use this tool in the metal detector industry, you can use it anywhere.
The power of conscious and deliberate loss of control is the underlying philosophical principle for the existence of this forum. Eric did the unthinkable and began releasing technical information into public view. When you realize that this forum is, in the final analysis, a kind of advertisement, when you look beneath its surface you discover that it testifies to the good character of the person who founded it in a way that can't be gainsaid.
...... So, in my opinion, the choice of manufacturer has implications that go way beyond electrical suitability.
A manufacturer who understood what this was about, would post here, tip their hand with at least a card or two face up, and ask that their loop be considered as a standard, at least to get the ball rolling.
--Dave Johnson
 
Dave and Dave:
We have used a wide variety of condictive paints, - from Nickle loaded paint - (Thinners based and smelly), - to Electrodag and Aquadag paints. There are limitations with most methods, - and many we havent tried.
The majority of coils we build as production coils are for Minelabs SD range which are probably not suitable as they have a very low Tx resistance and because of that they are heavy. On the other hand many of the US made PI coils are flimsy and 'crude' (I dont mean to offend), or not suitable.
I beleive most circuits need their own coil specs, - and I dont beleive that will present a problem. Simple PI 'Monoloop coils are not difficult to make, - but do need to be a little better than "wind 25 turns around a plywood disc and attach a shaft". The poor coil is often forgotten and I beleive many good designs have been let down by poor coils in the past. I would be happy to share information on basic construction techniques for simple Tx coils.
Thanks John
 
John,
Would you be willing to sell coil shells of what you already make? I was not familiar with your products so I took a look at your web site. Good selection. I like the 12x24, reminds me of the one I have for an old Garrett BFO.
- Carl
 
Carl,
Plan out a kit and I would be interested. Sounds interesting and fun. I would rather buy a coil than make one.
Rick
 
Dave... The Linux OS was developed by individuals from all over the world. There's no reason why it can't work here. A modular system with no soldering required would be excellent, if it could be done. (I never could get my Heathkit to work.)
 
The Fisher Impulse coils have low resistance, which makes them adaptable to energy-efficient designs (the Impulse itself being an example), and does not preclude their use in more conventional designs (just add a fixed resistor). And they've never been accused of being flimsy. Since they were designed for a machine which is fully static, the residual "resistive" signals are tightly controlled.
--Dave J.
 
I personally would like to keep this seperate to our normal products, - having said that it is very easy to make cover sets - fully sub assembled, for the sort of machine you are talking about, - any shape or size. Solid coils are easy, - see through designs with 'clip on skids' are not so easy to acheive with vaccum formed parts. That takes much greater tooling expense and much tighter production control.
John
 
What I'm thinking is that different folks might end up with different coil parameters. So the easiest thing to do is buy a shell, stuff it with whatever coil I want, and fill it with goo. Maybe with the right kind of goo I can even pull it out and reuse the shell.
I can certainly see that solid coils are easier to fabricate, but they're horrible in the surf. Even open-center coils like White's & Tesoro are hard to use, thin donut rings like Garrett work better.
- Carl
 
Sounds excellent, except I am not fond of the Tesoro printed circut coils. If you ever used them in water you will see the problem. If the connector is a problem on a factory coil, it can simply be cut off and a different one which would fit the box connector applied. Just use a standard waterproof type or something available from a large supplier. John
 
I haven't had any performance problems with my SandShark coil, just don't like the way it flops in the surf. Personally, I would prefer a skinny donut like the Garrett and what Eric makes.
Connectors are nice for swapping coils, but they increase the cost and increase the coil parasitics. Most people could probably just hardwire the coil. Personally, I like having a connector just because it makes wrapping the cable much easier. I hate switching over from long-stem surf mode to short-stem diver mode on my 1280x.
- Carl
 
Carl,
For a mono coil, I suggest doing what the Germans did on Pulsdetektor.de They used a BNC connector.The BNC fits right on the coaxial cable. It is cheap, and both the male and the female are available at Radio Shack stores etc. BNC's also stay on very well and can be waterproofed. At PI frequencies they do not contribute any measurable loss. Seems like an ideal choice to me.
 
Carl, you can buy a goopy waterproofing material that looks like chewing gum. Wrap and squeeze the goop around the connector and it's water proof. The stuff comes back off pretty easily.
 
But does this waterproof while allowing you to connect & disconnect all you want? Or do you connect, then goop and leave it, and peel the goop off to disconnect?
Speaking of waterproofing, anyone know where to buy the waterproof nuts used on pots?
- Carl
 
Flopping and uneven movement thru the water, exactly is what is wrong with Tesoro coils. On the Ikelite site there are waterproof connectors + other items of interest. They will probably be costly but waterproofing usually is. Have to get them thru a dealer, usually a dive shop can get them. If a kit becomes available, then maybe these or simular connectors will be available for those who want to waterproof. John
 
Yes I would hate Eric and Bill to miss out, but I aggree this is a great opportunity to do something unique. I have many ideas which I'd love to contribute, but I probably wouldn't have the expertise to fully assemble one, unless provided in a simple to follow kit form, where once completed I can tweak to my hearts content!
Perhaps Eric and Bill could assemble the circuit boards or sub assemblies, and then sell the unit in a kit form minus coil, shaft, battery, headphones etc which the buyer then adds to their taste.
Would be interesting to see what you all think
 
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