New Frankenproject -

[Pete the Builder]

Hope 3M and 7-up don't have patents...

or 7-11! Those three alone would stomp me!

Please consider all numbers, letters, hieroglyphs, and star-signs included in my caveat!

[Carl-NC]

Oh, yeah... before anyone gets sued by anyone beginning with any letter of the alphabet :

Hope 3M and 7-up don't have patents...

[Pete the Builder]

Pretty QED

Thanks everyone for your helpful comments. I appreciate the diverse opinions expressed - this is such a multicultural forum!

Carl's points make the issue very much clearer. As far as I can tell, from published information, the big deal was with the ground balance design Howard developed in software, from his own extensive knowledge of electronics and ground balancing. I put it that way for want of a better way of expressing "He didn't copy any patented design that anyone else had ever done", as far as is possible to know from the little that's out there. However, private correspondence has confirmed this to a reasonable extent.

So publishing the circuit exposes nothing of Minelabs', and infringes no patent. But of course, this is still a patented design! Since the ground balancing is done in software, and we do not have any software for this, it will not work. Please do not ask for the software, as at this stage it is not available under any circumstances! And, thanks to the dispute - and corresponding legal fallout - engineered by a company whose name starts with 'M' (and ends in 'inelabs'), the software will probably never be released in it's current form. However - you are free to write your very own metal detecting software, an exercise that should exercise your mind and keep your hands away from the Devil's work. Possibly for many months...

Now remember, I'm simply "prettifying" Howard's circuit as published; it is an "exact replica" (just like a $5 Rolex, although I wouldn't accept less than 8 bucks). It contains a number of excellent and quite deliberate mistakes, so that anyone trying to build the device from these plans with little or no knowledge of electronics or metal detecting is pretty much guaranteed to get a "surprise" upon power up. Perhaps more than one... Forum members knowledgeable about electronics should get a couple of laughs! BTW, I could've been a real ******* and swapped some pin numbers, but I couldn't bring myself to do that. Or could I? (Sigh. I didn't.)

So here's how it will go. I'm posting the QED circuit exactly as published, but rearranged so the various functions are more logically organised. I haven't labelled the various areas as per the original, although I may do so if enough people request it. It's a labour of love, not a work of art. You will note that I've kept the designer's rather unusual part identifiers wherever possible. However some Hs are now Ks (in line with European pin header naming conventions) and a couple of Us are now Qs. I also use the American style 'IC' instead of 'U', since at my age U's start to look like Vs sometimes. Deal with it.

You will need to (read : YOU ABSOLUTELY MUST) add a number of bypass caps to this circuit. This is critical, and pointless and time-consuming to add to this reference design. Figure on at least one 0.1uF monolithic cap per integrated circuit, plus an additional 10uF electrolytic or tantalum cap per 2 devices.

It's in A3 format, so unless you have a very expensive colour laser printer, you won't be able to read component values if you downsize to A4. However, you will still be able to clearly see all the components and circuit elements, so that should help you enhance your learning (there's that word!). Unfortunately, Altium uses some extremely dodgy methods of rendering some pretty crappy fonts, IMHO, but zooming in with your favourite PDF reader (I use PDFXChange) will result in hours of delight, since the fonts are at least embedded, so they render perfectly well at any resolution except A4.

There is a complete bill of materials for this, however it does NOT include the actual LCD, instead I've just provided the header. If you wish to wire up individual segments as the designer did, good for you.

I will make the schematic files available in as many formats as I have the tools to do. Right now, that means Protel or Altium. However, I'll consider alternatives, as I know (!) how time-consuming creating a new schematic from scratch.

'nuff said.

So, for your information and education :
Full Original Jan 2013 QED Schematic.pdf
Oh, yeah... before anyone gets sued by anyone beginning with any letter of the alphabet :
NOTICE FROM GEOTECH -- PLEASE READ
These schematics may contain design elements which are protected by US and/or Australian patents. Reproducing all or parts of this circuit may violate those patents. Any use of these schematics beyond the purposes of education or modifications to the existing QED should be discussed with the designer.

[Qiaozhi]

In short, I have no problem with posting, discussing, experimenting, modifying, and enhancing patented methods, so long as everyone understands that

1. You may not post copyrighted material (original company schematics or code)
2. You may not encourage people to infringe the patent
3. You may not use provocative language concerning the patent or the patent holder

I believe this will keep "problems" to a minimum.

- Carl

Perhaps this should be added to the "Rules of the Forum", as this question arises every so often.

[Carl-NC]

How much, or what sort, of change do I need to make to a circuit in order to avoid any patent infringement?

If you want to avoid infringement then you need to specifically avoid using any of the features spelled out in the patent claims. If you make an improvement to a patented feature that is probably not sufficient, as your improvement still likely infringes the original claim.

Can I post the patented schematic unchanged, for discussion or learning, or do I need to make a change to the actual design before I can do that?

Ah, discussion or learning... Yes! You can post the schematic unchanged for this purpose. As WM6 says, the inventor does not own a copyright on what's in the patent, so it is wide open for public use. Now here's the catch... patent law (I believe both US & Oz, caveat lector) allows for experimentation and verification of patent claims, so you can legally "infringe" a patent up to a point. That "point" is squishy and ill-defined, so be careful how far you take it. Ferinstance, to verify a ground cancel patent, you may have to build a fully working detector that you can take out to the field for testing. But any use beyond verification of the patent may put you in the realm of infringement.

Care should also be taken in open discussions of patented circuits. Most patent law includes an "induced infringement" clause whereby, if you encourage people to infringe a patent, you are also guilty of infringement. This is why I keep certain "provocative language" on a short leash around here. If you want to discuss and experiment with patented circuit, you should include a disclaimer such as the one I added to the SD2000 thread:

http://www.geotech1.com/forums/showthread.php?14001-Full-m-lab-SD2000-schematics&highlight=sd2000+schematic

In short, I have no problem with posting, discussing, experimenting, modifying, and enhancing patented methods, so long as everyone understands that

1. You may not post copyrighted material (original company schematics or code)
2. You may not encourage people to infringe the patent
3. You may not use provocative language concerning the patent or the patent holder

I believe this will keep "problems" to a minimum.

- Carl

[Aziz]

Pete,

if you re-draw and re-arrange the schematics and pcb, you can post it.
This is legit.
Cheers,
Aziz

[WM6]

Can I post the patented schematic unchanged, for discussion or learning, or do I need to make a change to the actual design before I can do that?

In this instance, I'd initially be simply posting the unmodified schematic - at least, that's been my plan all along.

If schematic was already posted in public (in patent, on web site, in papers...), you can repost it by indicating author and source (this is widely used practice, except if author has made explicit exclusion to this reposting practice along with his schematic, asking for his previous permit).

Patent reposting (in whole or per parts) cannot be limited, cause patent is official public book and author cannot made his own copyright on it. Author obtain by patent prior art to his patented design but not copyright on reposting patent text or drawings.

[Pete the Builder]

I'd like to ask a general question to anyone who's watching this thread - lurkers are most welcome to reply, so don't be shy.

How much, or what sort, of change do I need to make to a circuit in order to avoid any patent infringement?

I realise to some extent what the requirements are for a patent to be approved - unlike anything prior (prior art), a new functionality or feature that no-one else has considered, and so on. But there are many stories, most obviously urban legends, that just the title has to be changed, or that a function or feature is slightly improved, removed, or duplicated. But what's the real story about an existing patent? Can I post the patented schematic unchanged, for discussion or learning, or do I need to make a change to the actual design before I can do that?

In this instance, I'd initially be simply posting the unmodified schematic - at least, that's been my plan all along. I'm initially doing this privately, to understand how the circuit "hangs together", but it seems to me that it would be helpful for others to see the schematic in "normalised" form. Well, I've renamed some parts, but I've also modified a couple of connectors to bring power and ground to the offboard module and controls (that's missing on the original schematic), and I'll be using different parts (such as a self-contained LCD, and so on). Is that enough to make a difference?

I just want to cover my arse (and Carl's), while still doing something for the community, and to give BW his due. So if anyone has experience with this area, I'd appreciate any help or discussion. I think it would also benefit many others who, like me, consider this a bit of "black art".

Sorry for the long post. I wanted to explain the situation as clearly as I could to avoid too much to-and-fro. I hope you all enjoyed the long read!

Cheers,
PtB

[Tinkerer]

We are looking forward to the next update. Very interesting.

Tinkerer

[Pete the Builder]

Sorry it's been a bit quiet on this front. I'm moving home, and I've got to get all the paperwork to the right places and so on. Plus, I've been working on a few other projects simultaneously, and I'm not really a good juggler - I tend to focus on one thing until it's done. And that means Frankie has to go on the backburner for a while.

I've actually finished redoing the analogue TX and RX of the you-know-what project, which has taken nearly 4 days to sort out. The MCU is also done, and I'm going to try and get the last piece of the puzzle - the PSU - done by tomorrow afternoon (Monday local time). I have an appointment with a banker in the evening, so I also have to get a bit of paperwork done. But you can guess what I prefer doing...

But I have good news on the Frankie front - the replacement Arduino Due module arrived, together with the touch screen! Woo hoo! And after checking that it works (but not on Win7 x64, though ) I'm having to do all the development for the moment on the Macbook. As a touch typist, I'm having lots of fun constantly switching between 3 keyboards!! (The Compaq laptop is what I'm using for Altium Designer, the Macbook runs the Arduino IDE, and I hop on the main system to check for legal forms for the house and clean up the development folders. Oh, I forgot the iPad... It's driving me nuts! Ah, what a problem to have, huh?)

Anyway, I've managed to find a library for the touch screen, a bit dodgy but it compiles OK. So in between everything else, I'm peeling flat cable and crimping headers, soldering pins to the end, etc, etc. My goodness, those LCD modules are unbelievably crude. They just stick a bunch of display controllers on a board with the LCD and touch screen, and you have to program the chip's timing parameters, video paging, and memory mapping timing for each controller before you even get to say "Hello, World!"!! No wonder they're just US$22, they're like buying a car and finding it has no accelerator cable or clutch pedal, and you have to build the transmission and install it yourself. And don't expect seats or wheels!

Still, the two main parts of the support for Frankie are here - the MCU, which will do most of the hard work, and the display, so I can see what's going on and change parameters. Now, I just have to write some UI software... What was the formula for a chord again?

I'll keep updating here, hopefully I'll also have the display working tomorrow, but maybe not the touch screen... We'll see.

Cheers, and apologies,
PtB

[Pete the Builder]

Thanks Mick! But it had roughly the same decay time with no coil at all! I thought at first it might be Cgd, but I tried without the "fastening" circuit's active devices (diode and tranny), and sure enough, on the same board, I got under 60nS! So it's back to the drawingk board. Gosh darn it. But thanks for the suggestion, it made me put my thinking cap on properly.

In other news, I've been advised that my replacement signal generator/MCU could be 2 weeks away, as it's Chinese New Year (happy year of the Snake, everyone! Hope it's not a sign for us wanderers in the bush... ). So I have a bit of time up my sleeve, which I'm going to spend learning a lot more about the basics, and hopefully concentrate on the important bits step by step.

I'll keep everyone posted, I know you're all holding your collective breath!

Cheers,
Pete

[Mechanic]

Hi Pete,

Perhaps capacitance from the coil or another cct aspect is causing your stretched spec......

Cheers Mick

[Pete the Builder]

Ha!

For anyone reading, I think you'll appreciate this...

I was about to post a CRO dump of my über-fast TX coil FET design, to see if anyone had some feedback that would help improve the design... So I doubl-checked the specs for the FET (60nS), and compared my über-fast design real time data... Which was 120nS!

Perhaps I should patent this as a "Spec Stretcher" circuit instead?

As soon as I'm up again, I'll post the little schematic and screendump anyway, so we can all have a jolly old laugh...

*shakes head and sighs*

Cheers,
Pete the Pulse Stretcher

[Pete the Builder]

If you are doing PI then a TX boost reg can be difficult at high voltages. A typical TX with 2A@10V@10% requires 200mA from the boost reg. This level isn't difficult, but as you move up into the 20V or 5A level it is. Most boost reg datasheets describe how to calculate max output current given the inductor, duty cycle, input & output voltages. The more you try to boost (3V -> 20V) the worse it gets.

I suggest starting with modest goals. Use a 12V battery pack so you don't even need a boost reg, then use a buck reg for the circuitry. That gets into another problem... despite high-f switching the switching noise can still be an issue. Some regs are horrible, some not so bad. Use an IB coil or a cap-coupled front-end so you don't need an inverted supply, use a simple rail splitter instead.

I'm currently working on a PI that runs on a 6V battery pack, and just finished helping on a VLF design that runs on 2-AA batteries. Getting reasonable power supply designs was a fair challenge. Save that challenge for another day, and focus on making the PI part.

- Carl

Thanks for the tips, Carl, it's much appreciated.

I'm a HV kinda guy, so I'm reasonably happy working with boost converters, I've come up against nearly all their limitations! My biggest HV project was a coil gun, I'm still working on that, but it dumps around 7J into three coils in about 4uS via "hockey puck" SCRs. It's frustrating trying to maximise dV/dT in a portable device like that. But hey, it's fun!

I will be designing the detector around a 35W SLA 12V gel cell. I have about a dozen of these, after downgrading my studio UPS. I know and love the SLA technology, from discharge curve to recharger circuits, I really cut my teeth on 'em! I prefer them in many ways to LiPo technology - SLA doesn't have near the power density, but then it doesn't have the price or awful charging constraints either! Although the price has been steadily dropping for a year or more now (I'm using a pack of 35Cs in a quadcopter I'm designing and programming).

I understand what you mean about HF noise. I found out the hard way that although it does get "naturally" filtered through good layout and bypass techniques, it still radiates like crazy, especially under duress. Ground planes help, but again my maths lets me down a bit and it ends up being a "suck it and see" when it comes to actually testing out such a design.

Again, thanks for the suggestions, I really do appreciate the interest. I'm really hoping not to disappoint too much in the wash...

Cheers mate!
Pete

[Carl-NC]

If you are doing PI then a TX boost reg can be difficult at high voltages. A typical TX with 2A@10V@10% requires 200mA from the boost reg. This level isn't difficult, but as you move up into the 20V or 5A level it is. Most boost reg datasheets describe how to calculate max output current given the inductor, duty cycle, input & output voltages. The more you try to boost (3V -> 20V) the worse it gets.

I suggest starting with modest goals. Use a 12V battery pack so you don't even need a boost reg, then use a buck reg for the circuitry. That gets into another problem... despite high-f switching the switching noise can still be an issue. Some regs are horrible, some not so bad. Use an IB coil or a cap-coupled front-end so you don't need an inverted supply, use a simple rail splitter instead.

I'm currently working on a PI that runs on a 6V battery pack, and just finished helping on a VLF design that runs on 2-AA batteries. Getting reasonable power supply designs was a fair challenge. Save that challenge for another day, and focus on making the PI part.

- Carl