field test unit no 001 "model T"

[straton]

That's my dilemma! - Nop! No commercial product yet. lol After a few months of further improvements and an all, low cost, analog version that turned out to be the most sensitive but lacked the discrimination abilities of the digital one, I completely stopped the project. Was spending too much of my time and my "real" design for a living, was set back. Lost a lot of money... About a month ago, returned to the project and here I am again for a last "try". but since you all here, are talking about a differential front with a THAT1510 pre amp, here is my design, back in 2010. Good sensitivity, fully micro-controlled, all adjustable timings, but with stability problems...mediocre ground balancing.
Here is the prototype. Bottom side is where all digital electronics and controls reside. LCD display is on left side. Hope this post is not off topic. If it is, I apologize.

[moodz]

I never talked about amp noise except in the case of the servo loop, to justify my reasoning. I talked about other parameters that can be of importance to high gains. It is not my problem that some members like to get off the subject.
About your damping circuit, hope it works as you said, too bad you can't publish it, but may I ask why this will improve noise. Since it is damping the coil, it some has a resistance/reactance and it has inherent noise. The only way that I can see, to improve sensitivity in certain situations only, if it is dynamic in nature and over/under damps the coil at specific times.

The noise is improved by way of signal to noise improvement. By damping faster and having no damping resistor current ... Because there isn't one ...damping resistor current saps signal.

[Carl-NC]

believe it or not the most difficult thing has been adding some protective circuitry to prevent damage if the invention does not do its thing

Oh, I believe it. I've been working with a prototype that has a high-voltage TX circuit, and it has a nasty tendency to smoke the FETs on start-up.

It'll be interesting to see what you've come up with. BTW, have you done ground testing with a 5us sample delay? I've only found this to be useful in industrial detectors.

[Davor]

...since you all here, are talking about a differential front with a THAT1510 pre amp, here is my design, back in 2010.

Don't get me wrong, but going balanced leaves you with far more options than the overhyped THAT1510. I'd much rather build my own CFIA, or if forced to go THAT, it would be THAT1570 instead.
Being an amateur, or at least choosing an amateur stand point in the matters of electronics and metal detecting, I'd never go for a part that is difficult by any means. Difficult to obtain, difficult to pay for, difficult for care and feeding ... by any means difficult. I'll leave to my ingenuity to fill the gaps of the missing difficult parts instead.

Once the physics say go, the engineering makes it happen - this way or the other.

I'm a bit excited about the moodz' design because PI design may be further improved in Tx energy efficiency and S/N of the Rx. We'll see

[moodz]

Oh, I believe it. I've been working with a prototype that has a high-voltage TX circuit, and it has a nasty tendency to smoke the FETs on start-up.

It'll be interesting to see what you've come up with. BTW, have you done ground testing with a 5us sample delay? I've only found this to be useful in industrial detectors.

I would love to just press the submit button and get over it LOL ....however seriously I have spent about 3 years on this now and few grand in parts ...which admittedly has been alot of fun, electronics is one of my interests and solving problems gives a great deal of satisfaction ...and there are lots of things you coud do that would cost alot more in time and money. However in terms of the technology most of the pulse induction IP is premised on your standard damping of a decay curve ... sure there are fancy mechanisms for switching or manipulating the damping resistor both prior, during and post flyback ...however I do believe that by finding a "new" damping method all that dependant IP is now no longer applicable ... because this invention modifies the decay curve all the sampling, linearisation, ground balance etc techniques no longer apply because they are premised on the physics of "standard damping".
I also realise that no-one is going to believe this unless we get a working, doable detector into the field that substantiates these claims so thats what I am aiming to do next .... If I can cover off my patent costs I will be happy and end up with a few good detectors for my buddys.

Of course there are other fields ( no pun intended ) where damping a circuit in this manner would be useful ( sensing coils, medical electronics etc ) where pulsed coils are used.

On the question of early sampling ... I dont think sampling as early as 5us will be that useful in practice however it will result in very settled damping by 8 or 10 us.

Tx Power is an interesting subject ... on this circuit you can crank the coil voltage say over a range of 6 to 24 volts and the damping remains locked ( actually the flyback time does increase from around 3 us to 12 us but damping is still optimised ) whilst peak coil current changes from around 2.1 amps to just over 12 amps ... may be useful in driving ground loops and having a simple variable "pulse power" control on the detector.

Paul.

[Mustafa]

Hi Paul,

Congratulations for your latest progress.

If you don't mind I want to make a small donation to support your work.
I believe other geotechers can support some or all of your patent and r&d costs.
If you can give me a paypal account I am ready to send $100 for nothing in return.

Keep up the good work.
Regards,
Mustafa

[chudster]

with apologies to Monty Python ...
MANDY: Ohh, I hate wearing these beards.
BRIAN: Why aren't women allowed go to stonings, Mum?
MANDY: It's written. That's why.
HARRY THE HAGGLER: Pssst! Beard, madam?
DONKEY OWNER: Oh, look. I haven't got time to go to no stonings. He's not well again.
hee-haw hee-haw
HARRY THE HAGGLER: Stones, sir? MANDY: Naah. They've got a lot there, lying around on the ground.
HARRY THE HAGGLER: Oh, not like these, sir. Look at this. Feel the quality of that. That's craftsmanship, sir.
MANDY: Hmmm. Aah, all right. We'll have, uh, two with points and... a big flat one.
BRIAN: Could I have a flat one, Mum?
MANDY: Shh!
BRIAN: Sorry. Dad.
MANDY: Ehh, all right. Two points, ah, two flats, and a packet of gravel.
HARRY THE HAGGLER: Packet of gravel. Should be a good one this afternoon.
MANDY: Hehh?
HARRY THE HAGGLER: Local boy.
MANDY: Oh, good.
HARRY THE HAGGLER: Enjoy yourselves.

Thanks for the reply to my post Moodz. Helps put me on track. Looks like all the stones missed.

I see that you have put in your provisional patent app on this 'Pulse induction metal detector with improved coil damping and noise immunity'

Are you planning to wait until you file the full patent the before releasing any more details?

Chudster

[moodz]

Hi Paul,

Congratulations for your latest progress.

If you don't mind I want to make a small donation to support your work.
I believe other geotechers can support some or all of your patent and r&d costs.
If you can give me a paypal account I am ready to send $100 for nothing in return.

Keep up the good work.
Regards,
Mustafa

Mustafa,
thankyou for your kind words and very generous offer. However I cannot take it up at this time as I feel I should either be putting up some proof that the work I am doing now actually works or should be publishing the whole thing for the general benefit for all. I hope you understand and believe me that I am truly grateful for your assistance.

Regards,

Paul.

[moodz]

Thanks for the reply to my post Moodz. Helps put me on track. Looks like all the stones missed.

I see that you have put in your provisional patent app on this 'Pulse induction metal detector with improved coil damping and noise immunity'

Are you planning to wait until you file the full patent the before releasing any more details?

Chudster

I like that scene from the movie LOL ... my 'legal' advice at the moment is that since I have submitted full specifications ( ie abstract, claims, description, drawings etc etc ) as provisional patents even though they will never be made public they will ( have ) established a priority date for the invention and since the key aspects of the invention are quite fundamental and truly inventive ( ie new damping method and optimisation control of same ) they would be quite hard to knock off a full patent application referencing them even if "overpatented".
The really big issue for small inventors is "how to protect". Patents on their own offer no protection ... you still have to enforce them and that takes money ... even if you win you may not see any return for years in some cases.
Some of us on the forums have a thing against "patent trolls" ... however these companies may be the small inventors best friend. For example http://www.acaciaresearch.com
is a company that "aquires" patents and ideas from small inventors and others then proceeds to either have infringing companies pay royalties / licence fees or sue for patent violations. They enter into an agreement with the inventor to recieve a proportion of the monies recovered which is better than nothing that otherwise would be recieved by the inventor. Of course this would not be a good outcome for the detector industry as these patent companies dont really have an interest in progressing the detector industry .....on the other hand the detector industry does nothing for small inventors who come up with good ideas in the field of detector technology .. so I guess you reap what you sow. LOL.

So the short answer to your question is that I am exploring my options.

moodz.

[moodz]

I like that scene from the movie LOL ... my 'legal' advice at the moment is that since I have submitted full specifications ( ie abstract, claims, description, drawings etc etc ) as provisional patents even though they will never be made public they will ( have ) established a priority date for the invention and since the key aspects of the invention are quite fundamental and truly inventive ( ie new damping method and optimisation control of same ) they would be quite hard to knock off a full patent application referencing them even if "overpatented".
The really big issue for small inventors is "how to protect". Patents on their own offer no protection ... you still have to enforce them and that takes money ... even if you win you may not see any return for years in some cases.
Some of us on the forums have a thing against "patent trolls" ... however these companies may be the small inventors best friend. For example http://www.acaciaresearch.com
is a company that "aquires" patents and ideas from small inventors and others then proceeds to either have infringing companies pay royalties / licence fees or sue for patent violations. They enter into an agreement with the inventor to recieve a proportion of the monies recovered which is better than nothing that otherwise would be recieved by the inventor. Of course this would not be a good outcome for the detector industry as these patent companies dont really have an interest in progressing the detector industry .....on the other hand the detector industry does nothing for small inventors who come up with good ideas in the field of detector technology .. so I guess you reap what you sow. LOL.

So the short answer to your question is that I am exploring my options.

moodz.

PS... where are you searching for patent filings .... there are two more since the one you mention.

[Aziz]

Hi Paul,

I'm just curious, where you hide or treat of the coil energy E = 0.5*L*I².

I want to be surprised.

Cheers,
Aziz

[moodz]

Hi Paul,

I'm just curious, where you hide or treat of the coil energy E = 0.5*L*I².

I want to be surprised.

Cheers,
Aziz

I dont hide it anywhere ...

Clue 1.
we all ( should ) know that maximum power is transferred when source impedance = load impedance ... so a fixed damping resistor cannot possibly be the best damping solution for a wideband pulsed coil.

Clue 2.
What is the importance of power factor correction ?

[Davor]

...
Clue 2.
What is the importance of power factor correction ?

:duh: to reduce losses incurred by reactive currents ... so it is a capacitor after all.
You must have smoked a nice bunch of MOSFETs this way.

[moodz]

:duh: to reduce losses incurred by reactive currents ... so it is a capacitor after all.
You must have smoked a nice bunch of MOSFETs this way.

So close yet so far ... All coils have caopcitance.

Clue 3.

Calculate the complex FFT of a flyback and calculate the PF for each discrete term ... While you are at it integrate the instantaneous power over time and calculate the total uncorrected power dissipated in a fixed optimal damping resistance and see if it agrees with the real energy stored in the Coil magnetic field.

[Davor]

I like when you speak dirty