Let's made a PC-base metal detector with usb interface !!!

[moodz]

Thanks Aziz ... I am not sure that you have convinced me ... can you demonstrate a spectral analysis of the the half cos response versus the half sine response ? I think a side by side comparison would be useful.

Regards,

Moodz.

[Aziz]

Hi moodz,

Aziz ... the half sine waveform is nice however it is a voltage waveform ... not a current waveform ... dont we want the magnetic field to follow a half sine response ? The half sine pulse should be a half sine current pulse in the coil .. ???

moodz,

the IB-PI version produces exactly half cosine current wave form. The mono coil proposal 1/4 cosine current (half of half cosine) and this two times in different timings (interrupted half cosine current wave form).

If you apply the trigonometric rules, you can see the half cosine as a phase shifted partial sine wave form of course. But to be very accurate in naming convention, the current in the coil is a half cosine wave form at its important part. It is an ident cos(x) current wave form for x=0 .. pi.

The fine difference is heavy important to kick-*** all half sine current wave form patents.

Now the dI/dt at the cosine coil current:
Coil current:
I(t) = I0*cos(t) (I=coil current, I0=switch off coil current, t=time, t=0 switch off time)

First derivation of coil current (dI/dt):
dI(t)/dt = I0*cos(t)/dt = -I0*sin(t)

The coil current slope (dI/dt) has it's absolute maximum at pi/2 (at 1/4 cosine coil current) and will produce the highest target stimulation. That's also the time point, where the mono coil proposal begins to sample the responses if the target signals are strong and fresh (in Phase S1).

The mono coil proposal is difficult to implement. The coil energy buffer capacitor switch is not ideal and becomes a capacitor connected serial to the buffer capacitor. All the parasitic capacitances of the switch will increase the capacitive load to the coil and therefore the damping resistor for critical damping will be low. It takes long time to damp all the energy stored in the parasitic capacitances. But a high dynamic range sampling system should still be able to handle this disadvantage.


Aziz

[moodz]

Aziz ... can you explain more please.

Signals during continious mode operation:

Aziz ... the half sine waveform is nice however it is a voltage waveform ... not a current waveform ... dont we want the magnetic field to follow a half sine response ? The half sine pulse should be a half sine current pulse in the coil .. ???

moodz,

[WM6]

Hi WM6,

the principle is quite simple:
- charging the coil and recycling the energy: exponential behaviour as usual (even the coil is driven almost in linear mode, it isn't linear, it is exponential)
- coil energy buffering and current reversal: half cycle of a parallel LC resonant circuit.

We just seperate the whole process into different phases. On IB-PI there is no phase 3 delay necessary.

That's all. Nothing really new. Of course, not novel.

Aziz

Hi Aziz,

look at this, BFO but with some basic working similarities.

http://www.talkingelectronics.com/projects/MetalDetectorMkI/MetalDetector.html

[Mechanic]

Hi Wm6,

Yeah I like mono's! But if something else can get more depth with discrimination, I'm there.

I think if the current is sampled at multiple points during on time and flyback period that some more info can be gained on whats in the ground.



Cheers Mick

[WM6]

. I am definitely interested in the mono method, however I think that it would be better to be able to sample during the flyback as the target signal is strongest then, not to mention the discrimination ability too.

Cheers Mick

Hi Mick

nice to read that you are monogamic too, for some pressure at Aziz to speed Standard-PI (mono coil) project. Seems thatIB-PI (IB coil) bigamy are not widely acceptable.

[Mechanic]

Hi Aziz,

Good work! I am watching with keen interest. I am definitely interested in the mono method, however I think that it would be better to be able to sample during the flyback as the target signal is strongest then, not to mention the discrimination ability too. The other day I dug down about 2 foot to recover an old miners chisel sounded like a nice sweet 10 ounce nugget Not that I know what one sounds like!!

Anyway I will add some more parts to my shopping list as power efficiency/ amps into the coil are high on the list. Vaporising coils is too!

Cheers Mick

[Aziz]

Comparison of IB-PI and Standard-PI

Hi all,

well, I have reduced the power consumption radically now. High current pulses should not cause much heat now. Below is a brief comparison of both PI systems.

IB-PI (IB coil):
Disadvantages:
- requires very stable induction balanced coils
- difficult to build the coil
- requires good ground balancing and discriminating (mineralized ground)

Advantages:
- high power effciency, low battery drain
- good discriminating possibility
- simple driving logic
- high pulse currents

Standard-PI (mono coil):
Disadvantages:
- less discriminating possibility
- complex driving logic (circuit overhead)
- requires good ground balancing (mineralized ground)

Advantages:
- high power effciency, low battery drain (new feature )
- simple mono coil
- easy to build the coil
- high pulse currents
- good handling of mineralized ground

The latest proposals for the standard-PI detectors should make vapour detectors possible now. I can increase the coil current to vaporize the coil fully now.


Aziz

PS: You guys did not recognize the potential yet ... Someone is going to steal and patent the ideas now (if not already patented yet). I will be prepared with bad eggs or lead bullets.

[WM6]

Hi all,

have a look, what two rival competitors do in this field:
(on going things not known yet as it is not disclosed in the patent procedure - so there might be more parties involved)

Pulse induction metal detector having high energy efficiency and sensitivity (White's):

http://www.google.com/patents/about?id=SYzLAAAAEBAJ&dq=US+7649356

RECTANGULAR-WAVE TRANSMITTING METAL DETECTOR (MineLab):

http://www.wipo.int/pctdb/en/wo.jsp?WO=2009155648

Both rival competitor solutions use induction balance coils (TX, RX seperate). Do we getting the battle tighter now?


Aziz

PS: Who recognizes the big potential?

As I can see Whites patent was filed long ago Dec. 18. 2002 and isued Jan. 19. 2010. At least 8 years old ideas. Some cited reference are old 46 years. We are now back to mono PI coils as you explain in last posts here.

[Aziz]

Rival Competitor's Solutions.

Hi all,

have a look, what two rival competitors do in this field:
(on going things not known yet as it is not disclosed in the patent procedure - so there might be more parties involved)

Pulse induction metal detector having high energy efficiency and sensitivity (White's):

http://www.google.com/patents/about?id=SYzLAAAAEBAJ&dq=US+7649356

RECTANGULAR-WAVE TRANSMITTING METAL DETECTOR (MineLab):

http://www.wipo.int/pctdb/en/wo.jsp?WO=2009155648

Both rival competitor solutions use induction balance coils (TX, RX seperate). Do we getting the battle tighter now?


Aziz

PS: Who recognizes the big potential?

[Aziz]

Hi WM6,

the principle is quite simple:
- charging the coil and recycling the energy: exponential behaviour as usual (even the coil is driven almost in linear mode, it isn't linear, it is exponential)
- coil energy buffering and current reversal: half cycle of a parallel LC resonant circuit.

We just seperate the whole process into different phases. On IB-PI there is no phase 3 delay necessary.

That's all. Nothing really new. Of course, not novel.

Aziz

[WM6]

I will throw bad eggs, if someone tries to patent it. It is in the public domain now.

Aziz

Hi Aziz, I get bad eggs in tryind to understand working esence of this PI project.
For me not so clear explained as previous IB/PI project.
I will try to read all about this your idea again, then we will see if additional explanation is needed.
Thank you.

[Aziz]

BTW,

the coil current during phase 2 and 3 is a half cosine ( I(t) = I0*cos(t), t=0: switch-off time, I0=switch-off current ) . The self induced voltage in the coil Uind is (signal UTX):

Uind(t) = -L*dI/dt (Lenz's Law) = -L * I0*cos(t)/dt = L * I0 * sin(t)

So we get a half sine flyback voltage. The new mono coil method splits the half cosine coil current into two parts. Between of them (phase S1), the coil is damped and operated as receive coil.

The method could also be called as the 1/4 cosine method if you like.

Aziz

[Aziz]

Some Comments on Phase S2

Why is there an additional sampling phase S2?

This is compareable with the on-time sampling. Just the other way around. It is done after the recycling phase. The coil current slope (dI/dt) differs to the other phases 2 and 3 and one can get more infos about the target, ground and other effects.

This method should be novel.
I will throw bad eggs, if someone tries to patent it. It is in the public domain now.

Aziz

[Aziz]

High Efficiency Mono Coil Transmitter Signals.

Hi all,

below is the delayed phase 3 for mono coil configuration PI with efficient energy recovering described above. The delay is called phase S1. This phase is critically damped (damping resistor switched in, coil energy buffer capacitor switched out). After the damping, the samples can be taken directly from the TX coil. The delay period can be as long as necessary. The coil energy will be held in the capacitor during this time.

After the samples has taken, the phase 3 will be continued to recover the energy back. If the Phase 4 is finished, either another sampling is possible (phase S2) or it can be continiued with Phase 1 for continious operation.

Ignore the voltages and currents after phase 4. The control signals are not set and the coil has some minimum energy that begins to oscillate. The minimum energy left back in the coil or capacitor can be damped with the damping resistor if there is another sampling phase (phase S2).

The principle is quite high efficient and makes pure mono TX coils possible. If you don't make the damping resistor switchable, some energy will be lost. Best efficiency will be given, if the damping resistor is switched in at its usage only.

Aziz