DEEPER PI DETECTION DEPTH

[Aziz]

Reading through it again it also raises an extra complication that hasn't been mentioned. I think the ground and target effect will behave as what Richie describes as a 'lossy workpiece'. As well sapping energy and bringing the 95% efficiency dream southward it will also change the resonant frequency. So that's something that will need to be tracked and corrected for.

Midas,
the modulation of the coil current and frequency due to ground and targets is intended! All the necessary information is there.
How to process all the information?
Well, this is the holly grail and all the patent trolls are just waiting for its reveal.

Aziz

[Midas]

Reading through it again it also raises an extra complication that hasn't been mentioned. I think the ground and target effect will behave as what Richie describes as a 'lossy workpiece'. As well sapping energy and bringing the 95% efficiency dream southward it will also change the resonant frequency. So that's something that will need to be tracked and corrected for.

[Midas]

http://www.richieburnett.co.uk/indheat.html

This site has a lot of good information that is very applicable to what you guys are simulating. What maybe of particular interest is the different drive inverter designs. No need to limit yourself to the one switching component, half bridge, full bridge or even multiple parallel full-bridge is also achievable and quite possibly advantageous.

[Midas]

The yellow trace is again the coil current.

Hi Tinkerer,

Your colour blind I assume? The coil current trace is actually green. From left to right you have: Green, Blue, Red, Turquoise, Magenta, Grey

Midas

[Aziz]

More power to the people - ups - I mean targets!

Now split the coil L into two halves: upper and lower coil part with either equal or different winding turns (auto-transformer) and feed it at the center junction of the coils (capacitor over both coil parts). See below for more details.

This gives the target the freakin kicking at the expense of more battery power consumption of course. And you can crank up the freakin flyback voltage (kilo Volts region if you like), which gives more room the to limitted break down voltage of the mosfet and diode. The lower coil part (near the diode/mosfet) should have either equal winding turns or lesser.

You can find the correct inductance splitting formula in the spice model.
When Num1=1 and Num2=1, it's a center tapped coil.
When Num1=1 and Num2=2, the upper coil part has two times turns count of the lower coil part. Take care of splitting the resistance of the coils correct (LR1(lower) and LR2(upper)).

Beam me up Scotty!
Bzzzzzzzzzd.

Aziz

PS: I have added the zipped spice file for your convenience.
Cheers

PPS: Change the buffer caps on the right side to the same value (CB2 and CB4 = 10000µ).

[Tinkerer]

Below, again the traditional PI method, so that we can compare the amplitude of the target response.
About the same power consumption. (1A)

The yellow trace is again the coil current.

The PPS are very much less, about 1000PPS

The peak target response is 2.24A

About the amplitude of the target response: To be able to show the TX current and the target response on the same screen, so that one can see the relation, the scales had to be manipulated. Obviously the real target response is not 2.24 Amps, more like 224uA.

But the target response in itself is fairly accurate. This whole series of sims, use the same proportions so that they can be compared with each other.

Tinkerer

[Tinkerer]

Tinkerer,

this is now looking right.
The more efficiency is owed to the fact, that a lot of the energy is held in the resonant LC tank rather than moved in the whole TX circuit. Only losses will be injected into the LC tank.

Let's heat up the gold nuggets -> hot gold nuggets (induction heater principle).

Aziz

Maybe I should add, that the sim that I show, is not exactly optimal, I just tried quickly to adjust it for the same power consumption as the other sims, that is about 1A.
The method can be optimized for better results.

Tinkerer

[Aziz]

Tinkerer,

this is now looking right.
The more efficiency is owed to the fact, that a lot of the energy is held in the resonant LC tank rather than moved in the whole TX circuit. Only losses will be injected into the LC tank.

Let's heat up the gold nuggets -> hot gold nuggets (induction heater principle).

Aziz

[Tinkerer]

Aziz is right mine did have a diode and the wave form is sinewave ... it is part of my new project D-IGSL ( Digital IGSL ) it rocks

Ups, sorry for the mistake.

Here is the corrected sim.

Again, the yellow trace is the coil current.

The other 5 traces are the responses of resistive targets as could represent gold nuggets of different size.

As it is, this Moodz version uses about 10% less power than the TEM sim as shown above.

Tinkerer

[Aziz]

Aziz is right mine did have a diode and the wave form is sinewave ... it is part of my new project D-IGSL ( Digital IGSL ) it rocks

Hi Moodz,

let's revival the good old ideas. They are prior art and the patent trolls can go to the hell.

Aziz

[moodz]

Tinkerer,

that isn't the moodz's version (variation ok, why not). Connect the tuning capacitor to the anode of the diode (not cathode). You should get a sine like wave form at the resonance frequency.

Aziz

Aziz is right mine did have a diode and the wave form is sinewave ... it is part of my new project D-IGSL ( Digital IGSL ) it rocks

[Aziz]

Below is the Moodz variation.
The coil current is the yellow trace. Take note of the peak amperes.
Not much difference in the circuit, but different output. The pulses are positive only.
The power consumption is only very slightly more.
We get more PPS, that is good.
I added the target response of the 5 targets of different size. Take note of the signal amplitude.
The peak target amplitude is 472mA

Tinkerer

Tinkerer,

that isn't the moodz's version (variation ok, why not). Connect the tuning capacitor to the anode of the diode (not cathode). You should get a sine like wave form at the resonance frequency.

Aziz

[Tinkerer]

Oh I See. My bad, always leaping to the wrong conclusion. So is the only different between this sim and post #31 the diode?

Midas

The diode makes the big difference.
The sim has been adjusted for the power consumption to be about equal.

The induction is different.

The PPS is different.

Actually I got the TEM target response sim ready, so I post it here.



Below is the TEM method again.
Same power consumption, take note of the peak amperes of the yellow trace.
The pulses are bi-polar, this makes a big difference.
We get less PPS only about 4300 PPS. Still enough to do some integration to get a good S/N and keep the response fast.
Take note of the target signal amplitude. Same targets as the Moodz variation. These are 5 resistive targets like gold nuggets of different size.
You can see the peak target amplitude is over 6A
Tinkerer

[Midas]

Don't ask me, I only made and show the simulation of Moodz's circuit inpost #12, above.

Tomorrow I will post the signal response of the TEM circuit, for comparison.

Tinkerer

Oh I See. My bad, always leaping to the wrong conclusion. So is the only different between this sim and post #31 the diode?

Midas

[Tinkerer]

You've got me confused now Tinkerer. How are you proposing to integrated the TEM method with Moodz's coil which obviously isn't IB ?

Don't ask me, I only made and show the simulation of Moodz's circuit inpost #12, above.

Tomorrow I will post the signal response of the TEM circuit, for comparison.

Tinkerer