PI power recovery?

[joop]

2 questions

1) PI power recovery would require accurate timing, am I right? Because the 'recovery pulse' needs to be present when the coil energy buffer capacitor is fully charged.
2) Power recovery depends heavily on the coil parameters, especially the coil's parasitic capacity. Different coil -> different timing?

Just trying to understand the principle...

[Davor]

A simple diode (or a thyristor) can provide this "timing" by means of ceasing continuation of the waveform, as there is a zero (crossing) at the pulse end. The position in time of this zero depends on total capacitance and also the inductance of the coil that may also vary due to the proximity to ground or various targets, so accurate timing is not what you need.

[moodz]

Your point has been discussed at length on the Tinkerer forum. I asked if this continuous wave form should get a different name. The answers were nearly unanimous, saying that the TX is pulsed with a rectangular voltage pulse so it should be named Pulse Induction technology.
I always refer to the traditional PI and the TEM PI, to make the difference clear.

But the real problem is that the engineering focus is not finding power efficient waveforms but optimal detection waveforms ... Power saving is secondary. The current in your tx coil is clearly not a pulse train and that is what matters in a pi .. That's my opinion anyway .....

[Tinkerer]

2 questions

1) PI power recovery would require accurate timing, am I right? Because the 'recovery pulse' needs to be present when the coil energy buffer capacitor is fully charged.
2) Power recovery depends heavily on the coil parameters, especially the coil's parasitic capacity. Different coil -> different timing?

Just trying to understand the principle...

Parasitic capacitance and capacitor and inductor tolerances do make a difference in timing of fractions of us. Leaving one us timing leeway increases the power consumption by a negligible amount. The circuit will still function fine, even with 10% off timing, but the power saving is less.

A similar thing happens with the RX sample timing. High accuracy in sample timing gives superb results. Lack of accuracy reduces the discrimination accuracy.

We can sample at any time during the whole cycle, even at 1us after TX switch OFF, for very small targets.

[joop]

Thanks Tinkerer and Davor for your answer

[Tinkerer]

Hi Tinkerer

Have you posted on Geotech the schematic for the recycler driver.

Looks interesting !!!

Thanks in advance Bob..

Below is the full TX circuit and the data for an IB coil to use with it. This coil is very easy to build and balance. The numbers are relative for any coil size.

I also add the LYSpice file so you can experiment with it. As you see, there are several different targets, of different TC as well as different size with same TC.

If you change the inductance of the TX coil L1, you must also change the BU L3, coil to keep the IB balance, or you can change the k coupling between L1 and L3, this means different diameter relative to TX coil.

Enjoy and ask

[Teemo]

Do I understand correctly, that this is the circuit of the sending side of the detector. Just for sending pulses. The recieving and data analysis is done with some extra coil placed close?
Can you explain more why this bucking coil is used?

[Tinkerer]

Do I understand correctly, that this is the circuit of the sending side of the detector. Just for sending pulses. The recieving and data analysis is done with some extra coil placed close?
Can you explain more why this bucking coil is used?

Without an Induction Balanced coil, we have a Flyback voltage spike of several hundred volts.
The bucking coil eliminates this high voltage. With the coil well balanced, we have maybe 50mV of residual signal on the RX coil.

This way we can look at or sample the target response at any time during the whole cycle.

Attached is a full circuit. The audio could be improved.

You can also find the hex. file for the timing here:http://www.geotech1.com/forums/showt...947#post155947

[Teemo]

Tinkerer, thanks for the direct link.
What hex file are you writing about, I do not see any microcontroller in the circuit?

[Tinkerer]

Tinkerer, thanks for the direct link.
What hex file are you writing about, I do not see any microcontroller in the circuit?

You can find the PSU and TX at the post below.

http://www.geotech1.com/forums/showt...677#post155677

The hex file is for the Pic16F690. If you want to use a different PIC, I help you in getting the timing right.

This is a SB version, for Simple Basic. Just the bare minimum to try it out.

I recommend a regulated power supply for the TX.

[techo_bob]

Hi tinkerer

I will try this concept in real life tomorrow and do some sensitivity checks!!
I will use no tank capacitance, only the coils inherent capacitance and see how i fare.
Thank you very much for a speedy schematic.

Techo_Bob..

[Teemo]

You can find the PSU and TX at the post below.

http://www.geotech1.com/forums/showt...677#post155677

The hex file is for the Pic16F690. If you want to use a different PIC, I help you in getting the timing right.

This is a SB version, for Simple Basic. Just the bare minimum to try it out.

I recommend a regulated power supply for the TX.

Thanks, now it is making more sence.
Tinkerer, have you made prototype already with this circuit yourself?

[Tinkerer]

Hi tinkerer

I will try this concept in real life tomorrow and do some sensitivity checks!!
I will use no tank capacitance, only the coils inherent capacitance and see how i fare.
Thank you very much for a speedy schematic.

Techo_Bob..

Yes, you can do that, it must run at a very high pulse repetition rate then. You must calculate the PRR for the resonant frequency of the coil inductance and the stray coil capacitance and set the pulse timing accordingly to it.
Do not connect any RX circuitry before you have a balanced induction coil arrangement.

The sensitivity is very good and I have obtained power recycling efficiency up to 90%, but there are a few pitfalls, which I will be glad to explain.

[Tinkerer]

Thanks, now it is making more sence.
Tinkerer, have you made prototype already with this circuit yourself?

Yes, I have built several variations of the circuit and tested them. The results are very good, but there are many improvements possible.