Balanced VLF Tx

[WM6]

Who is going to make the DSP software part now?

Aziz

Don't look at me!

[ivconic]

Nice work ivconic. You use Davor's solution.

Can you post black-white slide too? And schematic (if) you draw. Seems R2 is missing in your PCB?

Davor's explanation does makes lot of sense, that's why i am interested in making it material.

[ivconic]

Hi Ivconic,

ok, I have provided the hardware part for the nice toy.
Who is going to make the DSP software part now?

This "comic" is a brilliant simple and powerful detector platform to implement the whole VLF detector technology in software. It looks really very simple ... (but can knock out a lot of VLF detectors *LOL*).

Cheers,
Aziz

Who!?
Man, at this point i can't imagine nobody else but you, for such task!

[Aziz]

A goody for you: More power efficiency (less losses)

(We are getting close to the ultimate solution to stop the earth warming *LOL*)

BTW, the pnp BJT transistors can be replaced by a small signal p-mos fets (requiring low switch-on gate voltage). You have to limit the zener diodes to the maximum gate voltage of (+/- 20 V). ZD 18 might be good enough. As p-mos fet the BS250 would do it. But mosfet solution requires a minimum input voltage (3-4 V minimum). And you can leave the base resistors (not required with mosfets).

Mosfet source (S) connect to V+, gate (G) to base and drain (D) connected to the collector junction (tp1, tp2).
The maximum input voltage should be limitted as the zener diodes shouldn't break down (clip voltage) in normal operation.

Cheers,
Aziz

[ivconic]

Nice work ivconic. You use Davor's solution.

Can you post black-white slide too? And schematic (if) you draw. Seems R2 is missing in your PCB?

Sure.
Yes i omit R2.
Can be added with one side on pcb (+in) and other in air...

[ivconic]

Ehmm... i agree with you but i am limited with material i have at home, so bjt version is all i can do by now.

[Aziz]

And if you put a gate projection circuit (Resistor - zener diode at gate) by limitting it to max. gate voltage, you can leave the other zener diodes and let the coil voltage rise to the mosfets limits (break-down voltage)...
That would give the right bang...
*LOL*
Aziz

[WM6]

Thank you, ivconic.

I wish to read Davor's comment on how to apply / adapt this Bal_VLF_Tx to working in regime usable for some "off resonance" design.

[Aziz]

P-Mosfet Variant

This is what I mean with the p-mosfet variant.
You can use other "better" p-mosfets of course.



Notice, that the sound card power source voltage isn't high enough to switch-on the mosfets. The battery solution should be used in this case. Best power efficiency is given by avoiding the break down voltage states (zener diode and mosfet).

Cheers,
Aziz

[Aziz]

This is the initial p-mosfet variant I have mentioned. Notice, that the gate voltage is limitted by the zener diodes at tp1 and tp2 node. You have to limit the battery voltage not to cause the breakdown state (power efficiency sucks).

This gives the best power efficiency. It can be further increased by better mosfets of course.



Cheers,
Aziz

[Aziz]

Ehmm... i agree with you but i am limited with material i have at home, so bjt version is all i can do by now.

I like the BJT version too.

A 9 V input voltage version achieves a coil current of ~ 1 A pp at one half (+/- 500 mA). Effectively a 2 A pp transmit magnetic energy at the whole coil (both halves taken into account). The voltage over the coil achieves ~55 V (Tp1 - Tp2) . And this at ~21 mA power consumption at 9 V.

A 2000 mAh battery set would last ~95 h (almost 4 days). Ok, that's acceptible for me.

Cheers,
Aziz

[Aziz]

Can't Get Enough?

Ok, this is the high voltage version using other transistors and zener diodes. That should give the ultimate bang to the targets.

(TX reference voltage should be reduced by reducing the C5 capacitor. Max. input voltage is approx. 20 V. Pay attention: you need high voltage rated electrolytic capacitor this time. Leave the transformator and the full bridge rectifier. We power the circuit from the 18 V battery. )

BTW, the coil current gets effectively 4 A pp (+/- 1 A over the half coil) and a voltage across the coil over 100 V pp.



Cheers,
Aziz

[Davor]

I like Ivconic's PCB. It is the basic design from which all the rest cross-quads can be made.

I wish to read Davor's comment on how to apply / adapt this Bal_VLF_Tx to working in regime usable for some "off resonance" design.

No idea. I did not test such case. I wouldn't expect much because of the self stabilising function.

[WM6]

Davor, what sort of C4 and C5 capacitor are to use in your Clapp variant? Electrolytic, tantalum, or?

[Davor]

I'm afraid none of the electrolytes would perform well, so it must be foil ... KT KP, MKP, Mylar ... something. Price-wise these are even priced or cheaper than non-polarized electrolytic capacitors of the same value, but they tend to be quite large.

Regular elko's ... pluses towards transistors, minuses towards a coil ... maybe. In that case I'd use also some pull down resistors on the coil side to reinforce their polarity. It could work that way when I think about it, but ... They'd have to be rated for over 30V, hence their ESR may become a serious issue.

I'd go for foil.