A DAMPING CIRCUIT FOR A COIL

[Carl-NC]

The people who like to stir up crap are Paul99, PatchesJr, Robby_h, Aziz, and Doug. Do I ban all of them, or none of them?

[Nupi]

The people who like to stir up crap are Paul99, PatchesJr, Robby_h, Aziz, and Doug. Do I ban all of them, or none of them?

That's up to you.
It is not about who like to stir up crap but who ignoring warnings from the admin, again and again and personal attacks.
Often one or two that it started and as impunity closing more and more. However, it is well-known.
Maybe not as often warn but act quickly? This is absolutely not attack you personally, but my opinion.
And I know it's still unfortunately a dilemma,
regards

[sinclairuser]

The people who like to stir up crap are Paul99, PatchesJr, Robby_h, Aziz, and Doug. Do I ban all of them, or none of them?

thats your call mate, personally i will support what ever you and george decide.
but i simply meant that if moodz has gone, archiving the board keeps the information here without attracting more spammy posts.

[WM6]

Basic rule of all forums is, that admin warnings must be respected. No debate. Otherwise consequences follow.

In this case (closed threads are really high admin warnings), i suggest to open moodz threads again to allow further technical discussion and clean last out of topic annoying posts only.

[Aziz]

The people who like to stir up crap are Paul99, PatchesJr, Robby_h, Aziz, and Doug. Do I ban all of them, or none of them?

Don't ban Paul99, PatchesJr, Robby_H please.
They also wouldn't want us getting banned.
They need us. We need them too.
The admins need us too.
And the many people who want to get entertained too.

The total thermo-nuclear melt-down is coming... *LOL*

^sif

[eclipse]

...the servo loop in the patent can be dispensed with and a fixed bias on the pass mosfet can be used instead as per the following example .... there is a conventional damping resistor used ( because the current sink is not functional ) Instead of using a messy frontend switch to block the flyback voltage we use the flyback voltage itself to do the switching. The 10 volt bias on the gate of pass mosfet M2 ensures it is hard on except during the flyback period ... note that this bias is higher than the TX voltage of 5 volts. D2 and D9 form a snubber which could be 200volts for example depending on the zener value. A high voltage cap in parallel with D2 will help the snubbing function. D3 prevents excessive negative excursions. W1 is the mosfet sampling switch or you could put the amp here .... The main benefits of this circuit are flyback voltage blocking, no need for switching, low impedance path from coil to first amplifier and simplicity and it may be covered by one or more patents.


200 volt zener is good but I also use 400 volt depend on M1 M2 breakdown voltage ... the higher you make this, the faster the flyback damping but you should try to avoid MOSFET breakdown in M1 and M2 .
Put a 10uF high voltage electrolytic cap in parallel with D2 zener for better switching/zener noise suppression.
M2 should be high voltage but low capacitance.
D1 and D9 should be fast recovery power diodes.
D3 can be a 1n4148. R1 is not needed ... it was part of an impedance circuit for an amplifier ... although the source of M2 should have some sort of impedance on it.
Switch W1 is also not needed if your first amplifier is fast recovery type.

moodz

Has anyone tried to reproduce this front end idea in real circuit?

[moodz]

That cct is just an auto flyback blocker .... ideally you would want to try the circuit in this patent ... http://www.ipaustralia.com.au/applic.../AU2013101058/

[eclipse]

moodz the patent is waaay hard to interpret...
I would need to settle for the voltage limiting part for now.

I noticed finding zener diode (D2) over 390V can be hard,
I have nice 1000V Mosfet to try this with, but blocking voltage would be too low for it with such zener.

[moodz]

moodz the patent is waaay hard to interpret...
I would need to settle for the voltage limiting part for now.

I noticed finding zener diode (D2) over 390V can be hard,
I have nice 1000V Mosfet to try this with, but blocking voltage would be too low for it with such zener.

... A 200 volt zener or a couple in series for 400 volts is fine ... these are commonly available ..... Much Better performance if a cap is put in parallel with zener eg 10uf 400volt ... ( keep your fingers away when charged ;-) )
The avalanche breakdown diodes used in mosfets are too noisy. If you want to go higher voltages you can by series more zeners ... however other factors like insulation breakdown will come into play.

[Elliot]

Moodz, I trust that you are still around here!

A question if I may? What reduction in time to sample could I realistically achieve by using the circuit at Post #51, if I am already obtaining a 5uS time to sample in my preamp? Thanks.

[moodz]

I am around now and then ... to answer that can supply a schematic of your front end?