A DAMPING CIRCUIT FOR A COIL

[moodz]

I smell trouble with this. Reading all this carefully, i'm pretty confident there are some issues whit method described, namely it may not work with real coils in all cases, as in simulation. Issue#1 (main one): this is fine for ideal, lumped element coil, but real coil is distributed parameter circuit, and fastest way to discharge it is by resistive load. Circuit will not “source” energy any faster than limited by natural LC, so cannot be “sinked” any faster with current sink, in effect highly nonlinear resistance during discharge period. Maybe I’m wrong on this, never tried, just my opinion.

... the aim is to remove the energy from the coil in the shortest time ... Damping resistor is dependant on L and C .... time constant is dependant on L and R unless C is very very big. The magic formula is 0.5xLxIxI = joules == KxRxixixt. The LHS is the energy charged in the coil during transmit, the RHS is the energy absorbed during flyback by current sinking... don't get confused between real and reactive or apparent power ... this is the trap. The current squared term is on both sides ... analysis shows that this equality results in linear time discharge of coil energy .. therefore no exponential term and shows fixed damping resistor is not optimal load. Here is another way of thinking about this problem .... what is the fastest way to transfer the energy out of a charged capacitor ?? ( shorting it is not the correct answer ... :-) ).

[moodz]

0.5xCxVxV == joules == Kxvxvxt/R .... a constant voltage load ... the voltage across the load will not change with current .... :-) technically a short circuit is a correct answer as its "constant" voltage is 0 no matter what the current is .... however as a 0 ohm circuit cannot dissipate power it should not be called a load.

[greylourie]

Hello Moodz

Does your damping system display similar benefits in surf/ beach/ waters edge situations as it has shown in difficult and erratically changing ground ? I am hoping that others with the means and who are more competent than myself will be encouraged to experiment with the simplified example that you so kindly posted.

I read so many posts on here where builders complain of the effects that the lapping surf has on their machines. Could your system be a solution ?

Regards

grey.

[moodz]

Hi Grey... It could be ...have not started water testing yet ... I would hope so based on what I know so far.

[6666]

Moodz would you mind suggesting a suitable value for the D2 zener please ?
thanks

[moodz]

Moodz would you mind suggesting a suitable value for the D2 zener please ?
thanks

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

[6666]

Thanks for the info Moodz.

[moodz]

Well because the administrators of this forum have failed to protect members interested in learning or contributing from serial pests ... This is my very last post or access to this board.

[Tepco]

You have missed my extensive comment on this issue, posted here, and few posts later, also one interesting proposal.


http://www.geotech1.com/forums/showt...893#post186893


My fault, later things spiraled out of control and went off-topic, ending up waging online war for Ukraine, confronting Friedman and Keynes and citing Dostoevsky on technical forum, so no one read it anymore. In meantime I tested on real hardware\prototype my proposal (in two versions, one of them failed completely) and proposed constant current sink method. Next 7-10days I will be offline (nice weather finally) and unable to participate or post, but later this can be nice opportunity to finally discuss something technical and detector related here.

[Davor]

Well because the administrators of this forum have failed to protect members interested in learning or contributing from serial pests ... This is my very last post or access to this board.

Too bad, but I understand you completely.

[sinclairuser]

george, or carl, since moods has now left the forum, and others are not prepared to leave it alone, why not lock and archive this thread, leaving it open will only draw more off topic posts.

[Paul99]

Well because the administrators of this forum have failed to protect members interested in learning or contributing from serial pests

More appropriate, Moodz, would be to say that Admin is not interested in defending the outrageous claims being made by a few when others dispute these claims. Do you think it may be because Admin has seen it all before and knows which bin these outrageous claims are going to end up in??

By the way Moodz, you cannot be that thin skinned. You suggesting how my posts can be hidden has been done because YOU don't have any answers. It's a pity you don't have the answers and therefore don't want to play with the big kids.

[Qiaozhi]

More appropriate, Moodz, would be to say that Admin is not interested in defending the outrageous claims being made by a few when others dispute these claims. Do you think it may be because Admin has seen it all before and knows which bin these outrageous claims are going to end up in??

The reason the thread was closed has nothing to do with any "outrageous" claims. It has to do with the constant bickering, sniping, taunting and swearing.

Please read the forum rules -> Basic Rules of the Forums
In particular, the parts where it says:

• Be polite. Write messages as if you are standing in front of someone talking to them.

• Criticism should be relevant and constructive. If you disagree with something, state your case, and move on.

• Personal attacks, whether directed at a participant or a non-participant, are not tolerated.

Posting a personal attack, even veiled, will result in an immediate 3-day suspension. Three such infractions will be met with a 3-month ban. This forum is not to be used to attack people or companies; if that is your desire I can recommend another forum that welcomes such behavior.

Aziz - I have removed your last inflammatory post to prevent further inappropriate responses.
In future, please think before posting, as (due to numerous complaints from other members) I will be enforcing the forum rules more rigorously from now on.
You have been warned.

[WM6]

I wish to not close, from start exclusively technical oriented and interesting, moodz's threads.

I wish to delete inappropriate debates only, which only pollute his treads. Even ban someone, after warning, if nothing helped to stay on Basic rules of the forum. This primarily, before close useful technical threads, as it is not the same, as to close some others of topic fighting threads.

I wish admin to clean moodz technical treads from last taunting and disturbing posts and to invite moodz back to continue its work.

More work for admin, I know, but I hope in interest of forum members.

[Nupi]

This is not a personal attack to a admin!!
I think, that this is a common dilemma for admins. To wait to long until they suspend someone.
They are often "afraid" (understandably) that a potential member permanently move to another.
With the result that it is out of control and eventually have to close a thread, pity.