field test unit no 001 "model T"

[Paul99]

Like I said before I only tested it, to see if it worked and thats all.

That is fair enough mickstv. However, would you like to analyse the circuit and comment upon what you think would be the simplest mod that you think you could make to the circuit to ensure M2 stays on permanently?

[mickstv]

That is fair enough mickstv. However, would you like to analyse the circuit and comment upon what you think would be the simplest mod that you think you could make to the circuit to ensure M2 stays on permanently?

So why are you asking me to analyse, surely you already know the answer if you have a background in electronics. But on the other hand if you have no background in electronics why are you here ?

Have you tested the circuit yourself ?



Like I've posted a few times now, apart from trying the circuit and seeing that it was able to block the flyback. I really couldn't give a sh!t about the circuit. I'm happy with my micro controlled blocking circuit.

[moodz]

Reply to Armchair Engineer ROBBY_H

As I said, I think it best to ask why others aren't using a particular method instead of assuming you have discovered something new.

I suppose it all depends on what you call a discovery. It could be something you didn't know but is well known to others.

Re Post 866 of this thread, you posted something very similar in 2009 here http://www.findmall.com/read.php?34,920760,page=1

That was almost 5 years ago and in recent posts on an Oz forum you say "it may have shortcomings" and needs "a lot of field testing". It would make more sense if you prove the concept before declaring it a major advance in detector design.

Well I have had the idea for a long time ... but I put it on the back burner because people kept telling me it could not work ... and I did not have the self switching blocking FET. It is a major advance .... the damping resistor solution is not an ideal load for the coil it just stops it ringing.

http://www.geotech1.com/forums/showt...025#post157025

Your pictures (post #340) show a grossly under damped waveform and picture three shows what we would expect to see when a non-ferrous target is presented to an under damped coil. The apparent phase shift though shown and highlighted in picture four is an illusion caused by an incorrect trigger, ie, you triggered off the trailing edge instead of the leading edge.

With this mistake corrected, it should then be obvious that the spike decays faster for non-ferrous objects and decays slower for ferrous objects, exactly as we would expect. The problem though is that highly susceptible material such as magnetite has the same affect as a ferrous object and will completely overwhelm any small change caused by a target at depth and you can't apply traditional GB to your waveform because it is heavily contaminated with the x component that we deliberately avoid in traditional designs.

And your definition of "damped" is different to the industry's definition. If Eric Foster said he had the spike damped in 8 usecs then most people here would assume he meant the spike had decayed to 0 volts in 8 usecs. You say you can sample at 1.8 usecs in one instance and at 4 usecs in another but the waveform is still settling somewhere off the page. This would be a disaster if we attempted to apply traditional sampling at the times you mention.

... I dont use sampling :-) ... that was my earlier mistake ... trying to sample utilising the old school techniques was a red herring ... I tried to use a QED backend but the sampling scheme is just not suitable. In the current system the spike is damped to a right angle pulse 0 volts if you like. Damping is the wrong word to use now. Pulse equalisation or compensation is a more correct term.

In Post 866 of this thread you mention period C, supposedly decaying for some 100s of microseconds but this decay doesn't exist in traditional PI where the the spike has ideally settled to effectively 0 volts before sampling begins.

.... period C "IS" the sampling period of a traditional PI and I was referring to the sampling time interval not implying the decay lasted 100's of microseconds. A is transmit, B is flyback spike, C is sampling.

Your automatic self switching rx switch also seems to be a bit iffy. http://www.geotech1.com/forums/showt...130#post179130
Picture at
http://www.geotech1.com/forums/attac...7&d=1381835423

You said elsewhere that this switch makes 6 patents that use front end switches obsolete but how is this possible when it must be followed by a conventional switch in order to work??? Connect any of the popular opamps directly to M2 and your switch turns on and stays on resulting in a cooked opamp. Wouldn't it be best to iron out these problems before declaring it a major achievement??[/QUOTE]

.... completely wrong ( and funny ) ... the wrong bit is as follows ... the self switching blocking FET ( SSBF ) is fully on at all times EXCEPT during the flyback spike. The second switch only stops the first amp seeing the transmit pulse which I dont desire to amplify ... the TX pulse voltage in most designs will not blow the amp... you dont absolutely need the second switch. The circuit posted works like a charm. Considering it dispenses with a messy ( and noisey -- the noise comes in via the gate capacitance from the CPU ) front end blocking fets and it provides a low ohm path from the coil to the amp during recieve ... I would consider that an achievement.

... the funny bit .... you mentioned using popular opamps .... are you suggesting that if I used unpopular opamps they would not blow up ?

ps ... suggest you read up on fet biasing.

[sido]

Hi Moodz, no go to my proposition...I understand...seems to be some conflicts going on as I read.

If any change, more than happy to have a talk without the on-going politics which continue here and there...

Regards Sid

[robby_h]

I assume by your lack of comments that you agree that everything in the following link is predictable and very well known and that your claimed phase shift is incorrect???
http://www.geotech1.com/forums/showt...025#post157025

And I assume you know that your definition of "damped" is entirely different to what is usually meant by "critically damped"??

You say, "... period C "IS" the sampling period of a traditional PI and I was referring to the sampling time interval not implying the decay lasted 100's of microseconds..."

So how long does this mysterious decay last??

So A is the tx period and B is the critically damped flyback period but you still claim there is an additional residual spike decay period during C and you say this decay period is somehow altered by your active damping circuit???? But this residual spike decay period doesn't exist in traditional PI??
http://www.geotech1.com/forums/attac...1&d=1350034465
You say this is damped in around 3 usecs but the green trace is ringing well off the page??

http://www.geotech1.com/forums/attac...0&d=1350219182
You say this is successful active damping but we see ringing, probably when a diode stops conducting, followed by a grossly under damped waveform??

Re your self switching switch... You have feed-though transient spikes every pulse due to the capacitance of M2. These would normally be clipped by a diode across R1, but this would turn your switch on and it would stay switched on.

Note that your preamp ground will be at V1=5v above system ground?

You say, "ps ... suggest you read up on fet biasing".

What do you think keeps the fet turned off during the HV spike Moodz??

[moodz]

A REPOST TO ROBBY'S RAMBLING

I assume by your lack of comments that you agree that everything in the following link is predictable and very well known and that your claimed phase shift is incorrect???
http://www.geotech1.com/forums/showt...025#post157025

And I assume you know that your definition of "damped" is entirely different to what is usually meant by "critically damped"??

You say, "... period C "IS" the sampling period of a traditional PI and I was referring to the sampling time interval not implying the decay lasted 100's of microseconds..."

So how long does this mysterious decay last??

So A is the tx period and B is the critically damped flyback period but you still claim there is an additional residual spike decay period during C and you say this decay period is somehow altered by your active damping circuit???? But this residual spike decay period doesn't exist in traditional PI??
http://www.geotech1.com/forums/attac...1&d=1350034465
You say this is damped in around 3 usecs but the green trace is ringing well off the page??

http://www.geotech1.com/forums/attac...0&d=1350219182
You say this is successful active damping but we see ringing, probably when a diode stops conducting, followed by a grossly under damped waveform??

Re your self switching switch... You have feed-though transient spikes every pulse due to the capacitance of M2. These would normally be clipped by a diode across R1, but this would turn your switch on and it would stay switched on.

Note that your preamp ground will be at V1=5v above system ground?

You say, "ps ... suggest you read up on fet biasing".

What do you think keeps the fet turned off during the HV spike Moodz??

Robby you are referencing posts that are from a completely different circuit that achieved similiar results by a different method.

Critically damped only applies to old school resistive damped circuits ... you just dont have any experience in active damping.

For the last time .... I am referring to a sampling interval not a decay.

Again for the last time ... A = transmit period .... B = spike C=decay / sample period ... this is old school PI.

The self switching switch does not stay switched on .... you obviously have not tested it.

You got one thing right ... the preamp ground is 5 volts ... this saves having to use a bipolar supply.

The HV spike itself controls the FET .... again ... study up on FET biasing to understand why.

[robby_h]

Robby you are referencing posts that are from a completely different circuit that achieved similiar results by a different method.

Critically damped only applies to old school resistive damped circuits ... you just dont have any experience in active damping.

For the last time .... I am referring to a sampling interval not a decay.

Again for the last time ... A = transmit period .... B = spike C=decay / sample period ... this is old school PI.

The self switching switch does not stay switched on .... you obviously have not tested it.

You got one thing right ... the preamp ground is 5 volts ... this saves having to use a bipolar supply.

The HV spike itself controls the FET .... again ... study up on FET biasing to understand why.

Robby you are referencing posts that are from a completely different circuit that achieved similiar results by a different method.

No Moodz, you have claimed earlier sampling with your design when in fact it doesn't allow earlier sampling at all.

Critically damped only applies to old school resistive damped circuits ... you just dont have any experience in active damping.

That's the problem, watching your active damping evolve was a bit like reliving my efforts but I didn't make the same mistakes. If your unproven idea fails, and I believe it will, then you will have to resort back to traditional sampling where your damping creates more problems than it solves.

For the last time .... I am referring to a sampling interval not a decay.

Yes but we can't apply traditional GB algorithms to your sampling interval C !!!!!!!!

Again for the last time ... A = transmit period .... B = spike C=decay / sample period ... this is old school PI.

Yes but once again, the old school PI has no residual spike decay during the sampling period!!!!!!!!!!

The self switching switch does not stay switched on .... you obviously have not tested it.

It will stay on if you strap a diode across R1 to clip the feed-though transient spikes that occur every pulse due to M2's capacitance. An inverting amplifier with the non-inverting terminal connected directly to V1 will also turn M2 on, and ............

You got one thing right ... the preamp ground is 5 volts ... this saves having to use a bipolar supply.

I actually didn't mean that but I hope you aren't using capacitive coupling??

The HV spike itself controls the FET .... again ... study up on FET biasing to understand why.

The gate voltage is fixed so it's the voltage on M2's source that decides if M2 is on or off, therefore it isn't wise to fit components to the source that will upset this rather iffy balance.

BTW, your "A REPOST TO ROBBY'S RAMBLING" is a childish cop out.

[moodz]

Robby you are referencing posts that are from a completely different circuit that achieved similiar results by a different method.

No Moodz, you have claimed earlier sampling with your design when in fact it doesn't allow earlier sampling at all.

Critically damped only applies to old school resistive damped circuits ... you just dont have any experience in active damping.

That's the problem, watching your active damping evolve was a bit like reliving my efforts but I didn't make the same mistakes. If your unproven idea fails, and I believe it will, then you will have to resort back to traditional sampling where your damping creates more problems than it solves.

For the last time .... I am referring to a sampling interval not a decay.

Yes but we can't apply traditional GB algorithms to your sampling interval C !!!!!!!!

Again for the last time ... A = transmit period .... B = spike C=decay / sample period ... this is old school PI.

Yes but once again, the old school PI has no residual spike decay during the sampling period!!!!!!!!!!

The self switching switch does not stay switched on .... you obviously have not tested it.

It will stay on if you strap a diode across R1 to clip the feed-though transient spikes that occur every pulse due to M2's capacitance. An inverting amplifier with the non-inverting terminal connected directly to V1 will also turn M2 on, and ............

You got one thing right ... the preamp ground is 5 volts ... this saves having to use a bipolar supply.

I actually didn't mean that but I hope you aren't using capacitive coupling??

The HV spike itself controls the FET .... again ... study up on FET biasing to understand why.

The gate voltage is fixed so it's the voltage on M2's source that decides if M2 is on or off, therefore it isn't wise to fit components to the source that will upset this rather iffy balance.

BTW, your "A REPOST TO ROBBY'S RAMBLING" is a childish cop out.

..at least your starting to make some sense ... My active damping is not evolving ...its patented ... I am working on other things now ... The self switching blocking fet works fine and some on this board have confirmed it ... An evolution of the self switching blocking fet has been patented as part of a coil damping damping system. Your attempts to discredit this are very poor ....hope this field is not your day job.

[robby_h]

..at least your starting to make some sense ... My active damping is not evolving ...its patented ... I am working on other things now ... The self switching blocking fet works fine and some on this board have confirmed it ... An evolution of the self switching blocking fet has been patented as part of a coil damping damping system. Your attempts to discredit this are very poor ....hope this field is not your day job.

Good Lawd moodz, the answers you give when you don't have an answer. What's the point of applying for patents when you let them lapse.

http://tinyurl.com/lew5oue

One unknown, one granted and five lapsed !!!!!! I hope writing patents isn't your day job.

An Oz forum owner just said that members have a right to expect that those in the race are sincere about finishing and they will do their utmost to bring a new detector to a commercial reality and not create unrealistic expectations or lead people up the garden path with something that will never see the light of day!

You replied with, "Actually they have no rights at all.... At least me and Al are providing free entertainment writing about the development of new detectors".

It's interesting to note that Al has been promising a detector since the year 2000. Do you plan to break his record?

[moodz]

Good Lawd moodz, the answers you give when you don't have an answer. What's the point of applying for patents when you let them lapse.

http://tinyurl.com/lew5oue

One unknown, one granted and five lapsed !!!!!! I hope writing patents isn't your day job.

An Oz forum owner just said that members have a right to expect that those in the race are sincere about finishing and they will do their utmost to bring a new detector to a commercial reality and not create unrealistic expectations or lead people up the garden path with something that will never see the light of day!

You replied with, "Actually they have no rights at all.... At least me and Al are providing free entertainment writing about the development of new detectors".

It's interesting to note that Al has been promising a detector since the year 2000. Do you plan to break his record?

Well I am not attacking other board users there are plenty of people and companies with more lapsed patents than me ... So your point is? I must be on a winner because of your persistence ...

[robby_h]

Well I am not attacking other board users there are plenty of people and companies with more lapsed patents than me ... So your point is? I must be on a winner because of your persistence ...

"Well I am not attacking other board users..."

Well moodz, and I'm not claiming to have discovered something that is incredibly well known or creates more problems than it solves.

"there are plenty of people and companies with more lapsed patents than me".

Do these people and companies just make extraordinary claims or actually make real detectors?

"I must be on a winner because of your persistence ... "

Weird logic. Does that mean the person you have a lengthy argument with must also be on a winner??

[Carl-NC]

Robby, do you have such a problem with Moodz' efforts that you feel the need to incessantly badger him? I don't understand the obsession with some of you guys. I personally have some doubts about his approach but I'm perfectly willing to be wrong. If you don't like what he's doing say, "I don't like what your doing" and let it go, or take it elsewhere.

[sido]

I don't understand the obsession with some of you guys. I personally have some doubts about his approach but I'm perfectly willing to be wrong. If you don't like what he's doing say, "I don't like what your doing" and let it go, or take it elsewhere.

I personally have some doubts about his approach but I'm perfectly willing to be wrong. If you don't like what he's doing say, "I don't like what your doing" and let it go, or take it elsewhere.

Totally right.......

Me too with the addition circus going on for so long...WHY though?

I am more of a small time (New) local investor trying to help a fellow enthuseast....with no go so far..
I will from (NOW) take my interest somewhere else.

Makes me wonder why I even bothered for so long. No offence to people directed personally....Given no choice though.

No correspondance so far, no more for me.....whatever happens, wish you all the best involved.

Makes me question the claims which seem to be fabricated. Patents seem to be a issue??....
????What is the negative to stop such a promising detector being released???? WHATS THE UNDERLING PROMBLEM?????

Good luck to you all involved.

You guys can figure it out!!

Sid

[KingJL]

Robby, do you have such a problem with Moodz' efforts that you feel the need to incessantly badger him? I don't understand the obsession with some of you guys. I personally have some doubts about his approach but I'm perfectly willing to be wrong. If you don't like what he's doing say, "I don't like what your doing" and let it go, or take it elsewhere.

AMEN!!!!

[Qiaozhi]

If anyone could be bothered to read the forum rules, it says:
"Criticism should be relevant and constructive. If you disagree with something, state your case, and move on."