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Projects by members => Projects by members => Sebosfato => Topic started by: sebosfato on August 18, 2015, 17:09:34 pm

Title: Mr. Feedback circuit
Post by: Login to see usernames on August 18, 2015, 17:09:34 pm
Hello i would like to ask if anyone had succeed in working with the feedback circuit...

i use an ic called lm318 which is an differential amplifiuer and it even have into it antiparallel diodes...

http://www.ti.com/lit/ds/snosbs8c/snosbs8c.pdf

I managed to make it work at the self resonant frequency of the vic but there are other lower resonant frequencies it is not able to lock to because the self resonance noise mess around with the waveform...

 Filtering mess around with phase.. so it won't lock at the peak of resonance...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 19, 2015, 01:58:10 am
Same here, the thing locked in all over the place. What bothered me was that the thing has to re-scan every time it gates and the scan frequency is very low. Tells me something major is being missed on our part and not revealed on his part. Apparently when that signal does happen there can be no mistaking it, that would take care of the false lock in's.

I have been able to obtain a classical capacitor charging signal from the toroid setup of meyers. That signal only happens at a specific resonance. To obtain that signal the circuit has to be gated just at the peak of the step charge.
It forms a single arcing line out of the pulses.
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 19, 2015, 14:33:51 pm
My frequency in the scanner is 0,7Hz so its little faster than stan...... its a triangle wave...

I also had it to lock at some unpredictable places... but i notice they are all sub harmonics..

i wonder if the pll wasn't mean to generate subharmonics since there were those frequency dividers... well actually it could be working as a multiplier...

i also wonder if my feedback is working as should since its following that one frequency...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 22, 2015, 21:47:44 pm
i believe my feedback circuit is working but the frequency mixer is creating a delay which cause the pll to lock little over the resonant frequency...  i will remove that add...

its very nice to have all waveforms going and all 3 led's light! the feed back pulse indicator, the lock in indicator and pulse on

the pll can maintain the frequency stable and follow as i move the wiper arm...


ps (i took the frequency mixer out of the system, but still it would not lock to the exact frequency... )

i start to think that or the uf4007 antiparallel diodes at the inputs of the opamp are creating unnecessary capacitance.. i mean unnecessary because it already have build in antiparallel diodes .. lm318
3

or the igbt + driver are not fast enough

or the waveform of the feedback circuit...

ohh i;m tired...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 22, 2015, 23:55:21 pm
take a break, my young friend..
Clear yr mind...Party a bit  :)
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 23, 2015, 00:11:07 am
take a break, my young friend..
Clear yr mind...Party a bit  :)

i will do just that after i get this working ;D 

i'm doing some tests on amp restriction... it seems my secondary is maybe too big.. its the same as the chokes size...

another thing i did today i connected some electrodes in series.. no result .. i'm getting only up to 20kv on this vic because above at this voltage the ends of the chokes becomes blue and will certainly break up soon... this is in air for  this first tests..

Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 25, 2015, 16:38:44 pm
my feedback circuit is ot locking at resonance i just figured why...

when we pulse the vic while its operating also when the primary sends a pulse on the coils on resonance are exctly at maximum negative voltage so when you apply the pulse it takes 90degre to the output of the feedback windings to start sending a pulse... so it will never lock to resonance in this way..

i´m figuring a way to make the feedback electromagnetic now...

i know that the opamp used have high comom mode rejection...

it just ocuured to me that when i hooked my pll with current feedback it detected the correct frequency... also when i used a simple antena coil.... that probably was working because of the electromagnetic field generated from the cell...

so the only way left is to make the feedback coil a biifilar winding and make dc current to pass thru it...

this makes a balanced circuit... where when the inductance of the core is changing there is a voltage, and if i remember well it should be just in quadrature... it was from a old book i had but left it in italy... i guess i have a pdf of it somewhere it was called practical transformers with a 3phase transfoermer in the front.. yelow pages..

actually it was not bifilar it was a kind of two cores that are arranged to not close flux between the two where the first core flux density induce a permeability change of the other core so changing the inductance of a coil wound arond it... if it has a constant current applied to it it will develop a voltage in quadrature..


just found this http://worldwide.espacenet.com/publicationDetails/originalDocument?CC=WO&NR=2010015025A1&KC=A1&FT=D&ND=&date=20100211&DB=&&locale=en_EP

the problem with current feedback is theres no where to get it since in my circuit suposedly at resonance no current should flow... it is a kind of series resonance to ground too .. though

Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 31, 2015, 09:25:42 am
well i think meyer feedback circuit was another part that was wrong placed to fool people about how should really operate...

although it seems a differential amplifier as i posted in the last post it generates a  90degrees dephased square wave relative to the input... this mean that the resonance takes on and it rules when the energy can be supplied or not by the primary..

this 90 degrees come from the fact that its acting as a zero crossing detector.. but its detecting the zero voltage crossing across the coil..

could be possible to make it detect only half wave after the zero crossing? or to detect the edge?

would be in phase?

well i will make sure of that!
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 31, 2015, 15:19:04 pm
i have a very strong believe that there is a secret in how the feedbackcoil develop its signal...

i believe it could have being used as a parametric oscilator,,, i mean feeding it with current thru a resistor and having it coupled to the core but not coupled to the flux...

this would be the analog of a condenser microfone ...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 31, 2015, 18:49:41 pm
many hours over it today to find out that...

its not a differential amplifier but a difference amplifier with positive feedback so it should latch the pulses with minimal signal in...

basically a comparator.. but the reduced gain increase stability and comom mode noise.. the last is not high depending on how to get the winding and the capacitor,,, the 5 volts  going into the inverting input also brings the circuit side to safe level..

i added a resistor in series with the antiparallel diodes 10 oohm and in series between them and the non inverting input 470... than reducing the capacitor to nf is possible to get 90degrees phase...

i did that to make the feedback of the opamp do its work... 

actually the circuit coulbe maybe be left as it is in the patent but that big capacitor on the vic cards is a huge mistake... the 5 volts goes to the inverting input and the rg also to the non inverting input...

I found in simulation the greater is the resistor in series with the input the greater the phase lag... the same is for bigger capacitor and shunt resistor..

if i understood well to keep the commom mode rejection the ratio between r1 and rf must = r2 to
ground


the problem i see with meyer circuit increase with frequency since the reactance of the capcacitor decrease and the resistors in the circuit remain the same...

that why the simple solution is a capacitor that has much greater reactance than the shunt resistance to keep 90dreegree current from voltage but still give enough current so the shunt resistor create enough difference voltage...
the resistor in series in the antiparallel diodes could be not needed... but is interesting to keep r1 and r2 small in theory...


so now let me see iit working



Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on August 31, 2015, 23:15:46 pm
i got it

the values work 2nf cap in series with 4 turns r1 and r2 10khohm each uf4007antiparallel diodes in parallel with a 220ohm ... having 1mehaohm from out to positive input and connecting 5 volts there too... 1 kiloohm from there to the antiparallel diodes too.. and the rests is just as stan show execpts no center tap...

it lock and the voltage is higher than manually tuning...

this is just thefirst test i did with minimummodifications to my circuit..

as this is to work at lower frequency this values seems okbut i´m reducing input and shunt resistors to get less phase lag
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 01, 2015, 07:17:56 am
well its locking,,,

as the phase comparator 2 is being used it locks to the minimum frequency... and has 0 degrees of phase diference...

it seems it loosed the ability to follow frequency... it will loose lock and the resonant scanning locks again if in the same range... otherwise an offset is also required to retune to a change in inductor..

maybe there is still phase lag,,, strangely it was able to follow when using a square wave... or when it was not locking to the correct resonant frequency as i described in the first posts...

i also detected some noize in my resonant scanning circuit when the gate is 0% is ok but when the signal goes up to 100% the scanning voltaged get noise... that maybe because i used big resistors... and its on the same board as the gate circuit.. . i will try adding filtering..

I´m thinking that maybe the first phase comparator could be a good idea to be tested.. but my board is little hard to switch to that since i designed it for working with the second comparator...

i´m planning to make a new simplified board for testing..
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 02, 2015, 18:50:48 pm
yesterday i was thinking.. hell if i´m getting it to lock why it would loose the lock when circuit parameters change...


after revieweing the pll and finding there were no erros in development... i thohught the only possible reason for it maybe that the capacitor is delaying the signal by 90... so in the end its allways in the end of the lock region somehow... but i thought if i add instead a coil to get this phase correction?

let me see the difference... of course circuit need to change for it a little... 

but in my opinion here the current will be just in phase with the pulse being applied so it will sit in the middle of the lock... and the inductors should not contribute to the resonance... and maybe would work as a filter at the same way... also the higher the frequency the better for the inductor... opose to the capacitor case...

http://www.n5dux.com/ham/files/pdf/Phase-Locked%20Loops.pdf

just interesting plls

Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 04, 2015, 18:16:06 pm
it worked, however the frequency is little out of the resonance peak by 3khz as there is a small phase difference between the feedback an pulse out...i´m trying to solve that... maybe my only option is a small toroid... with few turns of thick wire... i tried a coil with 22 awg 1mh 1ohm.. so maybe the size of wire messes around...

the resonant freq is 34khz in this case and the pll locks at 37khz...

a comertial capacitor is a better component than a coil regarding power dissipation... maybe thats why the capacitor worked better at first glance.

maybe simply having more turns on the feedback might just work...

Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 05, 2015, 07:03:31 am
oh mAN... The patent circuit is so wrong...

i added two input resistors and now it works much better.. it does not need feedback resistor at least its what seemed to me... i´m trying to get the delay out... now is really very little only 800hz from resonance

the patent shows all that is required to make it work..

the antiparallel diodes

the resistor connecting the positive side to ground...

the other voltage source

but the input resistors are misplaced... should be at the inputs after the antiparallel diodes not before otherwise the feedback can´t do its work correct, at least i guess (even if the internals of the opamp used have antiparallel diodes limiting the input to 1 volt extreme) ...

 i added a resistor in parallel with the diodes too to try speeding it up... ( the uf4007 antiparallel diodes)

maybe higher speed diodes would be much better... but here it costs a lot and i have no pair i could use now.. thats why the resistor... to negate the capacitance of the diodes...

i think there is no way to get the pll to show lock condition with phase comparator I since the input and pulses are 90 degress... it would only show locked condition if the pulses are in phase..

this tells the feedback has a secret and i solved a way to get it working correct...

blame on me

instead of voltage i´m getting a sort of current feedback...but 90degress apart... so with the resonance of the vic gets perfect in phase lock..

the nice thing about it is that as my pll is working at the higher freq range the bandwidth is also high so when locks i can vary the ofset and would not even loose lock.. only if get outside the range..

i raised the turns of the feedback as thought before.. and it improoved the phase... so the problems might be the chip having to drive the transistors for the feedback led migh be getting my slew rate down too.. probably would be good to add a buffer...

in a next board i plan to do i will make many real improvements i feel the need to.. like a voltage follower to the filter and other adds raising the stability...


from all that you get that if you get a motivation no pain can stop you!

the 5v i connect to the antiparallel diodes closer to the inverting input... so it kind of tells the chip allong with the 100k resistor on the other input of the opamp to stay down when no signal in..

it was very non intuitive  to exchange the components since both change the phase of current by 90

i just knew that one was positive and other negative..
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 05, 2015, 09:29:59 am
if anybody feel greatfull with all this... and feel like could help somehow here is a link for donations..

https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=sebosfato%40gmail%2ecom&lc=US&item_name=Sebosfato%20Probe%20Crowdfunding&item_number=1&currency_code=USD&bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted

i would be really honored to receive any help, because now i´m dedicating my all my time to this work and your help will let me get some components i need to work with like diodes and other equipment..

thanks in advance


Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 06, 2015, 20:17:08 pm
i will check if i´m able to do it from here (some dont allow non american citizen or living outside their region of interest)... my friends here are helping me to make a video to make a fundraiser here too.. but this networks have some very good intention people that are havituated to donate...


I just insisted with my friend on the paypall link as if you donate thru the fundraiser sites most of them keep up to 15% of it... so those who could donate directly would have help more with lower reduction of the donated money for me to receive...

as i said i will do it most because there is also their specific public too...

thanks really much for the idea
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 08, 2015, 08:30:57 am
as i promissed the feedback now workd and its circuit will be released with my major modifications to the pll circuit that makes the transistor never burn again, an incredible frequency range and stability... also i´m doing something to be able to gate while in autotune mode...

i´m willing to send in exchange for 1200$ a working full pll circuit box with scanning and gate... or in exchange for that 30kv differential probe

it takes me maybe a week to make it for i can send it... but the payment in advance... for i will need to make some buying of the probe and parts to make it..  i will make in such way that if you want to change the range you have trim pots for the parameters and make the changeble parts easy to access.. the only thing you will need is the variac and a dc capacitor or any dc source.. it will be bivolt and work from the wall or straight from car battery..

will have upgradable inputs for sense comands like gas pressure

no accelerator leds no digital

thats my another proposal to whoever can be interested in help and have something nice to work in hands.. 


thats my add.. but i will release as soon as i get the probe in my hands... i´m doing a lot of work trying to bring all my friends into this... maybe some help make it faster...

i even already described some of the modifications...

but i´m more likely to want to share full diagrams to who donated or wanted to help anyhow...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 10, 2015, 00:29:43 am
i have found another interesting fact...

the feedback circuit meyer proposed actually worked as i said even if is somewhat wrong..

but in the way it is originaly design in the patent it can be usefull to drive a resonant load... and in that way i had it working in 2008 in italy... now i know why it worked than...
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 21, 2015, 15:22:10 pm
From what I'm reading, you are saturating your coils.  Don't do that.
Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on September 21, 2015, 19:43:35 pm
i guess the core is saturating on resonance is not working like a normal transformer... its a ringing transformer...

the saturation may be at the top limit voltage along with corona discharges when the coils are not in oil...

i got up to 50kv in oil no proble.. but in that case there was two cores one with primary and secondary and the other with the chokes....

yes kitchen oil  :o

i notice the saturation in the primary when it start to decrease primary impedance.. i have a meter for that so basically the resonance is the top limit... is it that saturates the core.... should not be bad... but the more coils the lower energy dissipated on the core and probably higher voltage...  but also slower






Title: Re: Mr. Feedback circuit
Post by: Login to see usernames on January 20, 2016, 16:40:36 pm
for low frequency this is a good circuit for detecting zero current or max min voltage crossing by zero current crossing...

at this you see i added two 100nf capacitors for its to work at 60hz...

the 1 Megohm provide a positive feedback...

the 100kohm together with the 5v source and diode keeps the opamp signal down until it has the min level to revert the diode forward biased...

the input resistors as i described goes after the diodes...

you can use 741 for the low frequency case and should not give any problems..

the signal output won't be from rail to rail so you should add an inverter after it for some applications... for the pll is not needed as it uses a rise and fall edge detector on phase comparator 2

Regarding yet the pll i found that is useful to use one of the 4016 switches that is not used to switch the signal from pin 13 to the filter of the pll using the gate signal... this allow the pll to keep in tune with gating operations (did not tried yet but i´m damn sure this is the simplest workaround needed)
Title: THE FEEDBACK SECTION
Post by: Login to see usernames on August 06, 2018, 23:15:18 pm
for low frequency this is a good circuit for detecting zero current or max min voltage crossing by zero current crossing...

at this you see i added two 100nf capacitors for its to work at 60hz...

the 1 Megohm provide a positive feedback...

the 100kohm together with the 5v source and diode keeps the opamp signal down until it has the min level to revert the diode forward biased...

the input resistors as i described goes after the diodes...

you can use 741 for the low frequency case and should not give any problems..

the signal output won't be from rail to rail so you should add an inverter after it for some applications... for the pll is not needed as it uses a rise and fall edge detector on phase comparator 2

Regarding yet the pll i found that is useful to use one of the 4016 switches that is not used to switch the signal from pin 13 to the filter of the pll using the gate signal... this allow the pll to keep in tune with gating operations (did not tried yet but i´m damn sure this is the simplest workaround needed)