RELIC HAWK

[Max]

Again on coil;
yesterday for the first time i checked those datas for coil, included on schematic. Not accurate!
My original coil, like i posted earlier, are 41 ohm for RX and 3.1 for TX.
So... i took 0.2mm wire and wounded on 30cm diamm. circle, gave me over 100 ohms !!!!!?
So it is not 0.2mm wire, for sure!
Point is to draw 30cm circle and form former to wound wire.Later take off windings and squeeze them to form "D" shape. Formed that way "D" shapes perfectly matches original RH coil size. So...assuming that number of winidngs are correct, i checked resistance and like posted - not accurate.
Today i will try with thicker wire. My idea is first to match resistance and later measure inductance. Both values we do have - noted on schematic and of course i can measure and check on my original RH coil.
So...give me day or two i and will have most accurate datas for original coil.
Original or as close as possible to original coil must be made FIRST, to void any further missunderstandings about oscillators work, drifts, interferences and simillar....
Agree?
Regards!

Hi Ivconic,
I agree about coil... cause if we match original would be easier find mistakes on other stuff and leave troubleshooting on oscillator, cause will be no problems anymore there.

Anyway, I'm doing tests with that coil I've made... and it works... 26cm for 1eur in all metal... problem is at disc mode... doesn't work, at now.

I'm also awaiting for some wire delivery... but still not arrived!

I have made mods on oscillator transistors: put there bc327 and bc337 and seems works better... more than 16.5V on my tx coil now...the 20awg one.
On 0.50mm it works too but problem is it's still unstable... I will try with 0.57mm wire soon.

PS: with 30cm diameter you'll get 122.5meters at 130turns... so for 30AWG you get something 60ohm, not 42ohm.
On schematics I see 35ohm... that's compatible with 0.28mm (bare) copper wire, maybe is this the original wire size of rx coil ?

Kind regards,
Max

[ivconic]

Again on coil;
yesterday for the first time i checked those datas for coil, included on schematic. Not accurate!
My original coil, like i posted earlier, are 41 ohm for RX and 3.1 for TX.
So... i took 0.2mm wire and wounded on 30cm diamm. circle, gave me over 100 ohms !!!!!?
So it is not 0.2mm wire, for sure!
Point is to draw 30cm circle and form former to wound wire.Later take off windings and squeeze them to form "D" shape. Formed that way "D" shapes perfectly matches original RH coil size. So...assuming that number of winidngs are correct, i checked resistance and like posted - not accurate.
Today i will try with thicker wire. My idea is first to match resistance and later measure inductance. Both values we do have - noted on schematic and of course i can measure and check on my original RH coil.
So...give me day or two i and will have most accurate datas for original coil.
Original or as close as possible to original coil must be made FIRST, to void any further missunderstandings about oscillators work, drifts, interferences and simillar....
Agree?
Regards!

[amtech2005]

RELIC HAWK

Amazing MAX !!! Clean oscillation now , no distortion or envelope/modulaton like the first few simulation's from to much feedback . You have optimized the circuit with the BC327'S and the BC337 !! Now the TX coil will have some tolerance +,- , and not be so critical on it's specs .The oscillator circuit may be better than the original . So we are teaching the "student's" at the Minelab office again today . This project is going quite well !!!!!! ................Like "Crocodile Dundee" from down-under said : "Put another Shrimp on the Barbie".............Aziz , Your Smiley's are Cool , especially the "Tire Marks".... Good Day to everyone !!!....... I Gotta get back to my "Integrated Circuit" Writing's.............Eugene

[Aziz]

... maybe I would better try with tarots...and the pendulum stuff... like remote sensing folks do everyday!

Remote Sensing


Near Sensing


;-)

[Max]

Hi Eugene,
very good! We got it!

In the picture you can see simulation for 3.5ohm, about 24Vpp sinus!

I tested with 10ohm series resistance at coil! And works too now!

But at 10ohm one get just 11Vpp of signal... sure.

Kind regards,
Max

[Max]

HI! MAX

What coil do you using on RH project??

Regards

DIRCEU

Hi Dirceu,
I'm using a DD coil, like in TGS, same dimensions 137x255DD , about 11''.

The coil for TX is made of 20AWG (0.8125mm bare), now I'm using 45turns but I've made one with 42turns that had about same inductance.... depends on how you wind and tight the turns... Resistance is under 1ohm, inductance is 1mH exact.

The coil for RX is made by 140turns of 30AWG (0.25mm bare), resistance is of 45ohm, inductance is 15mH.

Using this and actual pcb (modified as above) I get 1eur at 26cm in all-metal.

Disc still doesn't work.

Kind regards,
Max

[Max]

Max , I was digging through the Geotech Archives again yesterday , I read a few comment's that were made about minelab coil's and also transistor's. Just wanted to mention a few thing's . Did the standard 8 inch minelab coil have an exact 1.014 millihenry inductance for tx , not 1.0 millihenry ???? Also is capacitor measured on tx circuit 0.6 micro-farad's ??? And finally transistors were not BC series but 2 number's were mentioned a C33740-ph90 and TR51-ph7 ???? I am checking now what they are . If this help's Great !!! If not then it's Just some assorted garbage I read yesterday...........Have a Good week !!!!!!..........Eugene

Hi Eugene,
all informations are good to me at now...

The TR51-ph7 is a BSR51 transistor, npn darlington + internal diode, we can use BC517 or C517 or similar without much problems.

The other one C33740-ph90 , is unknown kind, probably Japan made part... I'm not sure but are probably other labels for same european stuff... let me explain... I think transistors at oscillator are maybe something like C33740 and C32740 ... the -ph90 stays for "philippines, year 1990", country and year of production...

The C33740 is like european BC337 (NPN), and the C32740 is about a BC327 (PNP): I have both european kind, so can try them if needed... maybe this will solve the coil problem with higher resistance... better if I'll try first on simulator for that.

The capacitor is 1uF and so coil must be 1mH for sure... little differences are unimportant.

Anyway, thanks for providing very useful informations, now the story about transistors seems a bit more clear.

Kind regards,
Max

[DIRCEU]

Hi,
still have lot of instability in disc mode: device gives always a beep beep at variable frequency when I turn geb pot...

Don't know what's going on but seems self oscillations present...

In all-metal it works somehow like described above... about stable and with medium detection range on 1eur

Kind regards,
Max

HI! MAX

What coil do you using on RH project??

Regards

DIRCEU

[amtech2005]

Relic Hawk

Max , I was digging through the Geotech Archives again yesterday , I read a few comment's that were made about minelab coil's and also transistor's. Just wanted to mention a few thing's . Did the standard 8 inch minelab coil have an exact 1.014 millihenry inductance for tx , not 1.0 millihenry ???? Also is capacitor measured on tx circuit 0.6 micro-farad's ??? And finally transistors were not BC series but 2 number's were mentioned a C33740-ph90 and TR51-ph7 ???? I am checking now what they are . If this help's Great !!! If not then it's Just some assorted garbage I read yesterday...........Have a Good week !!!!!!..........Eugene

[Max]

Hi Max,
the variable frequency thing is very strange.Are you sure the 4066 is good? i have seen problems with those Cmos, sometimes gates just works weird.
Could it be that you are amplifing an harmonic? when sound is variating, is that progressive or jump one octave?
I wish i have my IC´s...but it will still take a some days for them to arrive.
I think i will make a new PCB with the mods and ground plane.There is less than 50% comonents on mine,so it is still time.

Regards!
Fred.

Hi,
no I think 4066 are ok: all brand new parts , genuine motorola mc14066

I noticed that moving both fixed geb trimpot (when on fixed on the switch) or the manual pot I get same behaviour... device change the beep frequency from 1Hz to some 3-4Hz... rapid beeps.

I see it also on the scope... the output of U7 goes up and down. At first I had a thought about speaker influence... but it isn't... I disconnected the 16ohm speaker and found same story: output goes up and down, locked in self oscillations at extremely low frequency.

I found a 250Khz harmonic down the path but it's extremely low amplitude... so it's sure not involved in that.

Don't know what to try now... maybe I would better try with tarots...and the pendulum stuff... like remote sensing folks do everyday!

Kind regards,
Max

[Fred]

Hi,
still have lot of instability in disc mode: device gives always a beep beep at variable frequency when I turn geb pot...

Don't know what's going on but seems self oscillations present...

In all-metal it works somehow like described above... about stable and with medium detection range on 1eur

Kind regards,
Max

Hi Max,
the variable frequency thing is very strange.Are you sure the 4066 is good? i have seen problems with those Cmos, sometimes gates just works weird.
Could it be that you are amplifing an harmonic? when sound is variating, is that progressive or jump one octave?
I wish i have my IC´s...but it will still take a some days for them to arrive.
I think i will make a new PCB with the mods and ground plane.There is less than 50% comonents on mine,so it is still time.

Regards!
Fred.

[Max]

Hi,
still have lot of instability in disc mode: device gives always a beep beep at variable frequency when I turn geb pot...

Don't know what's going on but seems self oscillations present...

In all-metal it works somehow like described above... about stable and with medium detection range on 1eur

Kind regards,
Max

[Fred]

Hi,
another little mistake found: 27K for 22K at unity gain inverter.

Changed to 22K.

Kind regards,
Max

Ok, i mistaken with other resistor.Twice...
regards,
Fred.

[nakky]

I don't understand it but try to copy it.Grt Nakky.

[nakky]

Very easy for you but not for me.Grt Nakky.