Classic III

[Geo]

Hi Fitos. Read at this thread first page the post of Ivconic for two spider Coils. Make one ready with shielding and after you can begin with the CL3.
Ευχες

[Geo]

Better sensitivity.

Hi. There is not time for anything i don't know why. So i can't experiment for long time with classic. But i saw that at disc mode there is not good sensitivity. I saw that when i turn full sensitivity pin6 and pin2 of ic4 (lm393) has 18mv so the signal must go bigger than 18mv to turn the ic on. So i changed the pin of VR2 that goes at 0v and connected it via a 2k2 resistor to -V. Now it has better sensitivity and i can't turn the sens potensiometer at full.
Ivconic Try it

[Geo]

Modified schematic

Hi. I attach here the schematic of CL3 a little modified for better sensitivity, single Power sulpy 12V (13.2 is better) and different audio . I tried it for 2 tone audio (one for ferrous and one for no ferrous). It operated but it want one op.amp yet :confused: at one channel. I let it, maybe another time .

[Leto]

missing IC's

Trying to build CLIII... pcb from Jackdetect protel file.
So here are some questions...
Can't find LF444, TLC274 and LF411 -> any known good replacements for them?
Now I have to make the coil (my first IB coil) - this will be hard work as I do not have oscilloscope... but Ivconic's said that's possible.
Can I detect ballance of coils with DMM (when I add or substract windings from feedback coil - Tx oscillating, Rx on DMM)?
What are inductances of Rx and Tx coil?
Also opened to any other suggestions..

Geo thanks for posted modifications..

[Geo]

Hi Leto. Congratulation.. Very good work...nice pcb.
You can use LM324 for LF444 and NE5534 for LF411. I made my CL3 with this IC's.
If you have not scope it is a little difficult to regulate the CL3. First regulate the trimmer at LF411 so the resistance to be 330...400 Ohm. If the resistance is lower you have better sensitivity but you will not have discrimination. Now about the coil... if you have a good digital multimeter do as follow: Connect only the Tx coil and power on the detector. Set the multimeter at 2V AC and try to balance the coil. A good balanced coil must have an output about 5mV. An indication between 5...15 mv is OK. The detector oscillator works at about 6.5 Khz so the multimeter must have the ability to measure at this frequency.
Good luck

[Leto]

one inch PP

Thanks Geo.. I used your replacements (NE5534, LM324)..everything is on board now.

*I connected device to two small (OD 13cm) testing coils in DD configuration (Tx 80turns,0.4mm, Rx100turns, 0.2mm) and nulled them to about 4mV dc
*Tuned the Tx coil with total 110nF capitance to 6.5kHz
*Tuned the Rx coil to highest response at 6.5kHz with total 210nF

(searching whole web and this forum I could not find well explained procedure for tuning the coils with caps - but I guess the setup is the same as free air resonance test??)

This is what I get:
No sound in Disc mode ,
output of NE5534 pin6 is at 0.093V, when I close up my iron hammer -> CLIII is just a bit scared and voltage rise to 0.330v - is this enough?
Still no sound but LM393 (U7) pin1 has 400Hz pulse.

In all-metal there is constant sound I can trim with 100K trimmer.
If I close my hammer again very close to the coils (2cm) pitch of sound changes so there is detection but very poor one .

Any suggestions??

How critical is tuning of Rx coil to Tx frequency?
Whats the purpose of Led on U7?

[Max]

Trying to build CLIII... pcb from Jackdetect protel file.
So here are some questions...
Can't find LF444, TLC274 and LF411 -> any known good replacements for them?
Now I have to make the coil (my first IB coil) - this will be hard work as I do not have oscilloscope... but Ivconic's said that's possible.
Can I detect ballance of coils with DMM (when I add or substract windings from feedback coil - Tx oscillating, Rx on DMM)?
What are inductances of Rx and Tx coil?
Also opened to any other suggestions..

Geo thanks for posted modifications..

Hi Leto,
you can use LS404 from STmicro instead of LF444, that is a very low noise quad. I think you could use LF356/LF357 instead of LF441 too, low noise and low drift.
These are good amplifiers and crossrefs, and though never tested in SLIII circuit, I think could be fine.

Best regards,
Max

[strujas]

HI Leto I am using for LF444 - TL084 ,,for LF411 - OP27GP

[Leto]

??

Thanks Max and Strujas:
LS404 is not produced anymore..will try with TL084.

..but this is not a problem as replacements suggested by Geo should also work.
What bothers me right now is:
No sound in Disc mode
Bad detection in all metall

as written in my previous post..

[kt315]

*Tuned the Tx coil with total 110nF capitance to 6.5kHz

original TX coil has 1 uF (ONE MICROFARAD) capacitor. please INcrease it to the value by DEcreasing the winding turns.

[Leto]

oscillator hates +0.75 uH values

original TX coil has 1 uF (ONE MICROFARAD) capacitor. please INcrease it to the value by DEcreasing the winding turns

My first setup was with 550uh coil BUT trying to tune it to 6.5kHz with +1uF capacitator oscillator stop working .

[ivconic]

...

I am using LM324 almost always....Tank cap. is 330nF...on Fisher 18cm coil i am using with CL3. But KT315 is right about 1mF on original White's coil....
As RX input i used LF356,LF357 and NE5534......
What to say? It will need a bit of effort to adjust coil without osci......Give it chance and be patient....
regards!

[Leto]

All Metal mode OK

Found a problem with that 22k resistor (U8-pin1)..
..Ivconic already wrote in previos posts about this resistor ->
As I can see now I have balanced those small coils well enough (15cm for a coin with 12cmOD DDcoils)

I used spectraLAB Spectral Analysis software with my PCsoundcard. This kind of software NEVER satisfied me with it's claustrofobic 20kHz bandwidith.
BUT
because of tuning the IB coils for the first time I gave it a try one more time - and it worked great even USEFULL.

Still having non-sound problems in discrimination mode. Look like problems with or around U3 LM324 will re-check everything again, confusing a bit are different pinouts on pcb layout as on shematic with LM324 - but this is just matter of how opamps in quad are used.??

Any ideas what should I inspect?

[ivconic]

DEJA VU...


Yo!
Besides everything mentioned here; i noticed a mistake on your
(very nice) pcb. Jackdetect didnt marked this in his work, why?
I do not know!?
But, at present pcb you MUST unsolder that 22K resistor from
pin 6. of 4066(4016). Other side of resistor should remain
soldered on pcb as it is. Unsoldered side of 22K you should
solder to vcc....for example, nearest point is pin 8. of LM393.
I tried to present this on posted picture below...
Also if you check schematic you'll notice quite obvious mistake
there....
I also had a lot of problems arround coil adjustments in the past.
Later i decided not to use hand made coil, but original Fisher small
spider coil (18cm coil - 20cm housing). That coil has not any tank
caps included inside, so you have to add one on pcb TX output...
I experimented with values between 220nF to 470nF....so i gained
best performances with tank capacitance arround 330nF with that coil.
Of course frequency could be shifted a bit from original, but dont worry!
My beloved handmade CL3 is working very good from 4.3kHz to 7kHz...
dependable of coil and tank cap...One more thing! When changing TX tank
cap. you MUST also readjust RX cap too! Right now, i have 22nF + 10nF in
parallel on my CL3 RX input, which makes 32nF....
I can agree that you may find a bit different values suitable for your
design, so you do not have to obey values i marked here. Those should
only give you some idea about overall setup. Geo already explained very
good way to adjust balance on coil so i do not have anything to add in that
matter....
Only one thing here i am confused about!? My CL3 is working very good - almost
excellent in both modes; all metal and disc. No noticeable differences...
A slice decrease in depth is present in PP mode...which is quite understandable
due character or type of this design; well, this is MOTION detector with already
PRESETED ground balance ("automatic ground balance") so it is quite clear that
in PP mode GEB is "cutting" sensitivity...no wonder. This is fact we can live with.
To avoid this we should change whole character of this design and add NO Motion
mode to it, with manual ground balance included....which should be another story..
Right now i think no need for that.
Huh! One more thing.....Sheeesh!! I almost forgot! Did you put those 3 jumpers
over ic's ???
Look in schematic....LM393 in TX part (with phase and GND trimms) and another as
on posted picture...
Also there is another - LAST mistake on pcb....Cut short line between pin 8. and
res.220K+47nF( should remain connected only with pin 7. - make that connection)
.........
So finally we established 4 (four) unintentional mistakes on pcb.....I am not sure
that those mistakes are mentioned in Jackdetect's files...
Anyway those are all....no more mistakes and pcb is very usefull. I made over 10
devices so far, using this pcb...All works very good...
If this helps you than i'll be glad...if not.....i am sorry!
best regards!
Zivio!
Sta ima novo u Sloveniji? Tako blizu a tako daleko......

[Max]

Thanks Max and Strujas:
LS404 is not produced anymore..will try with TL084.

..but this is not a problem as replacements suggested by Geo should also work.
What bothers me right now is:
No sound in Disc mode
Bad detection in all metall

as written in my previous post..

Hi Leto,
yes LS404 is not easy to find but is still in production at STmicro
(but it's discontinued):
you can find on mouser.com or also farnell.
Anyway, LM324 is very good for testing...robust...inexpensive etc
I've used too and also TL084.
If you have noise problems or too consumption switch to LS404 (if you can find some) or better MC33179 that is expensive but very good !
For the preamp. you can use inexpensive OP-07 too.

Best regards,
Max